Joint Committee on Aviation Pathology: XVI. Studies on the relation between carboxyhemoglobin concentration and toxicity.

A study was made on the effect of I.P. injection of 100% CO in dogs. Although elevated concentrations of COHb were obtained, no Co toxicity occurred. Inasmuch as the combination of CO and erythrocytes after I.P. injection of CO should be similar to that after inhaling CO, The lack of toxicity cannot be explained by Drabkin's "Haldane effect." It is suggested that the lack of CO toxicity after I.P. injection was due to removal of dissolved CO from the blood by passage through the lungs. On the contrary, when Co is inhaled there is significant dissolved CO in the blood leaving the lungs and when it reaches the organs, especially the heart and brain. To cause toxicity, dissolved CO must be present in the blood to cross into the tissues and interfere with the combination of O2 and cytochrome a3. It is concluded that random COHb values may not be related to those obtained in studies of the relationship of human responses to COHb concentrations.