The use of recording disposable electrodes of different sizes has recently become an increasingly popular practice. Determining the appropriate size of recording disposable electrodes is essential to have accurate nerve conduction study measures. The purpose of this study is to determine if there is a liner trend between the recording disposable electrodes by measuring distal motor latency (DML) and compound motor action potential (CMAP) of the median nerve when recording with three different disposable electrode sizes. Large electrodes have the capability to pick up more motor unit potentials during testing. It was hypthothesized that the greater the electrode size, the greater the significant difference in median DML and CMAP that is detected compared to a small size electrode. Twenty-two adult volunteers within the age range of 19-49 years old participated in the study. The Sierra II-a four Channel electromyograph (EMG) machine with a laptop computer and two channel amplifier was used in the study. Disposable electrodes of different sizes by Cadwell Laboratoraties, Inc. were used with Sierra II. The testing electrodes used in the study were Silver/ Silver chloride disposable tabs self-adhering electrodes of 1.61 cm (squared) surface area, Silver/ Silver chloride disposable tabs self-adhering electrodes of 5.65 cm (squared) surface area, and disposable disc self-adhering electrodes of 3.63 cm (squared) surface area. The Silver/ Silver chloride disposable electrodes of 14.11 cm (squared) surface were used as ground electrodes. A metal disc electrode of 1.03 cm (squared) surface area was also used in the study as a control measure to record median DML and median CMAP. This commonly used electrode in the clinical field is known to obtain recording with less artifact and with less evoked potential bias. Each test was applied to the dominant hand using supramaximal stimulation and following National Institute of Occupational Safety and Health (NIOSH) guidelines. General linear models regression analysis and repeated measures analysis of variance test (ANOVA) were used to determine if the mean readings for the four electrodes differed significantly. The results revealed no significant difference between the four disposable recording electrode sizes in detecting median DML and significant difference in detecting median CMAP when used electrode of 5.65 cm (squared) surface area in normal subjects. The results of this study rejected the predicted the hypothesis for DML and accepted the hypothesis for CMAP. Electrode size has no significance on median DML while it has significance on median CMAP recording. Recording electrodes with a surface area between 1.61 to 3.63 cm (squared) are recommended to be used for routine nerve conduction studies in order to have accurate measurements.
