To evaluate efficacy of artificial ventilation with 100 % oxygen for treatment of IgE-mediated anaphylaxis, we compared survival of control ventilated dogs with one of dogs with spontaneous ventilation. Fourteen dogs sensitized to Toxica canis were randomly assigned to two groups: spontaneous respiration group (Group S, n = 8) and artificial ventilation group (Group A, n = 6). All dogs were anesthetized with pentobarbital. In Group S, all dogs breathed spontaneously with constant flow of 4 l.min-1 of oxygen. Spontaneous respiration maintained an end-tidal CO2 level between 40 and 50 mmHg. In Group A, the dogs, paralyzed with pancuronium, were ventilated mechanically with 100 % oxygen, and the tidal volume was adjusted to maintain an end-tidal CO2 level between 35 and 40 mmHg. After measurements of pulmonary resistance (RL), dynamic compliance (Cdyn), and circulatory parameters at baseline, Ascaris suum antigen was administered intravenously into the systemic circulation to induce IgE-mediated anaphylaxis. RL, Cdyn and circulatory parameters were recorded continuously for 120 min after antigen challenge. Analysis of arterial blood gases was done throughout the study. Survival rates were 100 % and 50 % in Group A and Group S, respectively. In 7 of 8 dogs in Group S, apnea was observed during the period of 1 min to 5 min after antigen challenge, and the apnea continued during the period of 30s to 22 min. Four dogs died during the period of 20 min to 30 min after antigen challenge. In both groups, RL increased significantly and Cdyn decreased significantly after antigen challenge.(ABSTRACT TRUNCATED AT 250 WORDS)