AN OPTICAL MULTIPLE INDICATOR DILUTION TECHNIQUE TO MEASURE LUNG PERMEABILITY-SURFACE AREA - CALIBRATION AND BASE-LINE MEASUREMENT

A device was designed to measure the change in optical density (Delta OD) of blood at selected wavelengths as a function of the concentratio n of optically absorbing multiple indicator dilution (MID) tracers, Th e optical MID (OMID) tracers selected for this measurement device and their corresponding wavelengths are the following: indocyanine green(I CG)-bound albumin measured at 820 nm, sulfhemoglobinated erythrocytes (Shb-RBC's) measured at 620 nm, and 1,2-propanediol measured at 9.55 m u m. Arterial blood from cannulated anesthetized dogs was circulated t hrough an extracorporeal flow-through circuit which included this Delt a OD measurement device. Calibration of the 820 nm and 620 nm channels produced r(2) of greater than 0.95 for the optical density-tracer mas s regressions, The propanediol measurement channel (9.55 mu m) was als o linearly calibrated. An in vivo optical MID study was performed and compared to a radioisotope MID study, Lung vascular permeability-surfa ce area (PS) values calculated using the two methods were 5,76 and 5.7 3 mL/s. We concluded that this OMID technique is an acceptable alterna tive to radioisotope MID studies.