A Cochrane review [Abstract] 1 included 11 studies with a total of 172 subjects. Only one examined long-term oxygen therapy (28 participants, age> 12 years, receiving O2 therapy at night only). There was no statistically significant improvement in survival, lung, or cardiac health. There was an improvement in regular attendance at school or work in those receiving oxygen therapy at 6 and 12 months.
Four studies examined the effect of oxygen supplementation during sleep by polysomnography. Although oxygenation improved, mild hypercapnia was noted. Participants took less time to fall asleep and spent a reduced percentage of total sleep time in rapid eye movement sleep, but there were no demonstrable improvements in qualitative sleep parameters. In six studies, oxygen supplementation was evaluated during exercise. Again, oxygenation improved, but mild hypercapnia resulted. Participants receiving oxygen therapy were able to exercise for a significantly longer duration during exercise. Other exercise parameters were not altered by the use of oxygen.
Comment: The quality of evidence is downgraded by study quality (unclear allocation concealment), by imprecise results (few patients), and by indirectness (differences in studied interventions and reported outcomes).
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