Halothane and enflurane protect against bronchospasm in an asthma dog model.

Experimental asthma was induced in 6 dogs previously sensitized to ascaris antigen by ventilating them with aerosolyzed ascaris antigen for 10 minutes. Pulmonary resistance was calculated from simultaneous pressure and flow measurements at a long volume 200 ml above functional residual capacity. Prior to administration of aerosolyzed ascaris antigen, pulmonary resistance was 2.35 +/- 0.56 (mean +/- SEM) cm H2O/L/sec in dogs anesthetized with thiopental. Twenty minutes after the end of ascaris antigen administration, pulmonary resistance was 5.72 +/- 1.29 in dogs given additional thiopental, 3.18 +/- 0.62 in dogs anesthetized with halothane (0.87% inspired concentration), and 3.03 +/- 0.60 in dogs anesthetized with enflurane (2.2% inspired concentration). These differences in responses of pulmonary resistance were statistically significant at 0.05 level. Halothane and enflurane were equally effective in decreasing pulmonary resistance in an ascaris antigen dog model of asthma.