USEFULNESS OF SODIUM-CHLORIDE AS A NONDIFFUSIBLE INDICATOR IN THE MEASUREMENT OF EXTRAVASCULAR LUNG THERMAL VOLUME IN DOGS

The authors examined the usefulness of sodium chloride as a nondiffusi ble indicator during the first passage through dogs' lungs, before and after increased-permeability pulmonary oedema produced by an intraven ous injection of alloxan. With an injection of a mixture of ice-cold 3 per cent sodium chloride and indocyanine green dye (a nondiffusible r eference indicator), the authors simultaneously recorded three dilutio n curves from the aortic root: dye dilution, thermal and blood electri cal conductivity dilution curves in six dogs. The mean transit time of sodium chloride in the conductivity dilution curve was significantly different from, but fairly equal to, that of indocyanine green dye (6. 2 +/- 1.4 s (mean +/- SD) against 6.5 +/- 1.4 s (p < 0.01) in the base line period, and 7.6 +/- 1.9 s against 8.4 +/- 2.1 s (p < 001) in the oedema period, respectively). The calculated extravascular lung therma l volume with the thermal and conductivity dilution method (Y, mi kg-1 ) correlated well with the gravimetrically determined extravascular lu ng mass in a total of 12 dogs, including six other dogs without interv ention (x, g kg-1) (y = 0.72 x + 3.03, r = 0.96). The authors conclude that sodium chloride is useful as a nondiffusible indicator in the fi rst passage through the lungs, and that the thermal and conductivity d ilution method is also useful for measuring extravascular lung water m ass.