Where in the body does carbon monoxide combine with haemoglobin?
Absorbed through the lungs, carbon monoxide combines with haemoglobin, which normally carries oxygen to the body’s cells. Carbon monoxide replaces oxygen in the bloodstream causing hypoxia, an abnormal reduction of oxygen in the body tissues. CO binds tightly and rapidly to haemoglobin and crowds out oxygen. As C0 combines with oxygen, it forms carboxy-haemoglobin (HbC0). Carboxy-haemoglobin stifles the release of oxygen into the cells from normal haemoglobin. As little as one part of CO in 1500 parts of air can convert half of the body’s haemoglobin to carboxy-haemoglobin. The most characteristic sign of CO poisoning is a cherry colour of the skin and mucous membranes due to the bright red colour of carboxy-haemoglobin.