home          
       

The Journal of Maternal-Fetal & Neonatal Medicine

Comparison of positive pressure ventilation devices in a newborn manikin

Anne Lee Solevåg MD, PhD, Enrico Haemmerle PhD, Sylvia van Os RRT,Katinka P. Bach MD, PhD, Po-Yin Cheung MBBS, PhD & Georg M. SchmölzerMD, PhD

To cite this article:Anne Lee Solevåg MD, PhD, Enrico Haemmerle PhD, Sylvia van Os RRT,Katinka P. Bach MD, PhD, Po-Yin Cheung MBBS, PhD & Georg M. Schmölzer MD, PhD (2016):Comparison of positive pressure ventilation devices in a newborn manikin, The Journal ofMaternal-Fetal & Neonatal Medicine, DOI: 10.1080/14767058.2016.1180360

To link to this article:http://dx.doi.org/10.1080/14767058.2016.1180360

Accepted author version posted online: 18Apr 2016.
Submit your article to this journal
Article views: 13
View related articles
View Crossmark data

Comparison of positive pressure ventilation devices in a newborn manikin

Volume-controlled ventilation

Anne Lee Solevåg MD, PhD1,2,3, Enrico HaemmerlePhD4,Sylvia van OsRRT1,Katinka P.BachMD, PhD5, Po-Yin CheungMBBS, PhD1,2, Georg M. SchmölzerMD, PhD1,2

1Centrefor the Studies of Asphyxia and Resuscitation, Neonatal Research Unit, Royal Alexandra Hospital, Edmonton, Canada

2Department of Pediatrics, University of Alberta, Edmonton, Canada

3Department of Pediatric and Adolescent Medicine, Akershus University Hospital, Lørenskog, Norway

4School of Engineering, Auckland University of Technology, New Zealand

5Newborn Services, Auckland City Hospital, Auckland, New Zealand

Corresponding author:

Volume-controlled ventilation

Anne Lee Solevåg, MD, PhD
Neonatal Research Unit, Royal Alexandra Hospital,
10240 Kingsway Avenue NW,
T5H 3V9, Edmonton, Alberta, Canada
Telephone +1 780 655 0445, Fax: +1 780 735 4072, Email: a.l.solevag@medisin.uio.no
5Newborn Services, Auckland City Hospital, Auckland, New Zealand

Word count abstract: 200

Word count manuscript including abstract:2649

Key words: Tidal volume, resuscitation, ventilationrate

ABSTRACT

Objective

Tocompare tidal volume (VT)delivery and ventilation rate between devices for positive

pressure ventilation (PPV) during newborn resuscitation.

Methods

Neonatal Resuscitation Program providers(n=25)delivered PPV to a newbo rn manikin in a randomized order with: a self-inflating bag (SIB), a disposable T-piece, a non- disposable T-piece, a stand-alone infant resuscitation system T-piece,and the volume-controlled prototype Next StepTM device (KM Medical).All T-pieces used a peak inflation pressure of 20cmH2O and a 5cmH2O positive end-expiratory pressure (PEEP). The SIBneither had a PEEP valve nor manometer. The Next StepTM had a 5cmH2O PEEPvalve. The participants aimedto deliver a 5mL/kgVT (rate 40-60min-1) for 1min with each deviceand each of three compliances (0.5, 1.0 and 2.0mL/cmH2O).VTand ventilation rate were compared between devicesand compliance levels

Results

All devices, except the Next StepTM delivered a 4-5mL/kg VTat the low compliance, but three-to four-fold that of the target at the higher compliance levels. The Next StepTMdelivered a VT close to target at all compliancelevels. The ventilation rate was within 40-60min-1 with all devices and compliance levels.2.0mL/cmH2O).VTand ventilation rate were compared between devicesand compliance levels

Conclusions

Rou tinely used ventilation devices for newborn resuscitation can triple intended VT and requires further investigation.

To link to this article:http://dx.doi.org/10.1080/14767058.2016.1180360

INTRODUCTION

During lung liquid clearance at birth and initiation of breathing,lung mechanics rapidly change.[1]If positive pressure ventilation (PPV) is required the operator should adjust inflation pressure and time to deliver an adequate tidal volume (VT).[2]However, currently a set peak inflation pressure(PIP)is used during PPV with the assumption this will deliver an adequate VT. As airway compliance increases, excessive VT may be delivered unless VT measurementsare used to titrate inflation pressure. Increasing evidence suggests that excessive VTmight cause overexpansion of the lung leading to volutrauma.[3]Animal studies indicate that lung injury occurs after only a few large inflations[4]and pulmonary interstitial edema can be demonstrated after only 2-5min of PPV in rats.[5]Hernandez et al[6]made similar findings in rabbits. However,when VTwas controlled, little or no injury occurred.[6, 7]Similar results have been described for volume-targeted ventilation in the Neonatal Intensive Care Unit(NICU).[8]

Modern mechanical ventilators use flow sensors to deliver volume-targeted ventilation;however,commonly used neonatal resuscitation devices[9, 10](e.g. self-inflating bags or T- pieces) are pressure-limited. VT, airway pressure and ventilation rate are operator-dependent and highly variable, especially instressfulsituations, increasing the potential risk of volutrauma. Mask leak or airway obstructionfurther complicate VTdelivery.[11]

The aim of this study was to assess VT and ventilation rate with commonly used resuscitationdevices.For comparison, we added a prototype designed to deliver a predetermined V T and ventilation rate irrespective of airway compliance (Next StepTM, KM Medical, Auckland, NZ). We hypothesized that the VT delivered by pressure-limited devices would be higher than that by the volume-controlled Next StepTM device.

Methods

Environment and subjects

The study was performed at The Royal Alexandra Hospital, Edmonton, a tertiary perinatal center with >7,000 deliveries, and approximately 1,500 NICU admissions annually. In April 2015 Registered Neonatal Resuscitation Program (NRP) healthcare professionals were included in the study.

Randomization

This was a prospective randomized crossover study. All participants performed PPV with five ventilation devices in a randomized order. The primary investigator (ALS) conducted the randomization using an online tool (http://www.randomizer.org)and a code list. The trial was a manikin study and was not registered in the clinical trials database(clinicaltrials.gov).

Sample Size Estimation

A sample size of 25 NRP providers would be sufficient to detect a 40% lower VT with the volume-controlled Next Step TM compared to the pressure-limited devices, which we considered clinically important with 80% power and a 2-tailed alpha error of 0.05.

Manikin

We used aBaby Care Model Male (3B Scientific GmbH, Hamburg, Germany)with a leak-free ‘endotracheal tube’bypassing the manikin’s chest withthe VTflowing directly to three externally placed test lungs with different compliances. The manikin resembled a term infant and did not exhibit chest excursions during ventilation.

Test lungs

The aluminum cylinder test lungs were filled with copper wool for temperature stabilisation and calibrated to their respective compliance using a volume calibration syringe. InspiratoryVTwas determined by measuring pressure with a solid state low - pressure sens or inside the test lungs, sampled with an Analog-to-Digital Converter and converted to VT for a given compliance value using LabVIEW software(National Instruments Corp.,Austin, TX).Airway pressures were recorded in close proximity to the manikin valve using a solid state pressure sensor. In agreement with delivery room(DR)data,[12]the compliances used were i) 0.5mL/cmH2O, ii) 1.0mL/cmH2O, and iii) 2.0mL/cmH2O, respectively. The test lungs were kept in a case and connected to the manikin’s upper airways by rubber tubing, the ‘endotracheal tube’. Prior to each study day the test lungs were checked for accuracy using a10mL glass syringe.

Ventilation devices

Prior to study commencement the participants had time to get familiar with each device. 1) A self-inflating bag (SIB) with a 35cmH2O pop-off valve (Laerdal Medical, Stavanger, Norway), no positive end-expiratory pressure (PEEP) valve or manometer;2) Neo-Tee disposable T-piece(Mercury Medical, Clearwater, FL);3) NeopufTMInfant T-Piece (Fisher&Paykel, Auckland, NZ);4) Giraffe Stand-aloneInfant Resuscitation System T-Piece (GE Healthcare, Buckinghamshire, UK);and 5) TheNext StepTM with a 5cmH2O PEEP valve.All T-pieces were used with a peak inflation pressure (PIP) 20cmH2O and PEEP 5cmH2O.The Next Step™ (Figure I) controls VTand ventilation rate, but not pressures.The 800gprototype is operated via a laptop computer displaying real time PIP, PEEP and VT.According to the manufacturer, the device delivers VTwith an accuracy of 0.1-0.3mL and has an internal battery life of 4hin the standard configuration. The device can be attached to a JUST ACCEPTED Downloaded by [Auckland University of Technology] at 14:14 03 May 2016 facemask or endotracheal tube.

Experimental protocol

Each participant used all five ventilation devices consecutively in arandomized order, with each device used for 3 x 1min (1min for each compliance level)at a rate of 40-60 min-1.The set Next StepTMventilation rate was 50min-1. The 1min ventilation sessions were separated by a few seconds forchange ofairway compliance and/or device. The compliance levels were used in a predetermined order (0.5, 1.0, and 2.0mL/cmH2O)for each deviceto simulate the changing airway compliance after birth.[12, 13]Theparticipants knewthat thecompliancewould change, but were unaware of the order of the levelsfor each device. Since small preterm infants are the most prone to ventilation-induced lung injury,[14]the experiment simulated PPV in a1kg infantwith a 5mL target VT.[15]During the experiments, participants were reminded of the targeted VT, but could only use the T-piecemanometers for feedback on ventilation.After completion of the study participants answereda brief questionnaire. Questions included: i) “Difficulty of providing PPV with each device”; ii) “Comfort with each device toprovide PPV”; iii) Preferred device; as well as profession, years of experience, and gender. Questions i) and ii) wererated using a Likert Scale (1=verydifficult/uncomfortable to 5=very easy/comfortable).

Data processing and statistical analyses

Demographocal data and device preferences are presented as number (percent), or median (range)or (interquartile range(IQR)). The primary outcomesof the study wereVTandventilation rate with each device andcompliance level. The median VTIQRwascompared between devices as a measure of variability. Comparisons between devices and compliance levels were performed usingFriedman’s ANOVA followed by post hocanalysis withMann Whitney Utest.Statistical analyses were performed in IBM SPSS Statistics 22 (IBM Corporation, Armonk, NY). A p-value 0.05 was considered significant.Data are presented asmedian (range)or (IQR).

Data processing and statistical analyses

Demographocal data and device preferences are presented as number (percent), or median (range)or (interquartile range(IQR)). The primary outcomesof the study wereVTandventilation rate with each device andcompliance level. The median VTIQRwascompared between devices as a measure of variability. Comparisons between devices and compliance levels were performed usingFriedman’s ANOVA followed by post hocanalysis withMann Whitney Utest.Statistical analyses were performed in IBM SPSS Statistics 22 (IBM Corporation, Armonk, NY). A p-value 0.05 was considered significant.Data are presented asmedian (range)or (IQR).

Ethics statement

The Northern Alberta Neonatal Program Research Committee and Health Ethics Research Board, University of Alberta approved the study. Written informed consent was obtained from the participants

RESULTS

Twenty-five NRP providers participated(neonatologists (n=5), neonatal-perinatal fellows (n=3), neonatal nurse practitioners (n=3), registered respiratory therapists (n=7)and registered nurses (n=7)). Seventeen (68%) were female. Participants had a median (range) of 11 (1-32) years of neonatal experience, and 7 (1-24) months had passed since their last NRP update. Questionnaire resultsare presented in Table I. Eleven(44%)participants preferredtheNeopuff, eight(32%) the Next StepTM, four(16%) the Giraffe Stand-alone Infant Resuscitation System T-Piece, one(4%)the SIB, and one (4%) did not specify a preferred device.

Tidal volume delivery

The Next StepTM delivered the most consistent VTat all compliance levels (Table II). However, the accuracy was lower than described by the manufacturer (0.1-0.3mL). Atthe0.5mL/cmH2O compliance VTwith the SIB was closer to the 5mL/kgtarget and significantly higher than with all the other devices(Table II; p0.005). VT with thethree T-pieces was only closeto targetatthe0.5mL/cmH2O compliance. All devicesexcept the Next StepTMdelivered a 3-4 fold greater VT than target withincreasing compliance, with the highest VT delivered by the SIB(Table II).

Variability of VT delivery

The VT IQR for all devices was larger compared to the Next Step TMat all compliance levels (p0.001), with the largest variability for the SIB (p0.01)compared to each of the T-pieces. The VT IQR was not different between the T-pieces at any compliance level.

Ventilation rate

Ventilation rateThe ventilation rate with the Next StepTMwas 50min-1at all compliance levels. The ventilation rate was also within 40-60min-1at all compliance levels with the SIB and the T-pieces and not different between devices at any compliance level (data not shown).

DISCUSSION

Our study is the first to compare VTatdifferent airway compliancesusinga SIB,three T-piece resuscitators and a prototype volume-controlled resuscitator ina randomized, controlled fashion. VTwas3-4 fold higher thanrecommended with widelyused neonatal resuscitation devicesat high airway compliance,whereas VTwas in therecommended range withthe volume-controlled resuscitator. As the lung compliance increases rapidly after birth,[12]the risk of excessive VTis substantial i corrective actions during PPV are not taken. Interventions including ventilation strategy the first minutes after birth may have long-term consequences, particularlyto the extremely preterm infant.[16]Even brief exposure to high VT may cause bronchopulmonary dysplasia (BPD)in preterm infants. Mian et al[17]also showed that excessive VT during DRresuscitation may be associated with an increased risk of intraventricular haemorrhage. In our study,commonly used DR resuscitation devices delivereda 4-5mL/kg VTat low compliance. However, VTincreased3-4 fold as compliance increased. This is supported by other studies. Huynh et al[18]reported that using a SIB anda lung simulator a mean (standard deviation) VTof 4.0 (2.1) and 13.1 (5.0)mLwas deliveredat low (0.5mL/cmH2O) and high (1.0mL/cmH2O) compliance, respectively. In a 1kg leak-free intubated infant manikin with a lung compliance of 0.2mL/kPa (~2.0mL/cmH2O),Roehr et al[19]compared VTwith a SIB (1-14.6mL) and the Neopuff (1.3-5.7mL). Although we measured higher VT with both devices, our results confirm a higher and morevariable VT withthe SIB compared to the T-pieces.

Participants inthe current study could notadjust the T-piece PIP, which might have yieldeda higherVTthan if they coulddecrease PIP as compliance increased. However, although recent studiesindicate that compliance canbe sensed duringSIBPPV,[20]we did not demonstrate a lower VTwiththe SIB at higher compliances. In agreement with this, Hyunh et al[18]showed that most participants were unable to assess VTdelivery during compliance changes, and thus would have failed to take corrective actions (e.g. adjust PIP).
The lightweight and portableSIB is the most commonly used manual ventilation device globally.[21]T-piecesrequire a pressurized gas source, butdeliver more consistent VT[19]and pressure[10]thana SIB,and candeliver a sustained inflation and continuous positive airway pressure.[22]These advantages have been described for non-disposable T-pieceslike the Neopuff. Less is known about disposable T-piece resuscitators like theNeo-Tee.Krabbe etal[23]showed that for commonly used PIP and PEEP, the Neopuff and the Neo-Tee are comparable.No study has compared the integrated stand-alone infant resuscitation system (Giraffe) with the Neopuff or Neo-Tee, but our results indicate that theT-pieces deliver comparableVT.
Szyld et al[24]compared theSIB and Neopuffduring DRmask ventilation of infants ≥26 weeks’gestation. More infants ventilated with a SIB required DR intubation, and the SIB delivereda higher maxPIP and resultedin a lower SpO2thanthe Neopuff.In the very low birth weight infants, theincidence of BPDwas higher in theSIBgroup(p=0.04).This may have been due tohigher VTwith the SIB as demonstrated inour study.Szyld et al[24]did not measure VT, but as pressure is one of the determinants of VT, their results mightbe in agreement with the preterm animal data showingthat high VTventilation during resuscitation is harmful.[4]Interestingly, in the study by Szyld et al[24]the use of a manometer on the SIB did not prevent high and variable PIP delivery.
The SIB willlikelystill be usedbecause it is inexpensive and does not require a JUST ACCEPTEDDownloaded by [Auckland University of Technology] at 14:14 03 May 2016 pressurized gas source. Similarly, the Next StepTM
utilizes room air, is portable and inexpensive, and can deliver supplementary oxygen if connected to a gas source. Thesefeatures and the controlled VTdelivery,makesthe NextStepTM unique compared to both routinely used neonatal resuscitators and mechanical ventilators.The primary concern is volutrauma to the immature lung, n barotrauma. Thus, this study was not designed to assess ventilation pressures, and we used a Next StepTMprototype that didnot limit pressures. According to th manufacturer, a pressure limiting function will be incorporated in future generations of the Next StepTM.We used a newborn manikin to simulate DRresuscitation as opposed to ventilating straight into the test lungs. A limitation of the study wasthat the manikin resembled a term infant rather than a 1kg preterm infant.Thus, we repeatedly remindedtheparticipants about the target VT(5mL/kg). The manikin’s visual appearance mightstillhave caused higher VTdelivery, at least with the SIB.During real-life resuscitation clinicians use heart rate response andchest rise to adjust ventilation,which our manikin did not have. Similar to Roehr et al,[19]we comparedVTin a leak-free modelto reduce bias from various mask leaks. Mask PPV is often complicated by mask leak[25]andassessing the influence of leak on deviceperformancewas not the purpose of thisstudy.
In conclusion, except for in low-compliance, VTby pressure-limited devices was higher compared to the volume-controlled Next StepTMdevice.VTvaried with the T-pieces, but even more with the SIBat all compliance settings. Weconfirm that as the lung compliance increases, the risk of excessive VT with routinely used devices is substantial. Volume-targeted ventilation during neonatal resuscitation with devices like theNext StepTM may offer alung-protective strategy.

ACKNOWLEDGMENTS

We would like to thank the neonatal healthcare professionals whocontributed to this study.

DECLARATION OF INTEREST STATEMENT

KM Medical provided The Next Step™Neonatal Resuscitator for the study. The company was involved in the design of the study, but not in the data acquisition, data analysis, interpretation of the results, or writing of the manuscript. Dr Haemmerle was in 2008 involved as a University of Auckland Senior Lecturer in the prototype design of the Next Step™ under a research and consultancy agreement between Auckland UniServices Limited and KM Medical (Auckland, NZ). The test lung was designed and manufactured byAuckland University of Technology under the supervision of Dr Haemmerle. Ms van Os and Drs Solevåg, Bach, Cheung and Schmölzer have no potential competinginterest relevant to this article to disclose.

FUNDING

ALS is supported by the Canadian Institutes of Health Research (operating grant MOP299116, held by PYC and travel award to ALS) and the South-Eastern Norway Regional Health Authority. GMS is supported by a Heart and Stroke Foundation/University of Alberta Professorship for Neonatal Resuscitation andby a Heart and Stroke Foundatio of Canada Research Scholarship. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript

REFERENCES

[1] Hooper SB, Siew ML, Kitchen MJ et al. Establishing functional residual capacity in the
non-breathing infant. Semin Fetal Neonatal Med 2013;18:336-343.


[2]Kattwinkel J, Perlman JM, Aziz K et al. Part 15: neonatal resuscitation: 2010 American
Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency
Cardiovascular Care. Circulation 2010;122:S909-919


[3] Grover A, Field D. Volume-targeted ventilation in the neonate: time to change? Arch Dis
Child Fetal Neonatal Ed 2008;93:F7-13.


[4] Hillman NH, Moss TJ, Kallapur SG et al. Brief, large tidal volume ventilation initiates
lung injury and a systemic response in fetal sheep. Am J Respir Crit Care Med
2007;176:575-581.


[5] Dreyfuss D, Basset G, Soler P et al. Intermittent positive-pressure hyperventilation with
high inflation pressures produces pulmonary microvascular injury in rats. Am Rev
Respir Dis 1985;132:880-884.


[6] Hernandez LA, Peevy KJ, Moise AA et al. Chest wall restriction limits high airway
pressure-induced lung injury in young rabbits. J Appl Physiol (1985) 1989;66:2364-2368.


[7]Schmolzer GM, Te Pas AB, Davis PG et al. Reducing lung injury during neonatal resuscitation of preterm infants. J Pediatr 2008;153:741-745.


[8] Wheeler KI, Klingenberg C, Morley CJ et al. Volume-targeted versus pressure-limited ventilation for preterm infants: a systematic review and meta-analysis. Neonatology 2011;100:219-227.


[9] Schmölzer GM,Olischar M, Raith W, Resch B, Reiterer F, Müller W. Delivery room resuscitation. Monatsschr Kinderheilkd 2010;158:6.


[10] Leone TA, Rich W, Finer NN. A survey of delivery room resuscitation practices in the United States. Pediatrics 2006;117:e164-175.


[11] Finer NN, Rich W, Wang C, Leone T. Aiway obstruction during mask ventilation of very low birth weight infants during neonatal resuscitation. Pediatrics 2009;123:865-869.


[12] Hull D. Lung expansion and ventilation during resuscitation of asphyxiated newborn infants. J Pediatr 1969;75:47-58.


[13] Vilstrup CT, Bjorklund LJ, Werner O et al. Lung volumes and pressure-volume relations of the respiratory system in small ventilated neonates with severe respiratory distress syndrome. Pediatr Res 1996;39:127-133.


[14] Jobe AH, Hillman N, Polglase G et al. Injury and inflammation from resuscitation of the preterm infant. Neonatology 2008;94:190-196.


[15] Mian QN, Pichler G, Binder C et al. Tidal volumes in spontaneously breathing preterm infants supported with continuous positive airway pressure. J Pediatr 2014;165:702-706 e701.


[16] Vento M, Cheung PY, Aguar M. The first golden minutes of the extremely-low-gestational-age neonate: a gentle approach. Neonatology 2009;95:286-298.


[17] Mian Q, Cheung P-Y, Polglase G, O’Reilly M, Aziz K, Schmölzer GM. Does high tidal volume delivery during positive pressure ventilation at birth potentially cause brain injury in preterm infants? In: Pediatric Academic Societies Annual Meeting 2015. San Diego, CA; 2015.


[18] Huynh T HR, Perlman J. Assessment of effective mask ventilation is compromised during synchronized chest compressions. Arch Dis Child Fetal Neonatal Ed 2015;100:F39-F42.


[19] Roehr CC, Kelm M, Fischer HS et al. Manual ventilation devices in neonatal resuscitation: tidal volume and positive pressure-provision. Resuscitation 2010;81:202-205.


[20] Boldingh AM, Solevag AL, Benth JS et al. Newborn manikin study shows that physicians often fail to detect correct lung compliance when using a self-inflating bag. Acta Paediatr 2015.


[21] O'Donnell CP, Davis PG, Lau R et al. Neonatal resuscitation 2: an evaluation of manual ventilation devices and face masks. Arch Dis Child Fetal Neonatal Ed2005;90:F392-396.


[22] Dawson JA, Gerber A, Kamlin CO et al. Providing PEEP during neonatal resuscitation: which device is best? J Paediatr Child Health 2011;47:698-703.


[23] Krabbe VB, van Vonderen JJ, Roehr CC et al. Accuracy of a disposable compared toa non-disposable infant T-piece resuscitator. Eur J Pediatr 2014;173:1005-1009.


[24] Szyld E, Aguilar A, Musante GA et al. Comparison of devices for newborn ventilation in the delivery room. J Pediatr 2014;165:234-239 e233.


[25] Schmolzer GM, Dawson JA, Kamlin CO et al. Airway obstruction and gas leak during mask ventilation of preterm infants in the delivery room. Arch Dis Child Fetal Neonatal Ed 2011;96:F254-257.


[25] Schmolzer GM, Dawson JA, Kamlin CO et al. Airway obstruction and gas leak during mask ventilation of preterm infants in the delivery room. Arch Dis Child Fetal Neonatal Ed 2011;96:F254-257.


FIGURE LEGENDS


Figure I: Current prototype of the KM Medical Next StepTM

How difficult was ventilation with the device?(n=25) How comfortable was the use of the ventilation device?(n=25)
Self-inflating Bag 3 (2-3)* 3 (2-3)*
Neo-Tee disposable T-Piece 4 (3-4)* 4 (3-4)*
Neopuff Infant T-Piece 4 (4-5)* 4 (4-5)*
Giraffe Stand-alone T-Piece 4 (4-4.5)* 4 (4-4.5)*
Next Step 5 (5-5) 5 (5-5
Values are presented as median with interquartile range (IQR)
*p<0.05 vs. Next Step TM
Compliance 0.5mL/cmH2O(n=25) 1.0mL/cmH2O(n=25) 2.0mL/cmH2O(n=25)
Self-inflating Bag 4.8 (4.1-5.9)* 20.8 (13.3-26.6)* 22.7 (15.5-28.4)
Neo-Tee disposable T-Piece resuscitator 3.6 (3.4-4.0) 14.1 (13.0-14.9) 17.3 (16.4-20.3)
Neopuff Infant T-Piece Resuscitator 3.7 (3.3-3.9) 13.9 (13.1-15.0) 17.7 (15.4-20.1)
Giraffe Stand-alone Infant Resuscitation System T-Piece 3.7 (3.4-4.1) 14.2 (13.5-15.3) 18.1 (15.1-19.6)
Next Step 4.3 (4.3-4.3) 5.7 (5.7-5.8)** 5.7 (5.7-5.8)**
Values are presented as median with interquartile range (IQR)
*p-value <0.005 vs.all other devices
**p-value <0.001 vs.all other devices