obstructive pulmonary disease (COPD), and some kinds of sleep apnea. Supplemental oxygen by mask or nasal tubes may be provided to treat chronic hypoxia. Inhaled steroids that can dilate the airways may be used to treat asthma or other lung disease. Diuretics may be used to reduce edema in and around the lungs. Other types of medical hypoxia Hypoxemic hypoxia is a low oxygen tension in the arterial blood, due to the inability of the lungs to sufficiently oxygenate the blood. Causes include hypoventilation, impaired alveolar diffusion, and pulmonary shunting. This definition overlaps considerably with that of hypoxic hypoxia. Pulmonary hypoxia occurs when the lungs receive adequately oxygenated gas which does not reach the blood in sufficient quantities. It may be caused by: Ventilation perfusion mismatch, Pulmonary shunt Circulatory hypoxia, ischemic hypoxia or stagnant hypoxia may be caused by abnormally low blood flow to the lungs, which can occur during shock, cardiac arrest, severe congestive heart failure, or abdominal compartment syndrome, where the main dysfunction is in the cardiovascular system, causing a major reduction in perfusion. Arterial gas is adequately oygenated in the lungs, and the tissues are able to accept the oxygen available, but the flow rate to the tissues is insufficient. Venous oxygenation is particularly low. Anemic hypoxia or hypemic hypoxia is the lack of capacity of the blood to carry the normal level of oxygen. It can be caused by anemia or: Carbon monoxide poisoning Methemoglobinemia Cellular hypoxia occurs when the cells are unable to extract sufficient oxygen from normally oxygenated hemoglobin. Histotoxic hypoxia (Dysoxia) occurs when oxygen is transported to the tissues but they cannot use it effectively because the cells cannot extract oxygen from the blood. This is seen in cyanide poisoning. See also References Respiratory diseases