Pulmonary extravascular water volumes from transit time and slope data

Abstract

In single injection indicator-dilution experiments in the heart-lung system of anesthetized dogs, labeled water has a significantly greater distribution volume than simultaneously injected Na22 or T-1824, which have nearly identical concentration-time curves. Values for needle-to-needle vascular and aqueous compartments are calculated from the blood flow and the appropriate mean transit times. Values for the extravascular pulmonary water compartment, obtained by difference, are of the order of 4.3 ml/kg body wt. Similar calculations from the slope volumes (Newman et al., Circulation 4: 735, 1951) provide values of the order of 3.0 ml/kg body wt. The approximate concordance of the two sets of values is not considered validation of the slope calculation, which remains without an anatomically defined basis. Other limitations of the experimental procedures and calculations are considered. The value of 4.3 ml/kg body wt. obtained by the transit time calculation is considered to provide an upper limit to the volume of pulmonary tissue water involved in gas exchanges. Submitted on September 12, 1961