Figure 2.

Hypercapnic response for the five opioid drug treatments. Left panels: time course of the median slope (upper panel) and intercept (lower panel). Right panels: mean and 95% confidence intervals of the slope and abscissa intercept (apnoeic threshold) for the periods before, during and after drug treatment. Repeated measures analysis of variance on these ventilatory responses with treatment and period as within subject factors with subject as the repeated measure found significant differences between periods, but not between active drug treatments.

Abbreviations: M15 = morphine 15 mg, M10/O5 = morphine mg + oxycodone 5 mg; M7.5/O7.5 = morphine 7.5 mg + oxycodone 7.5 mg; M5/O10 = morphine 5 mg + oxycodone 10 mg; O15 = oxycodone 15 mg. M15 (○); M10/O5 (▵); M7.5/O7.5 (▿); M5/O10 (□); O15 (⋄); before (▪); during (); after ()