Pulmonary mechanics in normal rats

TLDR

Flow‑limiting behavior was demonstrated by graded forced expiratory maneuvers. The plethysmographic system yielded lung volumes and compliance values consistent with prior reports, while showing lower pulmonary resistance and chest wall compliance, frequency‑independent dynamic compliance, flow‑limiting behavior with effort‑independent maximal flow up to 40–50 % of vital capacity, linear flow‑recoil pressure relationships, and modest increases in forced expiratory flow with a low‑density gas mixture.

Abstract

A versatile, whole-body pressure, or volume plethysmographic system for the study of pulmonary mechanics in anesthetized, tracheotomized rats has been described. Lung volumes and lung compliance values were in good agreement with those previously reported. Pulmonary resistance and chest wall compliance values were lower than those previously reported. Total dynamic compliance remained independent of respiratory frequency between 40 and 320 breaths/min. Flow-limiting behavior was demonstrated from a series of imposed forced expiratory maneuvers of graded effort. With a deflation pressure of 30 cmH2O, the effort-independent range of maximum flow extended to 40-50% of vital capacity. Maximal flow-static recoil pressure relationships were essentially linear over the effort independent portion of the flow-volume curve. Substitution of a low-density gas mixture (80% He-20% O2) for air resulted in increased forced expiratory flow rates but the magnitude of the response was considerably less than that which has been reported in man.