Endoscopic lung volume reduction (ELVR) in COPD: Changes in lung mechanics with ELVR using the forced oscillation technique (FOT)

Introduction: ELVR improves static lung function and quality of life in carefully selected patients with COPD. The FOT is increasingly used to study lung mechanics during tidal breathing. The effect of ELVR on FOT parameters has not previously been described. Methods: Patients with severe COPD undergoing ELVR completed the St Georges9 Respiratory Questionnaire (SGRQ) and had resistance at 5Hz (R5) and reactance at 5Hz (X5) measured by FOT, spirometry, plethysmography and a six minute walk distance (6MWD) measured at baseline and 3 months post-ELVR. Paired t-test and correlation statistics were derived for changes in parameters. Results: In 9 subjects (age range 63-75 yrs), FEV1, R5 and X5 were unchanged, while residual volume (RV) trended from 203±21 %pred to 191±20 %pred (p=0.13). SGRQ scores improved from 63.41±5.90 to 46.75±3.81 units (p=0.02). The change in R5 correlated with the change in RV (r = -0.71, p=0.03) and there was a trend with the change in FVC (r = -0.61, p=0.08). The change in X5 correlated with the change in 6MWD (r = 0.83, p=0.04) but not with RV. Changes in 6MWD or SGRQ did not relate to changes in FEV1, FVC, or lung volumes. In the 4 patients with complete lobar collapse, FEV1 improved (39±4 %pred to 48±3 %pred; p Conclusions: Change in respiratory system resistance during tidal breathing correlates with volume changes induced by ELVR. Respiratory system reactance was minimally changed in this small cohort. The improvement in SGRQ post-ELVR is not explained solely by changes in lung mechanics.