There has long been interest in measuring the amount of carboxyhemoglobin in the blood of workers who might be exposed to carbon monoxide. CO-induced hypoxia is a real consequence. However, such measurements—when done in the conventional manner—are invasive and cumbersome.

It was first demonstrated in 1948, by Torgny Sjöstrand, that COHb saturation could be estimated from alveolar CO concentration. Pioneering work using infrared technology for this CO measurement was done by Coburn et al. in 1965, but it would be 1976 before a popular-priced method would be demonstrated.

This breakthrough work—from RD Stewart et al.—was published in JAMA in an article entitled “Rapid Estimation of Carboxyhemoglobin Level in Fire Fighters.” Alveolar CO samples were taken from firefighters, along with venous blood draws. Also invoked was the Haldane Effect, and its equation, expressing the relationship between COHb, CO tension, oxyhemoglobin, oxygen tension, and the affinity of CO for hemoglobin in a blood sample at equilibrium.

Based on this work, a curve was produced relating Carbon Monoxide In Alveolar Air (ppm) versus Carboxyhemoglobin in Blood (percent). Using best fit techniques, we offer a convenient chart relating these values. This material is also presented in another Knowledge Base article.

Only a few years after Stewart’s work was published, alveolar CO sampling became the de facto standard, and became essentially synonymous with blood-draw COHb. This technique has seen its greatest application in testing the breath of smokers, to determine compliance with smoking cessation programs.

Interscan is proud to have supplied many CO instruments for these applications. Please contact us for further information.

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