Influence of tramadol on the ventilatory response to hypoxia in humans

We studied the effect of tramadol on the ventilatory response to 7 min acut e isocapnic hypoxia (Sp(O2) 85.1 (sD 0.4)%) during steady mild hypercapnia (PE'(CO2) 0.7 kPa above normoxic baseline) in 14 healthy volunteers (seven male). The acute hypoxic response was measured before and 1 h after oral pl acebo or tramadol (100 mg). After tramadol, ventilation during mild hyperca pnia (mean 11.28 litres min(-1)) was significantly less (P<0.05) than durin g placebo baseline (13.93 litres min(-1)), tramadol baseline (14.63 litres min(-1)), or after placebo (14.95 litres min(-1)), confirming that tramadol has a small depressive effect on the hypercapnic ventilatory response. The re was no significant difference in the hypoxic ventilation/Sp(O2), respons e (1 min(-1) %(-1)) measured during the placebo baseline (0.99), placebo (1 .18), tramadol baseline (0.78) or tramadol (0.68) runs. These data suggest that tramadol does not depress the hypoxic ventilatory response.