Computer-based waveform subtraction for measuring refraction of neuromuscular transmission

The study demonstrated that computer-based waveform subtraction is a viable approach for the accurate determination of the refractory periods (RPs) of the neurally-evoked compound electromyograms (ncEMGs) and the refraction of neuromuscular transmission. Computer-based waveform subtraction can easily extract the R2 waveform from the complex ncEMGs and calculate accurate R2/R1 ratios. The method is more accurate and useful than the traditional “eyeballing,” which is the current method used. In the ncEMGs with twin stimuli, the interstimulus interval determines the time relationship between R2 and the R1. A short interstimulus interval obscures the R2 by the downward deflection of the R1. The emergence of the R2 is then delayed. Furthermore, the downward deflection elevates the baseline of the R2 waveform, making the measurement of the R2 amplitude difficult and unreliable by the traditional method. By use of computer-based waveform subtraction, the progression of R2 becomes smooth as the interstimulus intervals increase. The accurate R2 and the R2/R1 ratios are then available, and are suitable for evaluating the refraction of neuromuscular transmission. Applying the accurate R2/R1 in the study of neuromuscular physiology and pharmacology, a “dose-response” curve can be drawn and be used to investigate drug effects of many anesthetics and neuromuscular blocking drugs. In this study, the computer-based waveform subtraction resulted in an accurate dose response curve, similar to the traditional method but with a smaller refractory area