Consequences of Brief Exposure to High Concentrations of Carbon Monoxide in Conscious Rats

Exposure to high-concentration carbon monoxide (CO) is of concern in military operations. Experimentally, the physiologic manifestations of a brief exposure to elevated levels of CO have not been fully described. This study investigated the development of acute CO poisoning in conscious male Sprague-Dawley rats (220–380 g). Animals were randomly grouped (n = 6) and exposed to either air or 1 of 6 CO concentrations (1000, 3000, 6000, 10,000, 12,000, or 24,000 ppm) in a continuous air/CO dynamic exposure chamber for 5 min. Respiration was recorded prior to and during exposures. Mixed blood carboxyhemoglobin (COHb) and pH were measured before and immediately after exposure. Before exposure the mean baselines of respiratory minute volumes (RMVs) were 312.6 ± 43.9, 275.2 ± 40.8, and 302.3 ± 39.1 ml/min for the 10,000, 12,000 and 24,000 ppm groups, respectively. In the last minute of exposure RMVs were 118.9 ± 23.7, 62.1 ± 10.4, and 22.0 ± 15.1% (p < .05) of their mean baselines in these 3 groups, respectively....