Low-frequency pulmonary impedance in rabbits and its response to inhaled methacholine

Abstract

BATES. Low-frequency pulmonary impedance in rabbits and its response to inhaled methacholine. J. Appl. Physiol. 73(l): 290-295, 1992.-We assessed pulmonary mechanics in six open-chest rabbits (3 young and 3 adult) by the forced oscillation technique between 0.16 and 10.64 Hz. Under control condi-tions, pulmonary resistance (RL) decreased markedly between 0.16 and 4 Hz, after which it became reasonably constant. Mea-surements of alveolar pressure from two alveolar capsules in each rabbit showed that the large decrease of RL with increas-ing frequency below 4 Hz was due to lung tissue rheology and that tissue resistance was close to zero above 4 Hz. Estimates of resistance and elastance, also obtained by fitting tidal ventila-tion data at 1 Hz to the equation of the linear single-compart-ment model, gave values for RL motion that were slightly higher than those obtained by forced oscillations at the sam