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

Abstract

Background Noninvasive respiratory support continues to have high failure rates in small preterm infants. We previously demonstrated significantly improved in vitro CO2 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 (EtCO2) 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. EtCO2 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 2O. Results BCPAP and VCPAP EtCO2 levels decreased with oscillation (P < .001). BCPAP EtCO2 was significantly dependent on oscillation frequency (P < .001) with decreases of 18% to 47% and maximum effect at 10 Hz. Optimum VCPAP CO2 clearance occurred at 6 Hz with reductions of 30% and 39% at 6 and 8 cm H2O 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 H2O, respectively. Power spectrum analysis of non‐oscillated BCPAP showed bubbling‐only dominant peaks at 10 to 12 Hz corresponding with the maximum BCPAP EtCO2 reductions. Conclusion Application of high frequency oscillation to NCPAP improves CO2 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.

Carbon dioxide clearance using bubble CPAP with superimposed high frequency oscillations in a premature infant lung model with abnormal lung mechanics

“…This study was undertaken as a continuation of previous work performed in this laboratory in which a novel in-line flow interrupter device was evaluated to determine its efficacy as a simple means of improving carbon dioxide elimination in a nasal CPAP system 3,5 . We previously demonstrated that superimposing high frequency oscillation had better performance in improving carbon dioxide clearance when applied to a BCPAP system compared to the commonly used variable-flow type of nasal CPAP.…”

“…In particular, bubble nasal (BCPAP) has gained renewed interest not only due to its simplicity, but also because the random pressure oscillations caused by the bubbling have been suggested to improve gas exchange through mechanisms of action similar to those observed in high frequency ventilation 1,2 . In this regard, we have recently performed a series of in-vitro tests demonstrating improved carbon dioxide clearance when high frequency oscillations are superimposed onto the supply flow of a HFNC system 3,4 as well as onto the supply flow of a BCPAP system 5 . The aforementioned studies were exploratory proof-of-concept bench studies using a premature infant lung model having simulated normal, non-diseased, pulmonary mechanics.…”

Carbon dioxide clearance using bubble CPAP with superimposed high‐frequency oscillations in a premature infant lung model with abnormal lung mechanics

“…This study was undertaken as a continuation of previous work performed in this laboratory in which a novel in‐line flow interrupter device was evaluated to determine its efficacy as a simple means of improving CO 2 elimination in a nasal CPAP system 5 . We previously demonstrated that superimposing high‐frequency oscillation had better performance in improving CO 2 clearance when applied to a BCPAP system compared with the commonly used variable‐flow type of nasal CPAP.…”

“…1,2 In this regard, we have recently performed a series of in vitro tests demonstrating improved carbon dioxide (CO 2 ) clearance when high-frequency oscillations are superimposed onto the supply flow of an HFNC system 3,4 as well as onto the supply flow of a BCPAP system. 5 The aforementioned studies were exploratory proof-of-concept bench studies using a premature infant lung model having simulated normal, nondiseased, and pulmonary mechanics.…”

“…In particular, bubble nasal CPAP (BCPAP) has gained renewed interest not only due to its simplicity but also because the random pressure oscillations caused by the bubbling have been suggested to improve gas exchange through mechanisms of action similar to those observed in high‐frequency ventilation 1,2 . In this regard, we have recently performed a series of in vitro tests demonstrating improved carbon dioxide (CO 2 ) clearance when high‐frequency oscillations are superimposed onto the supply flow of an HFNC system 3,4 as well as onto the supply flow of a BCPAP system 5 . The aforementioned studies were exploratory proof‐of‐concept bench studies using a premature infant lung model having simulated normal, nondiseased, and pulmonary mechanics.…”