Background: Bubble continuous positive airway pressure (BCPAP) generates pressure oscillations which are suggested to improve gas exchange through mechanisms similar to high frequency (HF) ventilation. In a previous in-vitro lung model with normal lung mechanics, significantly improved CO2 washout was demonstrated using an HF interrupter in the supply flow of a BCPAP system. The effect of HF with BCPAP on delivered airway pressure (Paw) has not been fully investigated in a lung model having abnormal pulmonary mechanics.
Objective: To measure Paw in an infant lung model simulating normal and abnormal pulmonary compliance and resistance while connected to a BCPAP system with superimposed HF oscillations created using an in-line flow interrupter.
Design/methods: A premature infant lung model with either: normal lung mechanics, compliance 1.0 ml/cm H2 O, airway resistance 56 cm H2 O/(L/s); or abnormal mechanics, compliance 0.5 ml/cm H2 O, airway resistance 136 cm H2 O/(L/s), was connected to BCPAP with HF at either 4, 6, 8, 10, or 12 Hz. Paw was measured at BCPAPs of 4, 6, and 8 cm H2 O and respiratory rates (RR) of 40, 60, and 80 breaths/min and 6.0 ml tidal volume.
Results: Mean Paw averaged over all five frequencies showed no significant change from non-oscillated levels at all BCPAPs and RRs for both lung models. Paw amplitudes (peak-to-trough) during oscillation were significantly greater than the non-oscillated levels by an average of 1.7 ± 0.5 SD and 2.6 ± 0.5 SD cm H2 O (p < .001) for the normal and abnormal models, respectively.
Conclusions: HF oscillation of BCPAP using a flow interrupter did not alter mean delivered Paw compared to non-oscillated BCPAP for both normal and abnormal lung mechanics models. This simple modification to BCPAP may be a useful enhancement to this mode of non-invasive respiratory support.
Keywords: delivered airway pressure; non-invasive ventilation.
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