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, Fres, and AX, 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, Fres, and AX, 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.