Biofeedback-induced voluntary reduction of respiratory resistance in severe bronchial asthma.

Attempts to reduce asthmatic symptoms with respiratory resistance (Ros) biofeedback yielded heterogeneous results. The nature of treatment effects remained unclear (e.g. unspecific relaxation, visceral learning); little is known about clinical long-term effects. The present study investigated the suitability of a statistical single-case approach for an adequate evaluation. A female asthmatic underwent 12 Ros biofeedback sessions. Several breathing parameters were recorded during all sessions and pre/post investigations. The clinical course was observed with symptom diaries for 100 days. The subject achieved considerable voluntary control over her Ros, this control was based upon the expiratory flow. In general, the effects on the clinical course were weak; however, asthmatic attacks decreased in the follow-up period. Careful analyses of physiological, psychophysiological, and course variables allowed the identification of the main processes underlying the biofeedback effects. Further studies should investigate the worth of the expiratory flow as feedback variable.