The acceleration transducer--an assessment of its precision in comparison with a force displacement transducer

A new and simple acceleration transducer (ACT)-based system of neuromuscular monitoring has recently been introduced. The precision of this transducer has been evaluated as compared to a conventional force displacement transducer (FDT) in the present study. Ten progressions of spontaneous recovery from atracurium-induced block with simultaneous measurements using the ACT on one hand and the FDT on the other were studied. Five individuals undergoing elective surgery in modified neurolept anaesthesia and one ICU-patient requiring prolonged neuromuscular blockade, sedated with pentobarbital, were included. Measurements were carried out on the latter patient on 5 consecutive days. Train-of-four (TOF) stimulation was used, readings were given in twitch heights (TH) (T1/control value), and when four responses were obtained in TOF-ratios (T4/T1). Linearity was achieved after logit-transformation and the values regressed on time for each progression of recovery. Analysis of variance was applied to the regressions for the TH and TOF-ratio readings of each transducer. No significant differences were found, either between variation due to differences between slopes or variation due to technical error between the two transducers. The study indicates that the ACT is equal to the FDT with regard to precision in clinical recordings on atracurium-relaxed individuals.