Here you can read around as you please and create your own picture...but be careful: Studies are always carried out with certain perspectives and can never represent the entire reality. Your own experience is always the supreme discipline!
Study from Great Britain (Nottingham)
Cooper S, Oborne J, Newton S, Harrison V, Thompson Coon J, Lewis S, Tattersfield A Effect of two breathing exercises (Buteyko and pranayama) in asthma: a randomized controlled trial. Thorax 58, 674-679, 2003.http://thorax.bmjjournals.com/cgi/content/abstract/58/8/674
Study from New Zealand (Gisborne)
McHugh P, Aitcheson F, Duncan B, Houghton F Buteyko breathing technique for asthma: an effective intervention. The New Zealand Medical Journal 116 (1187), ……. 2003
UK (Glasgow) study
Study from Canada (Calgary)
Cowie RL, Conley DP, Underwood MF Reader PG: A randomized controlled trial of the Buteyko technique for asthma management. Proceedings of the American Thoracic Society 3, A530, 2006.
Cowie RL, Conley DP, Underwood MF, Reader PG: A randomized controlled trial of the Buteyko technique as an adjunct to conventional management of asthma. resp. Med. 102(5):726-32, 2008.
Abstract about rehabilitation measures in combination with the Buteyko method:
Clinic Bad Reichenhall, DRV Bayern Süd, 2012
Huidrom K. et al, 2016, Effectiveness of Buteyko breathing technique on respiratory physiological parameters among patients with bronchial asthma, International Journal of Recent Scientific Research, Vol. 7, Issue 5, pp. 11328-11331._cc781905-5cde-3194-bb3b -136bad5cf58d_
Study from Ireland
Efficacy of non-invasive respiratory techniques in the treatment of children with bronchial asthma: a randomized controlled trial. Ragab K Elnaggar, Mohammed A Shendy. Bulletin of the Faculty of Physical Therapy. Year: 2016, Volume: 21, Issue: 1, Page: 1-10.