Pulmonary transcapillary exchange of Na24 and P32-labeled phosphate in pulmonary emphysema.

In previous studies it was observed that 5 to 20 per cent of intravenously administered Na24 and P32-labeled phosphate and other electrolytes escaped from the circulation during a single transit through the cardiopulmonary pool (1). The relatively small transcapillary exchange of electrolytes in the lungs as compared with skeletal muscle and certain other viscera was attributed to a lesser permeability of the pulmonary capillaries (1). The fraction of intravascular tracer electrolyte transferred across the pulmonary capillaries during pulmonary transit was diminished in the presence of a rapid circulation time and increased in patients with congestive heart failure and a prolonged circulation time (1). The present study extends these observations in patients with pulmonary emphysema where the problem of structural and physiological alterations of the pulmonary vascular tree is of particular interest.