Figure 39-20 This diagram shows when the different modes of electrical nerve stimulation can be used during clinical anesthesia. Dark areas indicate appropriate use; light areas, less effective use. Modes of nerve stimulation: TOF, train-of-four stimulation; PTC, post-tetanic count; DBS, double-burst stimulation; and ?, indicating that TOF is less useful in the recovery room unless measured using mechano-, electro-, or acceleromyography. (See text for further explanation.)