Breath‐dependent pressure fluctuations in various constant‐ and variable‐flow neonatal CPAP devices

OBJECTIVE: In continuous positive airway pressure (CPAP) devices, pressure can be generated by two different mechanisms: either via an expiratory valve or by one or more jets. Valved CPAP devices are referred to as constant‐flow devices, and jet devices are called variable‐flow devices. Constant‐flow CPAP devices are said to reduce the imposed work of breathing due to lower breath‐dependent pressure fluctuations. The present study investigates the performance of various constant‐ and variable‐flow CPAP devices in relation to breath‐dependent pressure fluctuations. DESIGN: Experimental study comparing the pressure fluctuations incurred by seven neonatal CPAP devices attached to an active neonatal lung model. METHODOLOGY: Spontaneous breathing was simulated using a tidal volume of 6 ml at pressure levels of 5, 7, and 9 mbar. The main outcomes were respiratory pressure fluctuations, tidal volume, and end‐expiratory pressure. RESULTS: All CPAP devices tested showed respiratory pressure fluctuations, varying from 0.631 to 3.466 mbar. The generated tidal volume correlated significantly with the pressure fluctuations (r = −0.947; p = 0.001) and varied between 5.550 and 6.316 ml. CPAP devices with jets showed no advantage over CPAP devices with expiratory valves. End‐expiratory pressure in the nose deviated from the set pressure between −1.305 and 0.644 mbar and varied depending on whether the pressure was measured in the device or in the tube extending to the nose. CONCLUSION: During standard spontaneous breathing, breath‐dependent pressure fluctuations in constant‐ and variable‐flow devices are comparable. Pressure measurements taken in the tubing system can lead to a considerable deviation of the applied pressure.