Research ArticleA Randomized Comparison Simulating Face toFace Endotracheal Intubation of Pentax Airway ScopeC-MAC Video Laryngoscope Glidescope Video Laryngoscopeand Macintosh Laryngoscope

Hyun Young Choi1 Young Min Oh2 Gu Hyun Kang1 Hyunggoo Kang3

Yong Soo Jang1 Wonhee Kim1 Euichung Kim4 Young Soon Cho5 Hyukjoong Choi3

Hyunjong Kim6 and Gyoung Yong Kim7

1Department of Emergency Medicine College of Medicine Kangnam Sacred Heart Hospital Hallym UniversitySeoul 150-950 Republic of Korea2Department of Emergency Medicine College of Medicine Uijeongbu St Maryrsquos hospital The Catholic University of KoreaUijeongbu 480-717 Republic of Korea3Department of Emergency Medicine College of Medicine Hanyang University Seoul 133-791 Republic of Korea4Department of Emergency Medicine CHA University School of Medicine Seongnam-si Gyeonggi-do 463-712 Republic of Korea5Department of Emergency Medicine Soonchunhyang University Bucheon Hospital Bucheon 420-767 Republic of Korea6Department of Emergency Medicine Ilsan Paik Hospital Inje University Ilsan 411-706 Republic of Korea7Gyeonggi Fire Service Academy Yongin 449-882 Republic of Korea

Correspondence should be addressed to Gu Hyun Kang drkang9hanmailnet

Received 19 December 2014 Accepted 25 January 2015

Academic Editor Jestin Carlson

Copyright copy 2015 Hyun Young Choi et al This is an open access article distributed under the Creative Commons AttributionLicense which permits unrestricted use distribution and reproduction in any medium provided the original work is properlycited

Objectives Early airway management is very important for severely ill patients This study aimed to investigate the efficacy of faceto face intubation in four different types of laryngoscopes (Macintosh laryngoscope Pentax airway scope (AWS) Glidescope videolaryngoscope (GVL) and C-MAC video laryngoscope (C-MAC))Method Ninety-five nurses and emergency medical technicianswere trained to use the AWS C-MAC GVL and Macintosh laryngoscope with standard airway trainer manikin and face to faceintubation We compared VCET (vocal cord exposure time) tube pass time 1st ventilation time VCET to tube pass time tubepass time to 1st ventilation time and POGO (percentage of glottis opening) score In addition we compared success rate accordingto the number of attempts and complications Result VCET was similar among all laryngoscopes and POGO score was higher inAWS AWS andMacintosh blade were faster thanGVL andC-MAC in total intubation time Face to face intubation success rate waslower in GVL than other laryngoscopes Conclusion AWS and Macintosh were favorable laryngoscopes in face to face intubationGVL had disadvantage performing face to face intubation

1 Introduction

Intubation is one of the most important procedures attribut-ing prognosis in severely ill patients [1] Endotracheal intuba-tion success rates are variable depending on airway structurepatientrsquos clinical status practitionerrsquos skills and so forth [2 3]The video laryngoscopes recently and widely used are goodsubstitutes for conventional direct laryngoscope in difficult

airway management [4] They mount camera lens at the tipof laryngoscope and more curved blade so that intubationcan be performed safely and comfortably with clear andwide internal field of vision [5] Many emergency physiciansare concerned about the feasibility of urgent airway man-agement in limited space in means of transporting patientssuch as ambulances or helicopters in cases of traffic delayspatientsrsquo rapid deterioration of mental state or entrapped

Hindawi Publishing CorporationBioMed Research InternationalVolume 2015 Article ID 961782 7 pageshttpdxdoiorg1011552015961782

2 BioMed Research International

trauma casualties [6] In prehospital environment in whichpatients are on the ground or entrapped in vehicles itis difficult to perform conventional intubation [7ndash9] Fordecades conventional tracheal intubation was performed atupper side of patientrsquos head However mostly in entrappedpatients with restricted position there is not enough spaceon patientrsquos head side for tracheal intubation [1] For thissituation we can try face to face intubation in other wordsinverse intubation can be performed with the providerrsquosface at the same level as the patientrsquos face There is noneeded for another space on patientrsquos head side for trachealintubation in face to face intubation Therefore it can be avery useful method for performing tracheal intubation inrestricted position [10] But it is different from conventionaltracheal intubation in the position in which the glottis isviewed and the manipulation of the tube due to the reverselyprogressing direction Similarly since face to face intubationwith video laryngoscope differs from conventional intuba-tion untrained practitioner may feel difficulty performingit

As described above face to face intubation will be agood substitute for conventional endotracheal intubation forpatients who need urgent endotracheal intubation immedi-ately in limited space [11]

In this study after teaching the face to face intubationusing conventional laryngoscope and video laryngoscopes inmanikin model we analyzed the success rate time spent andcomplications caused by intubation procedure

2 Methods

The Institutional Review Board at Hallym University Kang-nam Sacred Heart Hospital approved this study IRB numberwas 2014-11-153

21 Subject Ninety-five nurses and emergency medical tech-nicians (EMT) participated in a 2-day long airway man-agement education program in Gyeonggi-do fire serviceacademy South Korea They were divided into 4 groups andeach group was trained in consecutive order

22 Study Design Instructors gave lectures during 2 hoursabout endotracheal intubation and airwaymanagementsThelecture session was followed by practice session They weredivided into 4 groups Each group took 4 different 50-minutelong practices which include endotracheal intubation usingMacintosh blade and video laryngoscopes and face to faceintubation It took 4 hours in total

After the practice session the subjects were divided intofour groups and each group took checklist for the test for tra-cheal intubation Four groups were divided by kinds of laryn-goscopes direct laryngoscope (Macintosh blade 4) Pentaxairway scope (AWS Hoya Tokyo Japan) C-MAC videolaryngoscope pocket with standard 3 blade model (C-MACKarl Storz Endoscopy Tuttlingen Germany) and Glidescopevideo laryngoscope with standard 3 blade model (GVLVerathon Medical Inc Bothell WA) And we used Laerdalairway management trainer (Laerdal Medical Corporation

Stavanger Norway) which is as widely used manikin fortraining of airway management

Instructors checked and recorded POGO (percentage ofglottis opening) and times when glottis was visible and whenendotracheal tube passed vocal cordThey also checked chestrising ofmanikin whichwas recorded as 1st ventilation usingtube ballooning and ventilation with bag-valve mask

All the tests were performed in separated space Beforetest every subject received random test sequence table Testsequence of laryngoscope types were determined by randomsample

23 Statistical Analysis Statistical analysis was carried outwith the 220 version of the SPSS program for windows(SPSS Inc Chicago IL USA) Data was presented as meanplusmn standard deviation (SD) In previous study total intubationtime for face to face intubation was 216 plusmn 101 seconds [10]To detect 20difference in total intubation timewith a powerof 09 and 120572 = 005 we estimate that 75 subjects would beadequate considering a 20 drop rate We used Shapiro-Wilktest for verifying normal distribution and Wilcoxon signedrank test for verifying the result which is not according tonormal distribution A significant difference was consideredwhen 119875 value was less than 005 For comparison in correla-tion of multiple variables we used Friedman test and appliedBonferronirsquos method for Post hoc analysis

3 Result

95 subjects participated in this study but we excluded 9subjects due to informational errors such as missing dataon evaluation form So 86 subjects were enrolled in thisstudy They consisted of 54 men (628) and 32 women(372) and were classified into 17 nurses (198) 68 1stlevel EMT (emergency medical technicians) (790) and 12nd level EMT (12) 1st level EMT was licensed to collegegraduates of emergency medical technology otherwise 2ndlevel EMT was licensed by passing written and practical testfor emergency situations In South Korea most of healthcareproviders in the field consisted of 1st level EMT 2nd levelEMT and nurses Mean age of subjects was 283 years oldmean career as healthcare provider was 36 years Most ofthem (83 of 86) experienced intubation less than 3 timesIn addition they never experienced intubation using videolaryngoscopes and face to face intubation (Table 1) Wedescribed the result divided into VCET (vocal cord exposuretime) POGO (percentage of glottis opening) score tubepass time and 1st ventilation time In addition we calculatedspent time from VCET to tube pass time and from tubepass time to 1st ventilation time We limited subjectrsquos data incase of successful endotracheal intubation achieved only in1st attempt We compared the success rate with the numberof attempts and regarded a failure in case of not achievingendotracheal intubationwithin 1minute because we assumedthe emergency situation in which subjects must achieve faceto face intubation in spite of very narrow space in otherwords they cannot wait for conventional intubation andneededmore space [6 12] Finally we described complicationby kinds of laryngoscope

BioMed Research International 3

Table 1 Demographic characteristics of subjects (119899 = 86)

Characteristics DataSex (119899 percent) Male (54 628)Age (years range) 283 (21ndash40)Work experience as healthcare provider (years) 36

0 (119899 percent) 27 (314)to 5 years 36 (419)gt5 years 23 (267)

LicenseNurse 17 (198)1st level EMT 67 (779)2nd level EMT 1 (12)

Intubation experienceMCL lt3 (times) 83 (965)Video laryngoscope lt3 (times) 86 (100)Face to face intubation lt1 86 (100)

EMT emergency medical technician MCL Macintosh laryngoscope

31 VCET Vocal cord exposure time (VCET)means the timetaken by the subject to hold a handle of laryngoscope to find avocal cord opening In Macintosh blade the VCET was 78 plusmn33 seconds and it was faster than other video laryngoscopesin AWS 109 plusmn 78 in GVL 84 plusmn 49 and in C-MAC 84 plusmn 46But no significant difference showed among laryngoscopes(119875 = 0199 in Friedman test) (Table 2)

32 POGO Score Percentage of glottis opening (POGO)score defined a certain extent of visualized vocal cord afterinsertion of laryngoscope to oral cavity If we canwatchwholevocal cord wemark it 100 and if we cannot find vocal cordwe mark it 0 In Macintosh blade (536 plusmn 223) POGOscore was lower than all kinds of laryngoscopes that we usedand showed significant difference Compared to Macintoshblade POGO score in AWS was 817 plusmn 183 (119875 = 0000) inGVLwas 654plusmn250 (119875 = 0000) and in C-MACwas 729plusmn208 (119875 = 0000) In comparison of video laryngoscopesAWS showed higher POGO score than GVL (119875 = 0000) andC-MAC (119875 = 0002) but there was no significant differencebetween GVL and C-MAC (119875 = 0188) (Tables 2 and 3)

33 Tube Pass Time Tube pass time means time spent bysubjects to grasp a handle of blade passing the vocal cordby endotracheal tube Macintosh blade (187 plusmn 73 sec) wasfaster than GVL (268 plusmn 100 sec 119875 = 0001) and C-MAC(228 plusmn 102 sec 119875 = 0000) and showed no difference withAWS (196 plusmn 95 sec 119875 = 0608) In comparison among videolaryngoscopes AWS was faster than GVL (119875 = 0005) butthere were no differences between AWS and C-MAC andGVL and C-MAC (119875 = 0011 119875 = 0108) (Tables 2 and 3)

34 1st Ventilation Time 1st ventilation time means timespent from holding a handle of laryngoscope and passingthe vocal cord by endotracheal tube to give 1st ventilationvia inserted endotracheal tube It also means total intubationtime There were no differences between Macintosh blade

(284 plusmn 77 sec) and AWS (296 plusmn 109 sec) and GVL (392 plusmn97 sec) and C-MAC (352 plusmn 104 sec) (119875 = 0530 119875 = 0207)However Macintosh blade was faster than GVL (119875 = 0000)and C-MAC (119875 = 0000) AWS was also faster than GVL(119875 = 0003) and C-MAC (119875 = 0000) (Tables 2 and 3)

35 VCET to Time of Endotracheal Tube Passing Vocal Cord(Tube Pass Time) It means time spent from vocal cordexposure to passing the endotracheal tube Macintosh blade(109 plusmn 59) and AWS (104 plusmn 109) showed similar result andthere is no significant difference (119875 = 0028) In GVL (228 plusmn271) and C-MAC (171 plusmn 143) they needed more time fromvocal cord exposure to endotracheal tube passing via vocalcord compared to Macintosh blade and AWS individually(Macintosh versus GVL 119875 = 0003 Macintosh versus C-MAC 119875 = 0001 AWS versus GVL 119875 = 0001 AWSversus C-MAC 119875 = 0000) No significant difference showedbetween GVL and C-MAC (119875 = 0161) (Tables 2 and 3)

36 Time of Endotracheal Tube Passing Vocal Cord (TubePass Time) to 1st Ventilation Time 96 plusmn 39 seconds areneeded from tube passing to 1st ventilation in Macintoshblade and that in AWS was 98 plusmn 37 seconds In GVL andC-MAC the results were 106 plusmn 97 seconds and 122 plusmn 45seconds In comparison with Macintosh blade AWS (119875 =0860) and GVL (119875 = 0060) did not show significantdifference but C-MAC (119875 = 0000) was meaningfully slowerthan Macintosh blade AWS was faster than C-MAC withsignificant difference (119875 = 0000) but there was no differencewith GVL (119875 = 0171) No significant difference was foundbetween GVL and C-MAC (119875 = 0165) (Tables 2 and 3)

37 Endotracheal Intubation Success Rate according to theNumber of Attempts 86 subjects performed face to face intu-bation using laryngoscopes we determined a failure in whichsubjects did not achieve endotracheal intubation within 1minute or accomplished esophageal intubation InMacintoshblade 72 subjects (837) achieved successful endotrachealintubation in first attempt and 85 (988) succeeded in sec-ond attempt At third attempt all subject (100) succeededin endotracheal intubation 71 subjects (825) succeeded inendotracheal intubation in first attempt usingAWS In secondattempt 84 (976) achieved successful endotracheal intuba-tion 85 (988) succeeded in third attempt all subject (100)succeeded in fourth attempt In GVL 37 subjects (430)succeeded in endotracheal intubation at first attempt and62 (720) succeeded in second attempt 70 subjects (813)succeeded in third attempt and 73 (848) in the fourth 13subjects (152) did not achieve successful intubation duringfour attempts 74 subjects (860) succeeded in endotrachealintubation in first attempt using GVL 83 subjects (965) insecond attempt and 85 (988) in third attempt 1 subject(12) failed in endotracheal intubation during four attempts(Figure 1 Table 4)

38 Complication Weexamined complications of face to faceintubation during procedure for tooth injury and esophageal

4 BioMed Research International

Table 2 Comparison of intubation time (sec) and POGO () according to laryngoscopes (mean plusmn SD)

MCL AWS GVL C-MAC 119875 valueVCET (sec) 78 plusmn 33 109 plusmn 78 84 plusmn 49 84 plusmn 46 0199POGO () 536 plusmn 223 817 plusmn 183 654 plusmn 250 729 plusmn 208 0000Tube pass time (sec) 187 plusmn 73 196 plusmn 95 268 plusmn 100 228 plusmn 102 00011st ventilation time (sec) 284 plusmn 77 296 plusmn 109 392 plusmn 97 352 plusmn 104 0000VCET to tube pass time (sec) 109 plusmn 59 104 plusmn 109 228 plusmn 271 171 plusmn 143 0000Tube pass time to 1st ventilation time (sec) 96 plusmn 39 98 plusmn 37 106 plusmn 97 122 plusmn 45 0000lowast

119875 value lt 005 is level of statistical significance according to Friedman testMCL Macintosh laryngoscope AWS Pentax airway scope GVL Glidescope video laryngoscope C-MAC C-MAC video laryngoscope

Table 3 Statistical significance (119875 value) among laryngoscopes for intubation time (sec) and POGO ()

MCL versusAWS

(119875 value)

MCL versusGVL

(119875 value)

MCL versusC-MAC(119875 value)

AWS versusGVL

(119875 value)

AWS versusC-MAC(119875 value)

GVL versusC-MAC(119875 value)

VCET 0008 0038 0217 0756 0090 0220POGO 0000lowast 0000lowast 0000lowast 0000lowast 0002lowast 0188Tube pass time 0608 0001lowast 0000lowast 0005lowast 0011 01081st ventilation time 0530 0000lowast 0000lowast 0003lowast 0000lowast 0207VCET to tube pass time 0028 0003lowast 0001lowast 0001lowast 0000lowast 0161Tube pass time to 1stventilation time 0860 0060 0000lowast 0171 0000lowast 0165lowast

119875 value lt 0008 is level of statistical significance according to Bonferronirsquos methodMCL Macintosh laryngoscope AWS Pentax airway scope GVL Glidescope video laryngoscope C-MAC C-MAC video laryngoscope

837

988 100 100

825

976 988 100

43

72813 84886

965 988 988

0

20

40

60

80

100

1st attempt 2nd attempt 3rd attempt 4th attempt

Succ

ess r

ate (

)

Number of attempts

MCLAWS

GVLC-MAC

Figure 1 Endotracheal intubation success rate according to thenumber of attempts Glidescope video laryngoscope (GVL) showedlower success rate compared with other laryngoscopes in all ofattempts MCL Macintosh laryngoscope AWS Pentax airwayscope GVL Glidescope video laryngoscope C-MAC C-MACvideo laryngoscope

intubation We included all attempts of endotracheal intuba-tion Tooth injury was considered when tester heard toothclick The number of tooth injuries in Macintosh blade wasone in AWS and GVL five and else in C-MAC three Oneesophageal intubation occurred in Macintosh blade and noesophageal intubation occurred in video laryngoscopes

4 Discussion

Endotracheal intubation is very important procedure inemergency department for severely ill patients [13 14] Inconventional intubation operator sets a location at the upperside of patientrsquos head grasps a laryngoscope with left handand inserts endotracheal tube by right hand For better visu-alization operator shift patientrsquos tongue to left using bladeLots of new techniques and machines are introduced foreasy successful intubation but until recently conventionalintubation is the most commonly used method for airwaymanagement Video laryngoscopes for difficult airway con-sist of a laryngoscope with a light source and a camera indistal blade In contrast to conventional blade having about151015840-visual field video laryngoscopes make wider visual anglebecause of the camera on distal blade [4] In special situationsuch as in ambulance or helicopter occasionally there is nospace at patientrsquos upper side for conventional intubation Sooperator has to intubate on lateral or frontal side of patient[9] In contrast to conventional laryngoscopy the practitionerholds the handle of the laryngoscope in his right hand withthe top of the blade in the upright position After the openingof patientrsquos airways the top of the laryngoscopersquos curved bladewill be in place in the left part of the patientrsquos mouth [10]

We examined this study to investigate whether videolaryngoscopes are helpful in special situation like beingentrapped in car or permitted narrow space and whethervideo laryngoscopes are more useful than conventional

BioMed Research International 5

Table 4 Success rate according to the number of attempts

MCL AWS GVL CMAC

Success at 1st attempt 72 (837) 71 (825) 37 (430) 74 (860)

Success at 2nd attempt 13 (151)(85 988)

13 (151)(84 976)

25 (290)(62 720)

9 (104)(83 965)

Success at 3rd attempt 1 (11)(86 100)

1 (11)(85 988)

8 (93)(70 813)

2 (23)(85 988)

Success at 4th attempt 0 1 (11)(86 100)

3 (34)(73 848) 0

Failure at 4th attempt 0 0 13 (151) 1 (11)MCL Macintosh laryngoscope AWS Pentax airway scope GVL Glidescope video laryngoscope C-MAC C-MAC video laryngoscope

intubation set (Macintosh blade) We choose several videolaryngoscopes AWS which has endotracheal tube-guidinggroove channel in distal blade (P blade) GVL with difficultblade for difficult airway that has elliptically tapered bladeshape rising to distal and C-MAC with conventional bladewhich has the same blade angle compared with Macintoshblade [4]

We discussed the course of face to face intubation catego-rized as VCET POGO score VCET to tube pass time tubepass time to 1st ventilation time success rate by number ofattempts and complications

41 Face to Face Intubation versus Supraglottic Airway DevicesInsertion In previous simulation study supraglottic airwaydevices (SAD) are faster than Macintosh laryngoscope inentrapped situation [15]Hence SAD insertion can be consid-ered to be more useful method compared with endotrachealintubation However in cases of lung injuries or massivebleeding or vomitus in oral cavity SAD alone is not enoughto secure airway In these cases endotracheal intubationis preferred to SAD insertion for providing high oxygenconcentration [16]

In case of severe injury with restricted position face toface intubation is a reasonable choice

42 Vocal Cord Exposure Time (VCET) No significant dif-ference was detected among all laryngoscopes (119875 = 0199)Macintosh blade had advantage of easy insertion to oral cavitybecause it had smaller blade than other video laryngoscopesdue to its simplicity however video laryngoscopes hadcamera at the mount of blade tip so subjects easily detectedvocal cord so long as blade of video laryngoscopewas insertedin oral cavity

43 POGO (Percentage of Glottis Opening) Score Macintoshblade showed lower POGO score than all laryngoscopes inAWS (119875 = 0000) and GVL (119875 = 0000) and C-MAC (119875 =0000) In comparison among video laryngoscopes AWSshowed higher POGO than GVL (119875 = 0000) and C-MAC(119875 = 0002) GVL with C-MAC did not show significantdifference (119875 = 0016 119875 = 0022) Video laryngoscopes weremade for difficult airway management and gave us advancedvision compared to Macintosh blade [17] In case of face toface intubation similar to conventional intubation the visual

field is wider and POGO is higher in video laryngoscopesthan Macintosh blade GVL with difficult blade had morecurved angle than other blades so it was difficult to exposevocal cord in face to face intubation performing on oppositeside of conventional intubation

44 VCET to Tube Pass Time VCET to tube pass timemeansspending time from vocal cord exposure to pass it BetweenMacintosh blade andAWS therewas no significant difference(119875 = 0028) Macintosh was faster than GVL (119875 = 0003) andC-MAC (119875 = 0001) Among video laryngoscopes AWS wasfaster than GVL and C-MAC (119875 = 0001 119875 = 0000) Therewas no significant difference between GVL and C-MAC (119875 =0161)

It may be due to eye-hand discordance In case of face toface intubation using Macintosh blade operator sets locationon upper side of patientrsquos head checks vocal cord with thenaked eye and inserts endotracheal tube to vocal cord Onthe other hand operator with video laryngoscopes will bewatching monitor showing view from end of video laryn-goscope which is in contrast angle to hand direction [18]Operator inserts endotracheal tube to vocal cord watchingscreen attached to video laryngoscopes but the direction ofmanipulating endotracheal tube and the location of vocalcord on screen to advanced direction of endotracheal tube isdifferent [19 20] So it is difficult to insert endotracheal tubequickly and precisely Difficult blade of GVL has larger angleof blade for difficult airway compared to conventional bladeso it is more difficult to manipulate endotracheal tube due tomore distorted up-and-down angle

45 Tube Pass Time to 1st Ventilation Time Macintosh wasfaster than C-MAC (119875 = 0000) and showed no significantdifference with AWS (119875 = 0860) and with GVL (119875 = 0060)In comparison among video laryngoscopes AWS was fasterthan C-MAC (119875 = 0000) AWS and GVL and GVL and C-MAC did not show significant difference (119875 = 0171 119875 =0165)

We did not know the definite cause of why C-MAC wasslower thanMacintosh blade and AWSMaybe in face to faceintubation the monitor attached to C-MAC was inverselyrotated Most operators in this study tried rotating C-MACmonitor to its original positon taking up more time Wethought it requires further investigation about other causes

6 BioMed Research International

46 Success Rate according to the Number of Attempts InMacintosh blade AWS and C-MAC they showed over 80success rate in first attempt (Table 4) Otherwise only 43 ofsubjects achieved successful intubation in GVL For secondattempt 72 of subjects succeeded in GVL the othersshowed over 95 success rate After fourth trial Macintoshand AWS showed 100 success rate C-MAC showed 988But GVL showed only 848 of success rate and 152 ofsubjects could not achieve successful face to face intubationduring four times of attempts (Figure 1) GVL had difficultblade for difficult airway in contrast to other laryngoscopeseye-hand discordance was more severe

47 Complication One tooth injury occurred in Macintoshfive injuries in AWS five injuries in GVL and three injuriesin C-MAC AWS had bigger and thicker blade than othersit contributed to tooth injury In performing intubationusing GVL as appeared by the result in which GVL showedlower successful face to face intubation rate subjects seemedto move more in oral cavity than other laryngoscopes forsuccessful intubation we guessed it influenced broken toothEsophageal intubation occurred once only in Macintoshblade it seemed to be meaningless

48 Limitation First we cannot exclude learning effect oflaryngoscopes Though subjects performed face to face intu-bation using multiple laryngoscopes via randomized serialsubjects might be trained four times of serial face to faceintubation and perform better as time goes by Second itis simulation study using manikin not a patient In thisstudy all manikins lay down on floor not in sitting positionFace to face intubation is very useful in patient of entrappedcar mostly sitting In addition there is enough space atupper manikinrsquos head side to perform face to face intubationcompared to narrow space such as ambulance and helicop-ter

It is not unusual that operator suffers poor visual field dueto secretion or blood or vomitus on performing CPR in fieldSometimes intubation was delayed for cleaning lens of videolaryngoscopesHowever in case ofMacintosh blade securingvisual field was faster because direct suction was possible ininsertion state of Macintosh blade So the result could notadapt to patients exactly Third subjects had no experienceof face to face intubation but they took lots of lectures aboutairway management using manikin So they have familiarityof intubation usingmanikin study compared to someonewhohas no prior education

Fourth we simulated this study and assumed an emer-gency situation in which the victim needed emergent faceto face intubation in limited study we determined that thefailure time of intubation was 1 minute We thought it mightbe a cause of low success rate in first intubation attempt usingGVL We compared spent time only in success cases at firsttime attempt of all kinds of laryngoscopes So we guessed thatGVL took a long time for face to face intubation comparedto our result Next study if that is possible it will give theopportunity for successful intubation without limited timeand it will be more correct in comparison to intubation timeamong laryngoscopes

5 Conclusion

In limited space and restricted position with emergent situa-tion face to face intubation is a useful substitute for conven-tional intubation However its success rate is different dueto multiple causes for example eye-hand discordance Mac-intosh blade and AWS showed significantly faster intubationtime than GVL and C-MAC in face to face intubation

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Authorsrsquo Contribution

Hyun Young Choi and Young Min Oh contributed equally tothis study

References

[1] P Schober R Krage D van Groeningen S A Loer and L ASchwarte ldquoInverse intubation in entrapped trauma casualties asimulator based randomised cross-over comparison of directindirect and video laryngoscopyrdquo Emergency Medicine Journalvol 31 pp 959ndash963 2014

[2] M Gellerfors A Larsson C H Svensen and D Gryth ldquoUseof the airtraq device for airway management in the prehos-pital settingmdasha retrospective studyrdquo Scandinavian Journal ofTrauma Resuscitation and Emergency Medicine vol 22 no 1article 10 2014

[3] H Al-Thani A El-Menyar and R Latifi ldquoPrehospital versusemergency room intubation of trauma patients in Qatar a-2-year observational studyrdquo North American Journal of MedicalSciences vol 6 no 1 pp 12ndash18 2014

[4] A Kilicaslan A Topal A Tavlan A Erol and S OtelciogluldquoEffectiveness of the C-MAC video laryngoscope in the man-agement of unexpected failed intubationsrdquo Brazilian Journal ofAnesthesiology vol 64 no 1 pp 62ndash65 2014

[5] A M Burnett R J Frascone S S Wewerka et al ldquoComparisonof success rates between two video laryngoscope systems usedin a prehospital clinical trialrdquo Prehospital Emergency Care vol18 no 2 pp 231ndash238 2014

[6] K B Wong C T Lui W Y W Chan T L Lau S Y H Tangand K L Tsui ldquoComparison of different intubation techniquesperformed inside a moving ambulance a manikin studyrdquo HongKong Medical Journal vol 20 no 4 pp 304ndash312 2014

[7] N Komasawa R Ueki M Itani H Nomura S-I Nishi andY Kaminoh ldquoEvaluation of tracheal intubation in several posi-tions by the Pentax-AWS Airway Scope a manikin studyrdquoJournal of Anesthesia vol 24 no 6 pp 908ndash912 2010

[8] T Asai ldquoTracheal intubation with restricted access a ran-domised comparison of the Pentax-Airway Scope and Macin-tosh laryngoscope in a manikinrdquo Anaesthesia vol 64 no 10pp 1114ndash1117 2009

[9] E Gaszynska P Samsel M Stankiewicz-Rudnicki A Wiec-zorek and T Gaszynski ldquoIntubation by paramedics using theILMA or AirTraq KingVision andMacintosh laryngoscopes invehicle-entrapped patients a manikin studyrdquo European Journalof Emergency Medicine vol 21 no 1 pp 61ndash64 2014

BioMed Research International 7

[10] K J Robinson K Donaghy and R Katz ldquoInverse intubationin air medical transportrdquo Air Medical Journal vol 23 no 1 pp40ndash43 2004

[11] R Amathieu J Sudrial W Abdi et al ldquoSimulating face-to-facetracheal intubation of a trapped patient a randomized compar-ison of the LMA Fastrachamptrade the GlideScopeamptrade andthe Airtraqamptrade laryngoscoperdquo British Journal of Anaesthe-sia vol 108 no 1 pp 140ndash145 2012

[12] M Tuma A El-Menyar H Abdelrahman et al ldquoPrehospitalintubation in patients with isolated severe traumatic braininjury a 4-YearObservational studyrdquoCritical Care Research andPractice vol 2014 Article ID 135986 6 pages 2014

[13] D Venezia A Wackett A Remedios and V Tarsia ldquoCompar-ison of sitting face-to-face intubation (two-person technique)with standard oral-tracheal intubation in novices aMannequinStudyrdquo Journal of Emergency Medicine vol 43 no 6 pp 1188ndash1195 2012

[14] S Sobuwa H B Hartzenberg H Geduld and C Uys ldquoOut-comes following prehospital airway management in severetraumatic brain injuryrdquo South African Medical Journal vol 103no 9 pp 644ndash646 2013

[15] W A Wetsch A Schneider R Schier O Spelten M Hellmichand J Hinkelbein ldquoIn a difficult access scenario supraglotticairway devices improve success and time to ventilationrdquo Euro-pean Journal of Emergency Medicine 2015

[16] J Mayglothling T M Duane M Gibbs et al ldquoEmergencytracheal intubation immediately following traumatic injury aneastern association for the surgery of trauma practice manage-ment guidelinerdquoThe Journal of Trauma and Acute Care Surgeryvol 73 no 5 pp S333ndashS340 2012

[17] T Arima O Nagata T Miura et al ldquoComparative analysis ofairway scope and Macintosh laryngoscope for intubation pri-marily for cardiac arrest in prehospital settingrdquo The AmericanJournal of Emergency Medicine vol 32 no 1 pp 40ndash43 2014

[18] S Rentsch and M K Rand ldquoEye-hand coordination duringvisuomotor adaptation with different rotation anglesrdquo PLoSONE vol 9 no 10 Article ID e109819 2014

[19] P Breedveld and M Wentink ldquoEye-hand coordination in lap-aroscopymdashan overview of experiments and supporting aidsrdquoMinimally Invasive Therapy amp Allied Technologies vol 10 no3 pp 155ndash162 2001

[20] KMaruyama S Tsukamoto S Ohno et al ldquoEffect of cardiopul-monary resuscitation on intubation using aMacintosh laryngo-scope the AirWay Scope and the gum elastic bougie aManikinStudyrdquo Resuscitation vol 81 no 8 pp 1014ndash1018 2010

Submit your manuscripts athttpwwwhindawicom

Stem CellsInternational

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MEDIATORSINFLAMMATION

of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Behavioural Neurology

EndocrinologyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Disease Markers

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioMed Research International

OncologyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Oxidative Medicine and Cellular Longevity

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

PPAR Research

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Immunology ResearchHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

ObesityJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Computational and Mathematical Methods in Medicine

OphthalmologyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Diabetes ResearchJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Research and TreatmentAIDS

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Gastroenterology Research and Practice

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Parkinsonrsquos Disease

Evidence-Based Complementary and Alternative Medicine

Volume 2014Hindawi Publishing Corporationhttpwwwhindawicom

2 BioMed Research International

trauma casualties [6] In prehospital environment in whichpatients are on the ground or entrapped in vehicles itis difficult to perform conventional intubation [7ndash9] Fordecades conventional tracheal intubation was performed atupper side of patientrsquos head However mostly in entrappedpatients with restricted position there is not enough spaceon patientrsquos head side for tracheal intubation [1] For thissituation we can try face to face intubation in other wordsinverse intubation can be performed with the providerrsquosface at the same level as the patientrsquos face There is noneeded for another space on patientrsquos head side for trachealintubation in face to face intubation Therefore it can be avery useful method for performing tracheal intubation inrestricted position [10] But it is different from conventionaltracheal intubation in the position in which the glottis isviewed and the manipulation of the tube due to the reverselyprogressing direction Similarly since face to face intubationwith video laryngoscope differs from conventional intuba-tion untrained practitioner may feel difficulty performingit

As described above face to face intubation will be agood substitute for conventional endotracheal intubation forpatients who need urgent endotracheal intubation immedi-ately in limited space [11]

In this study after teaching the face to face intubationusing conventional laryngoscope and video laryngoscopes inmanikin model we analyzed the success rate time spent andcomplications caused by intubation procedure

2 Methods

The Institutional Review Board at Hallym University Kang-nam Sacred Heart Hospital approved this study IRB numberwas 2014-11-153

21 Subject Ninety-five nurses and emergency medical tech-nicians (EMT) participated in a 2-day long airway man-agement education program in Gyeonggi-do fire serviceacademy South Korea They were divided into 4 groups andeach group was trained in consecutive order

22 Study Design Instructors gave lectures during 2 hoursabout endotracheal intubation and airwaymanagementsThelecture session was followed by practice session They weredivided into 4 groups Each group took 4 different 50-minutelong practices which include endotracheal intubation usingMacintosh blade and video laryngoscopes and face to faceintubation It took 4 hours in total

After the practice session the subjects were divided intofour groups and each group took checklist for the test for tra-cheal intubation Four groups were divided by kinds of laryn-goscopes direct laryngoscope (Macintosh blade 4) Pentaxairway scope (AWS Hoya Tokyo Japan) C-MAC videolaryngoscope pocket with standard 3 blade model (C-MACKarl Storz Endoscopy Tuttlingen Germany) and Glidescopevideo laryngoscope with standard 3 blade model (GVLVerathon Medical Inc Bothell WA) And we used Laerdalairway management trainer (Laerdal Medical Corporation

Stavanger Norway) which is as widely used manikin fortraining of airway management

Instructors checked and recorded POGO (percentage ofglottis opening) and times when glottis was visible and whenendotracheal tube passed vocal cordThey also checked chestrising ofmanikin whichwas recorded as 1st ventilation usingtube ballooning and ventilation with bag-valve mask

All the tests were performed in separated space Beforetest every subject received random test sequence table Testsequence of laryngoscope types were determined by randomsample

23 Statistical Analysis Statistical analysis was carried outwith the 220 version of the SPSS program for windows(SPSS Inc Chicago IL USA) Data was presented as meanplusmn standard deviation (SD) In previous study total intubationtime for face to face intubation was 216 plusmn 101 seconds [10]To detect 20difference in total intubation timewith a powerof 09 and 120572 = 005 we estimate that 75 subjects would beadequate considering a 20 drop rate We used Shapiro-Wilktest for verifying normal distribution and Wilcoxon signedrank test for verifying the result which is not according tonormal distribution A significant difference was consideredwhen 119875 value was less than 005 For comparison in correla-tion of multiple variables we used Friedman test and appliedBonferronirsquos method for Post hoc analysis

3 Result

95 subjects participated in this study but we excluded 9subjects due to informational errors such as missing dataon evaluation form So 86 subjects were enrolled in thisstudy They consisted of 54 men (628) and 32 women(372) and were classified into 17 nurses (198) 68 1stlevel EMT (emergency medical technicians) (790) and 12nd level EMT (12) 1st level EMT was licensed to collegegraduates of emergency medical technology otherwise 2ndlevel EMT was licensed by passing written and practical testfor emergency situations In South Korea most of healthcareproviders in the field consisted of 1st level EMT 2nd levelEMT and nurses Mean age of subjects was 283 years oldmean career as healthcare provider was 36 years Most ofthem (83 of 86) experienced intubation less than 3 timesIn addition they never experienced intubation using videolaryngoscopes and face to face intubation (Table 1) Wedescribed the result divided into VCET (vocal cord exposuretime) POGO (percentage of glottis opening) score tubepass time and 1st ventilation time In addition we calculatedspent time from VCET to tube pass time and from tubepass time to 1st ventilation time We limited subjectrsquos data incase of successful endotracheal intubation achieved only in1st attempt We compared the success rate with the numberof attempts and regarded a failure in case of not achievingendotracheal intubationwithin 1minute because we assumedthe emergency situation in which subjects must achieve faceto face intubation in spite of very narrow space in otherwords they cannot wait for conventional intubation andneededmore space [6 12] Finally we described complicationby kinds of laryngoscope

BioMed Research International 3

Table 1 Demographic characteristics of subjects (119899 = 86)

Characteristics DataSex (119899 percent) Male (54 628)Age (years range) 283 (21ndash40)Work experience as healthcare provider (years) 36

0 (119899 percent) 27 (314)to 5 years 36 (419)gt5 years 23 (267)

LicenseNurse 17 (198)1st level EMT 67 (779)2nd level EMT 1 (12)

Intubation experienceMCL lt3 (times) 83 (965)Video laryngoscope lt3 (times) 86 (100)Face to face intubation lt1 86 (100)

EMT emergency medical technician MCL Macintosh laryngoscope

31 VCET Vocal cord exposure time (VCET)means the timetaken by the subject to hold a handle of laryngoscope to find avocal cord opening In Macintosh blade the VCET was 78 plusmn33 seconds and it was faster than other video laryngoscopesin AWS 109 plusmn 78 in GVL 84 plusmn 49 and in C-MAC 84 plusmn 46But no significant difference showed among laryngoscopes(119875 = 0199 in Friedman test) (Table 2)

32 POGO Score Percentage of glottis opening (POGO)score defined a certain extent of visualized vocal cord afterinsertion of laryngoscope to oral cavity If we canwatchwholevocal cord wemark it 100 and if we cannot find vocal cordwe mark it 0 In Macintosh blade (536 plusmn 223) POGOscore was lower than all kinds of laryngoscopes that we usedand showed significant difference Compared to Macintoshblade POGO score in AWS was 817 plusmn 183 (119875 = 0000) inGVLwas 654plusmn250 (119875 = 0000) and in C-MACwas 729plusmn208 (119875 = 0000) In comparison of video laryngoscopesAWS showed higher POGO score than GVL (119875 = 0000) andC-MAC (119875 = 0002) but there was no significant differencebetween GVL and C-MAC (119875 = 0188) (Tables 2 and 3)

33 Tube Pass Time Tube pass time means time spent bysubjects to grasp a handle of blade passing the vocal cordby endotracheal tube Macintosh blade (187 plusmn 73 sec) wasfaster than GVL (268 plusmn 100 sec 119875 = 0001) and C-MAC(228 plusmn 102 sec 119875 = 0000) and showed no difference withAWS (196 plusmn 95 sec 119875 = 0608) In comparison among videolaryngoscopes AWS was faster than GVL (119875 = 0005) butthere were no differences between AWS and C-MAC andGVL and C-MAC (119875 = 0011 119875 = 0108) (Tables 2 and 3)

34 1st Ventilation Time 1st ventilation time means timespent from holding a handle of laryngoscope and passingthe vocal cord by endotracheal tube to give 1st ventilationvia inserted endotracheal tube It also means total intubationtime There were no differences between Macintosh blade

(284 plusmn 77 sec) and AWS (296 plusmn 109 sec) and GVL (392 plusmn97 sec) and C-MAC (352 plusmn 104 sec) (119875 = 0530 119875 = 0207)However Macintosh blade was faster than GVL (119875 = 0000)and C-MAC (119875 = 0000) AWS was also faster than GVL(119875 = 0003) and C-MAC (119875 = 0000) (Tables 2 and 3)

35 VCET to Time of Endotracheal Tube Passing Vocal Cord(Tube Pass Time) It means time spent from vocal cordexposure to passing the endotracheal tube Macintosh blade(109 plusmn 59) and AWS (104 plusmn 109) showed similar result andthere is no significant difference (119875 = 0028) In GVL (228 plusmn271) and C-MAC (171 plusmn 143) they needed more time fromvocal cord exposure to endotracheal tube passing via vocalcord compared to Macintosh blade and AWS individually(Macintosh versus GVL 119875 = 0003 Macintosh versus C-MAC 119875 = 0001 AWS versus GVL 119875 = 0001 AWSversus C-MAC 119875 = 0000) No significant difference showedbetween GVL and C-MAC (119875 = 0161) (Tables 2 and 3)

36 Time of Endotracheal Tube Passing Vocal Cord (TubePass Time) to 1st Ventilation Time 96 plusmn 39 seconds areneeded from tube passing to 1st ventilation in Macintoshblade and that in AWS was 98 plusmn 37 seconds In GVL andC-MAC the results were 106 plusmn 97 seconds and 122 plusmn 45seconds In comparison with Macintosh blade AWS (119875 =0860) and GVL (119875 = 0060) did not show significantdifference but C-MAC (119875 = 0000) was meaningfully slowerthan Macintosh blade AWS was faster than C-MAC withsignificant difference (119875 = 0000) but there was no differencewith GVL (119875 = 0171) No significant difference was foundbetween GVL and C-MAC (119875 = 0165) (Tables 2 and 3)

37 Endotracheal Intubation Success Rate according to theNumber of Attempts 86 subjects performed face to face intu-bation using laryngoscopes we determined a failure in whichsubjects did not achieve endotracheal intubation within 1minute or accomplished esophageal intubation InMacintoshblade 72 subjects (837) achieved successful endotrachealintubation in first attempt and 85 (988) succeeded in sec-ond attempt At third attempt all subject (100) succeededin endotracheal intubation 71 subjects (825) succeeded inendotracheal intubation in first attempt usingAWS In secondattempt 84 (976) achieved successful endotracheal intuba-tion 85 (988) succeeded in third attempt all subject (100)succeeded in fourth attempt In GVL 37 subjects (430)succeeded in endotracheal intubation at first attempt and62 (720) succeeded in second attempt 70 subjects (813)succeeded in third attempt and 73 (848) in the fourth 13subjects (152) did not achieve successful intubation duringfour attempts 74 subjects (860) succeeded in endotrachealintubation in first attempt using GVL 83 subjects (965) insecond attempt and 85 (988) in third attempt 1 subject(12) failed in endotracheal intubation during four attempts(Figure 1 Table 4)

38 Complication Weexamined complications of face to faceintubation during procedure for tooth injury and esophageal

4 BioMed Research International

Table 2 Comparison of intubation time (sec) and POGO () according to laryngoscopes (mean plusmn SD)

MCL AWS GVL C-MAC 119875 valueVCET (sec) 78 plusmn 33 109 plusmn 78 84 plusmn 49 84 plusmn 46 0199POGO () 536 plusmn 223 817 plusmn 183 654 plusmn 250 729 plusmn 208 0000Tube pass time (sec) 187 plusmn 73 196 plusmn 95 268 plusmn 100 228 plusmn 102 00011st ventilation time (sec) 284 plusmn 77 296 plusmn 109 392 plusmn 97 352 plusmn 104 0000VCET to tube pass time (sec) 109 plusmn 59 104 plusmn 109 228 plusmn 271 171 plusmn 143 0000Tube pass time to 1st ventilation time (sec) 96 plusmn 39 98 plusmn 37 106 plusmn 97 122 plusmn 45 0000lowast

119875 value lt 005 is level of statistical significance according to Friedman testMCL Macintosh laryngoscope AWS Pentax airway scope GVL Glidescope video laryngoscope C-MAC C-MAC video laryngoscope

Table 3 Statistical significance (119875 value) among laryngoscopes for intubation time (sec) and POGO ()

MCL versusAWS

(119875 value)

MCL versusGVL

(119875 value)

MCL versusC-MAC(119875 value)

AWS versusGVL

(119875 value)

AWS versusC-MAC(119875 value)

GVL versusC-MAC(119875 value)

VCET 0008 0038 0217 0756 0090 0220POGO 0000lowast 0000lowast 0000lowast 0000lowast 0002lowast 0188Tube pass time 0608 0001lowast 0000lowast 0005lowast 0011 01081st ventilation time 0530 0000lowast 0000lowast 0003lowast 0000lowast 0207VCET to tube pass time 0028 0003lowast 0001lowast 0001lowast 0000lowast 0161Tube pass time to 1stventilation time 0860 0060 0000lowast 0171 0000lowast 0165lowast

119875 value lt 0008 is level of statistical significance according to Bonferronirsquos methodMCL Macintosh laryngoscope AWS Pentax airway scope GVL Glidescope video laryngoscope C-MAC C-MAC video laryngoscope

837

988 100 100

825

976 988 100

43

72813 84886

965 988 988

0

20

40

60

80

100

1st attempt 2nd attempt 3rd attempt 4th attempt

Succ

ess r

ate (

)

Number of attempts

MCLAWS

GVLC-MAC

Figure 1 Endotracheal intubation success rate according to thenumber of attempts Glidescope video laryngoscope (GVL) showedlower success rate compared with other laryngoscopes in all ofattempts MCL Macintosh laryngoscope AWS Pentax airwayscope GVL Glidescope video laryngoscope C-MAC C-MACvideo laryngoscope

intubation We included all attempts of endotracheal intuba-tion Tooth injury was considered when tester heard toothclick The number of tooth injuries in Macintosh blade wasone in AWS and GVL five and else in C-MAC three Oneesophageal intubation occurred in Macintosh blade and noesophageal intubation occurred in video laryngoscopes

4 Discussion

Endotracheal intubation is very important procedure inemergency department for severely ill patients [13 14] Inconventional intubation operator sets a location at the upperside of patientrsquos head grasps a laryngoscope with left handand inserts endotracheal tube by right hand For better visu-alization operator shift patientrsquos tongue to left using bladeLots of new techniques and machines are introduced foreasy successful intubation but until recently conventionalintubation is the most commonly used method for airwaymanagement Video laryngoscopes for difficult airway con-sist of a laryngoscope with a light source and a camera indistal blade In contrast to conventional blade having about151015840-visual field video laryngoscopes make wider visual anglebecause of the camera on distal blade [4] In special situationsuch as in ambulance or helicopter occasionally there is nospace at patientrsquos upper side for conventional intubation Sooperator has to intubate on lateral or frontal side of patient[9] In contrast to conventional laryngoscopy the practitionerholds the handle of the laryngoscope in his right hand withthe top of the blade in the upright position After the openingof patientrsquos airways the top of the laryngoscopersquos curved bladewill be in place in the left part of the patientrsquos mouth [10]

We examined this study to investigate whether videolaryngoscopes are helpful in special situation like beingentrapped in car or permitted narrow space and whethervideo laryngoscopes are more useful than conventional

BioMed Research International 5

Table 4 Success rate according to the number of attempts

MCL AWS GVL CMAC

Success at 1st attempt 72 (837) 71 (825) 37 (430) 74 (860)

Success at 2nd attempt 13 (151)(85 988)

13 (151)(84 976)

25 (290)(62 720)

9 (104)(83 965)

Success at 3rd attempt 1 (11)(86 100)

1 (11)(85 988)

8 (93)(70 813)

2 (23)(85 988)

Success at 4th attempt 0 1 (11)(86 100)

3 (34)(73 848) 0

Failure at 4th attempt 0 0 13 (151) 1 (11)MCL Macintosh laryngoscope AWS Pentax airway scope GVL Glidescope video laryngoscope C-MAC C-MAC video laryngoscope

intubation set (Macintosh blade) We choose several videolaryngoscopes AWS which has endotracheal tube-guidinggroove channel in distal blade (P blade) GVL with difficultblade for difficult airway that has elliptically tapered bladeshape rising to distal and C-MAC with conventional bladewhich has the same blade angle compared with Macintoshblade [4]

We discussed the course of face to face intubation catego-rized as VCET POGO score VCET to tube pass time tubepass time to 1st ventilation time success rate by number ofattempts and complications

41 Face to Face Intubation versus Supraglottic Airway DevicesInsertion In previous simulation study supraglottic airwaydevices (SAD) are faster than Macintosh laryngoscope inentrapped situation [15]Hence SAD insertion can be consid-ered to be more useful method compared with endotrachealintubation However in cases of lung injuries or massivebleeding or vomitus in oral cavity SAD alone is not enoughto secure airway In these cases endotracheal intubationis preferred to SAD insertion for providing high oxygenconcentration [16]

In case of severe injury with restricted position face toface intubation is a reasonable choice

42 Vocal Cord Exposure Time (VCET) No significant dif-ference was detected among all laryngoscopes (119875 = 0199)Macintosh blade had advantage of easy insertion to oral cavitybecause it had smaller blade than other video laryngoscopesdue to its simplicity however video laryngoscopes hadcamera at the mount of blade tip so subjects easily detectedvocal cord so long as blade of video laryngoscopewas insertedin oral cavity

43 POGO (Percentage of Glottis Opening) Score Macintoshblade showed lower POGO score than all laryngoscopes inAWS (119875 = 0000) and GVL (119875 = 0000) and C-MAC (119875 =0000) In comparison among video laryngoscopes AWSshowed higher POGO than GVL (119875 = 0000) and C-MAC(119875 = 0002) GVL with C-MAC did not show significantdifference (119875 = 0016 119875 = 0022) Video laryngoscopes weremade for difficult airway management and gave us advancedvision compared to Macintosh blade [17] In case of face toface intubation similar to conventional intubation the visual

field is wider and POGO is higher in video laryngoscopesthan Macintosh blade GVL with difficult blade had morecurved angle than other blades so it was difficult to exposevocal cord in face to face intubation performing on oppositeside of conventional intubation

44 VCET to Tube Pass Time VCET to tube pass timemeansspending time from vocal cord exposure to pass it BetweenMacintosh blade andAWS therewas no significant difference(119875 = 0028) Macintosh was faster than GVL (119875 = 0003) andC-MAC (119875 = 0001) Among video laryngoscopes AWS wasfaster than GVL and C-MAC (119875 = 0001 119875 = 0000) Therewas no significant difference between GVL and C-MAC (119875 =0161)

It may be due to eye-hand discordance In case of face toface intubation using Macintosh blade operator sets locationon upper side of patientrsquos head checks vocal cord with thenaked eye and inserts endotracheal tube to vocal cord Onthe other hand operator with video laryngoscopes will bewatching monitor showing view from end of video laryn-goscope which is in contrast angle to hand direction [18]Operator inserts endotracheal tube to vocal cord watchingscreen attached to video laryngoscopes but the direction ofmanipulating endotracheal tube and the location of vocalcord on screen to advanced direction of endotracheal tube isdifferent [19 20] So it is difficult to insert endotracheal tubequickly and precisely Difficult blade of GVL has larger angleof blade for difficult airway compared to conventional bladeso it is more difficult to manipulate endotracheal tube due tomore distorted up-and-down angle

45 Tube Pass Time to 1st Ventilation Time Macintosh wasfaster than C-MAC (119875 = 0000) and showed no significantdifference with AWS (119875 = 0860) and with GVL (119875 = 0060)In comparison among video laryngoscopes AWS was fasterthan C-MAC (119875 = 0000) AWS and GVL and GVL and C-MAC did not show significant difference (119875 = 0171 119875 =0165)

We did not know the definite cause of why C-MAC wasslower thanMacintosh blade and AWSMaybe in face to faceintubation the monitor attached to C-MAC was inverselyrotated Most operators in this study tried rotating C-MACmonitor to its original positon taking up more time Wethought it requires further investigation about other causes

6 BioMed Research International

46 Success Rate according to the Number of Attempts InMacintosh blade AWS and C-MAC they showed over 80success rate in first attempt (Table 4) Otherwise only 43 ofsubjects achieved successful intubation in GVL For secondattempt 72 of subjects succeeded in GVL the othersshowed over 95 success rate After fourth trial Macintoshand AWS showed 100 success rate C-MAC showed 988But GVL showed only 848 of success rate and 152 ofsubjects could not achieve successful face to face intubationduring four times of attempts (Figure 1) GVL had difficultblade for difficult airway in contrast to other laryngoscopeseye-hand discordance was more severe

47 Complication One tooth injury occurred in Macintoshfive injuries in AWS five injuries in GVL and three injuriesin C-MAC AWS had bigger and thicker blade than othersit contributed to tooth injury In performing intubationusing GVL as appeared by the result in which GVL showedlower successful face to face intubation rate subjects seemedto move more in oral cavity than other laryngoscopes forsuccessful intubation we guessed it influenced broken toothEsophageal intubation occurred once only in Macintoshblade it seemed to be meaningless

48 Limitation First we cannot exclude learning effect oflaryngoscopes Though subjects performed face to face intu-bation using multiple laryngoscopes via randomized serialsubjects might be trained four times of serial face to faceintubation and perform better as time goes by Second itis simulation study using manikin not a patient In thisstudy all manikins lay down on floor not in sitting positionFace to face intubation is very useful in patient of entrappedcar mostly sitting In addition there is enough space atupper manikinrsquos head side to perform face to face intubationcompared to narrow space such as ambulance and helicop-ter

It is not unusual that operator suffers poor visual field dueto secretion or blood or vomitus on performing CPR in fieldSometimes intubation was delayed for cleaning lens of videolaryngoscopesHowever in case ofMacintosh blade securingvisual field was faster because direct suction was possible ininsertion state of Macintosh blade So the result could notadapt to patients exactly Third subjects had no experienceof face to face intubation but they took lots of lectures aboutairway management using manikin So they have familiarityof intubation usingmanikin study compared to someonewhohas no prior education

Fourth we simulated this study and assumed an emer-gency situation in which the victim needed emergent faceto face intubation in limited study we determined that thefailure time of intubation was 1 minute We thought it mightbe a cause of low success rate in first intubation attempt usingGVL We compared spent time only in success cases at firsttime attempt of all kinds of laryngoscopes So we guessed thatGVL took a long time for face to face intubation comparedto our result Next study if that is possible it will give theopportunity for successful intubation without limited timeand it will be more correct in comparison to intubation timeamong laryngoscopes

5 Conclusion

In limited space and restricted position with emergent situa-tion face to face intubation is a useful substitute for conven-tional intubation However its success rate is different dueto multiple causes for example eye-hand discordance Mac-intosh blade and AWS showed significantly faster intubationtime than GVL and C-MAC in face to face intubation

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Authorsrsquo Contribution

Hyun Young Choi and Young Min Oh contributed equally tothis study

References

[1] P Schober R Krage D van Groeningen S A Loer and L ASchwarte ldquoInverse intubation in entrapped trauma casualties asimulator based randomised cross-over comparison of directindirect and video laryngoscopyrdquo Emergency Medicine Journalvol 31 pp 959ndash963 2014

[2] M Gellerfors A Larsson C H Svensen and D Gryth ldquoUseof the airtraq device for airway management in the prehos-pital settingmdasha retrospective studyrdquo Scandinavian Journal ofTrauma Resuscitation and Emergency Medicine vol 22 no 1article 10 2014

[3] H Al-Thani A El-Menyar and R Latifi ldquoPrehospital versusemergency room intubation of trauma patients in Qatar a-2-year observational studyrdquo North American Journal of MedicalSciences vol 6 no 1 pp 12ndash18 2014

[4] A Kilicaslan A Topal A Tavlan A Erol and S OtelciogluldquoEffectiveness of the C-MAC video laryngoscope in the man-agement of unexpected failed intubationsrdquo Brazilian Journal ofAnesthesiology vol 64 no 1 pp 62ndash65 2014

[5] A M Burnett R J Frascone S S Wewerka et al ldquoComparisonof success rates between two video laryngoscope systems usedin a prehospital clinical trialrdquo Prehospital Emergency Care vol18 no 2 pp 231ndash238 2014

[6] K B Wong C T Lui W Y W Chan T L Lau S Y H Tangand K L Tsui ldquoComparison of different intubation techniquesperformed inside a moving ambulance a manikin studyrdquo HongKong Medical Journal vol 20 no 4 pp 304ndash312 2014

[7] N Komasawa R Ueki M Itani H Nomura S-I Nishi andY Kaminoh ldquoEvaluation of tracheal intubation in several posi-tions by the Pentax-AWS Airway Scope a manikin studyrdquoJournal of Anesthesia vol 24 no 6 pp 908ndash912 2010

[8] T Asai ldquoTracheal intubation with restricted access a ran-domised comparison of the Pentax-Airway Scope and Macin-tosh laryngoscope in a manikinrdquo Anaesthesia vol 64 no 10pp 1114ndash1117 2009

[9] E Gaszynska P Samsel M Stankiewicz-Rudnicki A Wiec-zorek and T Gaszynski ldquoIntubation by paramedics using theILMA or AirTraq KingVision andMacintosh laryngoscopes invehicle-entrapped patients a manikin studyrdquo European Journalof Emergency Medicine vol 21 no 1 pp 61ndash64 2014

BioMed Research International 7

[10] K J Robinson K Donaghy and R Katz ldquoInverse intubationin air medical transportrdquo Air Medical Journal vol 23 no 1 pp40ndash43 2004

[11] R Amathieu J Sudrial W Abdi et al ldquoSimulating face-to-facetracheal intubation of a trapped patient a randomized compar-ison of the LMA Fastrachamptrade the GlideScopeamptrade andthe Airtraqamptrade laryngoscoperdquo British Journal of Anaesthe-sia vol 108 no 1 pp 140ndash145 2012

[12] M Tuma A El-Menyar H Abdelrahman et al ldquoPrehospitalintubation in patients with isolated severe traumatic braininjury a 4-YearObservational studyrdquoCritical Care Research andPractice vol 2014 Article ID 135986 6 pages 2014

[13] D Venezia A Wackett A Remedios and V Tarsia ldquoCompar-ison of sitting face-to-face intubation (two-person technique)with standard oral-tracheal intubation in novices aMannequinStudyrdquo Journal of Emergency Medicine vol 43 no 6 pp 1188ndash1195 2012

[14] S Sobuwa H B Hartzenberg H Geduld and C Uys ldquoOut-comes following prehospital airway management in severetraumatic brain injuryrdquo South African Medical Journal vol 103no 9 pp 644ndash646 2013

[15] W A Wetsch A Schneider R Schier O Spelten M Hellmichand J Hinkelbein ldquoIn a difficult access scenario supraglotticairway devices improve success and time to ventilationrdquo Euro-pean Journal of Emergency Medicine 2015

[16] J Mayglothling T M Duane M Gibbs et al ldquoEmergencytracheal intubation immediately following traumatic injury aneastern association for the surgery of trauma practice manage-ment guidelinerdquoThe Journal of Trauma and Acute Care Surgeryvol 73 no 5 pp S333ndashS340 2012

[17] T Arima O Nagata T Miura et al ldquoComparative analysis ofairway scope and Macintosh laryngoscope for intubation pri-marily for cardiac arrest in prehospital settingrdquo The AmericanJournal of Emergency Medicine vol 32 no 1 pp 40ndash43 2014

[18] S Rentsch and M K Rand ldquoEye-hand coordination duringvisuomotor adaptation with different rotation anglesrdquo PLoSONE vol 9 no 10 Article ID e109819 2014

[19] P Breedveld and M Wentink ldquoEye-hand coordination in lap-aroscopymdashan overview of experiments and supporting aidsrdquoMinimally Invasive Therapy amp Allied Technologies vol 10 no3 pp 155ndash162 2001

[20] KMaruyama S Tsukamoto S Ohno et al ldquoEffect of cardiopul-monary resuscitation on intubation using aMacintosh laryngo-scope the AirWay Scope and the gum elastic bougie aManikinStudyrdquo Resuscitation vol 81 no 8 pp 1014ndash1018 2010

Submit your manuscripts athttpwwwhindawicom

Stem CellsInternational

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MEDIATORSINFLAMMATION

of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Behavioural Neurology

EndocrinologyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Disease Markers

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioMed Research International

OncologyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Oxidative Medicine and Cellular Longevity

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

PPAR Research

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Immunology ResearchHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

ObesityJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Computational and Mathematical Methods in Medicine

OphthalmologyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Diabetes ResearchJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Research and TreatmentAIDS

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Gastroenterology Research and Practice

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Parkinsonrsquos Disease

Evidence-Based Complementary and Alternative Medicine

Volume 2014Hindawi Publishing Corporationhttpwwwhindawicom

BioMed Research International 3

Table 1 Demographic characteristics of subjects (119899 = 86)

Characteristics DataSex (119899 percent) Male (54 628)Age (years range) 283 (21ndash40)Work experience as healthcare provider (years) 36

0 (119899 percent) 27 (314)to 5 years 36 (419)gt5 years 23 (267)

LicenseNurse 17 (198)1st level EMT 67 (779)2nd level EMT 1 (12)

Intubation experienceMCL lt3 (times) 83 (965)Video laryngoscope lt3 (times) 86 (100)Face to face intubation lt1 86 (100)

EMT emergency medical technician MCL Macintosh laryngoscope

31 VCET Vocal cord exposure time (VCET)means the timetaken by the subject to hold a handle of laryngoscope to find avocal cord opening In Macintosh blade the VCET was 78 plusmn33 seconds and it was faster than other video laryngoscopesin AWS 109 plusmn 78 in GVL 84 plusmn 49 and in C-MAC 84 plusmn 46But no significant difference showed among laryngoscopes(119875 = 0199 in Friedman test) (Table 2)

32 POGO Score Percentage of glottis opening (POGO)score defined a certain extent of visualized vocal cord afterinsertion of laryngoscope to oral cavity If we canwatchwholevocal cord wemark it 100 and if we cannot find vocal cordwe mark it 0 In Macintosh blade (536 plusmn 223) POGOscore was lower than all kinds of laryngoscopes that we usedand showed significant difference Compared to Macintoshblade POGO score in AWS was 817 plusmn 183 (119875 = 0000) inGVLwas 654plusmn250 (119875 = 0000) and in C-MACwas 729plusmn208 (119875 = 0000) In comparison of video laryngoscopesAWS showed higher POGO score than GVL (119875 = 0000) andC-MAC (119875 = 0002) but there was no significant differencebetween GVL and C-MAC (119875 = 0188) (Tables 2 and 3)

33 Tube Pass Time Tube pass time means time spent bysubjects to grasp a handle of blade passing the vocal cordby endotracheal tube Macintosh blade (187 plusmn 73 sec) wasfaster than GVL (268 plusmn 100 sec 119875 = 0001) and C-MAC(228 plusmn 102 sec 119875 = 0000) and showed no difference withAWS (196 plusmn 95 sec 119875 = 0608) In comparison among videolaryngoscopes AWS was faster than GVL (119875 = 0005) butthere were no differences between AWS and C-MAC andGVL and C-MAC (119875 = 0011 119875 = 0108) (Tables 2 and 3)

34 1st Ventilation Time 1st ventilation time means timespent from holding a handle of laryngoscope and passingthe vocal cord by endotracheal tube to give 1st ventilationvia inserted endotracheal tube It also means total intubationtime There were no differences between Macintosh blade

(284 plusmn 77 sec) and AWS (296 plusmn 109 sec) and GVL (392 plusmn97 sec) and C-MAC (352 plusmn 104 sec) (119875 = 0530 119875 = 0207)However Macintosh blade was faster than GVL (119875 = 0000)and C-MAC (119875 = 0000) AWS was also faster than GVL(119875 = 0003) and C-MAC (119875 = 0000) (Tables 2 and 3)

35 VCET to Time of Endotracheal Tube Passing Vocal Cord(Tube Pass Time) It means time spent from vocal cordexposure to passing the endotracheal tube Macintosh blade(109 plusmn 59) and AWS (104 plusmn 109) showed similar result andthere is no significant difference (119875 = 0028) In GVL (228 plusmn271) and C-MAC (171 plusmn 143) they needed more time fromvocal cord exposure to endotracheal tube passing via vocalcord compared to Macintosh blade and AWS individually(Macintosh versus GVL 119875 = 0003 Macintosh versus C-MAC 119875 = 0001 AWS versus GVL 119875 = 0001 AWSversus C-MAC 119875 = 0000) No significant difference showedbetween GVL and C-MAC (119875 = 0161) (Tables 2 and 3)

36 Time of Endotracheal Tube Passing Vocal Cord (TubePass Time) to 1st Ventilation Time 96 plusmn 39 seconds areneeded from tube passing to 1st ventilation in Macintoshblade and that in AWS was 98 plusmn 37 seconds In GVL andC-MAC the results were 106 plusmn 97 seconds and 122 plusmn 45seconds In comparison with Macintosh blade AWS (119875 =0860) and GVL (119875 = 0060) did not show significantdifference but C-MAC (119875 = 0000) was meaningfully slowerthan Macintosh blade AWS was faster than C-MAC withsignificant difference (119875 = 0000) but there was no differencewith GVL (119875 = 0171) No significant difference was foundbetween GVL and C-MAC (119875 = 0165) (Tables 2 and 3)

37 Endotracheal Intubation Success Rate according to theNumber of Attempts 86 subjects performed face to face intu-bation using laryngoscopes we determined a failure in whichsubjects did not achieve endotracheal intubation within 1minute or accomplished esophageal intubation InMacintoshblade 72 subjects (837) achieved successful endotrachealintubation in first attempt and 85 (988) succeeded in sec-ond attempt At third attempt all subject (100) succeededin endotracheal intubation 71 subjects (825) succeeded inendotracheal intubation in first attempt usingAWS In secondattempt 84 (976) achieved successful endotracheal intuba-tion 85 (988) succeeded in third attempt all subject (100)succeeded in fourth attempt In GVL 37 subjects (430)succeeded in endotracheal intubation at first attempt and62 (720) succeeded in second attempt 70 subjects (813)succeeded in third attempt and 73 (848) in the fourth 13subjects (152) did not achieve successful intubation duringfour attempts 74 subjects (860) succeeded in endotrachealintubation in first attempt using GVL 83 subjects (965) insecond attempt and 85 (988) in third attempt 1 subject(12) failed in endotracheal intubation during four attempts(Figure 1 Table 4)

38 Complication Weexamined complications of face to faceintubation during procedure for tooth injury and esophageal

4 BioMed Research International

Table 2 Comparison of intubation time (sec) and POGO () according to laryngoscopes (mean plusmn SD)

MCL AWS GVL C-MAC 119875 valueVCET (sec) 78 plusmn 33 109 plusmn 78 84 plusmn 49 84 plusmn 46 0199POGO () 536 plusmn 223 817 plusmn 183 654 plusmn 250 729 plusmn 208 0000Tube pass time (sec) 187 plusmn 73 196 plusmn 95 268 plusmn 100 228 plusmn 102 00011st ventilation time (sec) 284 plusmn 77 296 plusmn 109 392 plusmn 97 352 plusmn 104 0000VCET to tube pass time (sec) 109 plusmn 59 104 plusmn 109 228 plusmn 271 171 plusmn 143 0000Tube pass time to 1st ventilation time (sec) 96 plusmn 39 98 plusmn 37 106 plusmn 97 122 plusmn 45 0000lowast

119875 value lt 005 is level of statistical significance according to Friedman testMCL Macintosh laryngoscope AWS Pentax airway scope GVL Glidescope video laryngoscope C-MAC C-MAC video laryngoscope

Table 3 Statistical significance (119875 value) among laryngoscopes for intubation time (sec) and POGO ()

MCL versusAWS

(119875 value)

MCL versusGVL

(119875 value)

MCL versusC-MAC(119875 value)

AWS versusGVL

(119875 value)

AWS versusC-MAC(119875 value)

GVL versusC-MAC(119875 value)

VCET 0008 0038 0217 0756 0090 0220POGO 0000lowast 0000lowast 0000lowast 0000lowast 0002lowast 0188Tube pass time 0608 0001lowast 0000lowast 0005lowast 0011 01081st ventilation time 0530 0000lowast 0000lowast 0003lowast 0000lowast 0207VCET to tube pass time 0028 0003lowast 0001lowast 0001lowast 0000lowast 0161Tube pass time to 1stventilation time 0860 0060 0000lowast 0171 0000lowast 0165lowast

119875 value lt 0008 is level of statistical significance according to Bonferronirsquos methodMCL Macintosh laryngoscope AWS Pentax airway scope GVL Glidescope video laryngoscope C-MAC C-MAC video laryngoscope

837

988 100 100

825

976 988 100

43

72813 84886

965 988 988

0

20

40

60

80

100

1st attempt 2nd attempt 3rd attempt 4th attempt

Succ

ess r

ate (

)

Number of attempts

MCLAWS

GVLC-MAC

Figure 1 Endotracheal intubation success rate according to thenumber of attempts Glidescope video laryngoscope (GVL) showedlower success rate compared with other laryngoscopes in all ofattempts MCL Macintosh laryngoscope AWS Pentax airwayscope GVL Glidescope video laryngoscope C-MAC C-MACvideo laryngoscope

intubation We included all attempts of endotracheal intuba-tion Tooth injury was considered when tester heard toothclick The number of tooth injuries in Macintosh blade wasone in AWS and GVL five and else in C-MAC three Oneesophageal intubation occurred in Macintosh blade and noesophageal intubation occurred in video laryngoscopes

4 Discussion

Endotracheal intubation is very important procedure inemergency department for severely ill patients [13 14] Inconventional intubation operator sets a location at the upperside of patientrsquos head grasps a laryngoscope with left handand inserts endotracheal tube by right hand For better visu-alization operator shift patientrsquos tongue to left using bladeLots of new techniques and machines are introduced foreasy successful intubation but until recently conventionalintubation is the most commonly used method for airwaymanagement Video laryngoscopes for difficult airway con-sist of a laryngoscope with a light source and a camera indistal blade In contrast to conventional blade having about151015840-visual field video laryngoscopes make wider visual anglebecause of the camera on distal blade [4] In special situationsuch as in ambulance or helicopter occasionally there is nospace at patientrsquos upper side for conventional intubation Sooperator has to intubate on lateral or frontal side of patient[9] In contrast to conventional laryngoscopy the practitionerholds the handle of the laryngoscope in his right hand withthe top of the blade in the upright position After the openingof patientrsquos airways the top of the laryngoscopersquos curved bladewill be in place in the left part of the patientrsquos mouth [10]

We examined this study to investigate whether videolaryngoscopes are helpful in special situation like beingentrapped in car or permitted narrow space and whethervideo laryngoscopes are more useful than conventional

BioMed Research International 5

Table 4 Success rate according to the number of attempts

MCL AWS GVL CMAC

Success at 1st attempt 72 (837) 71 (825) 37 (430) 74 (860)

Success at 2nd attempt 13 (151)(85 988)

13 (151)(84 976)

25 (290)(62 720)

9 (104)(83 965)

Success at 3rd attempt 1 (11)(86 100)

1 (11)(85 988)

8 (93)(70 813)

2 (23)(85 988)

Success at 4th attempt 0 1 (11)(86 100)

3 (34)(73 848) 0

Failure at 4th attempt 0 0 13 (151) 1 (11)MCL Macintosh laryngoscope AWS Pentax airway scope GVL Glidescope video laryngoscope C-MAC C-MAC video laryngoscope

intubation set (Macintosh blade) We choose several videolaryngoscopes AWS which has endotracheal tube-guidinggroove channel in distal blade (P blade) GVL with difficultblade for difficult airway that has elliptically tapered bladeshape rising to distal and C-MAC with conventional bladewhich has the same blade angle compared with Macintoshblade [4]

We discussed the course of face to face intubation catego-rized as VCET POGO score VCET to tube pass time tubepass time to 1st ventilation time success rate by number ofattempts and complications

41 Face to Face Intubation versus Supraglottic Airway DevicesInsertion In previous simulation study supraglottic airwaydevices (SAD) are faster than Macintosh laryngoscope inentrapped situation [15]Hence SAD insertion can be consid-ered to be more useful method compared with endotrachealintubation However in cases of lung injuries or massivebleeding or vomitus in oral cavity SAD alone is not enoughto secure airway In these cases endotracheal intubationis preferred to SAD insertion for providing high oxygenconcentration [16]

In case of severe injury with restricted position face toface intubation is a reasonable choice

42 Vocal Cord Exposure Time (VCET) No significant dif-ference was detected among all laryngoscopes (119875 = 0199)Macintosh blade had advantage of easy insertion to oral cavitybecause it had smaller blade than other video laryngoscopesdue to its simplicity however video laryngoscopes hadcamera at the mount of blade tip so subjects easily detectedvocal cord so long as blade of video laryngoscopewas insertedin oral cavity

43 POGO (Percentage of Glottis Opening) Score Macintoshblade showed lower POGO score than all laryngoscopes inAWS (119875 = 0000) and GVL (119875 = 0000) and C-MAC (119875 =0000) In comparison among video laryngoscopes AWSshowed higher POGO than GVL (119875 = 0000) and C-MAC(119875 = 0002) GVL with C-MAC did not show significantdifference (119875 = 0016 119875 = 0022) Video laryngoscopes weremade for difficult airway management and gave us advancedvision compared to Macintosh blade [17] In case of face toface intubation similar to conventional intubation the visual

field is wider and POGO is higher in video laryngoscopesthan Macintosh blade GVL with difficult blade had morecurved angle than other blades so it was difficult to exposevocal cord in face to face intubation performing on oppositeside of conventional intubation

44 VCET to Tube Pass Time VCET to tube pass timemeansspending time from vocal cord exposure to pass it BetweenMacintosh blade andAWS therewas no significant difference(119875 = 0028) Macintosh was faster than GVL (119875 = 0003) andC-MAC (119875 = 0001) Among video laryngoscopes AWS wasfaster than GVL and C-MAC (119875 = 0001 119875 = 0000) Therewas no significant difference between GVL and C-MAC (119875 =0161)

It may be due to eye-hand discordance In case of face toface intubation using Macintosh blade operator sets locationon upper side of patientrsquos head checks vocal cord with thenaked eye and inserts endotracheal tube to vocal cord Onthe other hand operator with video laryngoscopes will bewatching monitor showing view from end of video laryn-goscope which is in contrast angle to hand direction [18]Operator inserts endotracheal tube to vocal cord watchingscreen attached to video laryngoscopes but the direction ofmanipulating endotracheal tube and the location of vocalcord on screen to advanced direction of endotracheal tube isdifferent [19 20] So it is difficult to insert endotracheal tubequickly and precisely Difficult blade of GVL has larger angleof blade for difficult airway compared to conventional bladeso it is more difficult to manipulate endotracheal tube due tomore distorted up-and-down angle

45 Tube Pass Time to 1st Ventilation Time Macintosh wasfaster than C-MAC (119875 = 0000) and showed no significantdifference with AWS (119875 = 0860) and with GVL (119875 = 0060)In comparison among video laryngoscopes AWS was fasterthan C-MAC (119875 = 0000) AWS and GVL and GVL and C-MAC did not show significant difference (119875 = 0171 119875 =0165)

We did not know the definite cause of why C-MAC wasslower thanMacintosh blade and AWSMaybe in face to faceintubation the monitor attached to C-MAC was inverselyrotated Most operators in this study tried rotating C-MACmonitor to its original positon taking up more time Wethought it requires further investigation about other causes

6 BioMed Research International

46 Success Rate according to the Number of Attempts InMacintosh blade AWS and C-MAC they showed over 80success rate in first attempt (Table 4) Otherwise only 43 ofsubjects achieved successful intubation in GVL For secondattempt 72 of subjects succeeded in GVL the othersshowed over 95 success rate After fourth trial Macintoshand AWS showed 100 success rate C-MAC showed 988But GVL showed only 848 of success rate and 152 ofsubjects could not achieve successful face to face intubationduring four times of attempts (Figure 1) GVL had difficultblade for difficult airway in contrast to other laryngoscopeseye-hand discordance was more severe

47 Complication One tooth injury occurred in Macintoshfive injuries in AWS five injuries in GVL and three injuriesin C-MAC AWS had bigger and thicker blade than othersit contributed to tooth injury In performing intubationusing GVL as appeared by the result in which GVL showedlower successful face to face intubation rate subjects seemedto move more in oral cavity than other laryngoscopes forsuccessful intubation we guessed it influenced broken toothEsophageal intubation occurred once only in Macintoshblade it seemed to be meaningless

48 Limitation First we cannot exclude learning effect oflaryngoscopes Though subjects performed face to face intu-bation using multiple laryngoscopes via randomized serialsubjects might be trained four times of serial face to faceintubation and perform better as time goes by Second itis simulation study using manikin not a patient In thisstudy all manikins lay down on floor not in sitting positionFace to face intubation is very useful in patient of entrappedcar mostly sitting In addition there is enough space atupper manikinrsquos head side to perform face to face intubationcompared to narrow space such as ambulance and helicop-ter

It is not unusual that operator suffers poor visual field dueto secretion or blood or vomitus on performing CPR in fieldSometimes intubation was delayed for cleaning lens of videolaryngoscopesHowever in case ofMacintosh blade securingvisual field was faster because direct suction was possible ininsertion state of Macintosh blade So the result could notadapt to patients exactly Third subjects had no experienceof face to face intubation but they took lots of lectures aboutairway management using manikin So they have familiarityof intubation usingmanikin study compared to someonewhohas no prior education

Fourth we simulated this study and assumed an emer-gency situation in which the victim needed emergent faceto face intubation in limited study we determined that thefailure time of intubation was 1 minute We thought it mightbe a cause of low success rate in first intubation attempt usingGVL We compared spent time only in success cases at firsttime attempt of all kinds of laryngoscopes So we guessed thatGVL took a long time for face to face intubation comparedto our result Next study if that is possible it will give theopportunity for successful intubation without limited timeand it will be more correct in comparison to intubation timeamong laryngoscopes

5 Conclusion

In limited space and restricted position with emergent situa-tion face to face intubation is a useful substitute for conven-tional intubation However its success rate is different dueto multiple causes for example eye-hand discordance Mac-intosh blade and AWS showed significantly faster intubationtime than GVL and C-MAC in face to face intubation

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Authorsrsquo Contribution

Hyun Young Choi and Young Min Oh contributed equally tothis study

References

[1] P Schober R Krage D van Groeningen S A Loer and L ASchwarte ldquoInverse intubation in entrapped trauma casualties asimulator based randomised cross-over comparison of directindirect and video laryngoscopyrdquo Emergency Medicine Journalvol 31 pp 959ndash963 2014

[2] M Gellerfors A Larsson C H Svensen and D Gryth ldquoUseof the airtraq device for airway management in the prehos-pital settingmdasha retrospective studyrdquo Scandinavian Journal ofTrauma Resuscitation and Emergency Medicine vol 22 no 1article 10 2014

[3] H Al-Thani A El-Menyar and R Latifi ldquoPrehospital versusemergency room intubation of trauma patients in Qatar a-2-year observational studyrdquo North American Journal of MedicalSciences vol 6 no 1 pp 12ndash18 2014

[4] A Kilicaslan A Topal A Tavlan A Erol and S OtelciogluldquoEffectiveness of the C-MAC video laryngoscope in the man-agement of unexpected failed intubationsrdquo Brazilian Journal ofAnesthesiology vol 64 no 1 pp 62ndash65 2014

[5] A M Burnett R J Frascone S S Wewerka et al ldquoComparisonof success rates between two video laryngoscope systems usedin a prehospital clinical trialrdquo Prehospital Emergency Care vol18 no 2 pp 231ndash238 2014

[6] K B Wong C T Lui W Y W Chan T L Lau S Y H Tangand K L Tsui ldquoComparison of different intubation techniquesperformed inside a moving ambulance a manikin studyrdquo HongKong Medical Journal vol 20 no 4 pp 304ndash312 2014

[7] N Komasawa R Ueki M Itani H Nomura S-I Nishi andY Kaminoh ldquoEvaluation of tracheal intubation in several posi-tions by the Pentax-AWS Airway Scope a manikin studyrdquoJournal of Anesthesia vol 24 no 6 pp 908ndash912 2010

[8] T Asai ldquoTracheal intubation with restricted access a ran-domised comparison of the Pentax-Airway Scope and Macin-tosh laryngoscope in a manikinrdquo Anaesthesia vol 64 no 10pp 1114ndash1117 2009

[9] E Gaszynska P Samsel M Stankiewicz-Rudnicki A Wiec-zorek and T Gaszynski ldquoIntubation by paramedics using theILMA or AirTraq KingVision andMacintosh laryngoscopes invehicle-entrapped patients a manikin studyrdquo European Journalof Emergency Medicine vol 21 no 1 pp 61ndash64 2014

BioMed Research International 7

[10] K J Robinson K Donaghy and R Katz ldquoInverse intubationin air medical transportrdquo Air Medical Journal vol 23 no 1 pp40ndash43 2004

[11] R Amathieu J Sudrial W Abdi et al ldquoSimulating face-to-facetracheal intubation of a trapped patient a randomized compar-ison of the LMA Fastrachamptrade the GlideScopeamptrade andthe Airtraqamptrade laryngoscoperdquo British Journal of Anaesthe-sia vol 108 no 1 pp 140ndash145 2012

[12] M Tuma A El-Menyar H Abdelrahman et al ldquoPrehospitalintubation in patients with isolated severe traumatic braininjury a 4-YearObservational studyrdquoCritical Care Research andPractice vol 2014 Article ID 135986 6 pages 2014

[13] D Venezia A Wackett A Remedios and V Tarsia ldquoCompar-ison of sitting face-to-face intubation (two-person technique)with standard oral-tracheal intubation in novices aMannequinStudyrdquo Journal of Emergency Medicine vol 43 no 6 pp 1188ndash1195 2012

[14] S Sobuwa H B Hartzenberg H Geduld and C Uys ldquoOut-comes following prehospital airway management in severetraumatic brain injuryrdquo South African Medical Journal vol 103no 9 pp 644ndash646 2013

[15] W A Wetsch A Schneider R Schier O Spelten M Hellmichand J Hinkelbein ldquoIn a difficult access scenario supraglotticairway devices improve success and time to ventilationrdquo Euro-pean Journal of Emergency Medicine 2015

[16] J Mayglothling T M Duane M Gibbs et al ldquoEmergencytracheal intubation immediately following traumatic injury aneastern association for the surgery of trauma practice manage-ment guidelinerdquoThe Journal of Trauma and Acute Care Surgeryvol 73 no 5 pp S333ndashS340 2012

[17] T Arima O Nagata T Miura et al ldquoComparative analysis ofairway scope and Macintosh laryngoscope for intubation pri-marily for cardiac arrest in prehospital settingrdquo The AmericanJournal of Emergency Medicine vol 32 no 1 pp 40ndash43 2014

[18] S Rentsch and M K Rand ldquoEye-hand coordination duringvisuomotor adaptation with different rotation anglesrdquo PLoSONE vol 9 no 10 Article ID e109819 2014

[19] P Breedveld and M Wentink ldquoEye-hand coordination in lap-aroscopymdashan overview of experiments and supporting aidsrdquoMinimally Invasive Therapy amp Allied Technologies vol 10 no3 pp 155ndash162 2001

[20] KMaruyama S Tsukamoto S Ohno et al ldquoEffect of cardiopul-monary resuscitation on intubation using aMacintosh laryngo-scope the AirWay Scope and the gum elastic bougie aManikinStudyrdquo Resuscitation vol 81 no 8 pp 1014ndash1018 2010

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Research and TreatmentAIDS

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Gastroenterology Research and Practice

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Parkinsonrsquos Disease

Evidence-Based Complementary and Alternative Medicine

Volume 2014Hindawi Publishing Corporationhttpwwwhindawicom

4 BioMed Research International

Table 2 Comparison of intubation time (sec) and POGO () according to laryngoscopes (mean plusmn SD)

MCL AWS GVL C-MAC 119875 valueVCET (sec) 78 plusmn 33 109 plusmn 78 84 plusmn 49 84 plusmn 46 0199POGO () 536 plusmn 223 817 plusmn 183 654 plusmn 250 729 plusmn 208 0000Tube pass time (sec) 187 plusmn 73 196 plusmn 95 268 plusmn 100 228 plusmn 102 00011st ventilation time (sec) 284 plusmn 77 296 plusmn 109 392 plusmn 97 352 plusmn 104 0000VCET to tube pass time (sec) 109 plusmn 59 104 plusmn 109 228 plusmn 271 171 plusmn 143 0000Tube pass time to 1st ventilation time (sec) 96 plusmn 39 98 plusmn 37 106 plusmn 97 122 plusmn 45 0000lowast

119875 value lt 005 is level of statistical significance according to Friedman testMCL Macintosh laryngoscope AWS Pentax airway scope GVL Glidescope video laryngoscope C-MAC C-MAC video laryngoscope

Table 3 Statistical significance (119875 value) among laryngoscopes for intubation time (sec) and POGO ()

MCL versusAWS

(119875 value)

MCL versusGVL

(119875 value)

MCL versusC-MAC(119875 value)

AWS versusGVL

(119875 value)

AWS versusC-MAC(119875 value)

GVL versusC-MAC(119875 value)

VCET 0008 0038 0217 0756 0090 0220POGO 0000lowast 0000lowast 0000lowast 0000lowast 0002lowast 0188Tube pass time 0608 0001lowast 0000lowast 0005lowast 0011 01081st ventilation time 0530 0000lowast 0000lowast 0003lowast 0000lowast 0207VCET to tube pass time 0028 0003lowast 0001lowast 0001lowast 0000lowast 0161Tube pass time to 1stventilation time 0860 0060 0000lowast 0171 0000lowast 0165lowast

119875 value lt 0008 is level of statistical significance according to Bonferronirsquos methodMCL Macintosh laryngoscope AWS Pentax airway scope GVL Glidescope video laryngoscope C-MAC C-MAC video laryngoscope

837

988 100 100

825

976 988 100

43

72813 84886

965 988 988

0

20

40

60

80

100

1st attempt 2nd attempt 3rd attempt 4th attempt

Succ

ess r

ate (

)

Number of attempts

MCLAWS

GVLC-MAC

Figure 1 Endotracheal intubation success rate according to thenumber of attempts Glidescope video laryngoscope (GVL) showedlower success rate compared with other laryngoscopes in all ofattempts MCL Macintosh laryngoscope AWS Pentax airwayscope GVL Glidescope video laryngoscope C-MAC C-MACvideo laryngoscope

intubation We included all attempts of endotracheal intuba-tion Tooth injury was considered when tester heard toothclick The number of tooth injuries in Macintosh blade wasone in AWS and GVL five and else in C-MAC three Oneesophageal intubation occurred in Macintosh blade and noesophageal intubation occurred in video laryngoscopes

4 Discussion

Endotracheal intubation is very important procedure inemergency department for severely ill patients [13 14] Inconventional intubation operator sets a location at the upperside of patientrsquos head grasps a laryngoscope with left handand inserts endotracheal tube by right hand For better visu-alization operator shift patientrsquos tongue to left using bladeLots of new techniques and machines are introduced foreasy successful intubation but until recently conventionalintubation is the most commonly used method for airwaymanagement Video laryngoscopes for difficult airway con-sist of a laryngoscope with a light source and a camera indistal blade In contrast to conventional blade having about151015840-visual field video laryngoscopes make wider visual anglebecause of the camera on distal blade [4] In special situationsuch as in ambulance or helicopter occasionally there is nospace at patientrsquos upper side for conventional intubation Sooperator has to intubate on lateral or frontal side of patient[9] In contrast to conventional laryngoscopy the practitionerholds the handle of the laryngoscope in his right hand withthe top of the blade in the upright position After the openingof patientrsquos airways the top of the laryngoscopersquos curved bladewill be in place in the left part of the patientrsquos mouth [10]

We examined this study to investigate whether videolaryngoscopes are helpful in special situation like beingentrapped in car or permitted narrow space and whethervideo laryngoscopes are more useful than conventional

BioMed Research International 5

Table 4 Success rate according to the number of attempts

MCL AWS GVL CMAC

Success at 1st attempt 72 (837) 71 (825) 37 (430) 74 (860)

Success at 2nd attempt 13 (151)(85 988)

13 (151)(84 976)

25 (290)(62 720)

9 (104)(83 965)

Success at 3rd attempt 1 (11)(86 100)

1 (11)(85 988)

8 (93)(70 813)

2 (23)(85 988)

Success at 4th attempt 0 1 (11)(86 100)

3 (34)(73 848) 0

Failure at 4th attempt 0 0 13 (151) 1 (11)MCL Macintosh laryngoscope AWS Pentax airway scope GVL Glidescope video laryngoscope C-MAC C-MAC video laryngoscope

intubation set (Macintosh blade) We choose several videolaryngoscopes AWS which has endotracheal tube-guidinggroove channel in distal blade (P blade) GVL with difficultblade for difficult airway that has elliptically tapered bladeshape rising to distal and C-MAC with conventional bladewhich has the same blade angle compared with Macintoshblade [4]

We discussed the course of face to face intubation catego-rized as VCET POGO score VCET to tube pass time tubepass time to 1st ventilation time success rate by number ofattempts and complications

41 Face to Face Intubation versus Supraglottic Airway DevicesInsertion In previous simulation study supraglottic airwaydevices (SAD) are faster than Macintosh laryngoscope inentrapped situation [15]Hence SAD insertion can be consid-ered to be more useful method compared with endotrachealintubation However in cases of lung injuries or massivebleeding or vomitus in oral cavity SAD alone is not enoughto secure airway In these cases endotracheal intubationis preferred to SAD insertion for providing high oxygenconcentration [16]

In case of severe injury with restricted position face toface intubation is a reasonable choice

42 Vocal Cord Exposure Time (VCET) No significant dif-ference was detected among all laryngoscopes (119875 = 0199)Macintosh blade had advantage of easy insertion to oral cavitybecause it had smaller blade than other video laryngoscopesdue to its simplicity however video laryngoscopes hadcamera at the mount of blade tip so subjects easily detectedvocal cord so long as blade of video laryngoscopewas insertedin oral cavity

43 POGO (Percentage of Glottis Opening) Score Macintoshblade showed lower POGO score than all laryngoscopes inAWS (119875 = 0000) and GVL (119875 = 0000) and C-MAC (119875 =0000) In comparison among video laryngoscopes AWSshowed higher POGO than GVL (119875 = 0000) and C-MAC(119875 = 0002) GVL with C-MAC did not show significantdifference (119875 = 0016 119875 = 0022) Video laryngoscopes weremade for difficult airway management and gave us advancedvision compared to Macintosh blade [17] In case of face toface intubation similar to conventional intubation the visual

field is wider and POGO is higher in video laryngoscopesthan Macintosh blade GVL with difficult blade had morecurved angle than other blades so it was difficult to exposevocal cord in face to face intubation performing on oppositeside of conventional intubation

44 VCET to Tube Pass Time VCET to tube pass timemeansspending time from vocal cord exposure to pass it BetweenMacintosh blade andAWS therewas no significant difference(119875 = 0028) Macintosh was faster than GVL (119875 = 0003) andC-MAC (119875 = 0001) Among video laryngoscopes AWS wasfaster than GVL and C-MAC (119875 = 0001 119875 = 0000) Therewas no significant difference between GVL and C-MAC (119875 =0161)

It may be due to eye-hand discordance In case of face toface intubation using Macintosh blade operator sets locationon upper side of patientrsquos head checks vocal cord with thenaked eye and inserts endotracheal tube to vocal cord Onthe other hand operator with video laryngoscopes will bewatching monitor showing view from end of video laryn-goscope which is in contrast angle to hand direction [18]Operator inserts endotracheal tube to vocal cord watchingscreen attached to video laryngoscopes but the direction ofmanipulating endotracheal tube and the location of vocalcord on screen to advanced direction of endotracheal tube isdifferent [19 20] So it is difficult to insert endotracheal tubequickly and precisely Difficult blade of GVL has larger angleof blade for difficult airway compared to conventional bladeso it is more difficult to manipulate endotracheal tube due tomore distorted up-and-down angle

45 Tube Pass Time to 1st Ventilation Time Macintosh wasfaster than C-MAC (119875 = 0000) and showed no significantdifference with AWS (119875 = 0860) and with GVL (119875 = 0060)In comparison among video laryngoscopes AWS was fasterthan C-MAC (119875 = 0000) AWS and GVL and GVL and C-MAC did not show significant difference (119875 = 0171 119875 =0165)

We did not know the definite cause of why C-MAC wasslower thanMacintosh blade and AWSMaybe in face to faceintubation the monitor attached to C-MAC was inverselyrotated Most operators in this study tried rotating C-MACmonitor to its original positon taking up more time Wethought it requires further investigation about other causes

6 BioMed Research International

46 Success Rate according to the Number of Attempts InMacintosh blade AWS and C-MAC they showed over 80success rate in first attempt (Table 4) Otherwise only 43 ofsubjects achieved successful intubation in GVL For secondattempt 72 of subjects succeeded in GVL the othersshowed over 95 success rate After fourth trial Macintoshand AWS showed 100 success rate C-MAC showed 988But GVL showed only 848 of success rate and 152 ofsubjects could not achieve successful face to face intubationduring four times of attempts (Figure 1) GVL had difficultblade for difficult airway in contrast to other laryngoscopeseye-hand discordance was more severe

47 Complication One tooth injury occurred in Macintoshfive injuries in AWS five injuries in GVL and three injuriesin C-MAC AWS had bigger and thicker blade than othersit contributed to tooth injury In performing intubationusing GVL as appeared by the result in which GVL showedlower successful face to face intubation rate subjects seemedto move more in oral cavity than other laryngoscopes forsuccessful intubation we guessed it influenced broken toothEsophageal intubation occurred once only in Macintoshblade it seemed to be meaningless

48 Limitation First we cannot exclude learning effect oflaryngoscopes Though subjects performed face to face intu-bation using multiple laryngoscopes via randomized serialsubjects might be trained four times of serial face to faceintubation and perform better as time goes by Second itis simulation study using manikin not a patient In thisstudy all manikins lay down on floor not in sitting positionFace to face intubation is very useful in patient of entrappedcar mostly sitting In addition there is enough space atupper manikinrsquos head side to perform face to face intubationcompared to narrow space such as ambulance and helicop-ter

It is not unusual that operator suffers poor visual field dueto secretion or blood or vomitus on performing CPR in fieldSometimes intubation was delayed for cleaning lens of videolaryngoscopesHowever in case ofMacintosh blade securingvisual field was faster because direct suction was possible ininsertion state of Macintosh blade So the result could notadapt to patients exactly Third subjects had no experienceof face to face intubation but they took lots of lectures aboutairway management using manikin So they have familiarityof intubation usingmanikin study compared to someonewhohas no prior education

Fourth we simulated this study and assumed an emer-gency situation in which the victim needed emergent faceto face intubation in limited study we determined that thefailure time of intubation was 1 minute We thought it mightbe a cause of low success rate in first intubation attempt usingGVL We compared spent time only in success cases at firsttime attempt of all kinds of laryngoscopes So we guessed thatGVL took a long time for face to face intubation comparedto our result Next study if that is possible it will give theopportunity for successful intubation without limited timeand it will be more correct in comparison to intubation timeamong laryngoscopes

5 Conclusion

In limited space and restricted position with emergent situa-tion face to face intubation is a useful substitute for conven-tional intubation However its success rate is different dueto multiple causes for example eye-hand discordance Mac-intosh blade and AWS showed significantly faster intubationtime than GVL and C-MAC in face to face intubation

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Authorsrsquo Contribution

Hyun Young Choi and Young Min Oh contributed equally tothis study

References

[1] P Schober R Krage D van Groeningen S A Loer and L ASchwarte ldquoInverse intubation in entrapped trauma casualties asimulator based randomised cross-over comparison of directindirect and video laryngoscopyrdquo Emergency Medicine Journalvol 31 pp 959ndash963 2014

[2] M Gellerfors A Larsson C H Svensen and D Gryth ldquoUseof the airtraq device for airway management in the prehos-pital settingmdasha retrospective studyrdquo Scandinavian Journal ofTrauma Resuscitation and Emergency Medicine vol 22 no 1article 10 2014

[3] H Al-Thani A El-Menyar and R Latifi ldquoPrehospital versusemergency room intubation of trauma patients in Qatar a-2-year observational studyrdquo North American Journal of MedicalSciences vol 6 no 1 pp 12ndash18 2014

[4] A Kilicaslan A Topal A Tavlan A Erol and S OtelciogluldquoEffectiveness of the C-MAC video laryngoscope in the man-agement of unexpected failed intubationsrdquo Brazilian Journal ofAnesthesiology vol 64 no 1 pp 62ndash65 2014

[5] A M Burnett R J Frascone S S Wewerka et al ldquoComparisonof success rates between two video laryngoscope systems usedin a prehospital clinical trialrdquo Prehospital Emergency Care vol18 no 2 pp 231ndash238 2014

[6] K B Wong C T Lui W Y W Chan T L Lau S Y H Tangand K L Tsui ldquoComparison of different intubation techniquesperformed inside a moving ambulance a manikin studyrdquo HongKong Medical Journal vol 20 no 4 pp 304ndash312 2014

[7] N Komasawa R Ueki M Itani H Nomura S-I Nishi andY Kaminoh ldquoEvaluation of tracheal intubation in several posi-tions by the Pentax-AWS Airway Scope a manikin studyrdquoJournal of Anesthesia vol 24 no 6 pp 908ndash912 2010

[8] T Asai ldquoTracheal intubation with restricted access a ran-domised comparison of the Pentax-Airway Scope and Macin-tosh laryngoscope in a manikinrdquo Anaesthesia vol 64 no 10pp 1114ndash1117 2009

[9] E Gaszynska P Samsel M Stankiewicz-Rudnicki A Wiec-zorek and T Gaszynski ldquoIntubation by paramedics using theILMA or AirTraq KingVision andMacintosh laryngoscopes invehicle-entrapped patients a manikin studyrdquo European Journalof Emergency Medicine vol 21 no 1 pp 61ndash64 2014

BioMed Research International 7

[10] K J Robinson K Donaghy and R Katz ldquoInverse intubationin air medical transportrdquo Air Medical Journal vol 23 no 1 pp40ndash43 2004

[11] R Amathieu J Sudrial W Abdi et al ldquoSimulating face-to-facetracheal intubation of a trapped patient a randomized compar-ison of the LMA Fastrachamptrade the GlideScopeamptrade andthe Airtraqamptrade laryngoscoperdquo British Journal of Anaesthe-sia vol 108 no 1 pp 140ndash145 2012

[12] M Tuma A El-Menyar H Abdelrahman et al ldquoPrehospitalintubation in patients with isolated severe traumatic braininjury a 4-YearObservational studyrdquoCritical Care Research andPractice vol 2014 Article ID 135986 6 pages 2014

[13] D Venezia A Wackett A Remedios and V Tarsia ldquoCompar-ison of sitting face-to-face intubation (two-person technique)with standard oral-tracheal intubation in novices aMannequinStudyrdquo Journal of Emergency Medicine vol 43 no 6 pp 1188ndash1195 2012

[14] S Sobuwa H B Hartzenberg H Geduld and C Uys ldquoOut-comes following prehospital airway management in severetraumatic brain injuryrdquo South African Medical Journal vol 103no 9 pp 644ndash646 2013

[15] W A Wetsch A Schneider R Schier O Spelten M Hellmichand J Hinkelbein ldquoIn a difficult access scenario supraglotticairway devices improve success and time to ventilationrdquo Euro-pean Journal of Emergency Medicine 2015

[16] J Mayglothling T M Duane M Gibbs et al ldquoEmergencytracheal intubation immediately following traumatic injury aneastern association for the surgery of trauma practice manage-ment guidelinerdquoThe Journal of Trauma and Acute Care Surgeryvol 73 no 5 pp S333ndashS340 2012

[17] T Arima O Nagata T Miura et al ldquoComparative analysis ofairway scope and Macintosh laryngoscope for intubation pri-marily for cardiac arrest in prehospital settingrdquo The AmericanJournal of Emergency Medicine vol 32 no 1 pp 40ndash43 2014

[18] S Rentsch and M K Rand ldquoEye-hand coordination duringvisuomotor adaptation with different rotation anglesrdquo PLoSONE vol 9 no 10 Article ID e109819 2014

[19] P Breedveld and M Wentink ldquoEye-hand coordination in lap-aroscopymdashan overview of experiments and supporting aidsrdquoMinimally Invasive Therapy amp Allied Technologies vol 10 no3 pp 155ndash162 2001

[20] KMaruyama S Tsukamoto S Ohno et al ldquoEffect of cardiopul-monary resuscitation on intubation using aMacintosh laryngo-scope the AirWay Scope and the gum elastic bougie aManikinStudyrdquo Resuscitation vol 81 no 8 pp 1014ndash1018 2010

Submit your manuscripts athttpwwwhindawicom

Stem CellsInternational

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MEDIATORSINFLAMMATION

of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Behavioural Neurology

EndocrinologyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Disease Markers

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioMed Research International

OncologyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Oxidative Medicine and Cellular Longevity

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

PPAR Research

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Immunology ResearchHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

ObesityJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Computational and Mathematical Methods in Medicine

OphthalmologyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Diabetes ResearchJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Research and TreatmentAIDS

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Gastroenterology Research and Practice

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Parkinsonrsquos Disease

Evidence-Based Complementary and Alternative Medicine

Volume 2014Hindawi Publishing Corporationhttpwwwhindawicom

BioMed Research International 5

Table 4 Success rate according to the number of attempts

MCL AWS GVL CMAC

Success at 1st attempt 72 (837) 71 (825) 37 (430) 74 (860)

Success at 2nd attempt 13 (151)(85 988)

13 (151)(84 976)

25 (290)(62 720)

9 (104)(83 965)

Success at 3rd attempt 1 (11)(86 100)

1 (11)(85 988)

8 (93)(70 813)

2 (23)(85 988)

Success at 4th attempt 0 1 (11)(86 100)

3 (34)(73 848) 0

Failure at 4th attempt 0 0 13 (151) 1 (11)MCL Macintosh laryngoscope AWS Pentax airway scope GVL Glidescope video laryngoscope C-MAC C-MAC video laryngoscope

intubation set (Macintosh blade) We choose several videolaryngoscopes AWS which has endotracheal tube-guidinggroove channel in distal blade (P blade) GVL with difficultblade for difficult airway that has elliptically tapered bladeshape rising to distal and C-MAC with conventional bladewhich has the same blade angle compared with Macintoshblade [4]

We discussed the course of face to face intubation catego-rized as VCET POGO score VCET to tube pass time tubepass time to 1st ventilation time success rate by number ofattempts and complications

41 Face to Face Intubation versus Supraglottic Airway DevicesInsertion In previous simulation study supraglottic airwaydevices (SAD) are faster than Macintosh laryngoscope inentrapped situation [15]Hence SAD insertion can be consid-ered to be more useful method compared with endotrachealintubation However in cases of lung injuries or massivebleeding or vomitus in oral cavity SAD alone is not enoughto secure airway In these cases endotracheal intubationis preferred to SAD insertion for providing high oxygenconcentration [16]

In case of severe injury with restricted position face toface intubation is a reasonable choice

42 Vocal Cord Exposure Time (VCET) No significant dif-ference was detected among all laryngoscopes (119875 = 0199)Macintosh blade had advantage of easy insertion to oral cavitybecause it had smaller blade than other video laryngoscopesdue to its simplicity however video laryngoscopes hadcamera at the mount of blade tip so subjects easily detectedvocal cord so long as blade of video laryngoscopewas insertedin oral cavity

43 POGO (Percentage of Glottis Opening) Score Macintoshblade showed lower POGO score than all laryngoscopes inAWS (119875 = 0000) and GVL (119875 = 0000) and C-MAC (119875 =0000) In comparison among video laryngoscopes AWSshowed higher POGO than GVL (119875 = 0000) and C-MAC(119875 = 0002) GVL with C-MAC did not show significantdifference (119875 = 0016 119875 = 0022) Video laryngoscopes weremade for difficult airway management and gave us advancedvision compared to Macintosh blade [17] In case of face toface intubation similar to conventional intubation the visual

field is wider and POGO is higher in video laryngoscopesthan Macintosh blade GVL with difficult blade had morecurved angle than other blades so it was difficult to exposevocal cord in face to face intubation performing on oppositeside of conventional intubation

44 VCET to Tube Pass Time VCET to tube pass timemeansspending time from vocal cord exposure to pass it BetweenMacintosh blade andAWS therewas no significant difference(119875 = 0028) Macintosh was faster than GVL (119875 = 0003) andC-MAC (119875 = 0001) Among video laryngoscopes AWS wasfaster than GVL and C-MAC (119875 = 0001 119875 = 0000) Therewas no significant difference between GVL and C-MAC (119875 =0161)

It may be due to eye-hand discordance In case of face toface intubation using Macintosh blade operator sets locationon upper side of patientrsquos head checks vocal cord with thenaked eye and inserts endotracheal tube to vocal cord Onthe other hand operator with video laryngoscopes will bewatching monitor showing view from end of video laryn-goscope which is in contrast angle to hand direction [18]Operator inserts endotracheal tube to vocal cord watchingscreen attached to video laryngoscopes but the direction ofmanipulating endotracheal tube and the location of vocalcord on screen to advanced direction of endotracheal tube isdifferent [19 20] So it is difficult to insert endotracheal tubequickly and precisely Difficult blade of GVL has larger angleof blade for difficult airway compared to conventional bladeso it is more difficult to manipulate endotracheal tube due tomore distorted up-and-down angle

45 Tube Pass Time to 1st Ventilation Time Macintosh wasfaster than C-MAC (119875 = 0000) and showed no significantdifference with AWS (119875 = 0860) and with GVL (119875 = 0060)In comparison among video laryngoscopes AWS was fasterthan C-MAC (119875 = 0000) AWS and GVL and GVL and C-MAC did not show significant difference (119875 = 0171 119875 =0165)

We did not know the definite cause of why C-MAC wasslower thanMacintosh blade and AWSMaybe in face to faceintubation the monitor attached to C-MAC was inverselyrotated Most operators in this study tried rotating C-MACmonitor to its original positon taking up more time Wethought it requires further investigation about other causes

6 BioMed Research International

46 Success Rate according to the Number of Attempts InMacintosh blade AWS and C-MAC they showed over 80success rate in first attempt (Table 4) Otherwise only 43 ofsubjects achieved successful intubation in GVL For secondattempt 72 of subjects succeeded in GVL the othersshowed over 95 success rate After fourth trial Macintoshand AWS showed 100 success rate C-MAC showed 988But GVL showed only 848 of success rate and 152 ofsubjects could not achieve successful face to face intubationduring four times of attempts (Figure 1) GVL had difficultblade for difficult airway in contrast to other laryngoscopeseye-hand discordance was more severe

47 Complication One tooth injury occurred in Macintoshfive injuries in AWS five injuries in GVL and three injuriesin C-MAC AWS had bigger and thicker blade than othersit contributed to tooth injury In performing intubationusing GVL as appeared by the result in which GVL showedlower successful face to face intubation rate subjects seemedto move more in oral cavity than other laryngoscopes forsuccessful intubation we guessed it influenced broken toothEsophageal intubation occurred once only in Macintoshblade it seemed to be meaningless

48 Limitation First we cannot exclude learning effect oflaryngoscopes Though subjects performed face to face intu-bation using multiple laryngoscopes via randomized serialsubjects might be trained four times of serial face to faceintubation and perform better as time goes by Second itis simulation study using manikin not a patient In thisstudy all manikins lay down on floor not in sitting positionFace to face intubation is very useful in patient of entrappedcar mostly sitting In addition there is enough space atupper manikinrsquos head side to perform face to face intubationcompared to narrow space such as ambulance and helicop-ter

It is not unusual that operator suffers poor visual field dueto secretion or blood or vomitus on performing CPR in fieldSometimes intubation was delayed for cleaning lens of videolaryngoscopesHowever in case ofMacintosh blade securingvisual field was faster because direct suction was possible ininsertion state of Macintosh blade So the result could notadapt to patients exactly Third subjects had no experienceof face to face intubation but they took lots of lectures aboutairway management using manikin So they have familiarityof intubation usingmanikin study compared to someonewhohas no prior education

Fourth we simulated this study and assumed an emer-gency situation in which the victim needed emergent faceto face intubation in limited study we determined that thefailure time of intubation was 1 minute We thought it mightbe a cause of low success rate in first intubation attempt usingGVL We compared spent time only in success cases at firsttime attempt of all kinds of laryngoscopes So we guessed thatGVL took a long time for face to face intubation comparedto our result Next study if that is possible it will give theopportunity for successful intubation without limited timeand it will be more correct in comparison to intubation timeamong laryngoscopes

5 Conclusion

In limited space and restricted position with emergent situa-tion face to face intubation is a useful substitute for conven-tional intubation However its success rate is different dueto multiple causes for example eye-hand discordance Mac-intosh blade and AWS showed significantly faster intubationtime than GVL and C-MAC in face to face intubation

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Authorsrsquo Contribution

Hyun Young Choi and Young Min Oh contributed equally tothis study

References

[1] P Schober R Krage D van Groeningen S A Loer and L ASchwarte ldquoInverse intubation in entrapped trauma casualties asimulator based randomised cross-over comparison of directindirect and video laryngoscopyrdquo Emergency Medicine Journalvol 31 pp 959ndash963 2014

[2] M Gellerfors A Larsson C H Svensen and D Gryth ldquoUseof the airtraq device for airway management in the prehos-pital settingmdasha retrospective studyrdquo Scandinavian Journal ofTrauma Resuscitation and Emergency Medicine vol 22 no 1article 10 2014

[3] H Al-Thani A El-Menyar and R Latifi ldquoPrehospital versusemergency room intubation of trauma patients in Qatar a-2-year observational studyrdquo North American Journal of MedicalSciences vol 6 no 1 pp 12ndash18 2014

[4] A Kilicaslan A Topal A Tavlan A Erol and S OtelciogluldquoEffectiveness of the C-MAC video laryngoscope in the man-agement of unexpected failed intubationsrdquo Brazilian Journal ofAnesthesiology vol 64 no 1 pp 62ndash65 2014

[5] A M Burnett R J Frascone S S Wewerka et al ldquoComparisonof success rates between two video laryngoscope systems usedin a prehospital clinical trialrdquo Prehospital Emergency Care vol18 no 2 pp 231ndash238 2014

[6] K B Wong C T Lui W Y W Chan T L Lau S Y H Tangand K L Tsui ldquoComparison of different intubation techniquesperformed inside a moving ambulance a manikin studyrdquo HongKong Medical Journal vol 20 no 4 pp 304ndash312 2014

[7] N Komasawa R Ueki M Itani H Nomura S-I Nishi andY Kaminoh ldquoEvaluation of tracheal intubation in several posi-tions by the Pentax-AWS Airway Scope a manikin studyrdquoJournal of Anesthesia vol 24 no 6 pp 908ndash912 2010

[8] T Asai ldquoTracheal intubation with restricted access a ran-domised comparison of the Pentax-Airway Scope and Macin-tosh laryngoscope in a manikinrdquo Anaesthesia vol 64 no 10pp 1114ndash1117 2009

[9] E Gaszynska P Samsel M Stankiewicz-Rudnicki A Wiec-zorek and T Gaszynski ldquoIntubation by paramedics using theILMA or AirTraq KingVision andMacintosh laryngoscopes invehicle-entrapped patients a manikin studyrdquo European Journalof Emergency Medicine vol 21 no 1 pp 61ndash64 2014

BioMed Research International 7

[10] K J Robinson K Donaghy and R Katz ldquoInverse intubationin air medical transportrdquo Air Medical Journal vol 23 no 1 pp40ndash43 2004

[11] R Amathieu J Sudrial W Abdi et al ldquoSimulating face-to-facetracheal intubation of a trapped patient a randomized compar-ison of the LMA Fastrachamptrade the GlideScopeamptrade andthe Airtraqamptrade laryngoscoperdquo British Journal of Anaesthe-sia vol 108 no 1 pp 140ndash145 2012

[12] M Tuma A El-Menyar H Abdelrahman et al ldquoPrehospitalintubation in patients with isolated severe traumatic braininjury a 4-YearObservational studyrdquoCritical Care Research andPractice vol 2014 Article ID 135986 6 pages 2014

[13] D Venezia A Wackett A Remedios and V Tarsia ldquoCompar-ison of sitting face-to-face intubation (two-person technique)with standard oral-tracheal intubation in novices aMannequinStudyrdquo Journal of Emergency Medicine vol 43 no 6 pp 1188ndash1195 2012

[14] S Sobuwa H B Hartzenberg H Geduld and C Uys ldquoOut-comes following prehospital airway management in severetraumatic brain injuryrdquo South African Medical Journal vol 103no 9 pp 644ndash646 2013

[15] W A Wetsch A Schneider R Schier O Spelten M Hellmichand J Hinkelbein ldquoIn a difficult access scenario supraglotticairway devices improve success and time to ventilationrdquo Euro-pean Journal of Emergency Medicine 2015

[16] J Mayglothling T M Duane M Gibbs et al ldquoEmergencytracheal intubation immediately following traumatic injury aneastern association for the surgery of trauma practice manage-ment guidelinerdquoThe Journal of Trauma and Acute Care Surgeryvol 73 no 5 pp S333ndashS340 2012

[17] T Arima O Nagata T Miura et al ldquoComparative analysis ofairway scope and Macintosh laryngoscope for intubation pri-marily for cardiac arrest in prehospital settingrdquo The AmericanJournal of Emergency Medicine vol 32 no 1 pp 40ndash43 2014

[18] S Rentsch and M K Rand ldquoEye-hand coordination duringvisuomotor adaptation with different rotation anglesrdquo PLoSONE vol 9 no 10 Article ID e109819 2014

[19] P Breedveld and M Wentink ldquoEye-hand coordination in lap-aroscopymdashan overview of experiments and supporting aidsrdquoMinimally Invasive Therapy amp Allied Technologies vol 10 no3 pp 155ndash162 2001

[20] KMaruyama S Tsukamoto S Ohno et al ldquoEffect of cardiopul-monary resuscitation on intubation using aMacintosh laryngo-scope the AirWay Scope and the gum elastic bougie aManikinStudyrdquo Resuscitation vol 81 no 8 pp 1014ndash1018 2010

Submit your manuscripts athttpwwwhindawicom

Stem CellsInternational

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MEDIATORSINFLAMMATION

of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Behavioural Neurology

EndocrinologyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Disease Markers

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioMed Research International

OncologyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Oxidative Medicine and Cellular Longevity

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

PPAR Research

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Immunology ResearchHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

ObesityJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Computational and Mathematical Methods in Medicine

OphthalmologyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Diabetes ResearchJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Research and TreatmentAIDS

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Gastroenterology Research and Practice

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Parkinsonrsquos Disease

Evidence-Based Complementary and Alternative Medicine

Volume 2014Hindawi Publishing Corporationhttpwwwhindawicom

6 BioMed Research International

46 Success Rate according to the Number of Attempts InMacintosh blade AWS and C-MAC they showed over 80success rate in first attempt (Table 4) Otherwise only 43 ofsubjects achieved successful intubation in GVL For secondattempt 72 of subjects succeeded in GVL the othersshowed over 95 success rate After fourth trial Macintoshand AWS showed 100 success rate C-MAC showed 988But GVL showed only 848 of success rate and 152 ofsubjects could not achieve successful face to face intubationduring four times of attempts (Figure 1) GVL had difficultblade for difficult airway in contrast to other laryngoscopeseye-hand discordance was more severe

47 Complication One tooth injury occurred in Macintoshfive injuries in AWS five injuries in GVL and three injuriesin C-MAC AWS had bigger and thicker blade than othersit contributed to tooth injury In performing intubationusing GVL as appeared by the result in which GVL showedlower successful face to face intubation rate subjects seemedto move more in oral cavity than other laryngoscopes forsuccessful intubation we guessed it influenced broken toothEsophageal intubation occurred once only in Macintoshblade it seemed to be meaningless

48 Limitation First we cannot exclude learning effect oflaryngoscopes Though subjects performed face to face intu-bation using multiple laryngoscopes via randomized serialsubjects might be trained four times of serial face to faceintubation and perform better as time goes by Second itis simulation study using manikin not a patient In thisstudy all manikins lay down on floor not in sitting positionFace to face intubation is very useful in patient of entrappedcar mostly sitting In addition there is enough space atupper manikinrsquos head side to perform face to face intubationcompared to narrow space such as ambulance and helicop-ter

It is not unusual that operator suffers poor visual field dueto secretion or blood or vomitus on performing CPR in fieldSometimes intubation was delayed for cleaning lens of videolaryngoscopesHowever in case ofMacintosh blade securingvisual field was faster because direct suction was possible ininsertion state of Macintosh blade So the result could notadapt to patients exactly Third subjects had no experienceof face to face intubation but they took lots of lectures aboutairway management using manikin So they have familiarityof intubation usingmanikin study compared to someonewhohas no prior education

Fourth we simulated this study and assumed an emer-gency situation in which the victim needed emergent faceto face intubation in limited study we determined that thefailure time of intubation was 1 minute We thought it mightbe a cause of low success rate in first intubation attempt usingGVL We compared spent time only in success cases at firsttime attempt of all kinds of laryngoscopes So we guessed thatGVL took a long time for face to face intubation comparedto our result Next study if that is possible it will give theopportunity for successful intubation without limited timeand it will be more correct in comparison to intubation timeamong laryngoscopes

5 Conclusion

In limited space and restricted position with emergent situa-tion face to face intubation is a useful substitute for conven-tional intubation However its success rate is different dueto multiple causes for example eye-hand discordance Mac-intosh blade and AWS showed significantly faster intubationtime than GVL and C-MAC in face to face intubation

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Authorsrsquo Contribution

Hyun Young Choi and Young Min Oh contributed equally tothis study

References

[1] P Schober R Krage D van Groeningen S A Loer and L ASchwarte ldquoInverse intubation in entrapped trauma casualties asimulator based randomised cross-over comparison of directindirect and video laryngoscopyrdquo Emergency Medicine Journalvol 31 pp 959ndash963 2014

[2] M Gellerfors A Larsson C H Svensen and D Gryth ldquoUseof the airtraq device for airway management in the prehos-pital settingmdasha retrospective studyrdquo Scandinavian Journal ofTrauma Resuscitation and Emergency Medicine vol 22 no 1article 10 2014

[3] H Al-Thani A El-Menyar and R Latifi ldquoPrehospital versusemergency room intubation of trauma patients in Qatar a-2-year observational studyrdquo North American Journal of MedicalSciences vol 6 no 1 pp 12ndash18 2014

[4] A Kilicaslan A Topal A Tavlan A Erol and S OtelciogluldquoEffectiveness of the C-MAC video laryngoscope in the man-agement of unexpected failed intubationsrdquo Brazilian Journal ofAnesthesiology vol 64 no 1 pp 62ndash65 2014

[5] A M Burnett R J Frascone S S Wewerka et al ldquoComparisonof success rates between two video laryngoscope systems usedin a prehospital clinical trialrdquo Prehospital Emergency Care vol18 no 2 pp 231ndash238 2014

[6] K B Wong C T Lui W Y W Chan T L Lau S Y H Tangand K L Tsui ldquoComparison of different intubation techniquesperformed inside a moving ambulance a manikin studyrdquo HongKong Medical Journal vol 20 no 4 pp 304ndash312 2014

[7] N Komasawa R Ueki M Itani H Nomura S-I Nishi andY Kaminoh ldquoEvaluation of tracheal intubation in several posi-tions by the Pentax-AWS Airway Scope a manikin studyrdquoJournal of Anesthesia vol 24 no 6 pp 908ndash912 2010

[8] T Asai ldquoTracheal intubation with restricted access a ran-domised comparison of the Pentax-Airway Scope and Macin-tosh laryngoscope in a manikinrdquo Anaesthesia vol 64 no 10pp 1114ndash1117 2009

[9] E Gaszynska P Samsel M Stankiewicz-Rudnicki A Wiec-zorek and T Gaszynski ldquoIntubation by paramedics using theILMA or AirTraq KingVision andMacintosh laryngoscopes invehicle-entrapped patients a manikin studyrdquo European Journalof Emergency Medicine vol 21 no 1 pp 61ndash64 2014

BioMed Research International 7

[10] K J Robinson K Donaghy and R Katz ldquoInverse intubationin air medical transportrdquo Air Medical Journal vol 23 no 1 pp40ndash43 2004

[11] R Amathieu J Sudrial W Abdi et al ldquoSimulating face-to-facetracheal intubation of a trapped patient a randomized compar-ison of the LMA Fastrachamptrade the GlideScopeamptrade andthe Airtraqamptrade laryngoscoperdquo British Journal of Anaesthe-sia vol 108 no 1 pp 140ndash145 2012

[12] M Tuma A El-Menyar H Abdelrahman et al ldquoPrehospitalintubation in patients with isolated severe traumatic braininjury a 4-YearObservational studyrdquoCritical Care Research andPractice vol 2014 Article ID 135986 6 pages 2014

[13] D Venezia A Wackett A Remedios and V Tarsia ldquoCompar-ison of sitting face-to-face intubation (two-person technique)with standard oral-tracheal intubation in novices aMannequinStudyrdquo Journal of Emergency Medicine vol 43 no 6 pp 1188ndash1195 2012

[14] S Sobuwa H B Hartzenberg H Geduld and C Uys ldquoOut-comes following prehospital airway management in severetraumatic brain injuryrdquo South African Medical Journal vol 103no 9 pp 644ndash646 2013

[15] W A Wetsch A Schneider R Schier O Spelten M Hellmichand J Hinkelbein ldquoIn a difficult access scenario supraglotticairway devices improve success and time to ventilationrdquo Euro-pean Journal of Emergency Medicine 2015

[16] J Mayglothling T M Duane M Gibbs et al ldquoEmergencytracheal intubation immediately following traumatic injury aneastern association for the surgery of trauma practice manage-ment guidelinerdquoThe Journal of Trauma and Acute Care Surgeryvol 73 no 5 pp S333ndashS340 2012

[17] T Arima O Nagata T Miura et al ldquoComparative analysis ofairway scope and Macintosh laryngoscope for intubation pri-marily for cardiac arrest in prehospital settingrdquo The AmericanJournal of Emergency Medicine vol 32 no 1 pp 40ndash43 2014

[18] S Rentsch and M K Rand ldquoEye-hand coordination duringvisuomotor adaptation with different rotation anglesrdquo PLoSONE vol 9 no 10 Article ID e109819 2014

[19] P Breedveld and M Wentink ldquoEye-hand coordination in lap-aroscopymdashan overview of experiments and supporting aidsrdquoMinimally Invasive Therapy amp Allied Technologies vol 10 no3 pp 155ndash162 2001

[20] KMaruyama S Tsukamoto S Ohno et al ldquoEffect of cardiopul-monary resuscitation on intubation using aMacintosh laryngo-scope the AirWay Scope and the gum elastic bougie aManikinStudyrdquo Resuscitation vol 81 no 8 pp 1014ndash1018 2010

Submit your manuscripts athttpwwwhindawicom

Stem CellsInternational

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MEDIATORSINFLAMMATION

of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Behavioural Neurology

EndocrinologyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Disease Markers

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioMed Research International

OncologyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Oxidative Medicine and Cellular Longevity

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

PPAR Research

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Immunology ResearchHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

ObesityJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Computational and Mathematical Methods in Medicine

OphthalmologyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Diabetes ResearchJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Research and TreatmentAIDS

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Gastroenterology Research and Practice

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Parkinsonrsquos Disease

Evidence-Based Complementary and Alternative Medicine

Volume 2014Hindawi Publishing Corporationhttpwwwhindawicom

BioMed Research International 7

[10] K J Robinson K Donaghy and R Katz ldquoInverse intubationin air medical transportrdquo Air Medical Journal vol 23 no 1 pp40ndash43 2004

[11] R Amathieu J Sudrial W Abdi et al ldquoSimulating face-to-facetracheal intubation of a trapped patient a randomized compar-ison of the LMA Fastrachamptrade the GlideScopeamptrade andthe Airtraqamptrade laryngoscoperdquo British Journal of Anaesthe-sia vol 108 no 1 pp 140ndash145 2012

[12] M Tuma A El-Menyar H Abdelrahman et al ldquoPrehospitalintubation in patients with isolated severe traumatic braininjury a 4-YearObservational studyrdquoCritical Care Research andPractice vol 2014 Article ID 135986 6 pages 2014

[13] D Venezia A Wackett A Remedios and V Tarsia ldquoCompar-ison of sitting face-to-face intubation (two-person technique)with standard oral-tracheal intubation in novices aMannequinStudyrdquo Journal of Emergency Medicine vol 43 no 6 pp 1188ndash1195 2012

[14] S Sobuwa H B Hartzenberg H Geduld and C Uys ldquoOut-comes following prehospital airway management in severetraumatic brain injuryrdquo South African Medical Journal vol 103no 9 pp 644ndash646 2013

[15] W A Wetsch A Schneider R Schier O Spelten M Hellmichand J Hinkelbein ldquoIn a difficult access scenario supraglotticairway devices improve success and time to ventilationrdquo Euro-pean Journal of Emergency Medicine 2015

[16] J Mayglothling T M Duane M Gibbs et al ldquoEmergencytracheal intubation immediately following traumatic injury aneastern association for the surgery of trauma practice manage-ment guidelinerdquoThe Journal of Trauma and Acute Care Surgeryvol 73 no 5 pp S333ndashS340 2012

[17] T Arima O Nagata T Miura et al ldquoComparative analysis ofairway scope and Macintosh laryngoscope for intubation pri-marily for cardiac arrest in prehospital settingrdquo The AmericanJournal of Emergency Medicine vol 32 no 1 pp 40ndash43 2014

[18] S Rentsch and M K Rand ldquoEye-hand coordination duringvisuomotor adaptation with different rotation anglesrdquo PLoSONE vol 9 no 10 Article ID e109819 2014

[19] P Breedveld and M Wentink ldquoEye-hand coordination in lap-aroscopymdashan overview of experiments and supporting aidsrdquoMinimally Invasive Therapy amp Allied Technologies vol 10 no3 pp 155ndash162 2001

[20] KMaruyama S Tsukamoto S Ohno et al ldquoEffect of cardiopul-monary resuscitation on intubation using aMacintosh laryngo-scope the AirWay Scope and the gum elastic bougie aManikinStudyrdquo Resuscitation vol 81 no 8 pp 1014ndash1018 2010

Submit your manuscripts athttpwwwhindawicom

Stem CellsInternational

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MEDIATORSINFLAMMATION

of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Behavioural Neurology

EndocrinologyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Disease Markers

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioMed Research International

OncologyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Oxidative Medicine and Cellular Longevity

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

PPAR Research

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Immunology ResearchHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

ObesityJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Computational and Mathematical Methods in Medicine

OphthalmologyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Diabetes ResearchJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Research and TreatmentAIDS

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Gastroenterology Research and Practice

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Parkinsonrsquos Disease

Evidence-Based Complementary and Alternative Medicine

Volume 2014Hindawi Publishing Corporationhttpwwwhindawicom

Submit your manuscripts athttpwwwhindawicom

Stem CellsInternational

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MEDIATORSINFLAMMATION

of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Behavioural Neurology

EndocrinologyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Disease Markers

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioMed Research International

OncologyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Oxidative Medicine and Cellular Longevity

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

PPAR Research

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Immunology ResearchHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

ObesityJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Computational and Mathematical Methods in Medicine

OphthalmologyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Diabetes ResearchJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Research and TreatmentAIDS

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Gastroenterology Research and Practice

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Parkinsonrsquos Disease

Evidence-Based Complementary and Alternative Medicine

Volume 2014Hindawi Publishing Corporationhttpwwwhindawicom