BACKGROUND: The pulmonary function test (PFT) has been the gold standard for measuring airflow limitation. This study aimed to correlate relevant FOT parameters among chronic obstructive pulmonary disease patients.

METHODS: A prospective analysis of 25 COPD and 25 control participants were assessed regarding airway resistance, reactance, and frequency dependence with an impulse oscillation system (IOS). Correlations with PFT parameters were conducted, such as forced expiratory volume in 1 sec (FEV1), forced vital capacity (FVC), FEV1/FVC ratio, and FEF correlations. Independent Sample T-test, Mann-Whitney U, and Chi-square test were used to determine the mean, rank, and frequency difference between normal and obstructive patients.

RESULTS: The findings of our investigation show a significant correlation of reactance (Xrs) in determining severity airflow limitation (FEV1) among COPD patients at lower frequencies X6 (r=0.5708, p <0.001), X10 (r=0.5481, p <0.001) and mean reactance 4-24 (r=0.4567, p <0.001). FOT reactance demonstrates a significant correlation between FVC at X6 (r=0.5311, p<0.001) and X10 (r=0.5180, p<0.001) as well as FEF 25-75 at X6 (r=0.5482, p<0.001) and X8 (r=0.4658, p<0.001) and X10 (r=0.4880, p<0.001), respectively.

CONCLUSION: FOT reactance (Xrs) exhibits an excellent correlation in most PFT parameters. In addition, the study's findings prove the significance of FOT in improving the diagnosis of COPD.