Reference values for respiratory impedance in adult men and women: data from the Austrian LEAD Study.

Abstract

<b>Background</b> Determination of reference values of respiratory impedance (Zrs) measured by forced oscillation technique (FOT) is of utmost importance in its clinical use. The aim of our study was to present reference values for whole-breath FOT measurements for adults (18-80 years). <b>Methods</b> 1264 adult healthy asymptomatic never-smokers of the Austrian LEAD Study cohort were included in the analysis. Nearly all participants had normal weight (BMI ≤ 35) and had normal lung volumes (total lung capacity (TLC) ≥ lower limit of normal). Data were collected with the Resmon Pro FULL device using a multiple frequency mode of 5-11-19 Hz. Sex-specific prediction equations were developed for Resistance (R) 5 Hz (5) expiratory (exp.), R5 inspiratory (insp.), R5 total (tot.), Reactance (X) 5 exp., X5 insp. and X5 tot. using the LMS (lambda, mu, sigma) method. Body height only showed a significant influence on the parameters chosen. Therefore, it was used as a single covariate. <b>Results</b> We created percentile curves and look up tables including reference values for a height from 143cm to 204cm. While R values in men decrease with height between 150cm and 180cm and flattened at higher length (&gt;180cm), R values in females progressively declined with higher height. X showed a progressive increase with height in men and a flattening of X at higher length (&gt;180cm) in women. <b>Conclusion</b> Our study provides highly accurate reference values for clinically useful Zrs parameters in the form of look up tables. Beside the establishment of reference values further research is required for the optimal positioning of Zrs in respiratory diagnostics.