The cardiopulmonary effects of an inelastic chest wall restriction

Abstract

We examined the effects of an inelastic chest wall restriction (CWR) on cardiopulmonaxy function during rest and exercise in an attempt to mimic a condition similar to that seen in chronic heart failure. Forced vital capacities were measured at the beginning of the study, after which point four canvas straps were applied tightly around the thorax and abdomen so that vital capacity was reduced by >35%. Data were acquired during resting, 25%. and 45% of the peak workload achieved during the subjects' screening visit. Vital capacity, total lung capacity, and residual volume were all significantly reduced during CWR conditions. Subjects exhibited significant increases in ventilation brought about by increases in breathing frequency, despite decreases in tidal volume. This breathing pattern elicited significant increases in the flow resistive work of breathing and the gastric pressure-time integral (>400%), and resulted in a decrease in the elastic work of breathing. Significant decreases in cardiac output (>lo%) during CWR conditions were brought about by decreases in stroke volume. Heart rate, blood pressure, and calculated a-v& difference were all significantly elevated during CWR exercise conditions. We conclude that CWR conditions significantly affect pulmonary and cardiovascular function, although the mechanisms causing the decrease in cardiac output during CWR exercise conditions remain unclear. Additionally, our data suggest that CWR conditions elicit breathing patterns and cardiac responses similar to those seen in chronic heart failure, implying that CWR may be used as a crude model to study CIS.