Previous studies suggested that NCPAP using variable‐flow generator caused greater lung recruitment and lower work of breathing than conventional NCPAP.3
Our study clearly shows that the patterns of breathing also differ with the NCPAP system. Increased tidal volume with the variable‐flow NCPAP generator probably results from improved thoraco‐abdominal synchrony and increased contribution of the rib cage to tidal volume. Moreover, low ΔEELV during the variable‐flow NCPAP indicates that the characteristic protective expiratory braking observed in preterm infants is decreased, suggesting effective passive increase in EELV. In contrast, higher ΔEELV with nasal cannulae suggests that the breathing strategy is oriented toward a dynamic elevation of EELV.
Controversies exist on the ability of variable‐flow NCPAP to alter the outcome, despite beneficial effects on the respiratory mechanics and the breathing pattern. In a recent study, no difference in extubation success rate was found between the variable‐flow CPAP and the conventional CPAP groups.6
In our study, O2
need and transcutaneous PaCO2
were similar with the 3 tested NCPAP devices. It is likely that the dynamic volume‐preserving mechanisms may have prevented from lung function impairment, at least for the short study period.
Because of the small sample size, clinical applicability of our data may be limited to a particular population of preterm infants.