A digital PID controller incorporating several modifications to accommodate
the characteristics of the neuromuscular blockade is described in this pap
er. The initial design was performed by the Ziegler-Nichols step response m
ethod. The controller gains are automatically adjusted to the specified tar
get by a gain-scheduling technique. The control system was evaluated in 30
patients. Subsequent analysis of all the data collected during surgery indi
cates that the variability of the patient responses is much wider than that
inferred from the literature. This observation clearly suggests the desira
bility of individual tuning of the controller parameters. A technique for a
n improved tuning of the PID controller parameters to the patient's individ
ual dynamics is presented. (C) 1998 Elsevier Science Ltd. All rights reserv
ed.