Pressure oscillations after flow interruption in relation to lung mechanics

The value of interrupter resistance measurements has been questioned because these depend on equilibration between alveolar (PA) and mouth pressure (PAO), which may not occur during airway obstruction or in measurements in children. In order to determine whether airway geometry and its interaction with the lung volume can be obtained without complete pressure equilibration, the postocclusional oscillatory airway opening pressure transients PAO(t) after flow interruption were studied in comparison to airway resistance (RAW), lung volumes (TGV, VC) and MEF50 in 9 healthy children (7-14 y) and 5 adults (28-37 y) in both time and frequency domains. The frequency of pressure oscillations was correlated to TGV (p < 0.01). Its damping properties (d) were correlated to MEF50 (p < 0.005). Performing airflow interruptions in the same subject showed that d increased at low lung volumes. During bronchial challenge test, d significantly increased with carbachol and decreased with salbutamol, whereas the frequency decreased with carbachol and increased with salbutamol. Therefore, the analysis of postocclusional pressure oscillations can be used to assess relative changes in airway mechanics and its interaction with lung volume during bronchial challenge tests in patients such as children with poor cooperation.