Comparison of two respiratory oscillometers in patients with a broad range of lung function patterns

Background Oscillometry provides a non-invasive assessment of respiratory system mechanics and has shown potential for early detection of lung disease. However, differences in device hardware and signal processing may limit comparisons between devices. The objective of this study was to evaluate agreement between two commercial forced oscillometry devices, Tremoflo C-100 (Thorasys Medical Systems, Canada) and Resmon Pro (Restech srl, Italy) in patients with a spectrum of abnormal lung physiology. Methods 49 patients with chronic lung disease and 27 healthy volunteers completed paired oscillometry using both devices in an alternating order. Measurements of resistance at 5 Hz (R5), resistance between 5 and 19 Hz (R5–19), reactance at 5 Hz (X5), the resonant frequency of the lungs (Fres), and area of reactance (AX) were compared using Wilcoxon signed-rank tests, Bland–Altman analysis, intraclass correlation coefficients (ICC), and effect size calculations. Results Significant differences were found between devices for all impedance measurements ( p ≤ 0.001). The Resmon Pro reported lower R5, R5–19, Fres, and AX, and less negative X5 than the Tremoflo C-100. ICC estimates ranged from 0.59 to 0.85, but Bland–Altman analysis demonstrated systematic bias and wide limits of agreement; for AX, the bias was −4.10 cmH₂O/L with limits of agreement from −14.99 to 6.80 cmH₂O/L. Conclusion Systematic biases and wide limits of agreement indicate that the devices should not be used interchangeably for longitudinal patient monitoring. Standardization of oscillometry device signal generation and processing is necessary to enable accurate cross-device comparison in both clinical and research applications.