Shunting by diffusion of inert gas in skeletal muscle.

The isolated cat gastrocnemius preparation was used to study shunting by diffusion of 133Xenon from arterial to venous blood. 133Xenon in saline, 51Chromium-labelled erythrocytes, and T1824-albumin were mixed and injected as a bolus into a side branch of the femoral artery. The muscle was autoperfused and stimulated electrically. Gas tight samples were taken every 0.7 to 1.0 s with a special technique developed for this purpose. The effluent blood from the muscle was collected in a 1.5 m long glass tube (i.d. 2 to 3 mm), and from a side branch at the inflow end of the tube mercury drops were led into the tube dividing the blood stream into samples. The inflow was stopped after 20 seconds and the contents of the two isotopes in the samples were measured by collimated counting externally over the tube. The T1824-analysis were performed spectrophotometrically. 133Xenon appeared in the venous samples before the intravascular reference tracers indicating that 133Xenon was shunted by diffusion from arterial to venous blood. The fraction of 133Xenon shunted by diffusion was estimated to about 11 per cent.