Direct measurement of human sympathetic nerve conduction velocity

We evaluated a method for direct measurement of conduction velocity (CV) in sympathetic nerves in humans using a double-recording method of skin sympathetic nerve activity (SSNA) by microneurography. SSNA in the tibial nerve was recorded simultaneously at proximal and distal sites in the popliteal fossa (short-distance study) or at the popliteal fossa and ankle (long-distance study). In both studies, CVs were determined by dividing the interelectrode distance on the skin by the difference in conduction time between the rising-phases (rising-phase analysis) or peaks of the integrated bursts (peak-to-peak analysis). The measurement using long distance and peak-to-peak analysis had the highest accuracy; it is an orthodromic conduction measurement, is unrelated to eliciting stimulus, has high temporal resolution, and is not affected by the effector organ conditions. The average CV of resting SSNA was 0.93 +/- 0.09 m/s.