THE TOF-GUARD NEUROMUSCULAR-TRANSMISSION MONITOR - A COMPARISON WITH THE MYOGRAPH-2000

The TOF-Guard neuromuscular monitor uses an accelerometer to measure t he response to nerve stimulation. In this study, we have compared it t o a standard mechanomyographic monitor, the Myograph 2000, for neuromu scular monitoring in 28 subjects. A train-of-four mode of stimulation was used in both cases. The times taken for onset of block, and for th e recovery of T1 (the first response in the train of four) to 25% of c ontrol, the time from recovery of T1 from 25-75% and for the recovery of the train of four ratio to 0.7 were compared with the two monitors. There was a good correlation between the two devices for both onset a nd recovery times. However, differences were highlighted when the data were analysed by the method of Bland and Altman. The 95% limits of ag reement for the T1 recovery to 25%, as measured by the TOF-Guard, rang ed from 5 min less to 8 min more than when measured by the Myograph 20 00. For recovery of the train of four ratio to 0.7, the limits of agre ement were approximately 6 min in either direction. The 95% limits for the TOF-Guard measured train of four ratio were from 0.47 to 0.99, at the Myograph reading of 0.7. We recommend that information from the T OF-Guard and the Myograph 2000 should not be used interchangeably. How ever, the TOF-Guard is likely to improve considerably on tactile evalu ation of the responses to stimulation.