The quality of evidence is downgraded by limitations in study quality (inadequate or unclear allocation concealment) and by inconsistency (variability in results across studies, heterogeneity in interventions and outcomes).
A Cochrane review on the efficacy of oxygen versus medical air for relief of subjective dyspnoea in non-hypoxaemic people with COPD included 44 studies with a total of 1105 subjects. 33 trials (901 participants) were included in the meta-analysis. Oxygen slightly reduced dyspnoea and breathlessness measured during exercise tests (table ). Oxygen did not affect health-related quality of life (HRQOL).
| Outcome | Difference (95% CI) | No of participants (studies) | Comment: Correspondance on a 1 - 10 scale |
|---|---|---|---|
| Breathlessness | SMD 0.31, SD lower (0.43 lower to 0.2 lower) | 865 (32) | 0.65 points lower (0.90 lower to 0.42 lower) |
| Breathlessness - subgroup analysis - during exercise test | SMD 0.34, SD lower (0.46 lower to 0.22 lower) | 591 (30) | 0.71 points lower (0.97 lower to 0.46 lower) |
| Health-related quality of life | SMD 0.12, SD higher (0.04 lower to 0.28 higher) | 267 (5) | 0.25 points higher (0.09 lower to 0.59 higher) |
Given the significant heterogeneity among the included studies, clinicians should continue to evaluate patients on an individual basis until supporting data from ongoing, large randomised controlled trials are available.
NoteDate of latest search: 12 July 2016