Effect of ethanol on interaction of hypoxia and PCO2 levels in rabbits.

The following three kinds of hypoxia were imposed on rabbits: the inhalation of two hypoxic gas mixtures (O2 2%-CO2 5%-N2 93% [CO2-added hypoxic] and O2 2%-N2 98% [CO2-free hypoxic]) and asphyxiation by tracheal occlusion. Ethanol (1.5g/kg of body weight) was given intravenously 30 min before the start of the hypoxia. A period up to the onset of apnea, as well as death, was shorter in the ethanol-treated group than in the non-treated group. This respiratory depressing effect of ethanol was evident in the hypoxic gas inhalation group. There was no significant difference in the PO2 value when apnea occurred. The animals inhaling the CO2-free hypoxic gas mixture became apneic sooner than those inhaling the CO2-added hypoxic gas mixture. The respiratory depressing interaction between hypoxia and hypocapnia was increased by ethanol. Gasping was observed in about half of the animals after apnea of various lengths. The rate of gasping was affected by neither ethanol nor the way by which hypoxia was induced.