By Lisa Rapaport

(Reuters Health) – Obese people who have bariatric surgery may have an easier time breathing afterward, a small study suggests.

To assess changes in lung function associated with the surgery, researchers examined results from lung CT scans for 51 obese individuals before their operations and again six months later.

“Weight loss as a result of bariatric surgery improves the appearances of the lungs and airways on CT scans and this corresponds with an improvement in breathlessness and lung function,” said lead study author Susan Copley of Imperial College Healthcare NHS Trust in London.

Obesity can make it harder for people to breathe, weakening respiratory muscles and requiring people to work harder to get air in and out of their lungs, the researchers note in Radiology. Few previous studies have examined the impact of obesity on breathing by looking at CT scans of the lungs and trachea, or windpipe, they note.

All but one patient in the current study underwent a Roux-en-Y gastric bypass procedure, which reduces the stomach to a pouch the size of an egg. Before surgery, patients’ average body mass index (BMI) was 44.5, making them extremely obese; afterwards they typically remained obese with an average BMI of 34.

Before surgery, and again six months later, researchers used CT scans to measure the size and shape of the trachea and assess air trapping – in which excess air remains in the lungs after exhaling, reducing lung function. Air trapping is an indirect sign of obstruction in the small airways of the lung.

Surgery and weight loss were associated with structural changes to the lung and trachea, the study found.

Post-surgery CT scans showed reductions in air trapping and a lower incidence of tracheal collapse, or blockage in the windpipe that makes it harder to breathe.

People who had the biggest reductions in air trapping on CT scans also had more improvement in shortness of breath.

The results suggest that some breathing problems related to obesity may improve after bariatric surgery, the authors conclude.

Beyond its small size, another limitation of the study is that researchers only took CT scans of small portions of the lung to minimize radiation doses, Copley said by email. This means the study may have underestimated the extent of abnormalities in the airways.

Even so, the results suggest improved respiratory function might be an added benefit of weight loss surgery, said Dr. Ninh Nguyen of the University of California Irvine Medical Center.

Breathing is harder for obese people because the fat tissue around the rib cage and abdomen leads to obstructions in the large and small airways, Nguyen, who wasn’t involved in the study, said by email.

The current study demonstrated objective evidence of increase in trachea diameter and less air trapping with weight loss after bariatric surgery, Nguyen said. “Additionally, (shortness of breath) symptoms improved after bariatric surgery, which was likely related to the improvement of respiratory mechanics and less air trapping” when patients exhaled.

SOURCE: Radiology, online January 28, 2020.