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Resuscitation 85 (2014) 553–559

Contents lists available at ScienceDirect

Resuscitation

j ourna l h o me pa g e : www.elsev ier .com/ locate / resusc i ta t ion

imulation and education

randomised control trial of prompt and feedback devices and theirmpact on quality of chest compressions—A simulation study�

oyce Yeunga,b, Robin Daviesc, Fang Gaoa,b, Gavin D. Perkinsa,c,∗

Academic Department of Critical Care, Anaesthesia and Pain, Heart of England NHS Foundation Trust, Birmingham B9 5SS, UKUniversity of Birmingham, College of Medical and Dental Studies, B15 2TT, UKUniversity of Warwick, Warwick Medical School, CV4 7AL, UK

r t i c l e i n f o

rticle history:eceived 20 July 2013eceived in revised form2 December 2013ccepted 5 January 2014

eywords:hest compressioneedback devicesrainingducation

a b s t r a c t

Aim: This study aims to compare the effect of three CPR prompt and feedback devices on quality of chestcompressions amongst healthcare providers.Methods: A single blinded, randomised controlled trial compared a pressure sensor/metronome device(CPREzyTM), an accelerometer device (Phillips Q-CPR) and simple metronome on the quality of chestcompressions on a manikin by trained rescuers. The primary outcome was compression depth. Secondaryoutcomes were compression rate, proportion of chest compressions with inadequate depth, incompleterelease and user satisfaction.Results: The pressure sensor device improved compression depth (37.24–43.64 mm, p = 0.02), theaccelerometer device decreased chest compression depth (37.38–33.19 mm, p = 0.04) whilst themetronome had no effect (39.88 mm vs 40.64 mm, p = 0.802). Compression rate fell with all devices(pressure sensor device 114.68–98.84 min−1, p = 0.001, accelerometer 112.04–102.92 min−1, p = 0.072and metronome 108.24 min−1 vs 99.36 min−1, p = 0.009). The pressure sensor feedback device reducedthe proportion of compressions with inadequate depth (0.52 vs 0.24, p = 0.013) whilst the accelerometerdevice and metronome did not have a statistically significant effect. Incomplete release of compres-sions was common, but unaffected by the CPR feedback devices. Users preferred the accelerometer and

metronome devices over the pressure sensor device. A post hoc study showed that de-activating thevoice prompt on the accelerometer device prevented the deterioration in compression quality seen inthe main study.Conclusion: CPR feedback devices vary in their ability to improve performance. In this study the pressuresensor device improved compression depth, whilst the accelerometer device reduced it and metronome had no effect.

. Introduction

Performing high quality cardiopulmonary resuscitation (CPR)s paramount to patient survival.1–3 Effective chest compressionsf adequate depth could improve coronary perfusion pressure4

nd increase the chance of defibrillation success.5 The chesthould be allowed to recoil between compressions as incom-lete release impedes ventricular filling thus reducing cardiac

utput.6 Interruptions during chest compressions are associatedith worse outcomes and should be minimised.5,7 Despite this evi-ence, observational studies revealed that poor quality CPR was

� A Spanish translated version of the abstract of this article appears as Appendixn the final online version at http://dx.doi.org/10.1016/j.resuscitation.2014.01.015.∗ Corresponding author at: University of Warwick, Warwick Medical School, CV4AL, UK.

E-mail address: g.d.perkins@warwick.ac.uk (G.D. Perkins).

300-9572/$ – see front matter © 2014 Elsevier Ireland Ltd. All rights reserved.ttp://dx.doi.org/10.1016/j.resuscitation.2014.01.015

© 2014 Elsevier Ireland Ltd. All rights reserved.

performed during resuscitation attempts in cardiac arrests in bothout-of-hospital and in-hospital settings.1,2,8,9 Performance must beimproved and quality of CPR in training should be delivered to thehighest standard10 and at optimal intervals.11,12

The unpredicted and often stressful nature of cardiac arrestsmeans that translating training to clinical practice remainschallenging.13 One particular problem was the lack of an objectivereal-time feedback available to guide resuscitation team perfor-mance. With the technological advances over the years, a growingnumber of different prompt and feedback devices have been devel-oped for use in both training and in real life.14 These range incomplexity from a simple metronome to audio-visual feedbackincorporated into defibrillators. A recent systematic review foundevidence that these devices may help rescuers improve CPR per-

formance in training and clinical setting.14 To this date, the use offeedback devices are still mostly confined to the research settingand have yet to prove popular or widespread in the clinical set-ting. This could be due to the lack of supporting evidence for their

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54 J. Yeung et al. / Resusc

se and proven improved patient outcome. Previous studies haveompared the use of prompt and feedback devices on the qualityf chest compressions, ventilation and hands off time comparedo control group with no device.15–19 To date, there are no ran-omised controlled trials comparing different devices against eachther. This study aims to compare the impact of different promptnd feedback devices on quality of chest compressions.

. Methods

.1. Setting and participants

The study protocol was approved by Coventry Research andthics Committee (09/H1210/4). This was a single centre ran-omised controlled study (Fig. 1). Participants attending Immediateife Support (ILS) courses at Heart of England Foundation NHS Trustrom December 2009 to August 2010 were invited to participate.n information letter and consent form was posted to each partic-

pant 2 weeks prior to the course date. Participants were excludedf they had previously taken part, or they withheld their consent orf they were physically unable to perform 2 min continuous chestompressions.

Sample size was calculated to detect a 5 mm difference in chestompression depth with 90% power at a significance level of 0.05. 24articipants would be required in each arm of the study. As followp testing would be carried out on the same day, there would beinimal loss to follow up, one extra person per group was recruited

ue to possible technical issues. A control group was needed toomplete the study making the total number of participants to beecruited to be 100.

The primary outcome of the study was chest compression depth.econdary outcomes were compression rate, proportion of chestompressions with inadequate depth and incomplete release andser satisfaction scores of each device.20

Before they could take part in the study, all participants had toemonstrate that they could perform chest compressions to theequired ILS standard. To ensure that all participants were familiarith the devices, devices were demonstrated with brief instruc-

ions of use and each participant had up to 15 min to practiceith each device. Participants were randomised in blocks of 4

nto groups: control (no device), CPREzy, QCPR and metronome,sing random numbers generated by Microsoft Excel 2007. Thearticipants were asked to perform continuous chest compressionsithout any device for 2 min on a manikin as baseline perfor-ance. After 1 h of rest, participants were asked to perform another

min of continuous chest compressions on a manikin using theirllocated devices. The control group was asked to perform chestompressions to a depth of 38–51 mm and at a rate of 100 min−1 tohe best of their ability with no device. Resusci® Anne AdvancedkillTrainer manikins used were calibrated using a LUCASTM-2evice (Physio-Control Inc., US) to ensure that uniformity in CPRensing performance. Quality of CPR parameters from the manikinas captured by PC SkillReporting software (Laerdal, UK).21 To sim-late cardiac arrests in hospital setting, all chest compressions werearried out on a manikin placed on a standard foam mattress in aed raised to mid-thigh level for optimum position.22 At the end ofheir tests, participants were asked to score the device on usability,omfort, distraction and confidence using a Likert score.

.2. Feedback and prompt devices tested

.2.1. Pressure sensor device with metronome (CPREzy)CPREzy is a portable real-time feedback device based on

ressure sensing technology. It is designed to be placed onatient’s sternum underneath the rescuers’ hands during chest

n 85 (2014) 553–559

compressions.16,23 The device gives an audible tone at 60 dB(30 cm from device) at a rate of 100 beats per minute and hasa spring mechanism which detects applied force and provides avisual indication of the correct pressure for patients in differentweight categories.24 The light displays include ‘child/40 kg’, ‘smalladult/55 kg’, ‘average adult/75 kg’, ‘large adult/90 kg’ and ‘extralarge adult’. In this study, the participants were instructed to aim fora weight of average size adult/75 kg and perform one compressionper beat of the device.

2.2.2. Accelerometer device integrated in a defibrillator (MRXQCPR)

The Phillips MRX QCPR Defibrillator Management and FeedbackTool consists of a reusable compression sensor to go between thehands of the CPR provider and the victims sternum during chestcompressions. Its accelerometer technology measures both forceand acceleration, enabling the capture of compression depth.25

Visual feedback of compression is displayed by wave for depthand a number for rate on monitor; verbal guidance is also pro-vided if depth or rate falls outside guidelines. The system usedwas set up according to the 2005 European Resuscitation Coun-cil Guidelines.26,27 A previous study has demonstrated that theaccelerometer feedback device could overestimate chest compres-sion depth by up to 35–40% when performed on manikin placedon foam mattress.28 To compensate for this, the participants wereasked to perform chest compress until the displayed waveformreached below the lower blue line (representing compressiondepth of 51 mm) and aimed for a displayed rate of 100 min−1.

2.2.3. MetronomeA simple mechanical metronome was used to provide audio tone

of 100 min−1. The participants were instructed to perform one com-pression per beat of the metronome. No further guidance on chestcompressions was provided by metronome other than rate.

2.3. Data collection and analysis

Background information about the participant was recordedincluded age, gender and height. Quality of CPR data was collectedand downloaded directly from manikin. Performance data includedrate and depth of chest compressions, number of compressionswith incomplete release. Normally distributed data was analysed 2sided t tests. Differences in proportions were compared by Mann UWhitney test. A p value of <0.05 was considered significant.

User satisfaction questionnaires were given to participantsusing Likert scales (0–5) were used to assess the ease of use, com-fort, level of distraction and confidence associated with allocateddevices.

3. Results

A total of 107 participants were invited to participate in thestudy. Four people were excluded from the study: one persondeclined to take part and three people had already taken part andwere repeating the course. At first testing, two participants wereunable to perform continuous chest compressions for 2 min andwithdrew from study (one from Pressure sensor feedback devicegroup and one from control group). A total of 41 546 chest com-pressions were analysed.

The mean age of participants was 35 years old with a range of

22–56 years old. The gender ratio of our sample was representativeof hospital nursing staff with 36 (36%) participants were men and65 (64%) women. The mean height of participants was 165 cm witha range of 147–188 cm. There were no significant differences in

J. Yeung et al. / Resuscitation 85 (2014) 553–559 555

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Fig. 1. RCT of feedback and prom

eight (p = 0.07), age (p = 0.768) and gender (p = 0.194) across thellocated groups (Table 1).

.1. Quality of chest compressions

.1.1. Mean chest compression depth (mm)There were no significant differences in baseline mean com-

ression depth (p = 0.824) between the groups (Table 2). The usef pressure sensor device significantly improved chest compressionepth from 37.24 mm to 43.64 mm (p = 0.02). The use of accelerom-ter device significantly decreased chest compression depth from7.38 mm to 33.19 mm (p = 0.04). The metronome did not affectompression depth (39.88 mm vs 40.64 mm, p = 0.802).

.1.2. Mean chest compression rate (n/min)There was no significant difference in baseline mean com-

ression rate (p = 0.622) between the groups (Table 2). The usef prompt and feedback devices led to significantly reduced

hest compression rate closer to 100 min−1 with pressure sensoreedback device (114.68–98.84 min−1, p = 0.001) and metronome108.24 min−1 vs 99.36 min−1, p = 0.009), with accelerometer

able 1haracteristics of participants.

Device Male/n (%) Mean age/years (SD) Mean height/cm (SD)

QCPR 7 (26.9%) 37.38 (9.86) 163.19 (5.09)CPREzy 6 (24%) 34.04 (9.46) 167.64 (9.14)Metronome 8 (31.6%) 32.88 (9.71) 166.12 (8.92)Control 6 (24%) 37.88 (9.20) 164.62 (7.17)

vices in ILS training (CONSORT).

feedback device approaching significance (112.04–102.92 min−1,p = 0.072).

3.1.3. Proportion of compressions with inadequate depth (%)Baseline performance of our participants was poor with up to

54% of compressions with depths lower than 38 mm (Table 3). Theuse of pressure sensor feedback device reduced the proportion ofcompressions with inadequate depth (0.52 vs 0.24, p = 0.013). Theuse of accelerometer feedback device increased the proportions ofcompressions with inadequate depth but did not reach statisticalsignificance (0.54 vs 0.82, p = 0.068).

3.1.4. Proportion of compressions with incomplete release (%)Almost a third of baseline chest compressions in our sample had

incomplete release (Table 3). Accelerometer feedback device wasthe only device which reduced the proportions of chest compres-sions with incomplete release but the result did not reach statisticalsignificance (0.29 vs 0.09, p = 0.079).

3.2. User satisfaction

Although the use of pressure sensor feedback device improvedthe performance, it scored poorly in ease and comfort of use inour study. The users also found it distracting to use with mediumconfidence in their performance when using the device. Both

metronome and accelerometer feedback device were well receivedby the users who found them easy and comfortable to use, withprovided users with confidence in their performance with minimallevels of distraction (Table 4).

556 J. Yeung et al. / Resuscitation 85 (2014) 553–559

Table 2Compression depth and rate with different device.

Mean compression depth (mm) (SD) Mean compression rate (n/min) (SD)

Base Test p Base Test p

QCPR 37.38 (8.9) 33.19 (4.9)↓ 0.04 112.04 (23.4) 102.92 (9.6) 0.072CPREzy 37.24 (10.0) 43.64 (8.8)↑ 0.02 114.68 (19.7) 98.84 (12.4)↓ 0.001Metronome 39.88 (11.7) 40.64 (9.6) 0.802 108.24 (13.9) 99.36 (8.0)↓ 0.009Control 38.48 (13.6) 39.2 (14.0) 0.855 109.32 (23.3) 105.96 (20.7) 0.592

Table 3Proportion of compressions too shallow and with incomplete release.

Proportion of compressions with inadequate depth (%) Proportion of compressions with incomplete release (%)

Base Test p Base Test p

Accelerometer device 0.54 (0.42) 0.82 (0.28)↑ 0.068 0.29 (0.48) 0.09 (0.14) 0.079Pressure sensor 0.52 (0.43) 0.24 (0.36)↓ 0.013 0.25 (0.38) 0.33 (0.43) 0.622Metronome 0.42 (0.45) 0.39 (0.43) 0.873 0.21 (0.34) 0.26 (0.34) 0.374Control 0.46 (0.47) 0.42 (0.44) 0.6 0.23 (0.36) 0.18 (0.28) 0.529

ILS par�cipant s (n=20)

Rand omise d (n=20 )

Allocated to ‘deep compression’ aud io feedba ck ON (n=10)

Allo cated to ‘dee p compression’ aud io feedback O FF (n =10)

Analysed (n=10) • Excluded (n=10)

Analysed (n=10) • Exclud ed (n=0)

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Lost to follow up (n=0 ) Lost to follow up (n=0 )

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Fig. 2. Extended study comparing ‘deep compres

.3. Post hoc evaluation of accelerometer feedback device deepompression feedback

Accelerometer feedback device performed poorly in our studyue to the previously reported inability to compensate for mattress

able 4edian user satisfaction score (score out of 5: 1 = worst, 5 = best).

Median scores Pressure sensor Accelerometer Metronome

Ease of use 2 5 5Comfort of use 1 4 4Level of distraction 2 4 4Level of confidence 3 4 4

udio feedback of accelerometer feedback device.

movement for up to 26.2 mm in foam mattress28 during the study.We hypothesised that by muting the deep compression feedbackfeature on the system would lead to a different result. The study wasextended and 20 additional trained ILS providers were randomisedinto two groups: accelerometer feedback deep compression on,accelerometer feedback deep compression off (Fig. 2). Followingthe same format of the original study, each participant performedcontinuous compressions for 2 min as baseline performance. After1 h rest, each participant then performed chest compression with

accelerometer feedback device according to their allocation (deepcompression on or off).

Baseline performance in chest compression depth (p = 0.968),rate (p = 0.7), proportion of compressions with insufficient depth

J. Yeung et al. / Resuscitation 85 (2014) 553–559 557

Table 5Effect on compression depth and rate with accelerometer device ‘compression too deep’ audio feedback.

Mean compression depth (mm) Mean compression rate

Base Test p value Base Test p value

Device audio ‘compression too deep’ ON 35.5 (12.6) 34.5 (9.2) 0.842 109.3 (10.3) 108.6 (8.5) 0.87Device audio ‘compression too deep’ OFF 35.7 (8.9) 38.0 (3.9) 0.463 106.4 (21.0) 100.8 (10.4) 0.46p value 0.968 0.282 0.70 0.083

Proportion of compressions with insufficient depth Proportion of compressions with incomplete release

Base Test p value Base Test p value

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0.907) and incomplete release (0.829) were not statistically dif-erent. With the muting of deep compression feedback, meanompression depth increased with a corresponding reduced pro-ortion of chest compression with inadequate depth but did noteach statistical significance (Table 5). The muting of the deepompression feedback led to significantly lower proportion of com-ressions with incomplete release, suggesting that incompleteelease feedback was more effective in this setup (p < 0.009).

. Discussion

Studies in the early 1990s first identified that better quality CPRould improve patient survival.29,30 Optimising chest compressionepth and rate and limiting interruptions in compressions (partic-larly before defibrillation) can improve patient outcome.27,5,31,32

o far, the evidence has been largely supportive in demonstrat-ng that feedback or prompt devices are associated with improveduality of CPR.14 However none of the studies to date have hadufficient power to show improved patient outcomes (return ofpontaneous circulation, neurologically intact survival, etc.) withPR feedback or prompt devices. A number of examples exist wherearly evidence of efficacy33,34 failed to translate into improvedatient outcomes (e.g. ACD-CPR35 and Autopulse chest compres-ion device36). There is an ongoing clinical trial evaluating thempact of real-time CPR feedback and post event debriefing onuality of CPR and patient outcome. The awaited results will shedurther light on the use of feedback devices.37

This study was the first randomised controlled trial that com-ared the impact of different prompt and feedback devices on theuality of chest compressions. Our results showed that althoughhe use of some feedback devices in trained ILS providers couldead to improved chest compression performance not all of themed to improvement.

Our study demonstrated that the use of pressure sensor feed-ack device improved quality of chest compressions similar torevious studies. Compressions were deeper, compliance with rateas better and more compressions were effective.16,23 Beckers et al.

ound similar improvements with pressure sensor feedback deviceCPREzy) in quality of chest compression in training but the posi-ive effect was lost after one week at retest.38 Perkins group alsohowed significant improvement with mean compression depthCPREzy device 42.9 mm vs no device 34.2 mm, p = 0.001) but inontrast to previous findings, they found a higher proportion ofhest compressions with incorrect hand position (device 26% vs noevice 3.9%, p < 0.001).17 95% of their participants reported handnd wrist discomfort and also a case of soft tissue injury resultedhen a participant’s finger was caught between the compression

late and the fixed light indicator box. Any discomfort experiencedould be explained by additional force but Van Berkom and col-eagues examined the amount of force associated with the use ofPREzy pressure sensor feedback device and found that no extra

0.796 0.164 (0.34) 0.172 (0.28) 0.2470.739 0.194 (0.27) 0.057 (0.08) 0.009

0.829 0.225

force was required but additional work of 21–26.5% was needed tocompress the springs to overcome the further distance.39

Our findings that a simple metronome improved chest com-pression rate but did not impact on chest compression depthconcurred with three non-randomised cross-over studies thatshowed improved chest compression rate and end-tidal CO2.15,40,41

It was reassuring that there was no deterioration in compres-sion depth as seen in Oh’s study when audible tone improved therates of chest compressions and ventilation but reduced depth ofcompressions.42 A metronome could also be designed to guide bothcompression and ventilation to limit hands off time.43,44 A recentstudy by Bohn found that even limited metronome and visual feed-back may be sufficient to improve performance and the addition ofvoice prompts provided no additional benefits.45

In contrast to previous positive studies showing that the intro-duction of CPR feedback or prompt devices in clinical practiceimproved CPR performance,27,46–49 accelerometer feedback deviceuse in our study led to reduced mean compression depth andincreased the proportion of compressions with insufficient depth.Kramer-Johansen et al. found that the introduction of real-timeautomatic audiovisual feedback (a prototype Phillips defibrilla-tor MRx Q-CPR) led to significant increase in chest compressiondepth with the percentage of chest compressions with correctdepth doubling and excessively high ventilation rates reduced inparamedics.27 Abella’s group also found an improvement in meanchest compression depth, rate, ventilation rate and no flow frac-tion after the introduction of accelerometer feedback device (QCPR)but these were not statistically significant and no survival benefitwas found.50 Niles and colleagues found that the accelerome-ter feedback system reduced incomplete release (feedback device1.6 kg vs no feedback 2.5 kg, p < 0.001) and lowered proportions ofchest compressions with incomplete release >2.5 kg (device 27%vs no feedback 50%, p < 0.0001) during paediatric resuscitation.51

Accelerometer feedback device did not reduce incomplete releasein the first part of our study but was instead reduced in the extendedpart of the study when deep compression was switched off, sug-gesting that participants may have been able to discern chest recoilwhen not overwhelmed by too many feedback prompts. By mut-ing the deep compression feedback in the extended part of ourstudy, we attempted to overcome the overestimation of chest com-pression depth by accelerometer feedback system. Our participantswere instructed to compress beyond the second line (usually indi-cating 51 mm) on the visual display. With the deep compression‘off’ setup, we were able to mitigate some but not all of the over-estimation of compression depth. Our small sample size in theextended study meant that no firm conclusions can be drawn andfurther investigation into audio feedback of chest compression

depth to guide users accurately is warranted.

Our participants did not like pressure sensor feedback device,scoring it low in ease of use, comfort and level of distraction.Our participants liked both the accelerometer feedback device and

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etronome and scored them highly. The authors believed thatanufacturers should design feedback devices with the users inind. An ideal device should give users confidence in their own

erformance, and is easy and comfortable to use with minimal dis-raction. Our study participants were allowed to test the devicesith minimal disruption to allow for optimal performance. Thisould be very different compared with real life cardiac arrestshen constant noise, interruptions and confusion are common.ew portable standalone device such as PocketCPR52 will add to

he armoury of devices available but this study had highlightedhat an ideal device does not yet exist.

One of the main drawbacks of this study was that it was carriedut on manikin in a training environment. The unpredictable naturef cardiac arrests meant that a similarly designed randomised con-rolled trial of feedback devices would be impractical to carry out inhe clinical setting. Whilst manikins are good tools in training, theyo not provide the same sensation or experience of chest compres-ions on patients. Our results suggest that pressure sensor feedbackevice was superior compared with the others, but this had noteen verified in the clinical setting. Our study only examined 3evices, ranging in complexity and types of feedback and promptsrovided. There were many other available devices that had noteen able to be included for logistics reasons.

We elected to concentrate on the evaluation of the quality ofhest compression performance on manikin in training condition.entilation was not tested in our study due to the inability toapture ventilation data accurately from many existing feedbackevices. Chest compression performance is a result of complex

nteractions and may not be fully explained by simply examiningepth, rate and incomplete release. Our study did not look at the

mpact of prompt and feedback devices on rescuer fatigue as ourarticipants were only asked to perform 2 min of continuous chestompressions during the test.

Our study participants were healthcare professionals who wereeceiving immediate life support training and our results mayot be applicable to layperson. Performances might have been

mproved if participants were given more time to practice andamiliarise themselves with the devices. However, brief instruc-ions were given intentionally to replicate how a rescuer whonly uses a device infrequently might perform in practice. In fact,ntroducing devices without proper training have not been showno be beneficial and can even be detrimental to CPR performance.ur study was undertaken according to 2005 resuscitation coun-il guidelines, it is unclear what the effects of feedback devices onuality of chest compression will be with the current 2010 guide-

ines.

. Conclusions

The use of pressure sensor feedback device improved chest com-ression depth and rate, but did not improve incomplete release.he use of metronome led to improved compression rate compli-nce without sacrificing adequate depth. Accelerometer feedbackevice led to a reduction in chest compression depth. Pressure sen-or feedback device was found to be the most unpopular devicen our participant sample. Whilst real time prompt and feedbackevices may be able to give objective assessment of our CPR per-ormance, they will not replace high quality effective training andimely refresher updates. The impact of different feedback devicesn CPR performance in the clinical setting is yet to be elucidated.

onflict of interest statement

JY was a Resuscitation Council UK research fellow. The authorseclared no conflict of interests.

2

n 85 (2014) 553–559

Acknowledgement

The authors would like to thank the participants and the Resus-citation Department at Heart of England NHS Foundation Trust.

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