Study reveals long-lasting airway blockages, even in medicated asthma patients

Feb 8 2009

Scientists now are able to get a much clearer picture of what happens inside the lungs of asthma patients, thanks to an innovative MRI technique being used at the University of Virginia Health System to visualize the flow of air within the lung.

In a new study published in the February issue of Radiology , the UVA team used this special technique to determine that asthma patients can continue to have persistent narrowing of airways over a span of a month or more - even while taking medication.

"A significant number of the same airways were consistently narrowed over time, irrespective of patients' medication use or the severity of their disease," says Eduard E. de Lange, M.D., professor of radiology at the UVA School of Medicine. "This suggests that asthma is a focal disease, meaning that it involves certain airways and not others."

Asthma is a chronic lung disease characterized by inflammation and narrowing of the lung's small and medium airways. Until now, it's been very difficult for scientists to get a clear picture of what happens within the lung of an asthma patient, explains de Lange.

"You can't biopsy a lung like you can the liver, for example," he says. "And with other scanning methods you get a picture of the lung, but you can't see where the air goes and where airways are blocked. But this technique gives us the greatest detail available today."

In the study, researchers had 43 asthma patients inhale hyperpolarized helium 3 (3He), a harmless gas visible inside the lungs during an MRI scan. In non-asthmatic patients, the gas is evenly distributed in the air spaces of the lung, but in asthma patients the MRI scan reveals the areas in the lung where the gas can't travel due to blockage of the airways.

To measure the size and location of these areas of decreased lung ventilation over time, researchers performed two same-day 3He MRI scans, less than 90 minutes apart, on 26 of the patients, while 17 patients underwent three separate 3He MRI scans over the course of 50 days, on average. The UVA team found that a significant number of the areas with decreased lung ventilation, also called ventilation defects, remained in the same location and stayed relatively the same in size for both patient groups.

"The 3He MRI technique has the potential to become an important research tool for scientists studying asthma," de Lange says. "Researchers could use this technique to determine whether certain asthma medications are effective, to help in differentiating asthma from other chronic pulmonary diseases and even to determine if there are different types of asthma."