Background: Respiratory system impedance obtained by forced oscillation technique (FOT) has been related to changes in functional exercise capacity after pulmonary rehabilitation (PR) in people with chronic obstructive pulmonary disease (COPD).

Objective: To evaluate changes in FOT parameters and functional exercise capacity and their relationship following PR in patients with COPD.

Methods: Cross-sectional study. Patients with COPD attended 20 sessions of a standard PR program. Respiratory function was assessed at baseline. Respiratory system resistance and reactance were assessed with FOT. Functional exercise capacity was measured with the six-minute walk distance (6MWD). Pre- and post-PR changes and relationships between FOT parameters and 6MWD were calculated.

Results: Seventy-eight patients with COPD (43% females; age 70 ± 8 years; FEV1 52 ± 22% of predicted) completed the study. 6MWD increased by 44 m after PR (p < 0.001). No changes were observed in FOT parameters. At baseline, there was a negative relationship between FEV1 and respiratory resistance (p < 0.001), whereas a positive relationship was observed between FEV1 and respiratory reactance (p < 0.001). No relationships were observed between changes in FOT parameters and 6MWD.

Conclusions: Respiratory impedance measured by FOT has not been found to be responsive to PR in patients with COPD. Moreover, there was no relationship between respiratory impedance parameters and changes in functional exercise capacity in patients with COPD. Therefore, the use of respiratory impedance to evaluate changes in functional exercise capacity in people with COPD seems to be not supported.