ASSESSMENT OF POSTPRESERVATION RAT LUNG-FUNCTION USING A NEW MODEL FOR EXTENDED VENOUS REPERFUSION

Understanding the physiological significance of biochemical events aft er lung preservation in rats has been hampered by the lack of a suitab le model for physiological assessment. We have developed an ex vivo pa racorporeal rat lung perfusion model that permits hemodynamic and gas exchange evaluation of lung function. After anesthesia and heparinizat ion, the heart-lung block was removed and the left lung was reperfused for 1 h at a constant flow of 4 ml/min with homologous venous blood d rained from the inferior vena cava of the paracorporeal (host) rat. Th e lung effluent was returned at the same flow rate to the host distal aorta. The model was validated by the assessment of lung function afte r room temperature ischemia. Animals were allocated into three groups (n = 6) according to the ischemic interval (group 1, 20 min; group 2, 3 h; group 3, 4 h). In groups 1 and 2, PO2, PCO2, mean airway pressure , and pulmonary arterial pressure were within the normal ranges and st able throughout the experiment. In contrast, lungs in group 3 demonstr ated higher pulmonary arterial pressure and lower blood effluent PO2 t han were found in either group 1 or 2. A significant weight gain durin g reperfusion was observed only in group 3 (4.23 +/- 0.9 g; P < 0.002) . For each lung, the final blood effluent PO2 correlated with the weig ht gain (R2 = 0.81; P < 0.0001). Our results indicate that this model can be used reliably to detect lung dysfunction after ischemic injury.