Fig. 1. The correlation between predicted and measured concentrations of plasma fentanyl in the lean group (Group L) and the obese group (Group O). The regression for Group L is: y = 0.89x + 0.80; r = 0.794, P < 0.001. For Group O: y = 1.12x + 1.38; r = 0.866, P < 0.001.