Hypothenar muscle action potential recorder

Drugs which block the transmission of excitation from motor nerve to voluntary muscle fibre are used routinely in anaesthesia. The action of this group of drugs may be studied by stimulating a motor nerve and observing the evoked muscle response. Simple nerve stimulators are widely available and are designed to achieve supramaximal stimulation of a convenient peripheral motor nerve. Quantitative observation of the evoked muscle response is achieved by measuring either the action potential or the tension developed by the contracting muscle. While such techniques are commonly used for research and teaching purposes, they are not widely available to the practising anaesthetist. Electrocardiography, on the other hand, id frequently used in operating theatres and recovery rooms, so that medical personnel are accustomed to using ECG recorders and are trained to interpret the displayed information. We have developed an EMG pre-amplifier and signal processor to produce a signal which can be displayed by ECG equipment.