Train-of-four (TOF) ratios are compared between a new homemade force pressure transducer and a commercially available accelerometer. Twenty adult patients were studied and 600 simultaneous TOF ratio pairs were recorded during anaesthesia with varying degrees of muscle relaxation. Laboratory testing revealed that the output from the homemade device was linear up to 900 g and that there was a linear relationship between the output from the new device and the accelerometer (y = 0.802x + 5.167, R = 0.943, t=69, P < 0.0001). Although the homemade device underestimates the accelerometer TOF ratio by 20%, it is a reliable and economic alternative to commercially available products for measuring TOF ratios.
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