Estimation of the distribution profile of airway resistance in the lungs

Abstract The distribution profile of resistance in a series lung model consisting of airways of 23 generations with alveoli was estimated in 10 healthy subjects and 7 subjects with chronic pulmonary emphysema. Forced oscillation was applied to the subjects at the mouth using a complex wave composed of sine waves at frequencies through the range 4 to 20 Hz in 1-Hz steps. The pleural pressure was measured with a catheter-tip micromanometer, which was installed in an esophageal balloon. The frequency dependency of the pulmonary impedance was analyzed using a penalty function method, and a stable estimate of the distribution profile of resistance in the lungs was thus obtained. The central airway resistance (defined as the resistance from generation 0 to generation 7) was estimated as 1.18 ± 0.37 cm H 2 O/liter/sec in the healthy subjects and 1.03 ± 1.13 cm H 2 O/liter/sec in the subjects with chronic pulmonary emphysema. The peripheral airway resistance (defined as the resistance from generation 8 to generation 23) was estimated as 0.06 ± 0.03 cm H 2 O/liter/sec in the healthy subjects and 6.38 ± 3.77 cm H 2 O/liter/sec in the subjects with chronic pulmonary emphysema.