Elsevier

Resuscitation

Volume 82, Issue 7, July 2011, Pages 920-924
Resuscitation

Simulation and education
Changing gas flow during neonatal resuscitation: A manikin study

https://doi.org/10.1016/j.resuscitation.2011.02.029Get rights and content

Abstract

Introduction

When using a T-piece device, resuscitators may try to improve airway pressures by increasing gas flow instead of correcting face mask position.

Aim

To measure the effects of changing gas flow during positive pressure ventilation (PPV) on peak inspiratory pressure (PIP), positive end expiratory pressure (PEEP), expiratory tidal volume (VTe) and mask leak.

Methods

Using a Neopuff T-piece device, 20 neonatal staff members delivered PPV to a modified, leak-free manikin. Resuscitation parameters were recorded. Study A: PPV for 4 min at PIP 30 cm H2O and PEEP 5 cm H2O. Each minute gas flow was increased (5, 8, 10, and 15 L/min). PIP and PEEP settings were unchanged. Study B: same pressure settings; PPV for 1 min with 5, 8, 10, and 15 L/min in a random order, at a rate of ∼60/min. The pressures were adjusted to maintain the same PIP and PEEP after each flow change.

Results

Study A: As gas flow increased (5, 8, 10 and 15 L/min) the median PEEP increased from 4.7 to 26.4 cm H2O (p < 0.002). Median VTe decreased from 10.0 to 0.8 mL (p < 0.001). PIP increased slightly from 30 cm H2O to 36 cm H2O at 15 L/min (p < 0.005). Mask leak increased from 14% to 98% (p < 0.001) because mask pressure increased. Study B: when PIP and PEEP were maintained there were no significant differences in VTe (p = 0.42) or mask leak (p = 0.51) with changing gas flow.

Conclusion

During PPV increasing gas flow dramatically increased PEEP and mask leak and in consequence reduced VTe. Gas flow should rarely be changed during T-piece resuscitation.

Introduction

The Neopuff Infant Resuscitator (Fisher & Paykel Healthcare, Auckland, New Zealand) is a T-piece device that is commonly used to provide positive pressure ventilation (PPV) for newborn infants in the delivery room.1, 2, 3 The object of PPV is to establish a functional residual capacity and deliver an appropriate tidal volume (VT) to achieve effective gas exchange.4 Failure to achieve a set airway pressure with a T-piece resuscitation device may be due to a large mask leak. This is a common, usually unrecognized problem and can lead to inadequate ventilation.5, 6, 7, 8, 9, 10 Resuscitators may try to increase the airway pressure by increasing gas flow instead of correcting face mask position. The Neopuff T-piece resuscitation device uses a flow resistor expiratory pressure valve system to generate a positive end expiratory pressure (PEEP) or continuous positive airway pressure (CPAP). It does so by imposing an adjustable orifice resistance to exhaled flow rate. When the flow rate is constant, the expiratory positive pressure varies inversely with the orifice size. The pressure generated is directly related to the resistance to the gas flow.11 A recent study by Hawkes et al. demonstrated that the peak inspiratory pressure (PIP) and positive end expiratory pressure (PEEP) valves of a Neopuff T-piece device can be overridden when the gas flow is increased. In that study the mean PEEP increased from 5 to 20 cm H2O and the mean PIP increased from 20 to 28 cm H2O when gas flow was increased from 5 to 15 L/min.12 Another study found that if the gas flow is increased to 15 L/min the PEEP rises to about 24 cm H2O, and PIP is similar to, or just above, the set PIP even when max PIP is set very high.13

No study has reported the effects of increasing gas flow on tidal volume and mask leak. Using a modified, leak free, manikin we investigated the effects of gas flow changes on delivered expiratory tidal volume (VTe), ventilating pressures and face mask leak during PPV.

Section snippets

Participants

Neonatal consultants, fellows (SpR grade), registrars (SHO grade) and nurses of The Royal Women's Hospital, Melbourne, Australia participated in this study. All had received training in neonatal resuscitation and mask handling technique. It is a tertiary perinatal care centre with about 6000 deliveries and admits more than 100 extremely low birth weight infants a year. Participants were acquainted with resuscitation research and may have participated in studies before.

Manual ventilation device and face mask

The Neopuff infant

Participants

Five neonatal consultants, 5 fellows, 5 registrars and 5 nurses participated in the study. The mean (SD) years of experience with mask ventilation were: consultants 15.0 (5.1) years, fellows 7.8 (3.1) years, registrars 0.7 (0.4) years and nurses 4.0 (2.4) years. A total of 9644 inflations were analysed; 3493 for study A and 3451 for study B. The mean (SD) number of inflations per participant used for analysis were 175 (41) in study A and 173 (43) in study B.

Study A

The median (IQR) PEEP increased with

Discussion

The objective of PPV is to deliver an adequate tidal volume. Failure to achieve a set airway pressure with a T-piece resuscitation device can be due various factors.16, 17, 18 Resuscitators may try to improve the airway pressure by increasing gas flow. With a Neopuff T-piece device, the pressure generated is directly related to the resistance that the flow resistor valve imposes on the gas flow through that valve. This rule only applies when the flow rate is constant.11 When the valve

Conclusion

When using a T-piece device for resuscitation clinicians should be aware of the effect of changing gas flow on airway pressures. We advise to choose a gas flow (about 8 L/min), then set the PIP and PEEP and to not change the gas flow during the resuscitation as set pressures will then change as well. If the airway pressures are not achieved this is likely to be due to poor mask technique which should be adjusted and not the gas flow. Increasing gas flow results in increased PEEP and decreased

Conflict of interest statement

None.

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    Te Pas et al.57 found that mask leak was greater at higher gas flow rates (24% at 5 L/min vs 80% at 10 L/min). This group59 also found that mask leak increased with increases in gas flow without adjustment of the pressure dials (14% at 5 L/min, 98% at 15 L/min), but this did not occur if the pressures remained constant (23% at 5 L/min, 22% at 15 L/min). The only study that did not find a difference in mask leak between the Neopuff and SIB was the manikin study by Dawson et al.47 (median mask leak: Neopuff 16%, SIB 16%, FIB 45%).

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A Spanish translated version of the summary of this article appears as Appendix in the final online version at doi:10.1016/j.resuscitation.2011.02.029.

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