Chest radiograph heterogeneity predicts functional improvement with volume reduction surgery

Using a historical cohort study model, we tested the hypothesis that heterogeneity of emphysematous changes on the preoperative chest radiograph correlated with favorable outcome of lung volume reduction surgery.

The test population consisted of 21 patients with severe emphysema who were being treated at a 1,000-bed university-affiliated tertiary teaching hospital. A simple but quantitative index of heterogeneity has been devised, whereby the preoperative posteroanterior chest radiographic lung fields are divided into four geometric quadrants. Each quadrant is scored (0 to 4) for emphysematous changes by two radiologists blinded as to subsequent patient management and outcome. Criteria for determining presence of emphysema were hyperlucency, decreased vascular markings, and parenchymal crowding indicating compressed lung. Heterogeneity index is the sum of the two highest scores minus the two lowest, with a maximum index of 8 and a minimum of 0. Preoperative chest radiographs and postoperative changes in forced expiratory volume in 1 second were examined.

The heterogeneity index was positively correlated with change in forced expiratory volume in 1 second after operation with an r2 of 0.31 and an average increase of 117 mL per unit increase in heterogeneity index (p < 0.009).

This simple index of heterogeneity may be useful as a predictor of improved pulmonary function after lung volume reduction surgery.