Comparison between Impulse oscillometry and Resmon Pro and the use of inspiratory parameters

Abstract

Background: The Resmon Pro system uses the forced oscillation technique (FOT) with sound waves at 5, 11 and 19 Hz, to avoid self-resonating waves. It separates inspiratory and expiratory resistance (Rinsp, Rexp) and reactance (Xinsp, Xexp), aiming to reflect obstruction, since expiration is affected by airway closure. Impulse oscillometry (IOS) use waves at 5-35 Hz, and does not separate the inspiratory phase from the expiratory. Aim: To validate the Resmon Pro system against IOS by Jaeger, and to define the uses of inspiratory and expiratory measurements in obstructive diseases. Methods: A total of 31 subjects (16 healthy, 9 COPD, 5 asthma) were included and performed FOT (Resmon Pro), IOS and spirometry in the given order. Results: Total resistance (R5) and central resistance (R20 or R19) correlated between IOS and FOT. FOT could detect increased total resistance in COPD, while IOS could not. The use of separating Rinsp from Rexp was most prominent in COPD, where R5exp was higher than R5insp. Peripheral resistance (R5-R20 or R5-R19) showed correlation between IOS and FOT, and only IOS detected differences between healthy and COPD. The elastic properties of the lungs (reactance; X5) also correlated between IOS and FOT, and both methods detected differences between healthy and COPD patients. When separated into insp and exp, Xinsp showed a smaller Confidence Interval, but did not detect any differences between COPD and healthy. Conclusion: Both systems showed similar results, but with different abilities to detect airway obstruction. Although less variation, the use of inspiratory resistance and reactance needs to be further investigated.