Small airway dysfunction in bronchiectasis patients with exercise-induced desaturation

BackgroundIn non-cystic fibrosis bronchiectasis, small airway airflow limitation is primarily driven by mucus plugging, chronic neutrophilic inflammation, and epithelial injury. These primary mechanisms lead to subsequent airway remodelling and luminal narrowing. Such functional impairment is clinically significant, as a reduced distance-saturation product (DSP) of <280 m% during the 6-minute walk test (6MWT) is associated with increased mortality.ObjectiveTo evaluate the association between small airway dysfunction (SAD), exercise-induced desaturation (EID), and impaired exercise capacity in patients with bronchiectasis.DesignA retrospective, cross-sectional study.MethodsThis retrospective study included 114 patients with bronchiectasis (non-desaturators, n = 57; desaturators, n = 57) and 53 non-bronchiectasis controls. Impulse oscillometry (IOS), spirometry, and 6MWT data were analysed. Desaturators were defined as a maximal decline in peripheral oxygen saturation (ΔSpO₂) ≤ -4% during the 6MWT.ResultsCompared with bronchiectasis non-desaturators (n = 57), desaturators (n = 57) exhibited more pronounced IOS-defined SAD, characterised by higher R₅-R₂₀, F_res, and A_X, and lower X₅, as well as spirometry-defined SAD with lower MMEF%pred and FEF50%pred. Desaturators also demonstrated a shorter 6-minute walk distance (6MWD). Greater R₅-R₂₀, F_res, and A_X, and lower X₅, MMEF%pred, and FEF50%pred were associated with a larger reduction in ΔSpO₂, shorter 6MWD, and lower DSP. The multiple linear regression showed age, BRICS, and R₅-R₂₀ are independent predictors for DSP. Among them, R₅-R₂₀(β=-0.345) is a stronger predictor than BRICS (β=-0.285) for DSP.ConclusionSAD is independently associated with EID and reduced exercise capacity in bronchiectasis, highlighting its potential role as a functional marker beyond structural disease severity.