Supplementary Material for: Reference equations for within-breath respiratory oscillometry in White adults

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 aims 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≤30kg/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 5-11-19Hz, 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: 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.