Platelets and leukocytes in the lungs after acute hypobaric hypoxia

To determine if decompression from sea level causes aggregation and embolization of platelets or leukocytes to the lungs, we have measured the accumulation of 51Cr-labeled platelets or 111In-labeled leukocytes in the lungs of rabbits decompressed to 440 or 350 Torr for 18 or 40 h. To be certain that any increased accumulation of labeled platelets (or leukocytes) in the lungs was not just caused by an increased pulmonary blood volume we also labeled the rabbits red blood cells with 59Fe. There was no detectable accumulation of labeled platelets in the lungs on decompression. In control animals there were 22 times as many labeled leukocytes in the lungs as could be accounted for by the volume of blood in the lungs. In experimental animals at 326 Torr for 18 h this figure was reduced to 13.6. Hypobaric hypoxia caused an increase in circulating granulocytes from a mean of 3.3 +/- 1.6 X 10(9)/l to 5.3 +/- 2.1 X 10(9)/l. (P less than 0.005). Our results suggest that decompressions to 6,100 m for 18 h does not cause platelet sequestration in the lungs but does cause a significant reduction in leukocytes in the lungs and a peripheral granulocytosis.