BRONCHIAL AND REVERSE PULMONARY VENOUS-BLOOD FLOW PROTECT THE LUNG FROM ISCHEMIA-REPERFUSION INJURY

We used an intact in vivo canine model of pulmonary ischemia-reperfusi on injury to evaluate whether the bronchial circulation or reverse pul monary venous blood flow would proteet the lung from injury during 2 h of unilateral pulmonary arterial (PA) occlusion and lung deflation. S erial measurements of regional extravascular density and transcapillar y protein flux were made after reperfusion by using the quantitative i maging technique of positron emission tomography. Twenty-one animals w ere divided into four experimental groups. In all experimental groups, the left PA was clamped and the left lung was allowed to collapse and remain unventilated for a period of 2 h. In addition, in group I (n = 5) the left bronchial circulation was disrupted and the left pulmonar y veins were clamped, in group II (n = 5) the bronchial circulation an d the pulmonary veins were left intact, in group III (n = 6) the bronc hial circulation was left intact but the pulmonary veins were clamped, and in group IV (n = 5) the bronchial circulation was disrupted but t he pulmonary veins remained patent. The rate of protein flux in the le ft lung was increased only in group I (complete ischemia with lung def lation) [mean 195 X 10(-4) min(-1) (range 85-453 X 10(-4) min(-1)) at 0.25 h and 114 X 10(-4) min(-1) (range 22-200 X 10(-4) min(-1)) at 3 h ] after reventilation and PA reperfusion (normal = 49 +/- 31 X 10(-4) min(-1)). Extravascular density increased significantly from 0.25 to 3 h only in group I. Thus, both the bronchial circulation and reverse p ulmonary venous flow are able to protect the lung from injury during s hort-term PA occlusion and deflation.