REPEATED ENFLURANE ANESTHETICS AND MODEL PREDICTIONS - A STUDY OF THEVARIABILITY IN THE PREDICTIVE PERFORMANCE-MEASURES

We quantified the total variability (reproducibility) and the within-p atient but between repeat anaesthetics variability (repeatability) in measures which are used to judge the predictive performance of our phy siological model. We studied 14 patients who received enflurane closed -circuit anaesthesia on two occasions. The end-tidal concentrations me asured and those predicted served to calculate the predictive performa nce measures of the model: root mean squared error (rmse=total error), bias (systematic error) and scatter (error around the bias). The over all results were: rmse 15 (7) %, bias 0 (14) % and scatter 9 (3) % (gr and mean (total SD)). The within-patient so Values were smaller for th e rmse (4%) and bias (10%), but not for scatter (3%). The repeat rmse values and biases were linked to the first results. This implies that these performance measures depended partly on the patient. As there wa s no association between the personal performance measures and age, se x, body weight, body surface area or body mass index, these characteri stics cannot be used to further tune the model.