Carbon Monoxide and Ventricular Fibrillation Threshold in Normal Dogs

In a blind, randomized study, the effect of breathing 100 ppm of carbon monoxide versus compressed, purified air for 2 hr on ventricular fibrillation threshold was investigated in twenty anesthetized normal open-chested dogs. The mean arterial carboxyhemoglobin level was 1.12% in the air control period, 0.99% after air, 1.10% in the carbon monoxide control period, and 6.48% after carbon monoxide. Carbon monoxide increased the mean arterial carboxyhemoglobin (P less than .001). Mean ventricular fibrillation thresholds were 19.9 +/- 6.5 mA in the carbon monoxide control period, 15.7 +/- 5.6 mA after carbon monoxide 20.8 +/- 6.3 mA in the air control period, and 24.5 +/- 9.5 mA after air. Carbon monoxide decreased the ventricular fibrillation threshold (P less than .005). These data show that breathing 100 ppm of carbon monoxide for 2 hr reduces the ventricular fibrillation threshold in anesthetized normal open-chested dogs.