Preoperative severity of emphysema predictive of improvement after lung volume reduction surgery - Use of CT morphometry

Study objective: To determine ho iv the volume and severity of emphysema me asured by CT morphometry (CTM) before and after lung volume reduction surge ry (LVRS) relates to the functional status of patients after LVRS. Design: A histologically validated CT algorithm was used to quantify the vo lume and severity of emphysema in 35 patients before and after LVRS: total lung volume (TLV), normal lung volume (<6.0 mL gas per gram of tissue), vol ume of mild/moderate emphysema (ME; 6.0 to 10.2 mt gas per gram of tissue), volume of severe emphysema (>10.2 mt gas per gram of tissue), surface area /volume (SAW; meters squared per milliliter), and surface area (SA; meters squared). Outcome parameters included maximal cardiopulmonary exercise (CPX ) performance in 21 patients and routine pulmonary function in all patients . We hypothesized that baseline CTM parameters predict response to LVRS and that the change in these parameters may offer insight into mechanisms of i mprovement. Patients and intervention: Thirty-live patients with severe emphysema who h ad successful LVRS. Results: The significant decrease in TLV following LVRS was entirely accoun ted for by a decrease in severe emphysema. The SA/V and the SA both increas ed significantly following LVRS. The change in maximal CPX in watts followi ng surgery correlated significantly with baseline values of severe emphysem a (r = 0.60), which was collinear with TLV, and SAW. The change in diffusin g capacity of the lung for carbon monoxide revealed a significant positive linear relationship with preoperative severe emphysema (r = 0.37) and a neg ative relationship with ME (r = -0.37). Change in watts revealed a strong r elationship with changes in severe emphysema (r = -0.75) and weaker but sig nificant relationships with change in TLV, ME, SA/V, and SA. Other measures of pulmonary function revealed significant albeit less dominant relationsh ips with baseline CTM and change in these indexes. Conclusion: Using CTM, we have identified a close relationship between base line severe emphysema, or change in severe emphysema, and the improvement i n CPX after LVRS. These observations support a potential role of CTM in fut ure clinical trials for predicting responders to LVRS and identifying mecha nisms of improvement.