Chronic oxygen therapy.

Chronic low flow oxygen is useful therapy for patients with chronic obstructive lung disease who are crippled by hypoxemia despite optimal programs of usual respiratory care. Patients should be considered for chronic oxygen therapy who have (a) a resting Pao2 less than 55 mm Hg while breathing room air; or (b) profound tissue hypoxemia measured by mixed venous Pao2 and suggested by symptoms such as cor pulmonale and congestive heart failure; or (c) pulmonary hypertension or polycythemia even though daytime Pao2 is greater than 55 mm Hg. Arterial blood must be obtained to demonstrate hypoxemia and assess the benefits of oxygen therapy. Patients on chronic oxygen must remain under close medical supervision. There are no absolute contraindications to chronic oxygen therapy, other than refusal of the patient to quit smoking. Complications of therapy appear to be negligible. The exciting suggestion of improved prognosis in patients with chronic obstructive lung disease on oxygen therapy and the possibility of delaying the long-term sequelae of chronic respiratory failure bear careful watching in the future.