Biofeedback and instructions in the modification of total respiratory resistance: an experimental study of asthmatic and non-asthmatic volunteers
Steptoe, A.; Phillips, J.; Harling, J.
Journal of Psychosomatic Research 25(6): 541-551
ISSN/ISBN: 0022-3999 PMID: 7320955 Accession: 004829072
The ability of asthmatic and non-asthmatic human subjects to exert voluntary control over pulmonary function was assessed in a short-term experimental context. Total respiration resistance (Rt) was monitored using the forced oscillation technique with a Siemens Siregnost FD5, while peak flow (PF) and forced expiratory volume (FEV1) were also recorded periodically. Sixteen nonasthmatic and 8 asthmatic volunteers attended 1 introductory and 4 experimental sessions. Each experimental session consisted of four 3-min trials, during which the participants tried to lower airways resistance, separated by rest periods. The asthmatic subjects, and 8 of the nonasthmatics, were provided with visual and auditory analog feedback of Rt throughout each trial in all sessions. The 2nd nonasthmatic group attempted voluntary control without feedback (instruction only) in sessions 1 and 2, and feedback was subsequently introduced for the final 2 sessions. Analysis of sessions 1 and 2 indicated that Rt was lower in the nonasthmatics given feedback compared with those in the instruction condition. During the final 2 sessions, differences between the 2 nonasthmatic groups disappeared. Trends also emerged within sessions, since Rt was higher in trials than rests early in sessions, while later this pattern was reversed. The average change between trials 1 and 4 in the last session was 7.1%. These effects were reflected to a limited extent in PF data. The asthmatic response was more variable. Two members of this group produced consistent decreases in Rt of 15-20% during trials compared with rests, while modifications in the reverse direction were recorded in 2 others. Patients may therefore have to be carefully selected for this approach to asthma management. The mechanisms responsible for these responses are uncertain.