Can impuls ocilometry show early lung function loss?

Spirometry is used to diagnose chronic obstructive pulmonary disease (COPD). The impulse oscillometry system (IOS) allows determination of respiratory impedance indices, which might be of potential value in early COPD, although previous experience is limited. Purpose of the study; is to investigate whether changes in lung function can be detected in the early period with impulse oscillometry. At the same time, we aimed to reveal the relationship between IOS parameters and pulmonary function test parameters. Method: The study basically consists of three patient groups. Patients over 40 years of age were included in the study for all groups. Group 1 included patients who were smokers and had no obstruction by spirometry, patients with a diagnosis of COPD in group 2, and healthy volunteers who did not smoke in group 3. A total of 182 patients were examined with spirometry, carbon monoxide diffusion test and IOS parameters. Results: 80 patients in group 1, 74 patients in group 2 and 42 patients in group 3 were included in the study. Difference in all spirometry measurements statistically significant difference was observed due to the 2nd group of COPD patients (p<0.001 for all values). A statistically significant difference was observed in the DLCO, TLC, RV/TLC ratios due to the 2nd group of COPD patients. There was no significant difference between the R5, R20, R5-R20 values between the 3 groups. X5 and X20 kPa/(L/s) values were found to be significantly more negative in the COPD group (p<0.001 and p=0.001). The AX value, defined as the reactance area, was also significantly increased in the COPD group (p=0.018). The correlation between % FEF25-75 and R5-R20 was examined and a moderate negative correlation was found (r=-0.430, p=<0.001). At the same time, a weak correlation was found between the RV/TLC ratio and R5-R20 (r=0.217, p<0.003). Conclusion: Higher pulmonary resistance and lower pulmonary reactance measured by IOS may indicate early COPD in patients who smoke and do not have spirometric obstruction according to the GOLD criteria. IOS may have the potential to detect COPD-related pathology earlier than spirometry.