Dynamic lung mechanics in late-stage emphysema before and after lung volume reduction surgery

This study evaluated the effects of lung volume reduction surgery (LVRS) on the heterogeneity of lung function in awake, late-stage emphysema patients with measurements taken before and after full recovery from LVRS. We assessed standard clinical measures of lung function and functional heterogeneity in six awake, late-stage emphysema patients before and 6 months after LVRS. Functional heterogeneity was quantified by measuring dynamic inspiratory resistance (RLinsp) and elastance (ELinsp) over a frequency range that included normal breathing (∼0.33–8 Hz). Since LVRS involves targeted resection of emphysematous regions of the lung, we hypothesized that emphysema patients would be functionally more homogeneous post-LVRS. We also compared our measures of functional heterogeneity with indices of anatomic heterogeneity and severity using high-resolution computed tomography (HRCT). After LVRS, 6 min walk distance increased by 22% (940 ± 91 versus 1158 ± 299, p = 0.031) and recoil pressure at TLC increased (9.0 ± 2.0 versus 14 ± 5, p = 0.031), but changes in RLinsp and ELinsp varied greatly between subjects. A measure of anatomic severity quantified using HRCT positively correlated with airway resistance (rs = 0.89, p = 0.048). These results suggest that subjects with more severe disease as assessed by HRCT criteria had reduced overall effective airway caliber consequent to active airway constriction, reduced parenchymal tethering, and/or loss of parallel lung units. Furthermore, LVRS may not necessarily improve lung function via a substantial reduction in mechanical heterogeneity.