Agreement of respiratory impedance measurements between two commercial forced oscillation technique devices: A randomized crossover study

The performance of forced oscillation technique (FOT) devices may vary due to differences in hardware and signal processing. This study examined the agreement of respiratory impedance (Zrs) measured by two commercial FOT devices in unselected adults with respiratory symptoms. The Zrs of 97 consecutive adults with respiratory symptoms were measured using the TremoFlo C-100 and Resmon Pro FULL V3, in a randomized crossover design. Paired t-tests and Bland–Altman plots with 95% limits of agreement (LoA) were used to compare Zrs measurements between the two devices. The average age of the cohort was 42.3 years, and 46% were women. R5 (p = 0.07) and R19 (p < 0.001) values were higher with Resmon Pro than with the TremoFlo. In contrast, R5–19 was significantly smaller with Resmon Pro, with a paired difference of −0.20 cm H₂O/L/s (p = 0.01). The within- and whole-breath X5 of Resmon Pro were significantly less negative than those of TremoFlo. The reactance area and resonant frequency of Resmon Pro were also significantly smaller than those obtained with TremoFlo. The bias for R5 (0.29 cmH 2 O/L/s; LoA: -2.69, 3.26) was broad and had random errors. The biases for whole-breath X5 (0.8 cmH 2 O/L/s; 95% LoA: -1.25, 2.85) was also wide and AX (-13.66 cmH 2 O/L/s; LoA: -45.46, 18.14) exhibited systematic errors. Zrs measurement differed significantly between the two FOT devices, particularly for reactance parameters. Therefore, normative values derived from one device should be avoided when interpreting results from another. • Respiratory impedance obtained from two oscillometers shows wide random and systematic variability. • Normative equations are device-specific and should not be used to interpret results obtained from other devices. • Standardization across oscillometers is crucial to ensure robust and reliable interpretation