carbon monoxide poisoning, a toxic condition in which carbon monoxide gas has been inhaled and binds to hemoglobin molecules, thus displacing oxygen from the red blood cells and decreasing the capacity of the blood to carry oxygen to the cells of the body. Characteristically, headache, dyspnea, drowsiness, confusion, cherry-pink skin, unconsciousness, and apnea occur in sequence as the level of carbon monoxide in the blood increases. Cherry-red skin is a late sign most commonly noted in fatalities. The most common source of carbon monoxide in cases of poisoning is exhaust fumes from an automobile.