© FD-Communications Inc. Obesity Surgery, 14, 2004 1171

Obesity Surgery, 14, 1171-1175

Background:The effect of patient position on the viewobtained during laryngoscopy was investigated.

Methods: 60 morbidly obese patients undergoingelective bariatric were studied. Patients were ran-domly assigned into one of two groups. In Group 1, aconventional “sniff” position was obtained by placinga firm 7-cm cushion underneath the patient’s head,thus raising the occiput a standard distance from theoperating-table while the patient remained supine. InGroup 2, a “ramped” position was achieved by arrang-ing blankets underneath the patient's upper body andhead until horizontal alignment was achievedbetween the external auditory meatus and the sternalnotch. Following induction of general anesthesia, tra-cheal intubation was performed using a VideoMacIntosh® laryngoscope. The laryngoscopy andintubation sequences were recorded onto videotape.Three independent investigators, unaware as towhich position the patient had been in at the time oftracheal intubation, then viewed the videotape andassigned a numerical grade to the best laryngeal viewobtained.

Results: The “ramped” position improved the laryn-geal view when compared to a standard “sniff” posi-tion, and this difference was statistically significant(P=0.037).

Conclusion: The “ramped” position is superior tothe standard “sniff” position for direct laryngoscopyin morbidly obese patients.

Key words: Morbid obesity, anesthesia, airway, laryn-goscopy, endotracheal intubation, patient positioning

Introduction

Laryngoscopy and tracheal intubation have beenstated to be more difficult in morbidly obesepatients compared to normal weight individuals.1-3

However, this has not been our clinical experience.We previously reported a low incidence of difficultywith laryngoscopy and tracheal intubation in mor-bidly obese patients.4 When we compared our find-ings with other published series that had reported ahigher incidence of problems,5 we postulated thatthe elevated head and neck position of our patientsmay have optimized laryngoscopy. Although a“ramped” position with the patient's upper body andhead elevated to create a horizontal alignmentbetween the external auditory meatus and the sternalnotch has been previously recommended to improvelaryngeal exposure in obese patients,6 no study hastested this hypothesis. We therefore performed aprospective, randomized, blinded study to comparethe “ramped” position with the “sniff” position forlaryngoscopy and tracheal intubation in morbidlyobese patients.

Methods

With permission from our Human SubjectsCommittee, 60 consecutive patients undergoingelective bariatric surgery at Stanford UniversityHospital consented to be studied. Height and weighton the day of surgery were used to calculate the

Laryngoscopy and Morbid Obesity: a Comparisonof the “Sniff” and “Ramped” Positions

Jeremy S. Collins, MB, ChB1; Harry J.M. Lemmens, MD, PhD1; Jay B.Brodsky MD1; John G. Brock-Utne, MD, PhD1; Richard M. Levitan, MD2

1Department of Anesthesia, Stanford University School of Medicine, Stanford, CA and 2Departmentof Emergency Medicine, University of Pennsylvania School of Medicine, Philadelphia, PA, USA

Reprint requests to: Jay Brodsky, MD, Department of Anesthesia,H3580, Stanford University Medical Center, Stanford, CA 94305,USA. Fax: 650-725-8544; e-mail: Jbrodsky@stanford.edu

body mass index (BMI), and only patients with aBMI ≥40kg/m2 were included in the study.

A complete medical history was obtained, andsignificant medical co-morbidities, including adefinitive diagnosis of obstructive sleep apnea(OSA), were recorded. Age and sex were noted.Neck circumference (cm) at the level of the thyroidcartilage, width of mouth opening (inter-incisor gap(cm)), thyromental distance (cm) and the ster-nomental distance (cm) were measured andrecorded. The visibility of oropharyngeal structureswas assessed with the patient sitting with his/herhead neutral and with full protrusion of the tonguewithout phonation, according to the Mallampaticlassification7 as modified by Samsoon and Young.8

Patients were then randomly assigned to either the“sniff” (Group 1) or the “ramped” (Group 2) posi-tion, using a computer-generated list. In order toprevent bias, each prospective position allocationwas placed in a sealed envelope by an independentperson and was opened only after the patient hadbeen recruited to the study and after Mallampatiscore had been ascertained. In order to prevent anunequal number of patients with high Mallampatiscores (III or IV) occurring in either of the two posi-tions by chance, the Mallampati score was used as astratification variable in the randomization.

In the operating room, patients in Group 1 had a7-cm Shea headrest® (Gyrus ENT LLC, Bartlett,TN) placed underneath their occiput (Figure 1). For

Group 2 patients, multiple folded blankets wereplaced under the patient's upper body, head andneck until horizontal alignment between the exter-nal auditory meatus and the sternal notch wasachieved (Figure 2).

Patients were preoxygenated for a minimum of 3minutes with 100% oxygen delivered via a close fit-ting facemask. After administration of fentanyl (100- 150 mcg IV), all patients then underwent a rapid-sequence intravenous anesthetic induction withpropofol (2.5 - 3.0 mg/kg ideal body weight) andsuccinylcholine (1.2 mg/kg lean body weight) whilecricoid pressure was applied. The same anesthesiol-ogist (JSC) performed all the laryngoscopies withthe Video Macintosh Laryngoscope® System(VMS) (Karl Storz Endoscopy-America Inc),9 usingeither a Macintosh 3- or 4-size laryngoscope blade.Although images during laryngoscopy wererecorded onto tape for later review, each patient'strachea was intubated under direct vision only andthe laryngoscopist was blinded from the monitorthat displayed the recorded fiberoptic view.Tracheas were intubated with a styletted endotra-cheal tube (8.0-mm-inner-diameter for men, 7.0-mm-inner-diameter for women).

Three other investigators then reviewed the real-time video recordings of each intubation sequence,and independently assigned a grade to the best viewobtained during each laryngoscopy. Grading was by

Collins et al

1172 Obesity Surgery, 14, 2004

Figure 1. In the operating-room, patients in Group 1 wereplaced supine and had a 7-cm headrest placed under-neath their occiput.

Figure 2. Patients in Group 2 had folded blankets placedunder their upper body, head and neck until horizontalalignment between the sternal notch space and the exter-nal auditory meatus was achieved.

the Cormack-Lehane classification wherein grade 1was complete visualization of the vocal cords, grade2 was partial view of the vocal cords or arytenoids,grade 3 was with only the epiglottis visible andgrade 4 was with no structures visible.10 When a dis-crepancy in a score for a patient occurred betweenany of the observers, the lowest (best) gradeassigned by any of the three scorers was used. Thenumber of attempts at tracheal intubation was noted,as well as the time interval between the start oflaryngoscopy and successful passage of the trachealtube into the trachea.

A power analysis based on previously reportedincidences of laryngoscopy views in morbidly obesepatients in the “ramped”4 and “sniff”5 positionsindicated that approximately 60 patients wouldresult in an 80% chance of obtaining data of statis-tical significance. Continuous variables were com-pared by a two-sample t-test. Categorical variableswere compared by using Fisher’s exact test orPearson's chi-square test. All analyses were per-formed with S-PLUS 6.2® (Insightful Corp, Seattle,WA). Data are reported as mean (±SD). P<0.05 wasconsidered statistically significant.

Results

Eight males and 52 females were studied. Therewere no differences in demographic parametersbetween the two groups (Table 1). There was no sta-tistical difference in thyromental distance and ster-nomental distance, but the inter-incisor gap wassmaller in Group 1 patients and neck circumferencewas larger in the Group 2 patients (Table 1). All tra-cheas were successfully intubated on the firstattempt. Mean intubation time was 21.1 sec ± 5.4 inGroup 1 and 20.6 sec ± 7.6 in Group 2.

In Group 1, the view of the larynx was grade 1 in18 patients and grade 2 in 9 patients. In Group 2, theview of the larynx was grade 1 in 29 patients, grade2 in 3 patients, and grade 3 in 1 patient. There wereno grade 4 views in either group (Table 2). The dif-ference in view on laryngoscopy was significantlydifferent (P=0.037) between the two groups.

Discussion

Some reports have claimed that tracheal intubationmay be more difficult in obese patients.11-13

Distinctions between difficulty with mask ventila-tion, with laryngoscopy and with actual tracheal

Laryngoscopy and Morbid Obesity

Obesity Surgery, 14, 2004 1173

Table 1. Patient characteristics are presented for group1 (supine in a standard “sniff” position) and group 2(“ramped” position with the head, neck and upper bodyelevated until a imaginary horizontal line can be drawnbetween the sternal notch space to the external ear)

GROUP 1 GROUP 2

GenderMale 2 6Female 25 27

Obstructive Sleep Apnea No 18 21

Yes 9 12Mallampati Score

1 9 152 9 113 9 64 0 1

Age (years±sd) 43.3±10.0 41.9±8.9BMI (kg/m2±sd) 46.9±7.1 49.9±6.9Inter-incisor gap * 4.4±0.5 4.8±0.6Thyromental distance 11.1±1.2 11.3±1.0Sternomental distance 16.7±1.5 16.7±1.5Neck Circumference * 43.4±6.7 47.9±5.3

All airway measurements are in centimeters(mean±sd).*P<0.05

Table 2. Comparison of views during laryngoscopy

GRADED VIEW* GROUP 1 (n) GROUP 2 (n)

1 18 292 9 33 0 14 0 0

Three anesthesiologists, unaware as to what positionthe patient had been in at the time of laryngoscopy,assigned grades for the best view obtained using thescale described by Cormack and Lehane. (CormackRS, Lehane J. Difficult tracheal intubation in obstetrics.Anaesthesia 1984; 39: 1105-11).n = number or patients*P=0.037 (Fischer's exact test)

intubation are usually not well defined in these stud-ies. However, several studies have attempted tograde the view obtained by laryngoscopy. In one, 19of 118 (16%) morbidly obese patients had Cormackgrade 3 or 4 views during direct laryngoscopy,14 andin another, 24 of 200 (12%) morbidly obese patientswere classed as grade 3.15 It is interesting to notethat in both these reports, patients were positionedin a standard supine “sniff” position. We observed amuch lower incidence of poor glottic visualizationin the present study. In all our patients, the tracheawas intubated after a single laryngoscopy and nopatient could be described as a “difficult intuba-tion”.

These results differ from a previous report by ourgroup.4 In that study, anesthesia residents were ran-domly assigned to each case and performed all thelaryngoscopies. For this study, all laryngoscopiesand intubations were by the same faculty anesthesi-ologist (JSC) with 15 years of clinical experience.This may partially explain the differences betweenour two reports. The VMS provides a much brighterlight source than a conventional battery-poweredMacIntosh laryngoscope that in turn may improvevisualization. In an attempt to simulate normal illu-mination of the larynx, the brightness setting of theVMS was reduced to 5% of its maximum value forthe present study.

The fiberoptic image on the video monitor comesfrom a light source at the midpoint of the laryngo-scope blade, so the view with the VMS is slightlydifferent from the image seen by the laryngoscopistduring direct laryngoscopy. The images on the mon-itor, which we used for grading, may give a view ofthe larynx that is not absolutely identical to theimage obtained by a standard laryngoscope. Actualintubations were performed using the VMS as a reg-ular laryngoscope, with the laryngoscopist unawareof the video view. We encountered no difficultieswith laryngeal exposure or tracheal intubation. Evenif using the VMS in this manner did provide a moreoptimal view than a conventional laryngoscopeblade, this would not explain the difference wefound, because the same intubation technique wasused for both groups. The VMS also allowed us touse a MacIntosh laryngoscope blade, a blade that isfamiliar to all anesthesiologists.

Since the endoscopist could not be blinded frompatient position during intubation, we used the VMS

to record the laryngoscopy. This allowed investiga-tors who were unaware of patient position to gradethe images, thus eliminating observer bias. To ourknowledge, this has not been done in any previousstudy of laryngoscopy in morbidly obese patients.

Patients in the “ramped” position had better laryn-geal exposure than patients in the “sniff” position.Two previous studies of normal weight patientsdemonstrated improved laryngeal exposure in thesame subject simply by increasing head and neckelevation.16,17 In normal weight patients, the optimalsniff position is achieved by raising the occiput 7cm. This produces approximately 35˚ of flexion ofthe lower cervical spine on the chest. This degree ofneck flexion cannot be achieved by this maneuver inmorbidly obese patients. Their anatomy requiresramping to achieve not only 35˚ of neck flexion onthe chest, but also 90˚ of extension of the head onthe neck at the atlantlo-occipital joint.18 It is possi-ble that ramping obese patients produces the samealignment of the axis of intubation that the sniff pro-duces in normal weight patients.

In conclusion, using two different positions weencountered little difficulty with laryngeal exposureor tracheal intubation in 60 morbidly obese patients.However, the “ramped” position in which the upperbody, neck and head are elevated to a point where animaginary horizontal line can be drawn from thesternal notch to the external ear improved the viewof the larynx during laryngoscopy. Placing morbidlyobese patients in this position could contribute to anincreased rate of successful tracheal intubation inthese patients.

References

1. Wilson ME, Spiegelhalter D, Robertson JA et al.Predicting difficult intubation. Br J Anaesth 1988; 61:211-6.

2. Juvin P, Lavaut E, Dupont H et al. Difficult trachealintubation is more common in obese than in leanpatients. Anesth Analg 2003; 97: 595-600.

3. Dominguez-Cherit G, Gonzalez R, Borunda D et al.Anesthesia for morbidly obese patients. World J Surg1998; 22: 969-73.

4. Brodsky JB, Lemmens HJM, Brock-Utne JG et al.Morbid obesity and tracheal intubation. Anesth Analg

Collins et al

1174 Obesity Surgery, 14, 2004

2002; 94: 732-6.5. Keller C, Brimacombe J, Kleinsasser A et al. The

Laryngeal Mask Airway™ as a temporary ventilatorydevice in grossly and morbidly obese patients beforelaryngoscope-guided tracheal intubation. AnesthAnalg 2002; 94: 737-40.

6. Levitan RM, Ochroch AE. Airway management anddirect laryngoscopy: a review and update. Crit CareClin North Am 2000; 16: 373-88.

7. Mallampati SR, Gatt SP, Gugino LD et al. A clinicalsign to predict difficult tracheal intubation: a prospec-tive study. Can Anaesth Soc J 1985; 32: 429-34.

8. Samsoon GL, Young JR. Difficult tracheal intubation:a retrospective study. Anaesthesia 1987; 42: 487 - 90.

9. Kaplan MB. A new video laryngoscope – an aid tointubation and teaching. J Clin Anesth 2002; 14: 620-6.

10.Cormack RS, Lehane J. Difficult tracheal intubationin obstetrics. Anaesthesia 1984; 39: 1105-11.

11.Benumof JL. Management of the difficult adult air-way: with special emphasis on awake tracheal intuba-tion. Anesthesiology 1991; 75: 1087-110.

12.Adams JP, Murphy PG. Obesity in anaesthesia and

intensive care. Br J Anaesth 2000; 85: 91-108.13. Fox GS, Whalley DG, Bevan DR. Anaesthesia for the

morbidly obese: experience with 110 patients. Br JAnaesth 1981; 53: 811-6.

14.Frappier J, Guenoun T, Journois D et al. Airway man-agement using the intubating Laryngeal Mask Airwayfor the morbidly obese patient. Anesth Analg 2003;96: 1510-5.

15.Ezri T, Medalion B, Weisenberg M et al. Increasedbody mass index per se is not a predictor of difficultlaryngoscopy. Can J Anesth 2003; 50: 179-83.

16.Levitan RM, Mechem CC, Ochroch EA et al. Head-elevated laryngoscopy position: improving laryngealexposure during laryngoscopy by increasing head ele-vation. Ann Emerg Med 2003; 41: 322-30.

17.Schmitt HJ, Mang H. Head and neck elevation beyondthe sniffing position improves laryngeal view in casesof difficult direct laryngoscopy. J Clin Anesth 2002;14: 335-8.

18.Benumof JL. Comparison of intubating positions: theend point for position should be measured.Anesthesiology 2002; 97: 750

(Received August 30, 2004; accepted September 22, 2004)

Laryngoscopy and Morbid Obesity

Obesity Surgery, 14, 2004 1175

publications comparing nerve stimu-lating versus nonstimulating cath-eters (4,5). These studies do not showany benefit of stimulating over non-stimulating catheters. The largest ofthese studies (419 patients), concluded,“a convincing argument has yet to bemade for the routine use of thestimulating catheter . . .” (6).

Ultrasound has been a welcomerelief for those of us who are seekinga better alternative to NS techniques.In 2005, Marhofer reported morethan 4000 blocks performed usingonly ultrasound guidance with suc-cess rates approaching 100% (7).Since that time, his numbers havealmost certainly increased. Regard-ing ultrasound techniques, Marhoferaccurately states, “Nerves are notblocked by the needle but by thelocal anesthetic.” Likewise, at theUniversity of Utah, we stopped usingthe nerve stimulator over 2 years ago.We too, have performed over 3500blocks (2000 catheters) using onlyultrasound guidance. It should be nosurprise that a technique successfulfor single injections would also workfor catheter placement. The result hasbeen a generation of residents fromour program who have learned to“stay away from the nerve with theneedle but reach the nerve with localanesthetic.” A prospective study atour institution shows a success rateof 97% for single blocks and cathetersplaced using only ultrasound guid-ance (8). This same study shows thecost savings (by eliminating the costof stimulating needles) to be more than$16,000/yr when performing morethan five nerve blocks per day.

Ultrasound is ideal for catheterplacement as a “stand alone” tech-nique. We believe the nerve stimu-lation will soon take its place besidethe copper kettle as a technique ofonly historical interest. In otherwords, yesterday’s “gold standard”has become today’s “old standard.”

Jeffrey D. Swenson, MD

Byron Bankhead, MDDepartment of Anesthesiology

University of Utah Orthopaedic CenterUniversity of Utah

Salt Lake City, Utahjeff.swenson@hsc.utah.edu

REFERENCES

1. Chidiac EJ, Perov S. Outpatient continu-ous peripheral nerve catheters. AnesthAnalg 2007;104:1303–4.

2. Hadzic A, Vloka J, Hadzic N, et al. Nervestimulators used for peripheral nerveblocks vary in their electrical characteris-tics. Anesthesiology 2003;98:969–74.

3. Urmey WF, Stanton JS. Inability to consis-tently elicit a motor response followingsensory paresthesia during interscaleneblock administration. Anesthesiology 2002;96:552–4.

4. Hayek SM, Ritchey RM, Sessler D, et al.Continuous femoral nerve analgesia afterunilateral total knee arthroplasty; stimu-lating versus nonstimulating catheters.Anesth Analg 2006;103:1565–70.

5. Morin AM, Eberhart LH, Behnke HK, etal. Does femoral nerve catheter placementwith stimulating catheters improve effec-tive placement? A randomized, controlled,and observer—blinded trial. Anesth Analg2005;100:1503–10.

6. Jack NT, Liem EB, Vonhogen LH. Use of astimulating catheter for total knee re-placement surgery: preliminary results.Br J Anaesth 2005;95:250–4.

7. Marhofer P, Greher M, Kapral S. Ultra-sound guidance in regional anesthesia.Br J Anaesth 2005;94:7–17.

8. Swenson J. Needle costs for ultrasoundvs. nerve stimulator guided single injec-tion and continuous nerve catheters.Cleveland, OH: S262, IARS Clinical andScientific Congress, 2007.

DOI: 10.1213/01.ane.0000260555.24441.53

An Inflatable,Multichambered Upper BodySupport for the Placement ofthe Obese Patientin the Head-ElevatedLaryngoscopy Position

To the Editor:Several articles have appeared in

the anesthesia literature promoting

the use of the head-elevated laryn-goscopy position to facilitate intu-bation in the obese patient (1–3).However, there are several disad-vantages with using blankets as thesupport device. If the initial ramp isnot adequate, the patient must situp again for readjustment. After thetrachea is intubated, the OR staffmust help the anesthesia personnellift the patient to remove the blanketsto reduce the likelihood of brachialplexus injury during the operation.It is almost impossible to replacethe blankets in order to realign thepatient for the best position forairway management after trachealextubation.

We have successfully tested apatent pending inflatable support de-vice on 30 patients undergoing lapa-roscopic gastric bypass surgery. Thedevice is constructed of seven plasticcylinders connected to a controllerthat can inflate all cylinders at onceor inflate three groups of cylindersindividually. This allows for the pa-tient’s back, shoulder, and head to beprecisely positioned to obtain theproper P–S relationship (See Fig. 1).Inflation pressure is provided by themedical air outlet available in everyOR and is attenuated to 3 psi by acontroller. Once the trachea is intu-bated, the air is gradually evacuatedfrom the pillow with a vacuum suc-tion device in the controller. No lift-ing of the patient is required, and thepillow is easily reinflated at the end

Figure 1. Pillow inflated to illustrate proper HELP position.

Vol. 104, No. 5, May 2007 © 2007 International Anesthesia Research Society 1305

Letters to the Editor

of the procedure to best manage theairway after extubation.

Mark D. Nissen, MD

James M. Gayes, MDDepartment of AnesthesiologyAbbott Northwestern Hospital

Minneapolis, MNjgayes@comcast.net

mnissen@aol.com

Conflict of Interest Statement:Drs. Nissen and Gayes are the in-ventors of the pillow discussed inthis Letter to the Editor. The pillow isnot in production and therefore, notcommercially available. There maybe actual or potential financial ben-efit to either author in the futureshould the patent be purchased.

REFERENCES

1. Brodsky JB, Lemmens HJ, Brock, UtneJG. Anesthetic considerations for bariat-ric surgery:proper positioning is impor-tant for laryngoscopy. Anesth Analg2002;95:4793.

2. Levitan RM, Mechem CC, Ochroch EA, etal. Head elevated laryngoscopy position:improving laryngeal exposure during la-ryngoscopy by increasing head elevation.Ann Emerg Med 2003;41:322–30.

3. Collins JS, Lemmons HJ, Brodsky JB, etal. Laryngoscopy and morbid obesity: acomparison of the “sniff” and “ramped”positions. Obes Surg 2004;14:1171–5.

DOI: 10.1213/01.ane.0000260556.78943.c3

Positioning of Obese Patientsin Out-of-OperatingRoom Locations

To the Editor:For the ever-increasing number

of anesthetizing sites out-of-the-operating room (OR), e.g., electro-convulsive therapy or colonoscopies,etc., an OR table is not readily avail-able and a transport gurney is oftenused instead. We have been using3-L bags of irrigation solution (Bax-ter) to achieve the same 25° head-upposition as described by Dixon et al.(1). We may use three to four solu-tion bags, depending on the size ofthe patient (Fig. 1). Two to threesolution bags will be placed behindthe shoulder, and one under thehead. A pillow will be placed overthe solution bags under the patient’sshoulder and another one placedover the solution bag under the head(Fig. 2).

A commercially available Pi’s

Pillow for positioning patients op-timally for intubation costs about$28.00 in the largest size. It is gen-erally not suitable for patients witha Body Mass Index (BMI) in excessof about 35 and is also typically notavailable in out-of-OR locations. Ir-rigation solution bags are availablein most hospitals. They help to padpressure points, and conform readilyto an individual’s body shape. Inaddition, we do not remove themfrom their external wrappings andthus are available for use later fortheir intended function.

One patient with a BMI of 41 wasreferred to our psychiatric depart-ment from an outside facility forelectroconvulsive therapy. He waspositioned easily on a gurney andsuccessfully underwent tracheal in-tubation 12 times using this posi-tioning technique.

Anne B. Wong, MD, MBA

Michael S. R. Moore, MD, MS, MScDepartment of Anesthesiology

University of CaliforniaIrvine Medical Center

Orange, CAsnoozdoc@yahoo.com

REFERENCE

1. Dixon BJ, Dixon JB, Carden JR, et al.Pre-oxygenation is more effective in the25 degree head-up position than in thesupine position in severely obese patients.Anesthesiology 2005;102:1110–5.

DOI: 10.1213/01.ane.0000260362.20204.b6

Preoperative AntibioticAdministration and theSurgical “Time Out”

To the Editor:Recently, O’Reilly et al. (1) de-

scribed the use of an electronic medi-cal record to track the incidence ofpreoperative antibiotic administra-tion. Our similar experience is that

Figure 1. Arrangement of irrigation bags and pillows.

Figure 2. Positioning of patient on irrigation bags.

1306 Letters to the Editor ANESTHESIA & ANALGESIA

Letters to the Editor