Hemodynamic effects of rapidly evacuating prolonged pneumothorax in rabbits

Clinical observations suggest that systemic hypotension may be caused by rapid evacuation of persistent pneumothorax. This observation has not been substantiated experimentally and the mechanism(s) are unknown. In this study, we measured systemic hemodynamic parameters in rabbits before and for 2 h during negative pressure evacuation of a right-sided pneumothorax of 7-9 days duration. Three groups of animals were studied: 10 rabbits breathed room air and were hypoxemic during pneumothorax (hypoxemic pneumothorax = HP); 10 rabbits breathed 40% O2-60% N2, which prevented arterial hypoxemia during pneumothorax (supraoxemic pneumothorax = SP); seven normal control animals were untreated during this time period (NC). Pneumothoraces in HP and SP were evacuated by negative pressure applied to the right pleural space for 2 h while animals were anesthetized and mechanically ventilated. The NC group was anesthetized and ventilated without prior pneumothorax. Serial hemodynamic measurements were made before and during pleural suction.(ABSTRACT TRUNCATED AT 250 WORDS)