Preserved pressure delivery during high-frequency oscillation of bubble CPAP in a premature infant lung model with both normal and abnormal lung mechanics.

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 CO 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 H O, airway resistance 56 cm H O/(L/s); or abnormal mechanics, compliance 0.5 ml/cm H O, airway resistance 136 cm H 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 H 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 H 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.