Analysis of distal airway pressure changes in a simulation model of continuous positive airway pressure (CPAP).

Background: Nasal continuous positive airway pressure (CPAP) is commonly used to treat respiratory failure in newborns with excellent results; however, pneumothorax is frequently reported, varying in frequency from 1.4% to 10.3%.Methods: In this study, we used a lung simulator to determine the cause of this variability by measuring the pressure in the CPAP system and in the interior of one balloon to simulate the lung, with repeat measurements with the nasal prongs sealed and unsealed. In addition, crying was simulated by blowing through a hole that simulated the mouth.Results: We found that when the nasal prongs were used, unsealed simulator distension existed. However, the pressure remained at zero when the nostrils were sealed, indicating that the pressure inside the simulated lung was equal to that inside the system. Simulated crying increased the pressure 4-fold.Conclusions: We conclude that the seal in the nostrils is a factor for the effectiveness of the procedure and increases the risk of pneumothorax, as well as alter the results of studies on nasal CPAP. Nostril seals should be considered for future studies on the efficacy and safety of nasal CPAP.