Characteristics of breathing pattern disorder in people with difficult asthma: an observational cross-sectional study.

BACKGROUND: Breathing pattern disorder (BrPD) in difficult asthma is heterogeneous and poorly understood. OBJECTIVES: We aimed to systematically characterise BrPD and determine the utility of previously proposed classifications for BrPD in this specific population. METHODS: Adults with difficult asthma and suspected BrPD underwent assessments for asthma control and quality of life, co-morbidities (pain and pelvic floor dysfunction), breathlessness, exercise capacity, and BrPD-specific outcomes. Distribution across symptom classification (hyperventilation [Nijmegen questionnaire ≥23]), breathing pattern categories (hyperventilation, thoracic dominant, periodic deep sighing, forced abdominal expiration, asynchrony) and multidimensional classifications (biochemical, biomechanical, psychophysiological) was evaluated, and principal component analysis was conducted to determine underlying constructs between characteristics. RESULTS: Sixty participants were evaluated (48 female, mean age 52 [SD 16] years, FEV1 80 [23] % predicted). Hyperventilation symptoms were common (n=34, 57%). Frequent breathing pattern categories were hyperventilation (n=37, 62%) and thoracic dominant breathing (n=23, 38%). Frequent BrPD dimensions were biomechanical (n=45 [75%]) and biochemical (n=37 [62%]). Few participants met the criteria across all categories (n=0) or dimensions (n= 7 [12%]). Principal component analysis (KMO= 0.74, Bartlett's p < 0.001) identified four principal characteristics of BrPD in difficult asthma: anxiety symptoms, respiratory symptoms, hyperventilation symptoms and observable breathing pattern abnormalities. CONCLUSION: Characteristics of BrPD in individuals with difficult asthma demonstrate four principal components. Existing BrPD classification frameworks do not fully describe the condition in this population. These findings support the need for both symptom and physical evaluation for BrPD in this population to improve clinical recognition and management.