Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (788 page)

   COHB is Hb with carbon monoxide (CO) instead of the normal oxygen bound to it. CO has a much great affinity than oxygen for Hb. The source of the CO may be exhaust (such as from a car, truck, boat, or generator), smoke from a fire, or tobacco smoke. COHB is formed in CO poisoning. The COHB level is useful in judging the extent of CO toxicity and in considering the effect of smoking on the patient. A direct correlation has been claimed between CO level and symptoms of atherosclerotic diseases, angina, and MI. Physiologically, COHB levels increase due to hemolysis. CO is a natural by-product of the breakdown of protoporphyrin to bilirubin.

   
Normal range:

   Nonsmokers: 0.5–1.5% saturation of Hb

   Smokers (1–2 packs/day): 4–5%

   Heavy smokers (>2 packs/day): 8–9%

   Use

   Verifying CO toxicity in cases of suspected exposure

   Interpretation

Increased In

   CO poisoning

   Hemolytic disease

   Blood in the intestine

   Reactions of intestinal bacteria

   Calorie reduction