Quantifying sympathetic nerve activity; problems and pitfalls, the need for standardization

Abstract

Since the first recording of sympathetic nerve activity (SNA) early last century numerous methods for presentation of the resulting data have developed. In this paper, we discuss the common ways to describe SNA and their application to chronic recordings. Suggestions on assessing the quality of SNA are made including the use of arterial pressure wave triggered averages and nasopharyngeal stimuli. Calculation of the zero level of the SNA signal from recordings during ganglionic blockade, the average level between bursts and the minimum of arterial pressure wave triggered averages are compared and shown to be equivalent. The use of normalisation between zero and maximal SNA levels to allow comparison between groups is discussed. We recommend that actual microvolt levels of integrated SNA be presented (with the zero/noise level subtracted) along with burst amplitude and frequency information whenever possible. We propose that standardisation of the quantifying/reporting of SNA will allow better comparison between disease models between research groups and ultimately allow data to be more reflective of the human situation.