Potential fetal toxicity due to the high affinity of fetal hemoglobin for CO makes HBO2 treatment for the pregnant CO intoxicated patient a firm indication. Carbon monoxide is the most common poisoning in the United States and is the most common cause of poison-related mortality. It has been estimated that between 1000 and 2000 accidental deaths occur per year due to CO toxicity. The signs and symptoms of CO toxicity are usually nonspecific and can appear as a flulike illness. Consider the possibility of CO toxicity in the differential of unexplained headache.
Venous levels are quite accurate for screening CO victims.
The variation of the half-life has no relation to the amount of COHb in the blood or to the duration of exposure. Additionally, the binding of CO to the heme molecule causes a leftward shift of the oxyhemoglobin dissociation curve that causes the allosteric configuration of heme molecule to be altered, preventing easy O2 release. A true measured O2 saturation by ABG's would easily discriminate this gap. Actually, clinical data are unclear as to what factors cause an increased risk for sequelae due to CO toxicity. Indeed, recent randomized clinical trials have produced conflicting results for even using HBO in CO poisoning.