The relationship between respiratory system impedance and lung function in asthmatics: A prospective observational study

Abstract

IntroductionThe aim was to elucidate the relationship between the annual changes in respiratory system impedance, measured by FOT, and lung function tests in patients with asthma. MethodsBetween March 2011 and March 2012, asthma outpatients who attended Kobe City Medical Center West Hospital were recruited. Lung function tests, FOT were conducted every 6 months until March 2016. The relationships between annual parameter changes were evaluated. Results and conclusionSixty-four patients were completed this study. The median follow-up period was 55 months. At enrollment, although resistance showed no relationship with forced expiratory volume in one second (%FEV1), the reactance was moderately correlated with X5 (r=0.524, r2=0.275, <0.001), Fres (r=−0.498, r2=0.248, <0.001) and ALX (r=−0.416, r2=0.173, p=<0.001). By contrast, the annual resistance change at 5Hz (R5) was highly and significantly associated with%FEV1 change (r=−0.564, r2=0.318, p<0.001). Longitudinal changes in airway resistance and reactance measured by FOT might be useful for the assessment of lung function in patients with asthma.