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Original article
Human or monitor feedback to improve mask ventilation during simulated neonatal cardiopulmonary resuscitation
  1. Corinna Binder1,
  2. Georg M Schmölzer1,2,3,
  3. Megan O'Reilly2,3,
  4. Bernhard Schwaberger1,
  5. Berndt Urlesberger1,
  6. Gerhard Pichler1,2,3
  1. 1Division of Neonatology, Department of Paediatrics, Medical University of Graz, Austria
  2. 2Department of Pediatrics, University of Alberta, Edmonton, Canada
  3. 3Neonatal Research Unit, Royal Alexandra Hospital, Edmonton, Canada
  1. Correspondence to Dr Georg M Schmölzer, Neonatal Research Unit, Royal Alexandra Hospital, 10240 Kingsway Avenue NW, Edmonton, Alberta, Canada T5H 3V9; georg.schmoelzer{at}me.com

Abstract

Objective To investigate if external chest compressions (ECC) increase mask leak, and if human or technical feedback improves mask ventilation during simulated neonatal cardiopulmonary resuscitation (CPR).

Study design In this observational study, 32 participants delivered positive pressure ventilation (PPV) to a modified, leak-free manikin via facemask. Mask leak, tidal volume (VT), positive end expiratory pressure (PEEP) and respiratory rate (RR) were measured with a respiratory function monitor (RFM). Participants had to perform four studies. In the first study, participants performed PPV alone as baseline. Thereafter, three studies were performed in random order. In the PPV+ECC+manometer group, participants had to observe the manometer while the RFM was covered; in the PPV+ECC+RFM group, the RFM was used while the manometer was covered; and in the PPV+ECC+verbal feedback group, the RFM and manometer were covered while a team leader viewed the RFM and provided verbal feedback to the participants.

Results Median (IQR) mask leak of all studies was 15% (5–47%). Comparing the studies, PPV+ECC+RFM and PPV+ECC+verbal feedback had significantly less mask leak than PPV+ECC+manometer.

Mean (SD) VT of all studies was 9.5±3.5 mL. Comparing all studies, PPV+ECC+RFM had a significantly higher VT than PPV and PPV+ECC+manometer. As well, PPV+ECC+verbal feedback had a significantly higher VT than PPV.

PEEP and RR were within our target, mean (SD) PEEP was 6±2 cmH2O and RR was 36±13/min.

Conclusions During simulated neonatal CPR, ECCs did not influence mask leak, and a RFM and verbal feedback were helpful methods to reduce mask leak and increase VT significantly.

  • infants
  • chest compressions
  • delivery room
  • neonatal resuscitation
  • respiratory function monitor

https://doi.org/10.1136/archdischild-2013-304311

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    What is already known on this topic

    • Chest compressions are rarely required during neonatal resuscitation.

    • Adequate ventilation is the most important component of neonatal resuscitation.

    • A respiratory function monitor may help reduce face mask leak.

    What this study adds

    • In simulated resuscitation using a manikin, chest compression did not increase mask leak.

    • Visual (from a respiratory function monitor) or verbal (from a team leader) feedback can improve tidal volume.

    Introduction

    External chest compressions (ECC) are rarely needed in delivery room (DR) resuscitations estimated to occur in 0.12% of newborn infants.1 ,2 Adequate positive pressure ventilation (PPV) remains the most important single procedure during neonatal resuscitation.3 ,4 International resuscitation guidelines recommend ECCs if heart rate is <60/min despite adequate PVV with supplementary oxygen for 30 s.3 ,4

    Recent mannequin studies reported respiratory parameters during simulated neonatal cardiopulmonary resuscitation (CPR). Schmölzer et al reported a 65% baseline mask leak during ECC, and listening to five different musical tunes did not reduce mask leak.5 Solevag et al reported higher C:V ratios compared with 3:1 compromised tidal volume delivery (VT) and minute ventilation.6 Additionally, human observational studies in the DR described several factors that can compromise VT delivery during PPV.7–11 Several studies during neonatal simulation reported that technical adjuncts (eg, pressure manometer or respiratory function monitor (RFM)) can be used to guide mask ventilation.12–14 Additionally, a recent randomised trial reported that an RFM can reduce mask leak during PPV in preterm infants in the DR.15 However, no study described the effect of technical or human feedback during neonatal CPR. The aim of our study was to investigate if human or technical feedback improves mask ventilation during simulated neonatal CPR.

    Methods

    Participants

    Neonatal consultants, paediatric registrars and neonatal nurses from the Department of Neonatology, Medical University of Graz were invited to participate in the study and all agreed. The Medical University of Graz Human Ethics Committee approved the study. All participants were trained in mask ventilation and neonatal resuscitation according to the European Resuscitation Council guidelines.3 We included a convenience sample of participants and performed no formal sample size calculation.

    Study protocol

    Participants were asked to perform mask PPV using a modified leak-free Laerdal neonatal manikin (Laerdal, Stavanger, Norway) unaware of the study aim.17–19 Prior to the study, participants had time to accustom themselves with the equipment and the manikin. For mask PPV, participants were instructed to roll the mask onto the face and use the ‘Two-point top hold’ described by Wood et al.16 During simulated CPR, participants were instructed to perform ECC and PPV using a 3:1 C:V ratio.3 ,4 ECCs were performed using the two-thumb encircling technique by a single operator (BS) in all studies. A metronome was used to achieve the targeted ECC rate. Participants were recorded for 90 s in four simulated resuscitations. After each study, participants had a 5 min break to reduce potential bias due to fatigue. Baseline parameters were obtained while participants provide mask PPV only with 40–60 inflations/minute while observing the inbuilt manometer of the resuscitation table (CosyCot; Fisher & Paykel Healthcare; Auckland, New Zealand).

    The three intervention groups were randomised: (1) PPV+ECC+manometer: participants used inbuilt manometer to guide inflations; (2) PPV+ECC+RFM: participants observed RFM to guide mask ventilation while the inbuilt manometer was covered and (3) PPV+ECC+verbal feedback: the inbuilt manometer and the RFM were covered for the participants, and a team leader (CB) was assigned to give verbal feedback to participants about mask leak, which was visible on the RFM screen only to the team leader. The team leader’s feedback was scripted, and positive and negative feedback were provided. Feedback was given every 10 s with prior defined phrases: ‘No mask leak <10%’, ‘Small mask leak between 10% and 50%’, or ‘Large mask leak >50%’.

    Ventilation device

    A Neopuff Infant T-Piece device (Fisher & Paykel Healthcare, Auckland, New Zealand) with a size 0/1 round silicone face mask (Laerdal, Stavanger, Norway) was used to deliver PPV. The Neopuff is a continuous flow, pressure limited device with a manometer, which is inbuilt on the CosyCot, and a positive end expiratory pressure valve. The default settings were gas flow of 8 L/min, peak inflation pressure of 30 cm H2O, and positive end expiratory pressure (PEEP) of 5 cm H2O.

    Respiratory function monitor

    A Florian Neonatal RFM (Acutronic Medical Systems AG; Zug, Switzerland) was used to measure and display ventilation parameters. A hot-wire anemometer flow sensor was placed between the mask and T-Piece device.13 ,16 ,18 ,20 VT was calculated by integrating flow signals, and mask leak was expressed as a percentage of the inspired VT.18 ,19 ,21 During the recordings, the RFM displayed VT and gas flow waveforms, which were used to identify mask leak. Participants were able to identify mask leak by observing (1) differences between expiratory and inspiratory VT and (2) areas under the flow curves were greater during expiration compared with inflation.

    Randomisation

    After baseline recording, the subsequent three studies were randomised, using a computer generated sequence (PPV+ECC+RFM; PPV+ECC+manometer; PPV+ECC+verbal feedback).

    Data acquisition and analysis

    The gas flow, VT and airway pressure data were recorded at 200 Hz using a computer with ‘α-trace digital MM’ (BEST Medical Systems, Vienna, Austria) multichannel system. Additionally, a video of each simulation was recorded. During the simulated resuscitation, the monitor's alarm was disabled.

    Statistical analysis

    Every pressure and flow waveform were analysed, and mask leak, VT, respiratory rate (RR) and PEEP for inflations were recorded every second for the periods of mask ventilation. Mask leak was calculated as a percentage of the inspired VT according to ((inspiratory VT—VTe) ÷ (inspiratory VT)×100).18 Results are presented as mean (±SD) for normally distributed continuous variables and median (IQR) for variables with a skewed distribution. In each participant for each simulated resuscitation values of mask leak, VT, RR and PEEP were calculated. For further analysis, either the mean or median of those mean values were calculated. ANOVA with Bonferroni posthoc test was used for group comparison. Statistical analysis was performed using StatView (Abacus Concepts, Berkeley, California) and GraphPad Prism 6 (GraphPad Software, La Jolla, California). A p value <0.05 was considered significant.

    Results

    In total, 32 participants (9 neonatal consultants, 7 paediatric registrars and 16 neonatal nurses) participated in this study. A total of 14 106 ECC and 7180 ventilations, with a mean (SD) of 145±30 ECC and 56±22 ventilations per study, were analysed.

    Mask leak

    Median (IQR) mask leak during PPV was 15% (7–46%) compared to PPV+ECC+manometer 32% (7–63%), PPV+ECC+RFM 10% (0–41%), and PPV+ECC+verbal feedback 14% (4–40%) (figure 1). Mask leak was significantly decreased in the PPV+ECC+RFM (p=0.017) and PPV+ECC+verbal feedback group compared to PPV+ECC+manometer (p=0.044).

    Figure 1
    Figure 1

    Face mask leak for each study. ECC=external chest compressions only (baseline recordings); PPV+ECC+manometer=resuscitation guided by using pressure manometer; PPV+ECC+RFM=observation of RFM during resuscitation; PPV+ECC+verbal feedback=resuscitation was guided by a team leader. Box plots show median (solid bar), IQR (margins of the box) and 95% CI. *Significant difference between studies. ECC, external chest compressions; PPV, positive pressure ventilation; RFM, respiratory function monitor.

    Tidal volume

    Mean (SD) VT of all four studies was 9.5±3.5 mL (PPV 8.4±3.4 mL, PPV+ECC+manometer 9.0±3.7 mL PPV+ECC+RFM 10.5±3.5 mL, and PPV+ECC+verbal-feedback 10.05±3.4 mL) (figure 2 and table 1). VT delivery was significantly increased between PPV+ECC+RFM (p<0.001) and PPV+ECC+verbal feedback (p=0.001) compared to PPV as well as PPV+ECC+manometer versus PPV+ECC+RFM (p=0.032).

    View this table:
    Table 1

    Tidal volume delivery (mL) in all groups

    Figure 2
    Figure 2

    Tidal volume for each study. ECC external chest compressions only (baseline recordings); PPV+ECC+manometer=resuscitation guided by using pressure manometer; PPV+ECC+RFM=observation of RFM during resuscitation; PPV+ECC+verbal feedback=resuscitation was guided by a team leader. Box plots show median (solid bar), IQR (margins of the box) and 95% CI. *Significant difference between studies. ECC, external chest compressions; PPV, positive pressure ventilation; RFM, respiratory function monitor.

    PEEP

    Mean (SD) PEEP of all four studies was 6±2 cm H2O (PPV 7±2 cmH2O, PPV+ECC+manometer 6±2 cmH2O, PPV+ECC+RFM 6±2 cm H2O, and PPV+ECC+verbal feedback 6±2 cm H2O) with no significant difference between the PEEP values.

    Ventilation rate

    Mean (SD) RR of all four studies was 36±13/min (PPV 48±19/min, PPV+ECC+manometer 30±8/min, PPV+ECC+RFM 32±5/min, and PPV+ECC+verbal feedback 31±7/min). There was a significant difference between PPV and PPV+ECC+manometer (p<0.001), PPV and PPV+ECC+RFM (p<0.001) and PPV and PPV+ECC+verbal feedback (p<0.001).

    Discussion

    We demonstrated that during simulated neonatal CPR, adequately provided ECC did not influence mask leak but that mask ventilation could be optimised by an RFM or verbal feedback. RFM and verbal feedback, instead of using a manometer, were able to reduce mask leak. Additionally, higher VT could be achieved when an RFM was used. To our knowledge, this is the first study evaluating the use of technical adjuncts (RFM or manometer) or verbal feedback (team leader) to guide mask ventilation and ECC during simulated neonatal resuscitation.

    There is little literature about quality of mask ventilation during CPR. Prior studies concentrated on the potential reduction of mask leak during neonatal resuscitation, but without ECC.13 ,15 ,16 ,20 ,22 A manikin study by Wood et al reported that mask leak can be more than halved when an RFM is used.13 Schmölzer et al demonstrated that an RFM can be used during real neonatal resuscitation in the DR to decrease in mask leak, more frequently adjusts mask position, and deliver less excessive VT.15 We observed similar results, with a significant reduction in mask leak when an RFM was used compared to a manometer when mask PPV and ECC are delivered. Wood et al reported a mean (SD) mask leak of 11.2%±13.1%, and Schmölzer et al a median (IQR) mask leak of 37% (21%–54%) while using an RFM.13 ,15

    In the present study, mask leak was also reduced by verbal feedback, given by a team leader. With verbal feedback, the participants were probably able to concentrate more on ventilation, mask positioning and mask holding. Although, mask leak was slightly higher in this group (PPV+ECC+verbal feedback) compared to PPV+ECC+RFM, this did not reach statistical significance. We hypothesise that this is due to the demand of self-control by looking on the RFM and getting a more immediate feedback. Furthermore, we do not know to what extent participants listened to the verbal feedback and tried to improve mask ventilation.

    A prerequisite for adequate PPV is mask seal, hence, mask leak can decrease VT delivery resulting in ineffective ventilation. VT delivery was statistically significantly increased, however, we can only speculate if the increased VT delivery would also be clinically significant. Solevag et al reported a median VT of 6.4 mL/kg during mask leak-free simulation CPR with a ECC to ventilation ratio of 3:1.6 In our study, a test lung with a fixed compliance was used, therefore, comparison of absolute VT values are difficult but, nevertheless, the use of RFM improved VT delivery.

    However, there are several limitations to our study. Although, the study was randomised, the presented study is a mannequin study, which lacks emotional factors of real-life resuscitations. Additionally, we did not add any noise distraction or human interactions, which are present in real-life situations. Adding these factors might have yielded a different result. Mask leak during our baseline recording of mask PPV was low compared to published data by Wood et al and Schmölzer et al.15 ,20 However, the study by Schmölzer et al investigated mask leak during the real-life scenario of mask PPV in the delivery room, which could have contributed to higher mask leaks.15 Our results are similar to a recent mannequin study by Tracy et al, which compared different mask-hold techniques.23 Mask leak in the control group was 10%, which was further reduced to 5% using a two-hand hold.

    Our results indicate that using an RFM or verbal feedback can improve CPR performances of mask ventilation in the DR. This is of clinical importance because adequate PPV is a central component of neonatal resuscitation and ECC is typically provided to infants who do not respond to ventilation with increased heart rate. In conclusion, our study showed that an RFM or verbal feedback, are helpful methods during neonatal resuscitation to reduce mask leak and increase VT delivery when ECC are provided.

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    Footnotes

    • Contributors Conception and design: GMS, MOR, GP. Collection and assembly of data: GMS, CB, BS, BU, GP. Analysis and interpretation of the data: GMS, CB, MOR, BS, BU, GP. Drafting of the article: GMS, CB, BS, MOR, BU, GP. Critical revision of the article for important intellectual content: GMS, CB, MOR, BS, BU, GP. Final approval of the article: GMS, CB, BS, MOR, BU, GP.

    • Competing interests None.

    • Provenance and peer review Not commissioned; externally peer reviewed.