Impulse Oscillometry System in Patients with Stable COPD: A Retrospective Study in Tehran-Iran

This study was aimed to evaluate the impulse oscillometry (R20/X5 in patients with COPD in Tehran, Iran. In a retrospective cross sectional study, we selected 101 patients who had PFT and impulse oscillometry records. We considered three groups for patients on the basis of spirometric findings: mild (FEV1 > 75%), moderate (FEV1 = 50%-75%), and severe (FEV1 < 50%) with FEV1/FVC <70% in all the groups. The analysis of variance (ANOVA) showed the statistically significant difference among mild and severe groups as well as among moderate and severe groups. But there was no significant difference between mild and moderate patients (p > 0.005). There was a significant positive correlation between R20, X5 and FEV1, FVC, PEF, TLC (p < 0.05). R20 was significantly correlated with FVC (r=0.362 for the moderate group and r=-0.275 for the severe group), FEV1 (only in mild group r=0.434) and FEVl/FVC (r=-0.265 for the mild group and r=0.223 for the moderate group). X5 was correlated with FEV 1 (only in the mild group r=0.282), and FEVl/FVC(r=0.491 for the mild group and r=0.349 for the severe group). Sensitivity for X5 in severe COPD group was 74% and in mild group, sensitivity of R20 was 81%. IOS can be used as an alternative of spirometry to assess COPD severity in patients with minimal cooperation.