Pulmonary parenchymal tissue volume measurements in graded degrees of pulmonary edema in dogs.

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Abstract
We investigated the accuracy and the sensitivity of a modification of the acetylene inhalation technique for the determination of lung tissue volume (Vt) during various grades of hemodynamic pulmonary edema in 23 dogs. After base-line acetylene measurements were obtained, intravascular driving force (pulmonary wedge pressure minus intravascular colloid osmotic pressure) was varied between -8 and +71 mm Hg by the inflation of an intra-aortic ballon and the infusion of isotonic saline. After 30 minutes at this new driving force, four timed acetylene samples were again collected. Vt (when factored by alveolar volume, VA) increased from base line to 0.23 plus or minus 0.07 ml/ml between a driving force of 0 and + 17 mm Hg. This same change in Vt/VA was accompanied by an increase in the lung wet weight-dry weight ratio from 3.84 plus or minus 0.31 to 5.2 plus or minus 0.25. Vt was 271 plus or minus ml compared with an actual lung wet weight of 288 plus or minus 57 g; Vt tended to overestimate lung wet weight in severe pulmonary edema. Alloxan-induced pulmonary edema (6 dogs) tended to parallel these data. We conclude that the acetylene method may ve a relatively accurate noninvasive method for the determination of increasing lung water in pulmonary edema.