Long-term oxygen therapy in COPD: what is the evidence?

Thomas L Petty was the founder of modern long-term oxygen therapy (LTOT).1 In 1967, Petty's group published the seminal study of six patients with severe chronic airway obstruction, in whom LTOT improved clinical status, exercise capacity, secondary erythrocythemia, and pulmonary hypertension.2 Notably, all patients had severe hypoxaemia (partial pressure of oxygen [PaO2] 41·5–46·5 mm Hg) and four patients were severely hypercapnic (partial pressure of carbon dioxide [PaCO2] 55·0–61·5 mm Hg). Thereafter, two randomised controlled trials that were initiated in the 1970s established a clear survival benefit related to LTOT in patients with chronic obstructive pulmonary disease (COPD) with severe resting hypoxaemia: the Nocturnal Oxygen Therapy Trial (NOTT)3 and the British Medical Research Council (BMRC) trial.