OPTICAL MEASUREMENT OF ISOLATED CANINE LUNG FILTRATION COEFFICIENTS AT NORMAL HEMATOCRITS

In this study, lung filtration coefficient (K-fc) values were measured in eight isolated canine lung preparations at normal hematocrit value s using three methods: gravimetric, blood-corrected gravimetric, and o ptical. Tile lungs were kept in zone 3 conditions and subjected to an average venous pressure increase of 10.24 +/- 0.27 (SE) cmH(2)O. The r esulting K-fc (ml.min(-1).cmH(2)O(-1).100 g dry lung wt(-1)) measured with the gravimetric technique was 0.420 +/- 0.017, which was statisti cally different from the K-fc measured by the blood-corrected gravimet ric method (0.273 +/- 0.018) or the product of the reflection coeffici ent (sigma(f)) and K-fc measured optically (0.272 +/- 0.018). The opti cal method involved the use of a Cellco filter cartridge to separate r ed blood cells from plasma, which allowed measurement of the concentra tion of the tracer in plasma at normal hematocrits (34 +/- 1.5). The p ermeability-surface area product was measured using radioactive multip le indicator-dilution methods before, during, and after venous pressur e elevations. Results showed that the surface area of the lung did not change significantly during the measurement of K-fc. These studies su ggest that sigma(f)K(fc) can be measured optically at normal hematocri ts, that this measurement is not influenced by blood volume changes th at occur during the measurement, and that the optical sigma(f)K(fc) ag rees with the K-fc obtained via the blood-corrected gravimetric method .