Within six months of undergoing weight loss surgery, obese patients showed structural changes on airway imaging that correlated with respiratory symptom improvements, researchers reported. Susan Copley, MD, of Hammersmith Hospital in London, and colleagues used inspiratory and expiratory chest computerized tomography (CT) imaging to evaluate changes in the respiratory systems of patients prior to undergoing bariatric surgery and six months after having the surgery, when significant weight loss had occurred. At six months, there were significant reductions in air trapping and less tracheal collapse, which correlated with improvements in symptoms as measured by dyspnea scores, the team reported. The study, published online in Radiology, is among the first to evaluate obesity-related CT morphologic appearance of the trachea in living patients before and after weight-loss surgery, Copley told MedPage Today. She explained that she got the idea for the study after observing significant differences in the chest CT images from obese and non-obese patients. She noted that there has been increased emphasis in recent years in using CT to evaluate other conditions commonly associated with obesity, including hepatic steatosis. For example, a postmortem study published last October showed fat tissue within the airway walls to be related to obesity, wall thickness, and inflammation. That group "found that the actual amount of inflammation in the airways correlated with obesity, and they wondered if this was reversible with weight loss," Copley said, adding that the findings from her team's study suggest that it is. Study Details The prospective, longitudinal analysis included 51 consecutive obese patients treated with bariatric surgery from November 2011 through November 2013. All patients underwent limited (three-location) inspiratory and end-expiratory thoracic CT before and after the surgery, with concurrent pulmonary function testing, body mass index calculation, and modified Medical Research Council (mMRC) dyspnea scale and Epworth scoring. Two thoracic radiologists evaluated the thoracic CTs, scoring mosaic attenuation, end-expiratory air trapping, and tracheal shape. Inspiratory and end-expiratory cross-sectional areas of the trachea were measured, and paired t test or Wilcoxon sign-rank test was used for pre- and postsurgical comparisons. The mean age of the patients was 52 ±8 years, and 20 were male. Prior to the weight loss surgery, air trapping extent correlated most strongly with decreased total lung capacity (Spearman rank correlation coefficient rs = -0.40, P=0.004), the researchers noted. After surgery, the following decreases were found: Percentage mosaic attenuation: 0% (interquartile range [IQR] 0%–2.5%) vs 0% (IQR 0%–0%), P<o.001 Air trapping: 9.6% (IQR: 5.8%–15.8%) vs 2.5% (IQR 0%–6.7%), P< 0.001 Tracheal collapse: 201 mm2 (IQR 181–239) vs 229 mm2 (IQR 186–284, P<0.001) After surgery, mMRC dyspnea score change correlated positively with air trapping extent change (rs = 0.46, P=0.001) and end-expiratory tracheal shape change (rs = 0.40, P=0.01), the team reported. Multivariable analysis revealed that air trapping was the strongest predictor of decreased dyspnea after surgery and weight loss (OR 1.2; 95% CI 1.1-1.2; P=0.03). "One really interesting finding was that what we saw on the CT scan correlated better with symptoms than measures of lung function," Copley said, adding that this suggests that CT may be a more useful pulmonary morphologic marker of airway inflammation in obesity than lung function testing is. Study limitations, the researchers said, included the limited (three) thin-section CT analysis of the lung, done to minimize radiation dosing. "By only scoring a small percentage of the lung, the findings were most likely underestimating the extent of mosaic attenuation and air trapping, but were still statistically significant," the team wrote. In addition, the limited lung CT data also precluded analysis of changes in airway wall thickness. Still, the study "demonstrated morphologic CT changes in the large and small airways secondary to obesity that were reversible after bariatric surgery and correlated with symptomatic improvement," Copley and co-authors stated. They noted that prospective longitudinal studies are needed to correlate CT morphologic appearances with inflammation markers and obesity-related complications. Source
