Carboxyhaemoglobin

• CO from car exhaust fumes and cigarettes (~5% CO) readily diffuses from alveoli and into erythrocytes; Hb combines 250x more easily with CO than O_2 (form carboxyhaemoglobin)
• Carboxyhaemoglobin is very stable (irreversible) so even low levels of CO (0.1% of air) can cause poisoning and asphyxiation; symptoms include dizziness, headaches and mental confusion
• CO poisoning can be treated by giving a mixture of pure O_2 (increase levels of oxyhaemoglobin) and pure CO_2 (stimulate the brain’s breathing centres)