A system-based study of the variation in the amplitude of the compound sensory nerve action potential recorded using...

This study arose from the impression that there is a wide variation in the amplitude of the compound sensory nerve action potential (SNAP) when recorded using surface electrodes. Both the physiological factors influencing the SNAP and the method of measurement itself can be viewed as inputs to a system that produces the recorded value as its output. Taking a systems approach to the analysis of the variation in the recorded value of the SNAP on repeat testing, the techniques of statistical process control and experimental design were used to study three electrodes. All showed wide variation of the results in a single control subject. Many different factors were studied but no single factor was found to be the cause for a significant amount of the variation. This finding, coupled to the wide variation demonstrated, has implications for the use of surface recording of the SNAP.