Blood flow rate in arteriovenous anastomoses and capillaries in thumb, first toe, ear lobe, and nose.

Measurements of blood flow rate in the pulp of the thumb, the first toe, the ear lobe, and the nose were performed using the heat-washout method, and the 133Xe-washout method under orthostatic changes in humans. Blood flow rate measured by the heat-washout method in the thumb was about 127.5 ml (100 g x min)-1 at heart level in two subjects, (n=10), and in the pulp of the first toe in 6 subjects (n=12) 49.3 ml (100 g x min)-1 at heart level. Above heart level blood flow rate decreased with the falling pressure head, and 50 cm below heart level blood flow remained unchanged compared to heart level. The arterioles supplying the capillaries in this region showed autoregulation of blood flow to 50 cm above heart level, but a veno-arteriolar reflex was not present. Blood flow rate in the ear lobe and on the side of the nose showed a similar pattern of reaction, with a blood flow rate in the arteriovenous anastomoses of about 100 ml (100 g x min)-1 in sitting position.