BackgroundMultiple breath washout (MBW) using sulfur hexafluoride (SF6) has the potential to reveal ventilation heterogeneity which is frequent in patients with obstructive lung disease and associated small airway dysfunction. However, reference data are scarce for this technique and mostly restricted to younger cohorts. We therefore set out to evaluate the influence of anthropometric parameters on SF6-MBW reference values in pulmonary healthy adults.MethodsWe evaluated cross-sectional data from 100 pulmonary healthy never-smokers and smokers (mean 51 (SD 20), range 20–88 years). Lung clearance index (LCI), acinar (Sacin) and conductive (Scond) ventilation heterogeneity were derived from triplicate SF6-MBW measurements. Global ventilation heterogeneity was calculated for the 2.5% (LCI2.5) and 5% (LCI5) stopping points. Upper limit of normal (ULN) was defined as the 95th percentile.ResultsAge was the only meaningful parameter influencing SF6-MBW parameters, explaining 47% (CI 33% to 59%) of the variance in LCI, 32% (CI 18% to 47%) in Sacin and 10% (CI 2% to 22%) in Scond. Mean LCI increases from 6.3 (ULN 7.4) to 8.8 (ULN 9.9) in subjects between 20 and 90 years. Smoking accounted for 2% (CI 0% to 8%) of the variability in LCI, 4% (CI 0% to 13%) in Sacin and 3% (CI 0% to 13%) in Scond.ConclusionSF6-MBW outcome parameters showed an age-dependent increase from early adulthood to old age. The effect was most pronounced for global and acinar ventilation heterogeneity and smaller for conductive ventilation heterogeneity. No influence of height, weight and sex was seen. Reference values can now be provided for all important SF6-MBW outcome parameters over the whole age range.Trial registration numberNCT04099225.

Multiple breath washout (MBW) using sulfur hexafluoride (SF 6 ) has the potential to reveal ventilation heterogeneity in obstructive lung disease. This is frequent in patients with small airway disease and missed by commonly used tests. However, reference data is scarce and mostly restricted to younger collectives. Lung clearance index (LCI) is the most commonly used MBW outcome parameter and represents global ventilation heterogeneity. We therefore set out to evaluate the influence of anthropometric parameters on SF 6 -MBW LCI reference values in pulmonary healthy adults. Methods: We prospectively evaluated 104 pulmonary healthy non-smokers and smokers (mean 51±20, range 20-88 years). LCI was derived from triplicate SF 6 -MBW measurements and calculated at the 2.5% stopping point. Upper limit of normal (ULN) was defined as the 95 th percentile. Results: Age was the only meaningful parameter influencing SF 6 -MBW parameters explaining 47% of the variance in LCI. Smoking accounted for only 2% of the variability in LCI. Mean LCI increases from 6.3 to 8.8 in subjects between 20 and 90 years (Figure). Upper limits of normal were calculated as of 7.4 to 9.9, respectively. Conclusions: LCI showed an age-dependent increase from early adulthood to senectitude. No influence of height, weight and gender was seen. Reference values can now be provided for SF 6 -MBW LCI over the whole age range.

No abstract