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    Hyperventilation Shows Benefits for Asthma; Evidence is Limited

    Authors of a comparative effectiveness review issued by the Agency for Healthcare Research and Quality conclude that hyperventilation reduction techniques "may be a useful tool in the larger asthma management toolbox, which also includes medication and other components as needed, such as environmental controls, symptom monitoring, and a plan for handling exacerbations." However, given that none of the studies included in the review were conducted in the United States, available evidence is limited in its strength and applicability to the US population, they add.     

    The authors searched MEDLINE; PsycInfo; Embase; Cumulative Index to Nursing and Allied Health Literature; Physiotherapy Evidence Database; Cochrane Central Register of Controlled Trials; AltHealthWatch; Allied and Complementary Medicine; Manual, Alternative and Natural Therapy Index System; and Indian Medical Journals from 1990 through December 2011. They supplemented searches with manual searching of reference lists and grey literature, including regulatory documents, conference abstracts, clinical trial registries, and websites of professional organizations.

    APTA member Anne Swisher, PT, PhD, CCS, served on the technical expert panel that provided input on the analytic framework, key questions, and review protocol. Two independent reviewers screened identified abstracts against predefined inclusion/exclusion criteria. Two investigators reviewed full-text articles and independently quality-rated those meeting inclusion criteria. Data from fair- and good-quality trials were abstracted into standardized forms and checked by another investigator. The authors summarized data qualitatively and, where possible, used random effects meta-analysis.

    The authors identified 4 types of interventions—hyperventilation reduction breathing techniques, yoga breathing techniques, inspiratory muscle training (IMT), and other nonhyperventilation reduction breathing techniques, which included physical therapy methods. They found the most robust body of evidence for hyperventilation reduction breathing techniques in adults, including the only large-scale trial (n=600, aged 14 and older). Hyperventilation reduction interventions (particularly those with 5 hours or more of patient contact) achieved medium to large improvements in asthma symptoms and reductions in reliever medication use of approximately 1.5 to 2.5 puffs per day, but did not improve pulmonary function. These trials also were more applicable, although still somewhat limited, to the United States than trials examining other interventions due to similarities in applicable treatment guidelines to US guidelines and similar levels of development in the countries in which these studies were conducted.

    Limited evidence suggested yoga breathing may improve pulmonary function in adults in addition to reducing asthma symptoms, but medication use was rarely reported and applicability to the United States was very low. Evidence for IMT and other breathing retraining techniques was limited to small, heterogeneous trials providing insufficient evidence to determine effectiveness. The only harms of breathing retraining techniques identified were minor annoyances associated with taping the participants' mouths. Almost all trials were limited entirely or primarily to adults.

    The authors include recommendations for future trials for hyperventilation reduction and other techniques in their review. 


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