Pulmonary alveolar macrophage response to hyperbaric carbon monoxide exposure

The sublethal effects of carbon monoxide (CO) in hyperbaric environments have not been adequately characterized. A physiologically sensitive indicator of sublethal effects of a contaminant is the pulmonary alveolar macrophage (PAM). The guinea pig PAM and its reaction to various CO concentrations at 8 atmospheres absolute (ATA) and the surface-equivalent concentrations at 1 ATA were studied in this experiment. In the absence of CO, PAM counts and viabilites from guinea pigs exposed to a helium-oxygen environment at either 1 or 8 ATA were not significantly different from one another. Mean PAM viability for guinea pigs exposed to CO concentrations at 2250--4200 mg/m3 at 8 ATA was 68.4 +/- 7.3% and was not significantly different from the 1-ATA viability value of 72.0 +/- 4.5% for the 1600--4200 mg/m3 CO range. The data show that at 1 to 8 ATA and CO concentrations of 1600--4200 mg/m3, the decrease in PAM viability was accompanied by dramatic five- to sixfold increases in PAM counts.