OPTICAL AND RADIOISOTOPE INDICATOR DILUTION MEASUREMENTS IN PULMONARY-EDEMA

The objective of this study was a validation of an optical multiple in dicator dilution technique for measuring microvascular exchange parame ters in edematous lungs by comparison to conventional radioisotope mul tiple indicator dilution methods. Six anaesthetized dogs were studied at baseline and after alloxan infusion to increase capillary permeabil ity. In addition, 11 isolated, perfused dog lungs were studied at base line and after edema was created by increasing venous pressure or by i nfusing alloxan to increase vascular permeability. Increased capillary permeability from alloxan infusion led to increases in most but not a ll capillary exchange parameters as analyzed by mathematical models an d measured by both optical and radioisotope methods. Increased vascula r pressure led to increased edema but no significant increases in capi llary exchange parameters. Two-way analysis of variance (ANOVA; variat ions in baseline versus pressure or alloxan and variation in optical v ersus radioisotope for each transport parameter derived from the mathe matical models) indicated few significant differences in capillary exc hange parameters between optical and radioisotope measures. Newman-Keu ls multiple comparison tests did uncover some variations between a few of the group-mean values derived from optical and radioisotope method s. However, optical and radioisotope parameter measurements were highl y correlated for all studies regardless of the mathematical model used for analysis. (C) 1998 Biomedical Engineering Society.