Dynamic respiratory mechanics in monkeys measured by forced oscillations

We measured impedances of the lungs (ZL) and respiratory system (Zrs) by discrete frequency (f) forced oscillations in adult bonnet monkeys at two lung volumes, FRC and at transrespiratory system pressure (Prs) of -5 cm H2O. Measurements were made from 2 to 32 Hz to study f dependence of effective resistances (Reff) and reactances, and from 1 to 8 Hz to study f dependence of effective pulmonary compliance (Ceff,L). Estimates of resistances (R), inertances (I) and compliances (C) of the lungs (L), chest wall (W) and respiratory system (rs) were obtained by fitting the 2-32 Hz data to a series RIC network model. Reff,L, Reff,W and Reff,rs were found to be f dependent. The magnitude of ZL was small relative to that of Zrs at all f with RL only 30% of Rrs and CL six times Crs. Decreasing lung volume from FRC to Prs = -5 cm H2O increased RL, RW and Rrs, slightly decreased CL, CW and Crs, slightly increased resonance frequencies, and increased the f dependent behavior of Ceff,L. Our results indicate both similarities and differences between the respiratory system of these primates and man.