Quantitation of regional ventilation during the washout phase of lung scintigraphy - Measurement in patients with severe COPD before and after bilateral lung volume reduction surgery

Study objectives: We sought to investigate the effect of lung volume reduct ion surgery (LVRS) on regional lung ventilation. Design: Retrospective analysis of routinely acquired data before and after LVRS. Setting: Large, urban, university medical center. Patients: Twenty-nine patients with severe emphysema. Intervention: Bilateral LVRS. Measurements and results: Xe-133 washout curves during lung scintigraphy ex hibit a bisphasic pattern (the first component of the washout curve [m(r)] corresponds to an initial rapid phase in washout that reflects larger airwa ys emptying, and the second component [m(s)] reflects a slower phase of was hout that is attributed to gas elimination via smaller airways). We analyze d six standardized regions of the lung (upper, mid, and lower zones of the right and left lung), and calculated m(r) and m(s) for each lung region. Th e mean (+/- SE) baseline FEV1 was 0.69 +/- 0.04 L, total lung capacity (TLC ) was 139 +/- 4% predicted, and the residual volume (RV)/TLC ratio was 65 /- 2%. The mean improvement in FEV1 3 months post-LVRS was 38%. Post-LVRS, m(r) and m(s) increased in 79 to 74 lung regions, respectively, and there w as no relationship with respect to lung regions that had or had not been op erated on. The increase in m(s), however, significantly correlated with the increase in FEV1 (r = 0.66; p < 0.0001) and the decrease in RV/TLC (r = -0 .67; p < 0.0001). An increase in m(s) also correlated with a decrease in Pa co(2) (r = -0.39; p = 0.03) but m(r) showed no relationship with any parame ter. Conclusions: Small airways ventilation in lung regions that had and had not been operated on is associated with a greater improvement in lung mechanic s following LVRS.