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

Abstract

Background: Impulse Oscillometry (IOS) is a novel tool that may be to comparable to spirometry. In asthmatics, differences in the resistance at low frequencies and high frequencies can indicate small airway involvement. The aim of this study was to assess the reproducibility of IOS measurements in healthy subjects and well-controlled asthmatics. Methods: In 24 healthy controls and 13 patients with well-controlled asthma, IOS and spirometry was performed at baseline and within 4 weeks. The reproducibility explored in Bland-Altman plots, expressed as bias with lower and higher limits of agreements (B; LLOA, ULOA). The relationship of IOS and spirometry was assessed by correlation. Results: In healthy subjects, the resistance at 5Hz and at 20Hz increased after 4 weeks (p=0.01) but remained in the normal range. For healthy controls, the reproducibility of FEV1 (-0.8%; -15.3%, 13.3%) and FVC (1.1%; -16.3%, 18.4%) and FEV1/FVC with (-1.6%; -11.8%, 8.6%) was better than that of X5 (-5.2%; -148.4%, 138%) and R5 (3,8%; -24%, 31,5%). For patients with well controlled asthma, the reproducibility of FEV1 at (-1,1% ; -12,9%; 10,7%), FVC at (-3.2%; -15.3%; 9.1%) and FEV1/FVC at (0.4%; -7.1%; 7.8%) was comparable with that of X5 at (1.3%; -23.5%; 26%) and R5 at -4.9%; -22.2%; 12.4%). There was no sign of a trend in any plot. X5 and R5 of controls (Spearmans R>0.59, p 0.79, p Conclusion: IOS measurements within a 4-week interval were reproducible in healthy controls and well-controlled asthmatics and correlated with spirometric data.