Agreement on Respiratory Impedance Measured by Two Commercial Forced Oscillation Technique Devices: A Randomized Crossover Study
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The performance of forced oscillation technique (FOT) devices may vary due to differences in hardware and signal processing.
Research question
Does the respiratory impedance (Zrs) measured by two commercial FOT devices agree?
Study Design and Methods
The Zrs of 97 consecutive adults with respiratory symptoms were measured using TremoFlo ® C-100 and Resmon™ Pro FULL V3, employing a random allocation and crossover design. The parameters between the devices were compared using paired t-tests and Bland-Altman plots with 95% limits of agreement (LoA).
Results
The average age of the study population was 42.3 years, with 46% were women. The resistance parameters (R5 and R19) of Resmon ™ were larger than those obtained with TremoFlo ® . However, R5-19 of Resmon ™ was significantly smaller than TremoFlo ® , with a paired difference of -0.20 cm H 2 O/L/s (95% CI: -0.35, -0.05; p = 0.01). The within- and whole-breath X5 of Resmon ™ were significantly less negative than those obtained with TremoFlo ® . The reactance area and resonant frequency of Resmon ™ were also significantly smaller than those obtained with TremoFlo ® . The bias for R5 (Bias: 0.29 cmH 2 O/L/s; LoA: - 2.69, 3.26) was broad and had random errors. The bias for X5 (bias: 0.8 cmH 2 O/L/s; 95% LoA: -1.25, 2.85) and Ax (Bias: -13.66 cmH 2 O/L/s; LoA: -45.46, 18.14) was also wide and exhibited systematic errors.
Interpretations
Respiratory impedance measured by the two FOT devices differed significantly, particularly for the reactance parameters. Normative Zrs generated by a particular oscillometer should be avoided when interpreting reports obtained from another device.
