A systematic review of randomized controlled trials examining the short-term benefit of ambulatory oxygen in COPD

Aim: To systematically review the short-term efficacy of ambulatory oxygen from single-assessment studies in COPD. Methods: Searches for relevant randomized controlled trials using predefined search terms were conducted on the Cochrane Airways Group Specialized Register of RCTs, the Cochrane Central Register of Controlled Trials, and other electronically available journals, databases, and search engines. All databases were searched from their inception until December 2004. Two reviewers (J.R., B.O.) independently assessed eligibility and extracted data. All trial data were combined using RevMan analyses 4.2.8 (Cochrane Collaboration; www.cochrane.org). Due to the crossover design of the studies, data were entered using the generic inverse variance method. Fixed-effect or random-effect models were used depending on the level of statistical heterogeneity observed. Results: Thirty-one studies (33 data sets; 534 participants) met the inclusion criteria of the review. Oxygen improved the primary outcomes relating to endurance and maximal exercise capacity. For the secondary outcomes of breathlessness, arterial oxygen saturation (Sao(2)), and minute ventilation (V-E), comparisons were made at isotime. Oxygen improved breathlessness, SaO(2)/PaO2, and V-E at isotime with endurance exercise testing. For maximal exercise testing, data were not available in a format suitable for metaanalysis for breathlessness, but the improvement in SaO(2)/PaO2 and VE at isotime was significant. Conclusion: This review provides evidence from single-assessment studies that ambulatory oxygen improves exercise performance in COPD; however, the clinical importance of this size of improvement is unclear. Prior to widespread prescription of ambulatory oxygen, future research is required to establish the net long-term benefit of ambulatory oxygen in patients with different levels of hypoxemia or exercise-induced desaturation.