The history of long-term oxygen therapy.

Early investigators of oxygen therapy reported an overall clinical improvement in persons with chronic lung disease who received oxygen. Later American and British studies showed that oxygen therapy could decrease pulmonary vascular pressures and red cell mass in some patients with pulmonary hypertension and polycythemia secondary to severe hypoxemia. The British Research Council Study showed that survival rates were significantly higher in patients receiving 15 hours of oxygen than in those receiving no oxygen. The Nocturnal Oxygen Therapy Trial showed that survival rates for persons receiving continuous oxygen therapy has also been shown to improve exercise tolerance and neuropsychiatric function. Further advances in the administration of long-term oxygen therapy and studies in the criteria for its use are needed.