Abstract
BackgroundThe forced oscillation technique (FOT) measures respiratory impedance during normal tidal breathing and requires minimal patient cooperation.ObjectiveTo compare IOS and AOS devices in patients with asthma and COPD.MethodsWe compared two different FOT devices, namely impulse oscillometry using a loudspeaker (IOS: Jaeger Masterscreen) and airwave oscillometry using a vibrating mesh (AOS: Thorasys Tremoflo) for pre- and post-bronchodilator measurements in 84 patients with asthma and COPD.ResultsThe overall pattern of measurement bias was for higher resistance with IOS and higher reactance with AOS, this being the case in asthma and COPD separately. There were small but significantly higher values using IOS for resistance at 5 Hz (R5) and 20(19) Hz (R20(19)). In converse, values for reactance at 5 Hz (X5), reactance area (AX) and resonant frequency (Fres) were significantly higher using AOS but to a much larger extent. The difference in AX between devices was more pronounced in COPD than in asthma. Salbutamol reversibility as % change was greater in asthma than COPD patients with AX but not FEV1.ConclusionOur study showed evidence of better agreement for resistance than reactance when comparing IOS and AOS, perhaps inferring that AOS may be more sensitive at measuring reactance in patients with airflow obstruction.
Highlights
Current guidelines for asthma and COPD advocate the use of spirometry to quantify the degree of airflow obstruction [1, 2]
This showed that patients with COPD had lower F EV1 (p < 0.001), FEF25-75 (p < 0.001), FEV1/FVC ratio (p < 0.001); higher resistance at 5 Hz (R5)–R20(19) (p < 0.05), AX (p < 0.001) and Fres (p < 0.05); lower X5 (p < 0.05) values compared to those with asthma
The main findings of the present study were a small degree of comparative bias between devices for resistance as R5 and R20(19) with relatively higher values being reported with impulse oscillometry using a loudspeaker (IOS)
Summary
Current guidelines for asthma and COPD advocate the use of spirometry to quantify the degree of airflow obstruction [1, 2]. Spirometry involves performing an artificial forced expiratory manoeuvre from total lung capacity to residual volume. As such spirometry induces volume dependent small airway closure. Different FOT methods have been developed with two commonly used commercial devices being impulse oscillometry using a loudspeaker source (IOS, Jaeger Masterscreen, Carefusion Hoechberg, Germany) and airwave oscillometry using a vibrating mesh (AOS, Tremoflo, Thorasys, Montreal). Methods We compared two different FOT devices, namely impulse oscillometry using a loudspeaker (IOS: Jaeger Masterscreen) and airwave oscillometry using a vibrating mesh (AOS: Thorasys Tremoflo) for pre- and post-bronchodilator measurements in 84 patients with asthma and COPD. Conclusion Our study showed evidence of better agreement for resistance than reactance when comparing IOS and AOS, perhaps inferring that AOS may be more sensitive at measuring reactance in patients with airflow obstruction
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