COPD: Effectiveness of Therapies (2007-2008)


Bradley JM, O'Neill B.  Short-term ambulatory oxygen for chronic obstructive pulmonary disease.  Cochrane Database Syst Rev 2005 Oct 19;(4):CD004356.

PubMed ID: 16235359
Study Design:
Meta-analysis or Systematic Review
M - Click here for explanation of classification scheme.
Quality Rating:
Positive POSITIVE: See Quality Criteria Checklist below.
Research Purpose:

To determine the efficacy of ambulatory oxygen in patients with COPD using single assessment studies.

Inclusion Criteria:
  • Only randomized controlled trials were included
  • Adult patients with stable COPD
  • COPD should have been diagnosed according to internationally accepted guidelines
  • Single assessment studies on COPD patients which compare performance during an exercise test using oxygen with performance during an exercise test using placebo air
  • Ambulatory oxygen is defined as the use of supplemental oxygen during exercise and activities of daily living
Exclusion Criteria:
  • Patients who did not have a diagnosis of COPD
  • Longer term studies assessing the efficacy of ambulatory oxygen therapy or studies assessing the efficacy of long-term oxygen therapy
Description of Study Protocol:


Cochrane Airways Group COPD register was searched with predefined search terms - (portable* or ambulat* or oxygen* or O2 or hypoxaemia* or hypoxemia*) and (therap*), as well as other electronically available databases such as CENTRAL.  Bibliographies were also reviewed.  Searches were current as of March 2005.

Design:  Systematic Review 

Blinding used (if applicable):  Studies did not have to be blinded.

Intervention (if applicable):  Both authors extracted and entered data into RevMan 4.2. 

Statistical Analysis

  • All trial data was combined using RevMan analyses 1.0.2.
  • Funnel plots were carried out to test for the presence of publication bias where possible
  • Due to crossover design of the studies, data was entered as generic inverse variance data
  • For continuous variables such as exercise capacity and breathlessness scores, a weighted mean difference was used
  • Random and/or fixed effects models were used depending on the level of statistical heterogeneity observed
Data Collection Summary:

Timing of Measurements

Studies had to compare oxygen and placebo when administered to people with COPD who were undergoing an exercise test.

Dependent Variables

  • Exercise capacity (distance, time or steps during maximal tests or endurance tests) 
  • Dyspnea scores (through Borg scores or visual analog scale)
  • Arterial oxygen saturation - SaO2
  • Physiological measurements such as VE during exercise 
  • Patient preference

Independent Variables

  • Oxygen or placebo

Control Variables


Description of Actual Data Sample:

Initial N: 60 studies were identified through the literature search.  31 studies, contributing 33 data sets, randomizing 534 participants met the inclusion criteria

Attrition (final N):  as above

Age:  mean age reported in included studies ranged from 47 to 73 years

Ethnicity:  not mentioned

Other relevant demographics:  sample sizes ranged from 5 to 41

Anthropometrics:  all trials were crossover in design

Location:   Worldwide studies


Summary of Results:

Other Findings

Oxygen improved all pooled outcomes relating to endurance exercise capacity (distance, time, number of steps) and maximal exercise capacity (exercise time and work rate).

Data relating to VO2max could not be pooled and results from the original studies were not consistent.

For the secondary outcomes of breathlessness, SaO2 and VE, comparisons were made at isotime.

In all studies except 2, the isotime is defined as the time at which the placebo test ended.

Oxygen improved breathlessness, SaO2/PaO2 and VE at isotime with endurance exercise testing.

There was no data on breathlessness at isotime with maximal exercise testing.

Oxygen improved SaO2/PaO2 and reduced VE at isotime. 

Author Conclusion:

This review provides some evidence from small, single assessment studies that ambulatory oxygen improves exercise performance in people with moderate to severe COPD.  The results of the review may be affected by publication bias, and the small sample sizes in the studies.  Although positive, the findings of the review require replication in larger trials with more distinct subgroups of participants.  Maximal or endurance tests can be used in ambulatory oxygen assessment.  Consideration should be given to the measurement of SaO2 and breathlessness at isotime as these provide important additional information.  We recommend that these outcomes are included in the assessment for ambulatory oxygen.  Future research needs to establish the level of benefit of ambulatory oxygen in specific subgroups of people with COPD.

Funding Source:
Government: North Ireland Research and Development
Reviewer Comments:
  • Authors note that the results of the review may be affected by publication bias and small sample sizes in studies.
  • Authors also note the lack of statistical heterogeneity in many of the meta-analyses - the studies differed in many ways, such as in the type of exercise test deployed, the method and amount of oxygen, whether participants were known to be able to exercise up to a certain capacity, whether studies were single or double blind, and the severity of the participants recruited to the studies
Quality Criteria Checklist: Review Articles
Relevance Questions
  1. Will the answer if true, have a direct bearing on the health of patients? Yes
  2. Is the outcome or topic something that patients/clients/population groups would care about? Yes
  3. Is the problem addressed in the review one that is relevant to dietetics practice? Yes
  4. Will the information, if true, require a change in practice? Yes
Validity Questions
  1. Was the question for the review clearly focused and appropriate? Yes
  2. Was the search strategy used to locate relevant studies comprehensive? Were the databases searched and the search termsused described? Yes
  3. Were explicit methods used to select studies to include in the review? Were inclusion/exclusion criteria specified andappropriate? Wereselectionmethods unbiased? Yes
  4. Was there an appraisal of the quality and validity of studies included in the review? Were appraisal methodsspecified,appropriate, andreproducible? Yes
  5. Were specific treatments/interventions/exposures described? Were treatments similar enough to be combined? ???
  6. Was the outcome of interest clearly indicated? Were other potential harms and benefits considered? Yes
  7. Were processes for data abstraction, synthesis, and analysis described? Were they applied consistently acrossstudies and groups? Was thereappropriate use of qualitative and/or quantitative synthesis? Was variation in findings among studies analyzed? Were heterogeneity issued considered? If data from studies were aggregated for meta-analysis, was the procedure described? Yes
  8. Are the results clearly presented in narrative and/or quantitative terms? If summary statistics are used, are levels ofsignificance and/or confidence intervals included? Yes
  9. Are conclusions supported by results with biases and limitations taken into consideration? Are limitations ofthe review identified anddiscussed? Yes
  10. Was bias due to the review's funding or sponsorship unlikely? Yes