Airway leak size in neonates and autocycling of three flow-triggered ventilators

Flow-triggered ventilators are susceptible to autocycling due to flow compensation to maintain positive end-expiratory pressure levels in the presence of an airway leak. The difference in autocycling is due to the maximum sensitivity setting of each ventilator, and not to intrinsic ventilator flowsensing or other software mechanisms. The 3.3-mL/sec setting was the least prone to autocycling and seems appropriate. The ventilator set at 2.5 mL/sec at the time of this study has been released instead at 4 mL/sec, due to these findings. The ventilator with the maximum setting at 1 mL/sec autocycled readily at leak size of > or = 10%. Since such a leak size was present in 70% of infants, this setting should be used with caution. Using these guidelines, autocycling of all three ventilators is likely to occur mainly in 8% of infants with leak size of > 30%. In these cases, lowering the sensitivity setting and/or positive end-expiratory pressure level may decrease autocycling, or may necessitate reintubation with a larger endotracheal tube.