Chest
Volume 131, Issue 1, January 2007, Pages 278-285
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Special Feature
A Systematic Review of Randomized Controlled Trials Examining the Short-term Benefit of Ambulatory Oxygen in COPD

https://doi.org/10.1378/chest.06-0180Get rights and content

Abstract

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.B., B.O.) independently assessed eligibility and extracted data. All trial data were combined using RevMan analyses 4.2.8 (Cochrane Collaboration;). 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 (Sao2), and minute ventilation (Ve), comparisons were made at isotime. Oxygen improved breathlessness, Sao2/Pao2, and Veat 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 Sao2/Pao2and Veat 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.

Section snippets

Materials and Methods

The search strategies as well as the methods for study eligibility, study quality, and data extraction followed the guidelines of the Cochrane Airways Group and fulfill the criteria outlined in the Quality of Reporting of Meta-analysis (QUOROM) statement7for reporting of systematic reviews.

Endurance Test Studies

For distance, there was heterogeneity (I2= 33%) between the eight studies9, 11, 14, 16, 21, 25, 27, 28that reported this outcome. Using a fixed-effect model, oxygen significantly improved exercise distance by 18.86 m (95% confidence interval [CI], 13.11 to 24.61 m, n = 238), and the significance of this result was not altered by a random-effect model (Fig 2].

Maximal Test Studies

For distance, there was low heterogeneity between the four studies12, 13, 22, 25that reported this outcome. Oxygen significantly increased

Discussion

This review provides evidence from good quality single-assessment studies that short-term ambulatory oxygen improves exercise capacity (time and distance) and measurements at isotime (breathlessness, Ve, Sao2/Pao2) in patients with COPD. Assessment of breathlessness, Ve, and Sao2/Pao2at isotime (the time at which the placebo/air test ended) is important, as these measurements are dependant on exercise capacity. The complexity of the proposed mechanisms that contribute to improved performance

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    This research was supported by NI Research and Development Cochrane Fellowship.

    No author has any conflict of interest.

    Reproduction of this article is prohibited without written permission from the American College of Chest Physicians (http://www.chestjournal.org/misc/reprints.shtml).

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