Quantitative neuromuscular monitors measure and quantify the degree of neuromuscular blockade and display the results numerically.
Quantitative assessment of the train-of-four fade by neuromuscular transmission monitors is the only suitable method to identify low but clinically meaningful levels of residual neuromuscular block. To determine whether full recovery of neuromuscular function has occurred at the time of tracheal extubation, quantitative monitors are required.
Mechanical techniques such as mechanomyography (MMG), acceleromyography (AMG), and kinemyography (KMG) measure muscle responses, using physics principles such as force, acceleration, or velocity.
Electromyography (EMG) is based on the measurement of the compound muscle action potential. EMG measures an electrical event that occurs at the neuromuscular junction; the release of acetylcholine from the pre-synaptic nerve endings (a chemical process) and activation of postsynaptic receptors that converts it to a mechanical response (excitation- contraction coupling that results in muscle contraction).
For this reason, EMG is less prone to interference from presynaptic or postsynaptic events and is a better indicator of pure neuromuscular function.