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.