Associations between ventilation heterogeneity and physiological markers of airway calibre and gas trapping in healthy adults

Abstract

Background: Multiple breath nitrogen washout (MBNW) indices provide insight into ventilation heterogeneity globally (LCI) and within the acinar (Sacin) and conducting (Scond) airways. Normal ageing leads to an accelerated deterioration of Sacin and LCI in later life, but little is known about the association between MBNW and pulmonary function indices reflecting airway calibre (FEV 1 /FVC, FEF 25-75 ) and gas trapping (RV/TLC) in healthy elderly subjects. Aim: To explore associations between MBNW indices and markers of airway calibre and gas trapping in healthy adults aged 22-89 years and to determine if relationships differ in elderly (≥50 years) vs. younger subjects ( Method: Healthy subjects (no cardiac/respiratory disease, smoking history Results: 41 elderly [49% male, mean age 65 yrs] and 38 younger subjects [47% male, mean age 33 yrs] were recruited. Across the entire cohort, after adjustment for age, sex, height and BMI, correlations existed between Sacin and FEV 1 /FVC (r=-0.34, p=0.002), Sacin and FEF 25-75 (r=-0.33, p=0.006), Scond and RV/TLC (r=0.37, p=0.002), LCI and RV/TLC (r=0.24, p=0.048). These were driven by correlations present within elderly but not younger subgroups: Sacin and FEV 1 /FVC (r=-0.49, p=0.001), Sacin and FEF 25-75 (r=-0.35, p=0.046), Scond and RV/TLC (r=0.45, p=0.009). Conclusion: In healthy adults aged ≥50 years, peripheral airways ventilation heterogeneity relates to normal variations in airway calibre and gas trapping. As these associations are not present in younger adults, they may reflect greater changes in peripheral airway architecture in the elderly.