The effect of external expiratory resistance on lung volume and pulmonary function in the neonate.

To investigate the acute physiologic effects of external expiratory resistance on lung function in extubated neonates recovering from respiratory disease, lung mechanics, respiratory patterns, and functional residual capacity were measured in ten neonates dueing a control period and immediately after application of an external expiratory resistance of 30 cm H2O/l/second via a face mask. Following application of EER, mean FRC increased by 40.8% (P less than 0.05). The work of breathing was significantly increased after the EER was applied; there was also a significant increase in measured expiratory resistance and a decrease in inspiratory-expiratory time ratio. The change in lung volume was rapid, requiring less than five seconds for the new end-expiratory level to be reached. Dynamic lung compliance, inspiratory resistance, and respiratory rate did not change during any phase of the study. The application of external expiratory resistance may have potential therapeutic value by increasing lung volume in infants recovering from respiratory disease.