Background Breathing exercises have been widely used worldwide as a non-pharmacological therapy to treat people with asthma. Breathing exercises aim to control the symptoms of asthma and can be performed as the Papworth Method, the Buteyko breathing technique, yogic breathing, deep diaphragmatic breathing or any other similar intervention that manipulates the breathing pattern. The training of breathing usually focuses on tidal and minute volume and encourages relaxation, exercise at home, the modification of breathing pattern, nasal breathing, holding of breath, lower rib cage and abdominal breathing. Objectives To evaluate the evidence for the efficacy of breathing exercises in the management of people with asthma. Search methods To identify relevant studies we searched The Cochrane Library, MEDLINE, Embase, PsycINFO, CINAHL and AMED and performed handsearching of respiratory journals and meeting abstracts. We also consulted trials registers and reference lists of included articles. The most recent literature search was on 4 April 2019. Selection criteria We included randomised controlled trials of breathing exercises in adults with asthma compared with a control group receiving asthma education or, alternatively, with no active control group. Data collection and analysis Two review authors independently assessed study quality and extracted data. We used Review Manager 5 software for data analysis based on the random-effects model. We expressed continuous outcomes as mean differences (MDs) with confidence intervals (CIs) of 95%. We assessed heterogeneity by inspecting the forest plots. We applied the Chi2 test, with a P value of 0.10 indicating statistical significance, and the I2 statistic, with a value greater than 50% representing a substantial level of heterogeneity. The primary outcome was quality of life. Main results We included nine new studies (1910 participants) in this update, resulting in a total of 22 studies involving 2880 participants in the review. Fourteen studies used Yoga as the intervention, four studies involved breathing retraining, one the Buteyko method, one the Buteyko method and pranayama, one the Papworth method and one deep diaphragmatic breathing. The studies were different from one another in terms of type of breathing exercise performed, number of participants enrolled, number of sessions completed, period of follow-up, outcomes reported and statistical presentation of data. Asthma severity in participants from the included studies ranged from mild to moderate, and the samples consisted solely of outpatients. Twenty studies compared breathing exercise with inactive control, and two with asthma education control groups. Meta-analysis was possible for the primary outcome quality of life and the secondary outcomes asthma symptoms, hyperventilation symptoms, and some lung function variables. Assessment of risk of bias was impaired by incomplete reporting of methodological aspects of most of the included studies. We did not include adverse effects as an outcome in the review. Breathing exercises versus inactive control For quality of life, measured by the Asthma Quality of Life Questionnaire (AQLQ), meta-analysis showed improvement favouring the breathing exercises group at three months (MD 0.42, 95% CI 0.17 to 0.68; 4 studies, 974 participants; moderate-certainty evidence), and at six months the OR was 1.34 for the proportion of people with at least 0.5 unit improvement in AQLQ, (95% CI 0.97 to 1.86; 1 study, 655 participants). For asthma symptoms, measured by the Asthma Control Questionnaire (ACQ), meta-analysis at up to three months was inconclusive, MD of -0.15 units (95% CI -2.32 to 2.02; 1 study, 115 participants; low-certainty evidence), and was similar over six months (MD -0.08 units, 95% CI -0.22 to 0.07; 1 study, 449 participants). For hyperventilation symptoms, measured by the Nijmegen Questionnaire (from four to six months), meta-analysis showed less symptoms with breathing exercises (MD -3.22, 95% CI -6.31 to -0.13; 2 studies, 118 participants; moderate-certainty evidence), but this was not shown at six months (MD 0.63, 95% CI -0.90 to 2.17; 2 studies, 521 participants). Meta-analyses for forced expiratory volume in 1 second (FEV1) measured at up to three months was inconclusive, MD -0.10 L, (95% CI -0.32 to 0.12; 4 studies, 252 participants; very low-certainty evidence). However, for FEV1 % of predicted, an improvement was observed in favour of the breathing exercise group (MD 6.88%, 95% CI 5.03 to 8.73; five studies, 618 participants). Breathing exercises versus asthma education For quality of life, one study measuring AQLQ was inconclusive up to three months (MD 0.04, 95% CI -0.26 to 0.34; 1 study, 183 participants). When assessed from four to six months, the results favoured breathing exercises (MD 0.38, 95% CI 0.08 to 0.68; 1 study, 183 participants). Hyperventilation symptoms measured by the Nijmegen Questionnaire were inconclusive up to three months (MD -1.24, 95% CI -3.23 to 0.75; 1 study, 183 participants), but favoured breathing exercises from four to six months (MD -3.16, 95% CI -5.35 to -0.97; 1 study, 183 participants). Authors' conclusions Breathing exercises may have some positive effects on quality of life, hyperventilation symptoms, and lung function. Due to some methodological differences among included studies and studies with poor methodology, the quality of evidence for the measured outcomes ranged from moderate to very low certainty according to GRADE criteria. In addition, further studies including full descriptions of treatment methods and outcome measurements are required.
