Frequency-dependency of pulmonary compliance and its relation to airway conductance

Dynamic compliance was determined in patients with 6 chronic obstructive lung diseases, 2 sarcoidosis and in 4 control healthy subjects at several breathing frequencies ranging between 0.2 and 1.3 Hz. The compliance exhibited an apparent fall with the increase in frequency of the patients, while it remained unaltered in the controls. A significant correlation was found between the frequency-dependency of compliance and the airway conductance determined plethysmographically. A similar relationship was also found in previous data appearing in the literature. Mathematical simulation based on the time constant theory revealed that the above correlation might be expected when airway obstruction occurred inhomogeneously in the peripheral region, of the lungs leaving the central airways intact.