The most comprehensive and detailed free instructions for the Buteyko breathing technique can be found on this web page: http://www.normalbreathing.com/learn.php
If one improves his breathing (breathing is measured using a stress-free breath holding time after exhalation, see the site for complete instructions) up to 25 s 24/7, no meds are necessary. If you get over 40 s 24/7, all lung function tests will be normal.