The authors concluded that longer duration pulmonary rehabilitation programs appeared to have a more favourable effect on health-related quality of life in individuals with chronic obstructive pulmonary disease, but results for exercise capacity were less clear. The authors' conclusions reflect the evidence presented and are likely to be reliable.

To determine the optimal duration of pulmonary rehabilitation for patients with chronic obstructive pulmonary disease (COPD).

PubMed, CINAHL, EMBASE, PEDro and The Cochrane Library were searched up to June 2010 with no language restrictions; search terms were reported. Reference lists of relevant articles were scanned, key author searches were conducted and the PubMed related articles function was used to locate additional articles. Studies where only an abstract was available were excluded.

Randomised controlled trials (RCTs) that comparing different lengths of pulmonary rehabilitation (exercise training with or without education) in patients with COPD were eligible for inclusion. To be included, more than 90% of participants of a trial had to have been clinically diagnosed with COPD and have either a best recorded forced expiratory volume in one second/forced vital capacity ratio of below 0.70 or best recorded forced expiratory volume in one second of below 80% predicted. Trials that only evaluated maintenance interventions were excluded. Outcomes of interest were exercise capacity, health-related quality of life and adherence.

Programs in the included trials varied with all including an aerobic exercise component (walking and/or cycling); most trials also including strength training. The mean age of participants was 69 years. The proportion of men ranged from 56% to 88%. Participants had moderately severe COPD with mean forced expiratory volume in one second below 80% predicted and 30% or more predicted; forced expiratory volume in one second/forced vital capacity ratio was below 70%. Duration of short programs ranged from four weeks to three months with frequency that varied between two to three times a week. The duration of longer programs ranged from seven weeks to 18 months with frequency that varied throughout the programme (where reported). Outcome measurement tools varied between trials.

Two reviewers independently selected studies for inclusion.

Two reviewers independently assessed quality using the Jadad and PEDro scales. The Jadad scale (maximum score 5 points) assessed randomisation, blinding and withdrawals. The PEDro scale (maximum score of 10 points) assessed: random allocation; concealment of allocation; similarity at baseline; blinding of participant, therapist and assessor; completeness of follow-up; intention-to-treat analysis; between group statistical comparison; and point and variability estimates.

One reviewer extracted data on length of rehabilitation program, exercise capacity, health-related quality of life and adherence. A clinically important change was defined as 54m for the 6-minute walk test, 0.5 units for the Chronic Respiratory Questionnaire, and 47.5m for the incremental shuttle walking test.

The studies were combined in a narrative synthesis with additional data presented in tables.

Five RCTs (451 patients, range 27 to 140) were included in the review. The mean PEDro score was 6 (range 3 to 8) and the mean Jadad score was 2 (range 1 to 3). Three RCTs reported allocation concealment and blinding of outcome assessors for at least one outcome. Only one trial reported details of randomisation.

Exercise capacity: Two RCTS reported a benefit in exercise capacity for longer term programs compared with short term programs, but two RCTs reported no significant differences between groups.

Health-related quality of life: Three RCTs reported a difference in favour of longer duration programs, but one RCT found no significant differences between groups.

Adherence: Two RCTs reported no differences between longer and shorter duration programs for adherence to exercise.

Longer duration pulmonary rehabilitation programs appeared to have a more favourable effect on health-related quality of life in individuals with chronic obstructive pulmonary disease. The results for exercise capacity were less clear. The limited literature prevented a more definitive conclusion on optimal duration of rehabilitation.

The review question was clear with appropriate inclusion criteria. Several relevant sources were searched with no language restriction, which limited the potential for language bias. No attempts were made to locate unpublished data and studies published as abstracts only were excluded, so there may be potential for publication bias. Appropriate methods to reduce reviewer error and bias were used for the selection of studies and assessment of trial quality, but not for data extraction.

An appropriate quality assessment was conducted and the results adequately reported. A narrative synthesis was appropriate given the differences between trial in duration and intensity of pulmonary rehabilitation, setting and outcome measures. The authors appropriately discussed some of the limitations of the data.

The authors' cautious conclusions reflect the evidence presented and are likely to be reliable.

Practice: The authors did not state any implications for practice.

Research: The authors stated that further well-designed RCTs were required to determine the optimal duration and frequency of pulmonary rehabilitation. Future trials should consider the benefits versus costs of longer duration programs, and the influence of gender, setting and training volume.

Canadian Institutes of Health Research; University of Toronto National Sanitarium Association.

This is a critical abstract of a systematic review that meets the criteria for inclusion on DARE. Each critical abstract contains a brief summary of the review methods, results and conclusions followed by a detailed critical assessment on the reliability of the review and the conclusions drawn.