Short-burst oxygen therapy has been traditionally used for symptomatic relief of breathlessness at rest, to preoxygenate before exercise and to alleviate breathlessness after exercise. Although this pattern of use is widespread, the evidence for its efficacy is limited. Assessing symptomatic improvement in breathlessness is difficult and this pattern of use is often driven by patients' requests for an oxygen cylinder. In 1989, nearly 1 million oxygen cylinders were supplied to patients' homes in England and Wales . These 1360-L cylinders last about 10h at 2L/min, but individual daily use has been shown to be low .
A small randomized controlled trial showed that short-burst oxygen used for 10min reduced breathlessness in patients with COPD and chronic hypoxaemia at rest . However, there are no good data in patients who are breathless at rest but not hypoxaemic. Oxygen given for 5 or 15min before exercise was found to be beneficial in one double-blind cross-over study in 10 patients with severe COPD . These patients walked significantly further, on both 6-min walking tests and treadmill walks, with a 10% increase in distance walked (20-30m improvement). Patients predosed with oxygen were also less breathless on treadmill walking. The patients were all 'pink puffers', with a mean PaO2 at rest of 9.7 kPa (73 mmHg), but saturation during exercise was not measured. There is also one study of 18 patients with severe COPD, known to have exercise-induced desaturation, demonstrating a beneficial effect of oxygen for 5 min either before or after climbing stairs in reducing the severity of breathlessness and desaturation . However, when the patients were asked their views, there was no significant preference for oxygen over air. A further difficulty is that the effects of oxygen may not be reproducible with time .
The recommendations in the 1999 UK guidelines acknowledge that the evidence for short-burst therapy is inadequate . Oxygen is recommended for episodic breathlessness not relieved by other treatments, with demonstration of improvements in breathlessness and/or exercise tolerance. A trial of 5min of oxygen therapy either before or after exercise for patients with COPD known to have exercise-induced desaturation, with continued short-burst therapy if there is symptomatic benefit, is indicated on current evidence. However, education about oxygen therapy needs to include information on the situations, such as short-burst therapy, where benefit is small or has not been demonstrated, so that prescribing of short-burst oxygen therapy is kept to a minimum and for clearly defined reasons.
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