Understanding the Impact of Pulmonary Rehabilitation on Airway Resistance in Patients with Severe COPD: A Single-Center Retrospective Study

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Purpose: We investigated the effect of pulmonary rehabilitation (PR) on airway resistance in chronic obstructive pulmonary disease (COPD) patients with severe airway obstruction and hyperinflation. Patients and Methods: This retrospective cohort study was conducted with data from severe COPD cases with those who underwent an 8-week PR program. Main inclusion criteria were having severe airflow obstruction (defined as a forced expiratory volume in one second (FEV 1 ) < 50%) and plethysmographic evaluation findings being compatible with hyperinflation supporting the diagnosis of emphysema (presence of hyperinflation defined as functional residual capacity ratio of residual volume to total lung capacity (RV/TLC) > 120%). Primary outcomes were airway resistance (R aw ) and airway conductance (G aw ) which were measured by body plethysmography, and other measurements were performed, including 6-minute walk test (6-MWT), modified Medical Research Council dyspnea scale (mMRC) and COPD assessment test (CAT). Results: Twenty-six severe and very severe COPD patients (FEV 1, 35.0 ± 13.1%; RV/TLC, 163.5 ± 29.4) were included in the analyses, mean age 62.6 ± 5.8 years and 88.5% males. Following rehabilitation, significant improvements in total specific airway resistance percentage (sR awtot %, p = 0.040) and total specific airway conductance percentage (sG awtot %; p = 0.010) were observed. The post-rehabilitation mMRC scores and CAT values were significantly decreased compared to baseline results (p < 0.001 and p < 0.001, respectively). Although there were significant improvements in 6-MWT value (p < 0.001), exercise desaturation (ΔSaO 2 , p = 0.026), the changes in measured lung capacity and volume values were not significant. Conclusion: We concluded that PR may have a positive effect on airway resistance and airway conductance in COPD patients with severe airflow obstruction. Keywords: airway resistance, body plethysmography, airflow limitation, emphysema, lung mechanics