Impulse Oscillometry is a reproducible assessment of airway resistance and reactance in well-controlled asthmatics and healthy controls

Abstract

<b>Background:</b> Impulse Oscillometry (IOS) is a novel, useful tool to assess airway resistance and reactance. In asthmatics, differences in the resistance at low frequencies and high frequencies can indicate small and large airway involvement. As IOS is performed during tidal breathing, it may be more reproducible than forced spirometry. <b>Aim of this study:</b> The aim of this study was to assess the reproducibility of IOS measurements in healthy subjects and well-controlled asthmatics. <b>Methods:</b> In 24 healthy control subjects and 13 patients suffering from well-controlled asthma, IOS and spirometry was performed at baseline and within 4 ensuing weeks. Reproducibility was assessed with a Bland-Altman test where the bias(B), upper limits of agreement (ULOA) and lower limits (LLOA) of agreement are calculated as % mean of collected data. These calculations will be written to as [B; ULOA; LLOA]. <b>Results:</b> We found both IOS and spirometry measurements reproducible in healthy controls and well-controlled asthmatics. In healthy subjects, the resistance at 5Hz and at 20Hz increased slightly after 4 weeks (p=0.01) but remained in the normal range. The Bland-Altman plots suggest a good agreement as the scatter gathered around the bias and the limits of agreement are narrow and do not show any trends. <b>Conclusion:</b> IOS measurements within a 4 week interval were reproducible in both healthy controls and well-controlled asthmatics.