Rationale: Respiratory resistance (Rrs) and reactance (Xrs) as measured by oscillometry and their intrabreath changes have emerged as sensitive parameters for detecting early pathological impairments during tidal breathing. Objectives: This study evaluates the prevalence and association of abnormal oscillometry parameters with respiratory symptoms and respiratory diseases in a general adult population. Methods: A total of 7,560 subjects in the Austrian LEAD (Lung, hEart, sociAl, boDy) Study with oscillometry measurements (computed with the Resmon Pro FULL; Restech Srl) were included in this study. The presence of respiratory symptoms and doctor-diagnosed respiratory diseases was assessed using an interview-based questionnaire. Rrs and Xrs at 5 Hz, their inspiratory and expiratory components, the area above the Xrs curve, and the presence of tidal expiratory flow limitation were analyzed. Normality ranges for oscillometry parameters were defined. Measurements and Main Results: The overall prevalence of abnormal oscillometry parameters was 20%. The incidence of abnormal oscillometry increased in the presence of symptoms or diagnoses: 17% (16-18%) versus 27% (25-29%), P, 0.0001. All abnormal oscillometry parameters except Rrs at 5Hz were significantly associated with respiratory symptoms/diseases. Significant associations were found, even in subjects with normal spirometry, with abnormal oscillometry incidence rates increasing by 6% (4-8%; P, 0.0001) in subjects with symptoms or diagnoses. Conclusions: Abnormal oscillometry parameters are present in one-fifth of this adult population and are significantly associated with respiratory symptoms and disease. Our findings underscore the potential of oscillometry as a tool for detecting and evaluating respiratory impairments, even in individuals with normal spirometry.

Background: Within-breath analysis of oscillometry parameters is a growing research area since it increases sensitivity and specificity to respiratory pathologies and conditions. However, reference equations for these parameters in White adults are lacking and devices using multiple sinusoids or pseudorandom forcing stimuli have been underrepresented in previous studies deriving reference equations. The current study aimed to establish reference ranges for oscillometry parameters, including also the within-breath ones in White adults using multi-sinusoidal oscillations. Methods: White adults with normal spirometry, BMI ≤30 kg/m2, without a smoking history, respiratory symptoms, pulmonary or cardiac disease, neurological or neuromuscular disorders, and respiratory tract infections in the previous 4 weeks were eligible for the study. Study subjects underwent oscillometry (multifrequency waveform at 5–11–19 Hz, Resmon PRO FULL, RESTECH Srl, Italy) in 5 centers in Europe and the USA according to international standards. The within-breath and total resistance (R) and reactance (X), the resonance frequency, the area under the X curve, the frequency dependence of R (R5–19), and within-breath changes of X (ΔX) were submitted to lambda-mu-sigma models for deriving reference equations. For each output parameter, an AIC-based stepwise input variable selection procedure was applied. Results: A total of 144 subjects (age 20.8–86.3 years; height 146–193 cm; BMI 17.42–29.98 kg/m2; 56% females) were included. We derived reference equations for 29 oscillatory parameters. Predicted values for inspiratory and expiratory parameters were similar, while differences were observed for their limits of normality. Conclusions: We derived reference equations with narrow confidence intervals for within-breath and whole-breath oscillatory parameters for White adults.

BackgroundOscillometry devices allow quantification of respiratory function at tidal breathing but device-specific reference equations are scarce: the present study aims to create sex-specific oscillometric reference values for children and adolescents using the Resmon PRO FULL device.MethodsHealthy participants (n=981) aged 6 to 17 years of the Austrian LEAD general population cohort were included. Subjects had normal weight (body mass index ≤99th percentile) and normal lung volumes (total lung capacity (TLC) ≥ lower limit of normal). Oscillometry data were collected using a single frequency mode of 8 Hz. Sex-specific prediction equations were developed for total, inspiratory and expiratory resistance (R) and reactance (X) as well as for the modulus of impedance (Z) value using the LMS (lambda, mu, sigma) method. Height was used as a single covariate.ResultsReference equations for all oscillometry parameters were created for Caucasian children aged 6 to 17 years with a height span from 101 to 183 cm and a lung volume span from 1.7 to 8.8 L TLC.RandZvalues progressively decrease andXvalues increase with increasing height. Oscillometry parametersversuslung volume curves differ from thoseversusheight curves. Stratified for lung size, no sex differences are found for oscillometry parameters.ConclusionOur study provides reference values for oscillometry parameters in children and adolescents using strictly defined criteria for weight and lung volumes. No sex-related differences in oscillometry parameters corrected for height or lung size are found.

"Reply to: Z-Scores or Fixed Cut-Off Values to Interpret Oscillometry: Opportunities from the LEAD Study." American Journal of Respiratory and Critical Care Medicine, 0(ja), pp.

Smoking is the main risk factor for COPD. Oscillometry is a easy to perform, not time-consuming technique with low patient burden that provides detailed assessment of respiratory impedance (Z) measurement. The study aims were to evaluate Z as a means to detect early airway abnormalities in past smokers (PS) and active smokers (AS) compared to non-smokers (NS). Methods: We included 7560 subjects (Age 18-82) of the Austrian LEAD general population cohort, a longitudinal single-centered, observational study. Z-measurements were obtained (Resmon Pro Full, Restech, Italy) as conducted by trained technicians. Resistance (R) and reactance (X) at 5 Hz were analysed as well as the area under X (AX) and frequency dependence of R (R5-R19). Data are reported as % of predicted (Berger et al., ERJ open 2021). Smokers were subdivided by the number of pack years (PY). Results: AS with > 10 PY had higher R5 values than NS and PS< 10 PY groups. In addition, this group has manifested higher AX than PS >10 PY. PS, irrespective of the number of PY, showed no Z differences compared to the NS (Table). * p<0.05 vs Smoker > 10 pack/years. Data are presented as median (IQR). Conclusion: Oscillometry is a feasible approach to identify Z changes in active smokers.

Small airway dysfunction (SAD) is a clinically important problem in asthmatics. Impedance (Z) measurement by oscillometry is considered a reliable, easy to perform and quick technique to determine SAD. Limited data are available about the presence of SAD in subjects with past history of asthma/asthmatic bronchitis. The aim of the current study is to assess SAD with Z in past (PA) and current asthmatics (CA). Methods: We included 7219 subjects aged 18-82 years from the Austrian LEAD study, a longitidinal population-based cohort study. Based on questionnaire data, we identified:(1) healthy participants without respiratory pathologies and symptoms (N=6559), (2) subjects reporting past diagnosis of asthma (N=315) and (3) subjects with current asthma (N=345). Resistance (R5) and Reactance (X5) at 5 Hz, the area under X (AX), and the frequency dependence of R (R5-R19) were analyzed. Results * p<0.05 with healthy. ° p<0.05 with Past asthma. % predicted according to Berger et al. (2021). Data are presented as median (IQR). Subjects with current asthma when compared to healthy subjects presented oscillometry parameters compatible with SAD. Subjects with past asthma presented with higher R5. Conclusion: Our population-based data confirm the presence of Z changes, indicative of SAD in current asthmatics. Oscillometry may identify SAD in asthmatics and sharpen therapy management.

Background The forced oscillation technique (FOT) is ideally suited to diagnose and manage respiratory diseases and requires only minimal patient cooperation. The present study aimed to create sex-specific reference equations for children and adolescents aged 6 to 17 years. Methods 981 healthy participants aged 6 to 17 years of the Austrian LEAD general population cohort were included. Nearly all participants had normal weight (BMI ≤ 99th percentile) and all had normal lung volumes (total lung capacity (TLC) ≥ lower limit of normal). FOT data were collected with the Resmon Pro FULL device using a single frequency mode of 8 Hz. Sex-specific prediction equations were developed for Resistance (R) 8 Hz (8) expiratory (exp.), R8 inspiratory (insp.), R8 total (tot.), Reactance (X) 8 exp., X8 insp. and X8 tot. using the LMS (lambda, mu, sigma) method. Since body height showed the most significant influence on the parameters chosen, we used it as a single covariate. Results We created percentile curves and look up tables including reference values for a height from 101 to 183 cm. Male and female children showed a progressive decline in R values over the height spectrum studied. Similarily, X values progressively increases with higher height. R values are higher in females than in males. Conclusion Our study provides highly accurate reference values for clinically useful respiratory impedance (Zrs) parameters in the form of look up tables. To the best of our knowledge, our cohort is the largest population in the age of 6 to 17 years studied so far concerning Zrs. Further studies have to link these height related geometric changes of the airway tree to related changes in lung size.

Background 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). Methods 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. Results 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 (>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 (>180cm) in women. Conclusion 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.

Despite being the golden standard to diagnose and classify airway diseases, the sensitivity of spirometry to detect early airway impairment can be questioned (Wouters et al, JCM 2021). The current study aims to investigate the association between abnormal oscillometry values and the presence of respiratory symptoms in subjects with normal spirometry. 5646 adults (18-90 years) from the Austrian LEAD general population cohort with normal spirometry (FEV1/FVC and FVC) were included. For each subject, within-breath oscillometry (RESMON PRO FULL, RESTECH Srl, Italy), spirometry, respiratory symptoms, and/or respiratory diseases were recorded on the same day. Abnormal FOT was defined according to Oostveen et al., ERJ 2013. We computed the risk ratios of presenting symptoms and/or diseases for subjects with 1) an abnormal oscillometry parameter (n=785), 2) abnormal resistance (Rrs; n=541), 3) abnormal reactance (Xrs; n=481)), 4) abnormal inspiratory parameters (n=351), and 5) abnormal expiratory parameters (n=667). Changes in FOT parameters are highly prevalent in subjects with normal spirometry and are consistently related to reported respiratory symptoms and past or present respiratory diseases (Figure). FOT is a simple, feasible and sensitive method to objectify respiratory conditions in normal spirometry.