To systematically review the evidence examining the use of incentive spirometry (IS) for the prevention of post-operative pulmonary complications (PPCs).

MEDLINE, CINAHL, HealthSTAR and Current Contents were searched from their inception to June 2000 using the key terms 'incentive spirometry', 'breathing exercises', 'chest physical therapy' and 'pulmonary complications'. The reference lists of all identified studies were examined. The search was limited to studies conducted in humans and published in the English language.

Study designs of evaluations included in the review

With the exception of reviews, commentaries, cost-analyses, surveys, patient monographs, letters and guidelines, all study designs seem to have been eligible for inclusion. Randomised controlled trials (RCTs), quasi-RCTs, crossover studies and case series were included in the review.

Specific interventions included in the review

IS used for the purpose of preventing PPC. Studies that used IS for other purposes, such as for inspiratory muscle training and bronchodilator administration or as a monitoring tool, were excluded. The various protocols of IS used in the included studies were: 8 breaths; 20 minutes, 4 times daily; 10 minutes; 10 repetitions, 4 times daily; 15 minutes every 2 hours; 20 repetitions every 2 hours; 15 minutes, 4 times daily; 150 to 200 times per day; and 30 breaths every hour. In one study, the intervention was IS plus physical therapy.

The included studies compared IS with the following: intermittent positive-pressure breathing; positive end-expiratory pressure; deep breathing exercises; early mobilisation with and without deep breathing exercise; continuous positive airway pressure with or without physical therapy; bilevel positive airway pressure with physical therapy; no treatment; deep breathing and coughing; and positive expiratory pressure with physical therapy.

Participants included in the review

Studies of people recovering from surgery were eligible for inclusion in the review. The patients in the included studies were recovering from upper and lower abdominal surgery, cardiac surgery, cardiac artery bypass graft surgery or median sternotomy. All studies dealt with adult patients.

Outcomes assessed in the review

Only studies with 'valid' outcome measures of PPC were accepted, although these were not defined. Some included studies reported the short-term physiologic effects of IS (e.g. diaphragmatic movement, vital capacity, partial arterial oxygen pressure, end-expiratory pulmonary pressure). The others reported the incidence of atelectasis, prevention of PPCs, return of lung volume to pre-operative values, pulmonary function tests (functional residual capacity, forced expiratory volume in 1 second, functional vital capacity, and ratio between the latter two), vital capacity, venous admixture, gas exchange and preservation of lung volumes.

How were decisions on the relevance of primary studies made?

The authors do not state how the papers were selected for the review, or how many of the reviewers performed the selection.

The authors developed their own checklist to assess the studies. This assessed issues including randomisation, blinding, treatment protocol, statistical analysis, drop-outs, bias, contamination, cointervention, compliance, validity of outcome measures, and any other reliability or validity issue affecting the results and conclusions. Each study was critically appraised by one of three pairs of team members. A pilot critical appraisal form was independently completed by each member of the pair, and the pair then met to reach a consensus. Each study was then presented to the entire review team for discussion and group agreement on the validity of the conclusions of the study.

The data appear to have been extracted onto the same pilot critical appraisal forms as the validity assessment, which would mean that the same process was followed with regard to the number of reviewers and the resolution of any disagreements. In addition to the criteria used for the validity assessment, data were also extracted on: study purpose, participant age, surgery type, inclusion and exclusion criteria, study design, sample size, treatment groups, outcome measures, and statistical significance.

How were the studies combined?

The study results were tabulated and summarised in a narrative synthesis.

How were differences between studies investigated?

The authors state that, owing to the wide heterogeneity of patient populations and the variety of outcome measures, the study results were not pooled.

Forty-six studies originally met the inclusion criteria, of which only 11 (n=656) passed the group discussion of the validity of their conclusions and were accepted. Of these 11 included studies, 8 were RCTs, one was a crossover study and 2 were case series.

None of the 3 studies of short-term effects supported the proposed theoretical benefits of IS. The critical appraisal of the 8 articles on treatment effects indicated 7 nonsupportive studies and one supportive study. The supportive study reported that IS, deep breathing exercises and intermittent positive-pressure breathing all were more effective than no treatment. No adverse events were reported in the 46 studies appraised.

At present, the evidence does not support the use of IS for decreasing the incidence of PPCs following cardiac or upper abdominal surgery.

The review question was supported by clear study selection criteria in terms of the study design, intervention and participants. However, the 'valid' outcome measures criterion, which was used to exclude some studies, was not defined. The literature search was reasonable but was limited to English language publications, which may have resulted in some studies being missed. No attempt was made to identify unpublished studies. The authors developed a validity assessment tool, which was used to exclude 35 relevant studies; however, it is unclear whether the 11 studies that were not excluded met all the validity criteria, or if there was a threshold. Some details of the 11 included studies were tabulated, but the review's authors seem to have taken the conclusions of the studies rather than presenting any numerical data. If numerical data had been presented, it would have been clear whether the study authors' conclusions reflected the results.

While the decision not to pool data is justified owing to clinical heterogeneity in the interventions, outcomes and participants, the lack of numerical data presented makes it impossible to judge whether the review's conclusions are valid.

Practice: The authors state that IS should not be used following cardiac or abdominal surgery.

Research: The authors state that a study of IS in patients who have undergone major head and neck surgery is required. In addition, an RCT is needed to assess treatment benefit related to the short-term effect of increasing inspiratory volume in patients recovering from surgery, trauma or critical illness.

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.