Reference equations for oscillometry in adults: data from the Austrian LEAD study.

Background: Determination of reference values of respiratory impedance (Z) measured by oscillometry is of utmost importance for its clinical usefulness. The aim of our study was to develop reference values for within-breath and total oscillometry measurements in adults (18-90 years of age). Methods: Healthy asymptomatic never-smoking adults of the Austrian LEAD study cohort were included in the analysis. Healthy never-smoking adults without any respiratory disease, with normal weight (body mass index (BMI) ≤35 kg·m-2) and normal lung volumes (total lung capacity ≥ lower limit of normal) were included. Data were collected with the Resmon Pro FULL® device using a multiple frequency mode of 5-11-19 Hz. Sex-specific reference equations were developed for within-breath and total resistance, reactance and the impedance modulus, as well as for the frequency dependence of resistance (R 5-R 19), the resonant frequency and the area under the reactance curve using the lambda, mu, sigma method. Results: A total of 887 participants were included in the analysis. We developed sex-specific reference equations for 30 total and within-breath oscillometry parameters. Height, age and BMI were included in the modelling, and height showed the strongest association. Predicted values showed a narrower normality range compared with existing reference equations. Conclusion: Our study provides highly accurate, adult reference equations derived from a large sample size with a wide age span. Development of reference equations supports further research on positioning of oscillometry in respiratory diagnostics.