Consideration of the physiological variables that determine the blood carboxyhemoglobin concentrations in man

Numerous publications have considered the effects of inspiring high concentrations of CO on the venous blood carboxyhemoglobin concentra-tion [COHb] in man (14). It appears, how-ever, that no previous study has considered the physiological variables that determine [COHb] under conditions where inspired air CO concen-trations are in the normal range. It has become apparent in recent years that CO is endogenously produced in normal man as a by-product of hemo-globin catabolism (and probably other hemo-proteins as well) and therefore that the body CO stores are influenced by endogenous as well as exogenous CO (5, 6). The development of a method of measuring the rate of endogenous CO production (Vco) in man (6) has made it possible to study the relationship of Vco and other vari-ables to [COHb]. This is of particular interest since the latter has been used as an index of hemolysis (7). The Vco has been shown to reflect quantitatively the rate of circulating erythrocyte hemoglobin destruction in normal subjects (8) and in patients with hemolytic anemia (9), and the accuracy of this index would depend on how closely [COHb] reflects Vco. In this paper we have developed equations that appear to describe the major physiological variables that determine blood [COHb] under steady state and transient state conditions. We * Submitted for publication May 10, 1965; accepte