Evaluation of a breathing retraining intervention to improve quality of life in asthma: quantitative process analysis of the BREATHE randomized controlled trial

Objective: Explore qualitative differences between interventions (DVD and booklet (DVDB) versus face-to-face and booklet (F2FB) versus usual care) in the BREATHE (Breathing Retraining for Asthma Trial of Home Exercises) trial of breathing retraining for asthma. Design: Quantitative process analysis exploring group expectancy, experience and practice before and after intervention delivery for the main trial. Setting: Primary care. Subjects: Adults with asthma (DVD and booklet, n = 261; F2FB, n = 132). Main measures: Baseline - expectancy about breathing retraining; follow-up 3, 6 and 12 months - self-efficacy, treatment experience (enjoyment of treatment, perceptions of physiotherapist, perceptions of barriers), amount of practice (weeks, days/week, times/day), continued practice; all time points - anxiety (Hospital Anxiety and Depression Scale), AQLQ (Asthma Quality of Life Questionnaire). Results: No group differences in baseline expectancy. Statistically significant results (P < 0.05) indicated that at follow-up, F2FB participants perceived greater need for a physiotherapist than DVD and booklet participants (3.43 (0.87) versus 2.15 (1.26)). F2FB participants reported greater enjoyment of core techniques (such as stomach breathing: 7.42 (1.67) versus 6.13 (1.99) (DVD and booklet)). Fewer F2FB participants reported problems due to doubts (24 (22.9%) versus 90 (54.2%)). F2FB participants completed more practice sessions (75.01 (46.38) versus 48.56 (44.71)). Amount of practice was not significantly related to quality of life. In the DVD and booklet arm, greater confidence in breathing retraining ability explained 3.9% of variance in quality of life at 12 months. Conclusion: Adults with asthma receiving breathing retraining face-to-face report greater enjoyment and undertaking more practice than those receiving a DVD and booklet. Greater confidence in ability to do breathing retraining is associated with improved QoL.