The Study Of Impulse Oscillometry In Obstructive Ventilatory Dysfunction

Objective Impulse oscillometry system (IOS) assesses pulmonary resistance and reactance. We set out to investigate which IOS measurements are related to airflow obstruction and lung volumes in chronic obstructive pulmonary disease (COPD) and asthma.Methods The IOS parameters of 200 cases of the two diseases were measured and compared with those of 100 normal cases. IOS measurements (R5, R20, and their difference R5-R20, X5, Fres, Rc&Rp), the conventional pulmonary function (TLC, RV, FEV1, FVC and FEV1/FVC) were performed. Spearman correlation determined the relationships between IOS and other measurements.Results Compared with those of the normal group, the resistance at 5Hz and 20Hz (R5, R20) and their difference (R5-R20), resonance frequency (Fres), central resistance (Rc) and peripheral resistance (Rp) in the COPD and asthma group increased significantly, while reactance at 5Hz (X5) decreased obviously (P<0.01). In the COPD and asthma group, R5, Fres, Rp, R5-R20 were all correlated negatively with FEV1%, FEV1/FVC, but X5 was correlated positively with FEV1%(r= 0.419, P＜0.01) and FEV1/FVC (r=0.254, P<0.01). TLC was correlated with R5 (r=0.216, P<0.01), R5-R20(r=0.250, P＜0.01), X5(r=-0.180, P＜0.05), Fres (r=0.154, P＜0.05). RV was correlated with R5-R20(r=0.266, P＜0.01), X5(r=-0.196, P＜0.05), Fres (r=0.226, P<0.05), Rp (r=0.180,P<0.05). However, R20 was not related to any of these measurements. The strongest associations were observed between FEV1% and the reactance measurements X5 (r=0.419) and Fres (r=-0.553). The sensitivities of Fres, X5 and R5 diagnosing airflow obstruction was 99.9%,94.5%,49.0% respectively.Conclusions IOS reactance measurements are more closely related than resistance measurements to other pulmonary function measurements in COPD and asthma patients. The IOS reactance measurements appear to be indicative of changes in pulmonary compliance caused by airflow obstruction. IOS parameters can be used to evaluate airway obstruction. Among IOS parameters, X5 was the most sensitive parameter, which is also significantly correlated with spirometrie parameters.