Chronic resistive loading induces diaphragm injury and ventilatory failure in the hamster

The purpose of this study was to examine the effects of tracheal banding for 30 days on arterial blood gases, and diaphragm structure and function. Hamsters were tracheal banded (TB) or underwent a sham procedure (C) (n = 16 and 18, respectively). After 30 days, arterial blood gases from awake TB hamsters showed hypoxemia and a respiratory acidosis. Histochemical analysis of diaphragm cross-sections showed a five-fold greater area fraction of abnormal muscle; a greater variation in fiber size; and a 3% higher proportion of type 1 fibers in TB than C hamsters. In vitro physiologic studies of costal strips from TB hamsters showed lower stress (45-70% over 10-100 Hz) than C values. Maximal esophageal pressure during occlusion was 45% higher and normalized diaphragm mass was 10% higher in TB hamsters than C hamsters. We conclude that the lower stress in vitro was attributable, at least in part, to diaphragm injury. Hypercapnea was present in spite of the higher diaphragm mass and maximal esophageal pressures in banded hamsters.