Journal of Applied Physiology, Vol 63, Issue 5 1711-1718, Copyright © 1987 by American Physiological Society
Mechanics in rats by end-inflation occlusion and single-breath methods
P. H. Saldiva, W. V. Cardoso, M. P. Caldeira and W. A. Zin
Instituto do Coracao-FMUSP, Brazil.
In six mechanically ventilated anesthetized (pentobarbital sodium, 30
mg/kg) paralyzed rats (187-253 g body wt) volume, airflow, and tracheal,
esophageal, and transpulmonary pressures were measured. Respiratory system
elastic and resistive properties were partitioned into their lung and chest
wall components after end-inflation occlusion of the airways subsequent to
constant-flow inspirations and during relaxed expiration ensuing release of
occlusion. The values provided by both methods were similar. Mean
respiratory system, lung, and chest wall elastances amounted to,
respectively, 5.536, 3.440, and 2.097 cmH2O.ml-1. Mean values of intrinsic
respiratory system, pulmonary, and chest wall resistances (at flows of 3.5
ml.s-1) were 0.235, 0.144, and 0.091 cmH2O.ml-1.s, respectively. Resistive
pressure-flow relationships for the respiratory system, lung, and chest
wall were also determined during the entire tidal expiration. A linear
relationship was found for the former, whereas power functions best
described the others: the pulmonary pressure-flow relationship exhibited an
upward concavity and that for the chest wall presented an upward convexity.
