High-inspired oxygen concentration further impairs opioid-induced respiratory depression

Hyperoxaemia depresses the output of peripheral and central chemoreceptors. Patients treated with opioids often receive supplemental oxygen to avert possible decreases in oxygen saturation (SpO2). We examined the effect of a single dose of remifentanil in healthy volunteers inhaling room air vs air enriched with 50% oxygen. Twenty healthy volunteers received i.v. 50 μg remifentanil (infused over 60 s) at anormoxic (N) or hyperoxic (FIO2 0.5, H) background on separate occasions. Minute ventilation (Vi), respiratory rate (RR), end-tidal Pco2, and SpO2 were collected on a breath-to-breath basis. The occurrence of apnoea was recorded. During normoxia, remifentanil decreased Vi from 7.4 (1.3) [mean (sd)] to 2.2 (1.2) litre min−1 (P