Fig. 2.
Ventilatory response to hypercapnia of an elderly participant under placebo conditions (breath ethanol concentration of 0 g/l infusion) and during coadministration of ethanol (breath concentration of 1 g/l) and 20 mg oxycodone immediate release. Squares denote resting data points without added inspired carbon dioxide; circles denote data obtained at added inspired carbon dioxide. All data points are 1-min median values obtained at steady-state ventilation. The line through the data is the data fit. The horizontal part of the data fit represents the estimation of resting ventilation, the linear ramp is the hypercapnic ventilatory response curve. The continuous vertical gray line depicts VE55 or the extrapolated minute ventilation at an end-tidal partial pressure of carbon dioxide (Pco2) of 55 mmHg; the continuous gray arrow is the decline in VE55 due to oxycodone and 1 g/l ethanol. The brokengray arrow is the decline in resting ventilation due to oxycodone and 1 g/l ethanol.