The Margin of Safety of Neuromuscular Transmission in the Muscle of the Diaphragm

Recovery from neuromuscular block is commonly assessed by examining the response of a limb muscle to stimulation of its motor nerve. However, it is in the muscles of respiration, particularly the diaphragm, that the degree of recovery is most crucial. Therefore, the diaphragm has been compared with the tibialis anterior with respect to margin of safety of neuromuscular transmission. When the twitch of the tibialis anterior has returned to normal during recovery from d-tubocurarine, the diaphragm has almost twice as many receptors free as are barely necessary to produce a maximal twitch response. Thus, recovery in the periphery is a conservative index of recovery in the diaphragm.