Train-of-Four (TOF) ratio
The Train-of-Four (TOF) ratio measures neuromuscular blockade using four supramaximal stimuli to the ulnar nerve; TOF ratio = T4/T1 × 100%. TOF ratio ≥ 0.9 indicates adequate recovery and safe extubation. Anaesthesia trainees use TOF to guide NMBA dosing, reversal (neostigmine or sugammadex), and prevent residual blockade, which is associated with significant pulmonary complications.
