Intermittent pneumatic compression of legs increases microcirculation in distant skeletal muscle

Intermittent pneumatic compression has been established as a method of clin ically preventing deep vein thrombosis, but the mechanism has not been docu mented. This study observed the effects of intermittent pneumatic compressi on of legs on the microcirculation of distant skeletal muscle. The cremaste r muscles of 80 male rats were exposed, a specially designed intermittent p neumatic-compression device was applied to both legs for 60 minutes, and th e microcirculation of the muscles was assessed by measurement of the vessel diameter in three categories (10-20, 21-40, and 41-70 mu m) for 120 minute s. The results showed significant vasodilation in arterial and venous vesse ls during the application of intermittent pneumatic compression, which disa ppeared after termination of the compression. The vasodilation reached a ma ximum 30 minutes after initiation of the compression and could be completel y blocked by an inhibitor of nitric oxide synthase, N-G-monomethyl-L-argini ne (10 mu mol/min). A 120-minute infusion of N-G-monomethyl-L-arginine, beg inning coincident with 60 minutes of intermittent pneumatic compression, re sulted in a significant decrease in arterial diameter that remained at almo st the same level after termination of the compression. The magnitude of th e decrease in diameter in the group treated with intermittent pneumatic com pression and N-G-monomethyl-L-arginine was comparable with that in the grou p treated with N-G-monomethyl-L-arginine alone. The results imply that the production of nitric oxide is involved in the positive influence of intermi ttent pneumatic compression on circulation. It is postulated that the rapid increase in venous velocity induced by intermittent pneumatic compression produces strong shear stress on the vascular endothelium, which stimulates an increased release of nitric oxide and thereby causes systemic vasodilati on.