HYPOXIC VENTILATORY DRIVE IN THE DOG UNDER ALTHESIN ANAESTHESIA

Althesin was administered i.v. to eight dogs, using two differentrates of infusion (6.55 +mn; 2.13 µl kg^–1 min and12.80 +mn; 2.00 µl kg^–1 min). Ventilation (T_I, T_E,RR, T_I/T_tot, V_T, V_E, V_T/T_I) and arterial blood-gas tensionswere measured in air and during a 10-min period of 100% oxygenbreathing. For both rates of Althesin infusion the ventilatoryresponse to oxygen was identical: there was significant depressionof ventilation (decrease in V_E and of the ventilatory drive,V_T/T_I) from the 1st min of inhalation lasting up to the 10thmin. This decrease in ventilation was more marked and persistentthan the decrease noticed in the unanaesthetized dog. We concludethat the hypoxic ventilatory drive persists in the dog underAlthesin anaesthesia.