RESUMO
OBJECTIVE: A device for the application of continuous positive airway pressure to switch injected breathing gas to the outlet during expiration, known as Infant Flow, claims to reduce work of breathing and peak pressure change. So far the Infant Flow system has been investigated in lung models with tidal volumes of not <12 mL. However, premature neonates below 1000 g of weight generate a tidal volume of approximately 4 mL only. The aim of this study was to compare work of breathing and peak pressure change of the Infant Flow and another system that uses nasal prongs, Baby Flow, with conventional continuous positive airway pressure delivered by a pharyngeal tube. DESIGN: Laboratory investigation, basic research. SETTING: University research laboratory. MODEL: A piston pump simulating the spontaneous breathing of premature neonates was connected without leak to three different continuous positive airway pressure devices (pharyngeal tube, Baby Flow, and Infant Flow) and with a produced leak to the systems using nasal prongs (Baby Flow and Infant Flow). INTERVENTION: The pressures of the airway and continuous positive airway pressure systems and airway flow were recorded. Peak pressure change and work of breathing were determined for all systems and settings. Percentages of reduction of peak pressure change and work of breathing in relation to the continuous positive airway pressure delivered by pharyngeal tube were calculated. MEASUREMENTS AND MAIN RESULTS: The switching of injected breathing gas to the outlet during expiration of Infant Flow systems require a tidal volume of at least 5 mL. It was possible to decrease peak pressure change and work of breathing: Baby Flow system at a tidal volume of 4 mL (Inspiration: peak pressure change 82%, work of breathing 80%; Expiration: peak pressure change: 68%, work of breathing: 61%) and at a tidal volume of 8 mL (Inspiration: peak pressure change 75%, work of breathing 73%; Expiration: peak pressure change: 67%, work of breathing: 57%). Infant Flow system at tidal volume of 4 mL (Inspiration: peak pressure change 50%, work of breathing 55%; Expiration: peak pressure change: 46%, work of breathing: 43%) and at a tidal volume of 8 mL (Inspiration: peak pressure change 47%, work of breathing 46%; Expiration: peak pressure change: 24%, work of breathing: 23%), related to the continuous positive airway pressure delivered by pharyngeal tube without leak.Even under conditions of leak peak pressure change and work of breathing could be reduced: Baby Flow system at a tidal volume of 4 mL (Inspiration: peak pressure change 59%, work of breathing 64%; Expiration: peak pressure change: 68%, work of breathing: 59%) and at a tidal volume of 8 mL (Inspiration: peak pressure change 45%, work of breathing 43%; Expiration: peak pressure change: 54%, work of breathing: 53%). Infant Flow system at a tidal volume of 4 mL (Inspiration: peak pressure change 49%, work of breathing 53%; Expiration: peak pressure change: 44%, work of breathing: 40%) and at a tidal volume of 8 mL (Inspiration: peak pressure change 48%, work of breathing 43%; Expiration: peak pressure change: 36%, work of breathing: 40%), related to the continuous positive airway pressure delivered by pharyngeal tube without leak. CONCLUSION: Peak pressure change and work of breathing were decreased by Baby Flow and Infant Flow systems, even under conditions of leak.
