Is the impedance modulus (Z) an adequate summary of oscillometry parameters in the general population?

<bold>Background:</bold> Oscillometry measures the respiratory system's resistance (R) and reactance (X). The modulus of the impedance (Z), combining both R and X, may represent a single, simple, and more comprehensible measure of the condition of the respiratory system. <bold>Aims:</bold> To compare the association of abnormal resistance, reactance and modulus of impedance with respiratory symptoms and respiratory diseases in a general adult population. <bold>Methods:</bold> We included 8184 subjects (mean age=48y, Females=52%) of the Austrian LEAD general population cohort. Resistance (R), reactance (X), and the modulus of the impedance (Z) at 5 Hz were measured by oscillometry (Resmon Pro Full, Restech, Italy). On the same day, respiratory symptoms and diseases were assessed by a questionnaire. Abnormal parameters were defined according to Veneroni et al., ERS2023. We computed the risk ratios of presenting symptoms and/or disease for subjects with 1) an abnormal Z, 2) abnormal R or X, 3) abnormal R, and 4) abnormal X. <bold>Results:</bold> Performances were similar among the different oscillometry parameters. The number of subjects with abnormal R or X and Z were different (Figure). <fig><object-id>erj;64/suppl_68/PA3056/F1</object-id><object-id>F1</object-id><object-id>F1</object-id><graphic></graphic></fig> <bold>Conclusions:</bold> Our results suggest that X is more sensitive to the onset of symptoms, but Z provides a single measure that adequately represents lung pathophysiology.