A Cochrane review [Abstract] 1 included 13 studies with a total of 906 subjects. The studies were different from one another in terms of type of breathing exercise performed, number of participants enrolled, number and duration of sessions completed, outcomes reported and statistical presentation of data. Asthma severity in participants ranged from mild to moderate, and the samples consisted solely of outpatients. Eleven studies compared breathing exercise with inactive control, and 2 with asthma education control groups. All eight studies that assessed quality of life reported an improvement in this outcome. An improvement in the number of acute exacerbations was observed by the only study that assessed this outcome. Six of 7 included studies showed significant differences favouring breathing exercises for asthma symptoms. Effects on lung function were more variable, with no difference reported in 5 of the 11 studies that assessed this outcome, while the other 6 showed a significant difference for this outcome, which favoured breathing exercises. Due to heterogeneity among the studies, meta-analysis was possible only for asthma symptoms and changes in the Asthma Quality of Life Questionnaire (AQLQ). Each meta-analysis included only two studies and showed a significant difference favouring breathing exercises (MD -3.22, 95% CI -6.31 to -0.13 for asthma symptoms; MD 0.79, 95% CI 0.50 to 1.08 for change in AQLQ).
Comment: The quality of evidence is downgraded by inconsistency, and by imprecise results (few patients and outcome events).
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