An in-line high frequency flow interrupter applied to nasal CPAP: Improved carbon dioxide clearance in a premature infant lung model.

BACKGROUND

Noninvasive respiratory support continues to have high failure rates in small preterm infants. We previously demonstrated significantly improved in vitro CO washout by applying oscillations to a high flow nasal cannula system.

OBJECTIVE

To develop a high frequency flow interrupter that could be applied to commonly used nasal continuous positive airway pressure (NCPAP) devices and to determine the effect of oscillations on end-tidal carbon dioxide (EtCO ) levels in an infant lung model.

DESIGN/METHODS: NCPAP was applied to a premature infant lung simulator using either bubble (BCPAP) or variable-flow (VCPAP) CPAP. Supply gas was interrupted with a solenoid pinch valve. EtCO was measured before and during oscillation and repeated at 4, 6, 8, 10, and 12 Hz oscillation and CPAP pressures of 4, 6, and 8 cm H O.

RESULTS

BCPAP and VCPAP EtCO levels decreased with oscillation (P < .001). BCPAP EtCO was significantly dependent on oscillation frequency (P < .001) with decreases of 18% to 47% and maximum effect at 10 Hz. Optimum VCPAP CO clearance occurred at 6 Hz with reductions of 30% and 39% at 6 and 8 cm H O CPAP respectively. BCPAP and VCPAP mean airway pressures remained unchanged transitioning from nonoscillation to oscillation. Oscillated BCPAP and VCPAP average amplitudes were 8.3 ± 0.5 and 8.4 ± 2.3 SD cm H O, respectively. Power spectrum analysis of non-oscillated BCPAP showed bubbling-only dominant peaks at 10 to 12 Hz corresponding with the maximum BCPAP EtCO reductions.

CONCLUSION

Application of high frequency oscillation to NCPAP improves CO clearance in a premature infant lung model. This simple modification to NCPAP delivery devices may prove to be an effective enhancement of this mode of noninvasive respiratory support.