OPTICAL MEASUREMENT OF ISOLATED CANINE LUNG FILTRATION COEFFICIENTS AFTER ALLOXAN INFUSION

In this study, lung filtration coefficient (Kf,) was measured in eight isolated canine lung preparations by using three methods: standard gr avimetric (Std), blood-corrected gravimetric (BC), and optical. The lu ngs were held in zone III conditions and were subjected to an average venous pressure increase of 8.79 +/- 0.93 (mean +/- SD) cmH(2)O. The p ermeability of the lungs was increased with an infusion of alloxan (75 mg/kg). The resulting K-fc values (in milliliters.min(-1) . cmH(2)O(- 1).100 g dry lung weight(-1)) measured by using Std and BC gravimetric techniques before vs. after alloxan infusion were statistically diffe rent: Std, 0.527 +/- 0.290 vs. 1.966 +/- 0.283; BC, 0.313 +/- 0.290 vs . 1.384 +/- 0.290. However, the optical technique did not show any sta tistical difference between pre-and postinjury with alloxan, 0.280 +/- 0.305 vs. 0.483 +/- 0.297, respectively. The alloxan injury, quantifi ed by using multiple-indicator techniques, showed an increase in perme ability and a corresponding decrease in rejection coefficient for albu min (sigma(f)). Because the optical method measures the product of K-f c and sigma(f), this study shows that albumin should not be used as an intravascular optical filtration marker when permeability is elevated . However, the optical technique, along with another means of measurin g K-fc (such as BC), can be used to calculate the sigma(f) of a tracer (in this study, sigma(f) of 0.894 at baseline and 0.348 after injury) . Another important finding of this study was that the ratio of baseli ne-to-injury K-fc values was not statistically different for Std and B C techniques, indicating that the percent contribution of slow blood-v olume increases does not change because of injury.