*The primary complaint is that studies in Buteyko breathing were small, few, and according to some critics, done outside stringent scientific protocol. Be that as it may, in 2014, the Global Initiative for Asthma, a collaboration among the World Health Organization, the National Heart, Lung, and Blood Institute, and the National Institutes of Health, gave Buteyko an “A” rating (later revised to a “B”) for supporting evidence.