Mechanical Factors Affecting the Evoked Pressures from a Simple Twitch Monitor

A syringe and aneroid manometer have been employed to quantitate neuromuscular blockade. The most important factors shown to vary its response were its air volume and the angulation of the syringe from the vertical. But even when these were held constant, the resultant pressures were not linearly related to the generative impulses. It is suggested that although this type of apparatus is not very accurate, the simple and inexpensive mechanism could benefit the practical anaesthetist monitoring nondepolarizing relaxants, providing its limitations are appreciated.