ERYTHROCYTE AND POLYMORPHONUCLEAR CELL TRANSIT-TIME AND CONCENTRATIONIN HUMAN PULMONARY CAPILLARIES

Pulmonary capillary transit times were examined in patients who requir ed lung resection by use of Tc-99m-labeled macroaggregates (Tc-99-MAA) and chromium-labeled erythrocytes (Cr-51-RBC) to measure regional blo od flow and volume in the resected lung. Cell flow (cells.ml(-1).s(-1) ) to each resected lung sample was determined by multiplying the numbe r of polymorphonuclear leukocytes (PMN) per milliliter of circulating blood by the blood flow to that sample. Capillary blood volume was obt ained by multiplying the morphometrically determined fraction of pulmo nary blood in capillaries by the total Cr-51-RBC volume in each sample . Cell concentrations (cells/ml) in capillary blood were calculated mo rphometrically, and capillary transit times were obtained by dividing cell concentration by cell flow. The results show that PMN transit tim es were 60-100 times longer than the RBC transit times, with a 22% ove rlap between their distributions. We conclude that PMN are concentrate d with respect to RBC in pulmonary capillary blood because of differen ces in their transit times and that these long transit times provide a n opportunity for PMN-endothelial interactions.