Longitudinal differences of susceptibility to ischaemia in human sensory nerve fibres

The effect on the median nerve of ischaemia induced by a tourniquet (at a pressure of 250 mm Hg) placed on the upper arm was investigated in 12 young volunteers. In 6 of these 12 persons a second cuff, applying the same pressure as the first, was placed on the mid-forearm. In both groups the decrease in sensory action potentials and in nerve conduction velocity was more rapid in the proximal than in the distal segments. No other difference was detected between the two groups. It is concluded that the pressure induced by the cuff was not responsible for the changes and it is suggested that this phenomenon is due to internodal lengths being greater in the proximal than in the distal segments.