Carbon monoxide and ventricular fibrillation threshold in dogs with acute myocardial injury

In a blind, randomized study, the effect of breathing 100 p.p.m. of CO versus compressed, purified air for 2 hours on ventricular fibrillation threshold (VFT) was investigated in 21 dogs with acute myocardial injury. The mean arterial carboxyhemoglobin was 1.16 per cent in the air control period, 1.07 per cent after air, 1.08 per cent in the CO control period, and 6.34 per cent after CO. In comparison to air, CO increased the mean arterial carboxyhemoglobin (P less than 0.001). One dog developed spontaneous ventricular fibrillation 100 minutes after CO. Mean VFTs in the other 20 dogs were 12.8 +/- 6.8 milliamperes after CO, 11.2 +/- 6.0 milliamperes in the air control period, and 15.0 +/- 5.1 milliamperes after air. In comparison to air, CO decreased the VFT (P less than 0.001). These data show that breathing 100 p.p.m. of CO for 2 hours reduces the VFT in dogs with acute myocardial injury.