Effect of airway constriction on ventilation inhomogeneity: multiple-breath washout indices and intrapulmonary reverse flow

BACKGROUND: Small airway dysfunction is an early and clinically important feature of many respiratory diseases but remains difficult to detect using conventional physiological tests. Multiple-breath washout (MBW) is widely used to assess ventilation heterogeneity; however, its sensitivity to the specific location and severity of airway narrowing is not fully understood. METHODS: ) were evaluated alongside a novel intrapulmonary reverse flow (RF) metric. Sensitivity to airway structural changes was assessed using Spearman's rank correlation and multiple linear regression analyses. RESULTS: (0.564). CONCLUSIONS: reflects a broader spectrum of ventilation disturbances than previously assumed, providing a new mechanistic basis for interpreting MBW indices.