Train of Four 1.0

The assessment of neuromuscular blockade during general anesthesia is optimally achieved through the train-of-four (TOF) ratio technique. This method employs a nerve stimulator in conjunction with a measurement device, such as mechanomyography. During TOF stimulation, a nerve stimulator delivers a brief burst of stimulation, eliciting four muscle twitches. The amplitude of these twitches correlates with the extent of neuromuscular blockade. The TOF ratio is calculated by comparing the height of the fourth twitch to that of the first, with a ratio greater than 0.9 deemed safe for the extubation of the endotracheal tube and indicative of complete reversal of neuromuscular blockade.

Despite the broad availability of nerve stimulators among anesthesiologists, access to suitable measuring devices remains limited. Consequently, practitioners frequently rely on twitch counts and pharmacological reversal as alternative evaluation strategies. This approach presents challenges, as research indicates that even mild residual paralysis (TOF ratios between 0.7 and 0.9) can significantly compromise respiratory and pharyngeal muscle function. Numerous studies have reported that many patients enter the postanesthesia care unit with TOF ratios below 0.9.

In response to this issue, we have developed an innovative method for measuring the TOF ratio utilizing the built-in accelerometer of the iPhone alongside a dedicated app. The development team comprised an anesthesia resident (RB) and an attending physician (MP), who provided medical insights, along with a computer programmer (KT) tasked with realizing this vision in software form. The next phase involves conducting a validation study to compare the predictive accuracy of TOF ratios measured via iPhone against traditional mechanomyography devices and visual assessments.