Long-term oxygen therapy

Abstract

This chapter reviews the known effects of chronic oxygen therapy, its indications, and the various delivery systems now available. Oxygen therapy has become very important in the treatment of severe chronic obstructive pulmonary disease (COPD). Long-term oxygen improves survival in hypoxemic COPD. Other benefits of oxygen include better exercise tolerance, decreased dyspnea, and improvements in neuropsychological performance. In addition, there appear to be beneficial effects on pulmonary hemodynamics, sleep quality, reduced minute ventilation, and WOB. Hypoxemia is defined as an abnormally low arterial oxygen tension Pinfa/infOinf2/inf. The physiologic causes of hypoxemia include a low inspired partial pressure of oxygen, abnormal ventilation-perfusion relationship, decreased diffusion capacity, alveolar hypoventilation, and right to left shunt. Oxygen therapy increases the Finfi/infOinf2/inf and is the primary treatment for hypoxemia resulting from the first three causes. The hypoxemia of alveolar hypoventilation is best treated by increased ventilation while a true shunt is by definition unresponsive to hyperoxia. Although the reason for increased survival with oxygen is not clear, there is evidence that Oinf2/inf can improve pulmonary hemodynamics and leads to reduced cardiac work and greater oxygen delivery. The consequences of exercise induced and nocturnal desaturation are not absolutely known. Clinicians should be aware of air travel-induced hypoxemia in COPD and be able to identify those who need oxygen in flight. Once a patient meets the criteria for oxygen prescription, the physician must complete the certificate of Medical Necessity Form specifying the indication for oxygen, type of system and liter flow at rest, exercise and sleep.