CHANGES IN BRONCHIAL AND PULMONARY ARTERIAL BLOOD-FLOW WITH PROGRESSIVE TENSION PNEUMOTHORAX

We studied the effects of unilateral tension pneumothorax and its rele ase on bronchial and pulmonary arterial blood flow and gas exchange in 10 adult anesthetized and mechanically ventilated sheep with chronica lly implanted ultrasonic flow probes. Right pleural pressure (Ppl) was increased in two steps from -5 to 10 and 25 cmH(2)O and then decrease d to 10 and -5 cmH(2)O. Each level of Ppl was maintained for 5 min. Br onchial blood flow, right and left pulmonary arterial flows, cardiac o utput (Q over dot T), hemodynamic measurements, and arterial blood gas es were obtained at the end of each period. Pneumothorax resulted in a 66% decrease in Q over dot T, bronchial blood flow decreased by 84%, and right pulmonary arterial flow decreased by 80% at Ppl of 25 cmH(2) O (P < 0.001). At peak Ppl, the majority of Q over dot T was due to bl ood flow through the left pulmonary artery. With resolution of pneumot horax, hemodynamic parameters normalized, although abnormalities in ga s exchange persisted for 60-90 min after recovery and were associated with a decrease in total respiratory compliance.