The use of the Laerdal infant resuscitator results in the delivery of high oxygen fractions in the absence of a blender

Summary

Background

High oxygen increases morbidity and mortality. Current guidelines in Neonatal Resuscitation Programme (NRP) state if self-inflating bags are used with an input FiO₂ of 1.0 without an oxygen reservoir a delivered safe FiO₂ of approximately 0.40 is achieved. This conflicts with manufacturer findings (Laerdal infant resuscitator^® (LIR)). We assessed FiO₂ delivery by the LIR, varying oxygen reservoir (OR) use, ventilation and input flowrates.

Methods

A test lung was connected to the LIR and oxygen analyzer. FiO₂ delivery was measured under these four conditions: LIR plus OR and FiO₂ 1.0 or FiO₂ 0.40; LIR minus OR and FiO₂ of 1.0 and 0.40. Variations of ventilation patterns in random order, assessed tidal volumes (from 20 and 40 mL), ventilation rates (from 30, 40 and 60 breaths/min), and input flowrates (from 1, 3, 5, 8, and 10 Lpm). A wash-out period of 1 min of ventilation was followed by measure of FiO₂ during manual ventilation.

Results

The measured FiO₂ with the LIR delivered the same source FiO₂ under all experimental conditions for flowrates of 5 Lpm and greater; irrespective of the OR presence or absence. At flowrates of 1 and 3 Lpm, FiO₂ was lower, with and without the reservoir, but the reservoir was visibly identified as not filled.

Conclusion

Our findings support the manufacturers performance specification that high input FiO₂ results in high delivered FiO₂ with/without an OR. These results dispute the 2006 NRP guidelines that state “in the absence of a reservoir (oxygen) the delivered oxygen is reduced to about 40%”.

Introduction

The delivery of high oxygen fractions to premature infants carries a potential for increased mortality during newborn resuscitation. Recently, a systematic review provides strong evidence to argue for a reduction in the FiO₂ used at newborn resuscitation to below 1.0.¹ The Neonatal Resuscitation Program (NRP) of the American Heart Association acknowledges this evidence and is currently amending its recommendations.2, 3, 4 However how technically to achieve this may require re-consideration. Currently, the American Heart Association Neonatal Resuscitation Programme Guidelines² advise that with the self-inflating bag, a high fraction of oxygen (FiO₂) is not achieved when the oxygen reservoir is removed. This is in direct conflict with the Laerdal infant resuscitator^® (LIR) findings.⁵

An existing discrepancy between the LIR manufacturer recommendations and the NRP guidelines is of potential concern. The most widely used generic resuscitation device in newborns, is the self-inflating bag, as identified by 33 out of 40 neonatal intensive care centres across 19 countries.⁶ Although a 2006 global inventory lists over 100 trade-brands of self-inflating bags,⁷ the Laerdal infant resuscitator^® was identified as the most widely used self-inflating bag.⁶ The LIR manufacturers state that a high FiO₂ of 0.97–1.0 is delivered to the patient with or without the oxygen reservoir, when connected to an oxygen source. These recommendations are based on testing at tidal volumes of 20 mL and ventilation rates of 40–60 bpm, and flowrates of 3, 8, and 10 Lpm.⁵ In contrast, NRP currently states the FiO₂ delivered is reduced to approximately 0.40 by a self-inflating bag without the oxygen reservoir; the test methods of this data are not detailed by NRP though they acknowledge that the ventilation pattern will influence the actual FiO₂ delivered.²

Our objectives were first, to explore this discrepancy by determining whether the FiO₂ delivered by the LIR does vary with and without a reservoir; and second to determine if a FiO₂ less than 1.0 can be delivered by the LIR when connected to an O₂ source. If a consistent FiO₂ less than 1.0 can be delivered from the self-inflating bag, this would be reassuring for use during newborn resuscitation. Finally, we wished to determine the influence of tidal volume, ventilation rate, and gas flowrate (to the LIR) upon the FiO₂ delivery with and without the reservoir. We hypothesized that there would be great variability in the FiO₂ delivery without the reservoir, and that FiO₂ delivery would be inconsistent depending on tidal volume, ventilation rate and gas flowrate.