Long term oxygen therapy (LTOT) is one of the few treatments which has significant survival benefits in patients with severe hypoxaemia. It may modify disease progression, as indicated by a slower progression of hypoxia induced pulmonary hypertension,^1–4 and the acute reduction in pulmonary hypertension to oxygen administration has been suggested as predictive for the survival benefit in individual patients. Reduced pulmonary vascular resistance and hence the reduced load on the right heart is probably the most important working mechanism of LTOT. In less severe hypoxaemic patients the benefits of LTOT on survival are less clear.⁵ Other benefits of oxygen administration are generally accepted. Reduced ventilation, especially during exercise, helps to avoid dynamic hyperinflation and hence reduces symptoms and increases exercise tolerance in the majority of patients with chronic obstructive pulmonary disease (COPD), even in patients with mild hypoxaemia.⁶ There is also some evidence to support the suggestion that LTOT may improve cognitive function in hypoxaemic COPD patients⁷ and may improve health related quality of life.⁸

LTOT is therefore a recognised treatment in hypoxaemic patients …