Automatic monitoring of patient relaxation status

The authors describe the development and operation of a simple inexpensive method to monitor neuromuscular transmission (NMT). The device provides quantitative information on the level of muscle relaxation in patients who have received neuromuscular blocking drugs during anesthesia. NMT is monitored by activating a motor nerve with four consecutive stimuli with 2-Hz frequency and quantitatively determining the magnitude of the thumb twitches relative to a prerelaxant reference value. The monitoring unit was designed around a patented position/movement detector and a microprocessor. One end of the position detector is connected to the thumb via a tiny flexible rod and the other end to a spring. Two LED (light-emitting diode) bargraphs provide a direct real-time readout of the first (T1) and fourth (T4) thumb twitches. A third bargraph displays the ratio of T4/T1 as a percentage. The monitor and stimulator are enclosed in a thin enclosure attached to the patient's arm with velcro straps. >