SEARCH

SEARCH BY CITATION

Keywords:

  • infant;
  • newborn;
  • PEEP;
  • resuscitation;
  • ventilation

Abstract

  1. Top of page
  2. Abstract
  3. What is already known on this topic
  4. What this study adds
  5. Background
  6. Methods
  7. Results
  8. Discussion
  9. Conclusions
  10. References

Background:  Self-inflating bags are used to provide ventilation during neonatal resuscitation. However, they cannot provide positive end expiratory pressure (PEEP) unless a PEEP valve is attached. The ability of Laerdal neonatal self-inflating bags fitted with PEEP valves to reliably deliver PEEP is unclear. The aim of this study was to measure the delivered PEEP at different set PEEP levels and inflation rates.

Methods:  We connected disposable and non-disposable 240 mL Laerdal self-inflating resuscitation bags fitted with PEEP valves to a leak-free test lung. We measured PEEP delivered with the valve set at 5, 7 and 10 cm H2O whilst inflating the test lung at rates of 20, 40 and 60 min. Studies were done with 8 L/min of gas flow and with no gas flow.

Results:  The PEEP delivered was close to the set level immediately after inflation but declined rapidly between inflations. The mean PEEP was higher with faster ventilation rates. When PEEP was set at 7 cm H2O, using a non-disposable bag, and an inflation rate of 60/min the mean (SD) PEEP was 5.4 (0.19) cm H2O. The PEEP delivered was unrelated to the gas flow into the device.

Conclusion:  The 240 mL Laerdal self-inflating bag with a PEEP valve delivers PEEP that loses pressure quickly. The level of PEEP delivered is less than that set, particularly at rates below 40/min.


What is already known on this topic

  1. Top of page
  2. Abstract
  3. What is already known on this topic
  4. What this study adds
  5. Background
  6. Methods
  7. Results
  8. Discussion
  9. Conclusions
  10. References
  • • 
    Some infants will require assistance to start breathing in the delivery room.
  • • 
    PEEP may be beneficial during neonatal resuscitation.
  • • 
    PEEP can be provided by a flow-inflating, T-piece or self-inflating bag with a PEEP valve.

What this study adds

  1. Top of page
  2. Abstract
  3. What is already known on this topic
  4. What this study adds
  5. Background
  6. Methods
  7. Results
  8. Discussion
  9. Conclusions
  10. References
  • • 
    A Laerdal self-inflating resuscitation bag fitted with a PEEP valve does provide clinically useful levels of PEEP only if it is inflated at 40/min or more.
  • • 
    The PEEP achieved is less than the set PEEP.
  • • 
    PEEP declines between inflations particularly when the inflation rate is less than 40/min.

Background

  1. Top of page
  2. Abstract
  3. What is already known on this topic
  4. What this study adds
  5. Background
  6. Methods
  7. Results
  8. Discussion
  9. Conclusions
  10. References

Neonatal resuscitation is one of the most frequently performed medical interventions, with 3–5% of infants' worldwide requiring some assistance to initiate breathing.1 Clinicians can choose from a flow-inflating, self-inflating bag or a T-piece device. Self-inflating bags are the most commonly used device.2 There is little evidence to assist clinicians in choosing a device.3 Flow-inflating bag and T-piece resuscitators both provide some positive end expiratory pressure (PEEP) during ventilation although only a T-piece device can provide continuous positive airway pressure (CPAP). A self-inflating bag does not provide PEEP or CPAP,4 however, some models can be fitted with a PEEP valve.5

It is known that PEEP and CPAP are important for maintaining end expiratory lung volume in infants with respiratory difficulties.6,7 Failure to provide PEEP may lead to atelectrauma due to repetitive inflation and collapse of terminal airways and alveoli.8,9 The Australian Resuscitation Council recommends using at least 5 cm H2O of CPAP or PEEP for the resuscitation of very preterm infants.10 The Canadian Neonatal Resuscitation Program Steering Committee recommends using 3–6 cm H2O of PEEP during ventilation, stating that a self-inflating bag with a PEEP valve is acceptable for this purpose.11 Leone et al., in a US survey of delivery room resuscitation practices, found that 76% of 342 respondents provided PEEP or CPAP in the delivery room. A self-inflating bag with PEEP valve was used in 25% (88/342) of the surveyed units.5 Bennett et al.12 compared different resuscitation devices. They showed that a self-inflating bag with a PEEP valve generated less PEEP than a flow-inflating bag or a T-piece resuscitator.

The aims of this study were to measure accurately the PEEP delivered, by Laerdal neonatal self-inflating bags when a PEEP valve was fitted and to assess the effect of different set pressures, inflation rates and gas flows.

Methods

  1. Top of page
  2. Abstract
  3. What is already known on this topic
  4. What this study adds
  5. Background
  6. Methods
  7. Results
  8. Discussion
  9. Conclusions
  10. References

We studied the most commonly used self-inflating device,2 a Laerdal® 240 mL silicone infant resuscitator (model number 850050) fitted with a 600-mL reservoir bag (Laerdal Medical, Stavanger, Norway) and the disposable Laerdal BAG-II made of PVC (model number 845031). The self-inflating device was fitted with a Laerdal disposable PEEP valve (model number 845040) connected via an expiratory diverter (model number 845080) (Fig. 1). When the self-inflating device is squeezed, gas is pushed past the one-way fish-mouth valve. Passive exhalation occurs as the pressure falls and the expired gas flows via the expiratory diverter through the expiratory valve of the PEEP device. PEEP is generated by adjusting the tension spring, using the markings to set the desired level of PEEP.

image

Figure 1. A picture showing the Laerdal Infant Resuscitator with the expiratory diverter and positive end expiratory pressure (PEEP) valve attached and a test lung and pressure line in place.

Download figure to PowerPoint

The test device was connected to a 50-mL leak-free test lung (Dräger, Lubeck, Germany). Airway pressures were measured by a Florian Respiratory Monitor (Acutronic Medical Systems AG, Zug, Switzerland) connected between the test lung and the resuscitation device (Fig. 1). Analogue signals from the Florian monitor were digitised and analysed using Spectra respiratory data acquisition and analysis software (Grove Medical, London, UK).

One operator tested one disposable and one non-disposable device. During each inflation, the bag was squeezed to deliver a peak pressure of about 30–35 cm H2O. The PEEP between each inflation was recorded and measured. Each bag was inflated at a rate of 20, 40 or 60/min with the PEEP valve set on the ring to 5, 7 and 10 cm H2O. We tested each bag with 8 L/min of gas flow and then no gas flow. We used a metronome to accurately time the inflation rates. We also tested each device without the PEEP valve. To assess the ability of the PEEP valve to generate CPAP, we measured the expiratory pressure when the valve was fitted and the bag was not being squeezed.

Data analysis

We analysed the first 20 inflations for each rate PEEP/flow combination and measured minimum, maximum and mean PEEP, peak inspiratory pressure (PIP) and inflation rates delivered by each device. To investigate whether the PEEP changed between inflations, we measured the PEEP at the end of each inflation and then before the next inflation. Comparisons between the disposable and non-disposable models were made with two-tail t-tests. A P-value <0.05 was considered significant. We analysed the data using Stata (Intercooled 10.0, Statacorp, College Station, TX, USA).

Results

  1. Top of page
  2. Abstract
  3. What is already known on this topic
  4. What this study adds
  5. Background
  6. Methods
  7. Results
  8. Discussion
  9. Conclusions
  10. References

Two devices and 720 inflations were analysed (360 each for disposable and non-disposable bags). The PEEP level at the end of inflation was close to the set PEEP but declined rapidly between inflations with both devices. Figure 2 shows the decay of PEEP between inflations when the set PEEP was 5, 7 and 10 cm H2O at an inflation rate of 20/min with a disposable bag. Figure 3 shows a smaller decline in PEEP when the inflation rate was 60/min. The higher the inflation rate, the less the PEEP fell and the higher the mean PEEP. The relationship between inflation rates for disposable and non-disposable devices is shown in Figure 4a and b.

image

Figure 2. Recordings showing the decay of positive end expiratory pressure (PEEP) when the inflation rate was 20/min with three set PEEP pressures: A = 5 cm H2O, B = 7 cm H2O and C = 10 cm H2O.

Download figure to PowerPoint

image

Figure 3. Recordings showing the decay of positive end expiratory pressure (PEEP) when the inflation rate was 60/min with three set PEEP pressures: A = 5 cm H2O, B = 7 cm H2O and C = 10 cm H2O.

Download figure to PowerPoint

image

Figure 4. (a) Effect of inflation rate on mean positive end expiratory pressure (PEEP) at three set PEEP pressures using a disposable resuscitator. (b) Effect of inflation rate on mean PEEP at three set PEEP pressures using a non-disposable resuscitator.

Download figure to PowerPoint

The mean (SD) PEEP was lower than the set PEEP for all pressures and rates tested and for both devices (Tables 1,2). At an inflation rate of 60/min and a set PEEP of 7 cm H2O with a non-disposable bag the mean (SD) PEEP was 5.5 (0.18) cm H2O. There were statistically significant differences (P < 0.05) between the PEEP achieved by the disposable and non-disposable devices. The non-disposable bags tended to achieve a higher PEEP than did the disposable bags, particularly with PEEP pressures and inflation rates likely to be used clinically. The PEEP was not influenced by the gas flow into the device at any inflation rate or set PEEP (Table 2). When the PEEP valve was not attached to the self-inflating bag, no PEEP was generated (Fig. 5). When the PEEP valve was attached but the bag was not squeezed (i.e. attempted CPAP), pressure fell quickly to 0 cm H2O (Fig. 6).

Table 1.  Mean (SD) positive end expiratory pressure (PEEP) achieved at different (PEEP) pressures and inflation rates with a gas flow into each Laerdal resuscitator of 8 L/min
Inflation rate/minPEEP measured – mean (SD)
PEEP set at 5 cm H2OPEEP set at 7 cm H2OPEEP set at 10 cm H2O
DisposableNon-disposablePDisposableNon-disposablePDisposableNon-disposableP
  1. P-values are the comparison between disposable and non-disposable devices at each set PEEP and each inflation rate.

201.9 (0.10)1.3 (0.26)0.00013.3 (0.10)3.9 (0.23)0.00015.9 (0.56)6.0 (0.22)0.46
402.4 (0.20)2.8 (0.22)0.00014.4 (0.17)5.5 (0.14)0.00017.5 (0.45)8.1 (0.18)0.0001
602.8 (0.15)3.0 (0.11)0.00015.2 (0.15)5.5 (0.18)0.00018.6 (0.24)8.4 (0.20)0.0068
Table 2.  Mean (SD) positive end expiratory pressure (PEEP) achieved at three different set PEEP pressures and three inflation rates with no added gas flowing into the bag
Inflation rate/minPEEP measured – mean (SD)
Set at 5 cm H2OSet at 7 cm H2OSet at 10 cm H2O
DisposableNon-disposablePDisposableNon-disposablePDisposableNon-disposableP
201.8 (0.12)1.1 (0.14)0.00013.3 (0.12)3.9 (0.22)0.00016.1 (0.61)5.9 (0.23)0.18
402.5 (0.14)2.8 (0.28)0.00014.3 (0.21)5.5 (0.18)0.00017.5 (0.54)8.1 (0.17)0.0001
602.8 (0.17)3.1 (0.14)0.00015.2 (0.14)5.4 (0.19)0.0058.4 (0.19)8.4 (0.26)1.0
image

Figure 5. A recording with inflations at 60 bpm showing that no positive end expiratory pressure (PEEP) is generated when a PEEP valve is not fitted.

Download figure to PowerPoint

image

Figure 6. A recording showing that no positive end expiratory pressure (PEEP) is generated when a PEEP valve is not used and there are no inflations.

Download figure to PowerPoint

Discussion

  1. Top of page
  2. Abstract
  3. What is already known on this topic
  4. What this study adds
  5. Background
  6. Methods
  7. Results
  8. Discussion
  9. Conclusions
  10. References

Our study shows that the Laerdal self-inflating bag with a PEEP valve can generate PEEP but the pressure falls to almost zero in about 10 s. Animal studies have shown that PEEP plays an important part in establishing and maintaining functional residual capacity at birth along with preservation of surfactant function on the alveolar surface.13,14 Probyn, showed improved oxygenation and increased compliance of respiratory system when very premature lambs were resuscitated with a PEEP of 4 and 8 cm H2O.7 Muscedere et al., studied rats whose lungs were lavaged to remove surfactant and showed that end-expiratory lung volume was important in determining the degree and site of lung injury during positive-pressure ventilation.8 Therefore, providing PEEP may be important during resuscitation of newly born preterm infants.

It is desirable that devices used in the delivery room deliver the set PIP and PEEP and be easy for clinicians to use. Bennett et al.12 tested the ability of experienced clinicians to deliver PIP of 20 or 40 cm H2O and a PEEP of 5 cm H2O at a rate of 40–60 bpm to a mannequin via a face mask using a T-piece device, a flow inflating bag and a self-inflating bag with a PEEP valve. She found that the self-inflating bag provided significantly less PEEP than both the T-piece and the flow inflating bag (3.6 cm H2O, 4.4 cm H2O, 4.4 cm H2O; P < 0.005), respectively. Finer et al.3 also measured the performance of clinicians using a face mask, a disposable flow-inflating bag, a non-disposable flow-inflating bag and a Neopuff (T-piece resuscitator) to ventilate a mannequin. They did not test the self-inflating bag. An important finding was that respiratory therapists were more able to accurately deliver PIP and PEEP than less experienced health professionals. Moreover, all participants could generate the target PEEP with the Neopuff (P < 0.05). O'Donnell et al.15 tested clinicians' ability to give positive pressure ventilation to a leak-free mannequin with a Neopuff or Laerdal self-inflating resuscitator without PEEP valve. They found no difference between the devices to provide PIP, however, the Laerdal device delivered little PEEP. In the Bennett et al.,12 Finer et al.3 and O'Donnell et al.15 studies, participants were more likely to achieve target PIP and/or PEEP more consistently with the Neopuff when compared with other resuscitation devices.

During newborn resuscitation, it can be difficult to prevent gas leakage between a mask and an infant's face. When a PEEP valve is used, any leak between the face and mask is likely to be exacerbated because there is increased pressure in the mask during expiration as well as inflation. Hussey et al.4 tested the ability of operators to ventilate a leak-free intubated mannequin at 40/min with a PIP/PEEP of 20/4 cm H2O with each type of manual inflation device. However, they did not use a PEEP valve with the self-inflating bag. The mean (SEM) PEEP for self-inflating bag, anaesthetic bag and T-piece were 0.15 (0.03), 2.83 (0.23), and 4.41 (0.08) cm H2O (P < 0.001), respectively. In a leak-free test environment and without a PEEP valve, the self-inflating bag did not generate any useful PEEP.4,15

Whilst a self-inflating bag can be used to provide free-flow oxygen to spontaneously breathing infants16, it cannot be used to give CPAP even when a PEEP valve is attached. Our study only tested one model of self-inflating bag, other self-inflating bags with PEEP valves may perform differently.

Conclusions

  1. Top of page
  2. Abstract
  3. What is already known on this topic
  4. What this study adds
  5. Background
  6. Methods
  7. Results
  8. Discussion
  9. Conclusions
  10. References

A Laerdal 240-mL self-inflating bag with a PEEP valve can deliver PEEP but the pressure falls rapidly and so it cannot be used to give CPAP. When set to deliver 7 cm H2O of PEEP, the mean PEEP is 5.4 cm H2O but only when the bag was squeezed at least 60/min. When this resuscitation bag is fitted with a PEEP valve, the pressure delivered is less than that set, particularly at rates below 40/min.

References

  1. Top of page
  2. Abstract
  3. What is already known on this topic
  4. What this study adds
  5. Background
  6. Methods
  7. Results
  8. Discussion
  9. Conclusions
  10. References
  • 1
    Maternal and Newborn Health/Safe Motherhood Unit. Basic Newborn Resuscitation: A Practical Guide. Geneva: World Health Organization, 1997.
  • 2
    O'Donnell CP, Davis PG, Morley CJ. Positive pressure ventilation at neonatal resuscitation: review of equipment and international survey of practice. Acta Paediatr. 2004; 93: 5838.
  • 3
    Finer NN, Rich W, Craft A, Henderson C. Comparison of methods of bag and mask ventilation for neonatal resuscitation. Resuscitation 2001; 49: 299305.
  • 4
    Hussey SG, Ryan CA, Murphy BP. Comparison of three manual ventilation devices using an intubated mannequin. Arch. Dis. Child. Fetal Neonatal Ed. 2004; 89: F4903.
  • 5
    Leone TA, Rich W, Finer NN. A survey of delivery room resuscitation practices in the United States. Pediatrics 2006; 117: e16475.
  • 6
    O'Donnell CPF, Davis PG, Morley CJ. Resuscitation of premature infants: what are we doing wrong and can we do better? Biol. Neonate 2003; 84: 7682.
  • 7
    Probyn ME, Hooper SB, Dargaville PA et al. Positive end expiratory pressure during resuscitation of premature lambs rapidly improves blood gases without adversely affecting arterial pressure. Pediatr. Res. 2004; 56: 198204.
  • 8
    Muscedere JG, Mullen JB, Gan K, Slutsky AS. Tidal ventilation at low airway pressures can augment lung injury. Am. J. Respir. Crit. Care Med. 1994; 149: 132734.
  • 9
    Probyn ME, Hooper SB, Dargaville PA, McCallion N, Harding R, Morley CJ. Effects of tidal volume and positive end-expiratory pressure during resuscitation of very premature lambs. Acta Paediatr. 2005; 94: 176470.
  • 10
    Australian Resuscitation Council. Guideline 13.1 Introduction to resuscitation of the newborn infant. Australian Resuscitation Council, 2006. Available from: http://www.resus.org.au/[accessed 20 October 2009].
  • 11
    Canadian NRP Steering Committee. Recommendations for Specific Treatment Modifications in the Canadian Context. Canadian NRP Steering Committee, 2008. 22-1-0008. Available from: http://www.cps.ca/English/ProEdu/NRP/addendum.pdf[accessed 20 October 2009].
  • 12
    Bennett S, Finer NN, Rich W, Vaucher Y. A comparison of three neonatal resuscitation devices. Resuscitation 2005; 67: 11318.
  • 13
    Jobe AH, Kramer BW, Moss TJ, Newnham JP, Ikegami M. Decreased indicators of lung injury with continuous positive expiratory pressure in preterm lambs. Pediatr. Res. 2002; 52: 38792.
  • 14
    Michna J, Jobe AH, Ikegami M. Positive end-expiratory pressure preserves surfactant function in preterm lambs. Am. J. Respir. Crit. Care Med. 1999; 160: 6349.
  • 15
    O'Donnell CPF, Davis PG, Lau R, Dargaville PA, Doyle LW, Morley CJ. Neonatal resuscitation 2: an evaluation of manual ventilation devices and face masks. Arch. Dis. Child. Fetal Neonatal Ed. 2005; 90: F3926.
  • 16
    Dawson JA, Davis PG, O'Donnell CP, Omar FK, Morley CJ. Free-flow oxygen delivery to newly born infants. Arch. Dis. Child. Fetal Neonatal Ed. 2007; 92: F1324.