I. Continuous oxygen (ideally for 19 hours or more per day) is indicated to improve longevity and quality of life when:

• Stable daytime PaO2 is <55mmHg at rest; or
• Stable daytime PaO2 is 55-59mmHg and there is evidence for hypoxic organ damage (including right heart failure, pulmonary hypertension or polycythaemia).

Flow rate should be set to maintain PaO2 >60mmHg (SaO2>90%) during waking rest. This will usually need to be increased by 1L/min during sleep, exertion and air travel.

II. There is less evidence for the unequivocal long term benefit of intermittent home oxygen. The Society takes the position that intermittent oxygen should be prescribed as follows:

• Nocturnal oxygen to relieve demonstrated sleep desaturation to an SaO2<88% (PaO2<55mmHg). The role of continuous positive airway pressure or other ventilatory support needs to be considered and may replace or complement oxygen therapy. If oxygen is indicated, a concentrator will be the least expensive mode of delivery and can also be used to provide oxygen during daytime exertion at negligible extra cost.
• A small cylinder of oxygen for emergency use by the patient with severe asthma who is prone to sudden life-threatening episodes.
• Home oxygen to relieve symptoms in terminally ill patients who will usually have a life expectancy less than three months. Oxygen use may become continuous as symptoms progress.

III. It may be of benefit to prescribe oxygen therapy to improve exercise capacity using ambulatory systems of delivery, where the other criteria are not met. However, the other indications should command first call on community resources as there is no evidence yet that extension of exercise capacity in this manner prolongs life. A possible exception is the use of ambulatory oxygen to help patients in rehabilitation programs, including those awaiting lung transplantation or lung reduction surgery, to keep an increased level of fitness which will improve their prognosis. Although there is no direct evidence that treatment of exercise hypoxaemia retards long term pulmonary hypertension, analogy with sleep hypoxaemia would indicate that it is reasonable to relieve exercise hypoxaemia where there is symptomatic benefit during common daily activities, when it can be demonstrated that these activities cause arterial oxygen desaturation to 88% or less.

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