Measured remifentanil plasma concentrations during a 15-min fixed dose infusion (0.05, 0.1, or 0.15 μg · kg^-1 · min^-1) in patients with obstructive sleep apnea (red symbols) and without obstructive sleep apnea (black symbols). Time is relative to the start of the remifentanil infusion. Results are show as the mean ± SD (n = 5 for each group).