Lung parenchymal and tracheal CT morphology: Evaluation before and after bariatric surgery

Abstract

Background: There is significant pulmonary functional deficit related to obesity, but no prospective CT studies have evaluated the effects of obesity on the lungs and trachea. Purpose: To evaluate lung parenchymal and tracheal CT morphology before and 6 months after bariatric surgery, with functional and symptomatic correlation. Materials and Methods: A prospective longitudinal study of 51 consecutive individuals referred for bariatric surgery was performed (from November 2011 to November 2013). All individuals had undergone limited (three-location) inspiratory and end-expiratory thoracic CT before and after surgery, with concurrent pulmonary function testing, body mass index calculation, and modified Medical Research Council (mMRC) dyspnea scale and Epworth scoring. Two thoracic radiologists scored the CT extent of mosaic attenuation, end-expiratory air trapping, and tracheal shape. The inspiratory and end-expiratory cross-sectional areas of the trachea were measured. The paired t test or Wilcoxon signed-rank test was used for pre- and postsurgical comparisons. Spearman correlation and logistic regression were used to evaluate correlations between CT findings and functional and symptom indexes. Results: A total of 51 participants (mean age, 52 years 6 8 [standard deviation]; 20 men) were evaluated. Before surgery, air trapping extent correlated most strongly with decreased total lung capacity (Spearman rank correlation coefficient [rs] = -0.40, P = .004). After surgery, there were decreases in percentage mosaic attenuation (0% [interquartile range {IQR}: 0%–2.5%] vs 0% [IQR: 0%–0%], P , .001), air trapping (9.6% [IQR: 5.8%–15.8%] vs 2.5% [IQR: 0%–6.7%], P , .001), and tracheal collapse (201 mm2 [IQR: 181–239 mm2] vs 229 mm2 [186–284 mm2], P , .001). After surgery, mMRC dyspnea score change correlated positively with air trapping extent change (rs = 0.46, P = .001) and end-expiratory tracheal shape change (rs = 0.40, P = .01). At multivariable analysis, air trapping was the main determinant for decreased dyspnea after surgery (odds ratio, 1.2; 95% confidence interval: 1.1, 1.2; P = .03). Conclusion: Dyspnea improved in obese participants after weight reduction, which correlated with less tracheal collapse and air trapping at end-expiration chest CT.