More than 15 million people have been diagnosed with chronic obstructive pulmonary disease, or COPD, according to the Centers for Disease Control and Prevention. Millions more may be unaware they have it. The disease is the third leading cause of death in the U.S., after heart disease and cancer. COPD costs nearly $30 billion in direct health care expenditures.

Some patients with severe cases of COPD may be referred for surgery, during which the diseased part of the lung is removed. But the risky and costly procedure isn't often used, partly because recovery is long and many patients experience complications after surgery.

More than two dozen U.S. medical centers are currently testing a technique that places metal coils into the lung using special scopes inserted through the mouth or nose. Once in place, the coils compress the diseased tissue and allow the healthier parts of the lung to breathe more freely. Other hospitals are investigating a small-umbrella shaped valve that redirects air from less healthy to more healthy parts of the lung.

'If successful, we will be able to help a significant number of patients have an improved quality of life, and potentially improve survival in a noninvasive manner,' says Atul C. Mehta, an interventional pulmonologist at Cleveland Clinic, one the centers participating in the coils trial.

In Europe, where the coils have been approved for use since 2008, studies have shown the treatment is safe for patients and results in significant improvements in pulmonary function, exercise capacity and quality of life. Current U.S. research is being funded by PneumRx Inc., the Mountainview, Calif., maker of the coils. While smokers can prevent COPD by quitting before it develops, once the lungs are damaged it isn't reversible. Most patients are managed with the use of inhaled medications called bronchodilators, oxygen and pulmonary rehabilitation.

Mary Morgan, a nurse who lives in Parma, Ohio, was diagnosed seven years ago with emphysema, a form of COPD. Still, she continued to smoke for a few more years because the disease 'wasn't bothering me,' she says. Two years ago, the 55-year-old came down with pneumonia and had to call 911 because she couldn't breathe. She quit smoking but needed to be on oxygen all the time. She gasped for breath often and wasn't able to speak more than a few words at a time. 'It gets to the point where you are living in such misery that you just don't want to go on,' Ms. Morgan says.

After completing a pulmonary rehabilitation program, Ms. Morgan was accepted into the coils trial at the Cleveland Clinic last December. Dr. Mehta and another pulmonologist placed 12 of the small devices in her right lower lung. She was discharged from the hospital after just one night and says she felt improvements almost immediately. Tests a month later showed her breathing had improved by 30%. She is still on supplementary oxygen and is scheduled to have additional coils inserted in her left lung later this month.

COPD includes two main conditions, emphysema and chronic bronchitis, and most patients have elements of both. Emphysema, as it advances, destroys the air sacs, or alveoli, that exchange air between the lungs and surrounding tissue and bloodstream. Diseased portions of the lung overinflate, become inelastic and trap air. Meanwhile, the expanded sacs push against the lung's healthier areas. Patients may feel as if they are suffocating. Medications may cease to work.

More severe cases of COPD affect an estimated three to four million people in the U.S. Dr. Mehta estimates as many as one million may be candidates for some form of lung volume reduction through surgery or the new less-invasive coil procedure. The surgery requires a large incision, or several small ones, in the chest to excise diseased tissue. The aim is to allow the patient to breathe easier with the remaining healthier portion of the lungs.

In a large study a decade ago, called the National Emphysema Treatment Trial, the surgery didn't show an overall survival advantage over medical management. It did show an advantage in patients whose disease was worse in upper lobes of the lungs and whose exercise capacity was low. Still, the procedure is little used. Complication rates are high. Relatively few centers in the country offer the procedure.

'In the right patients, we've proven that lung reduction surgery works, but doctors aren't referring patients for the procedure and patients aren't interested in doing major surgery,' says Frank Sciurba, director of the Pulmonary Function and Exercise Physiology Lab at the University of Pittsburgh Medical Center and principal investigator for its part of the coils-implant trial. One aim of the trial, he says, is to determine which patients have the right lung structure and physiology to benefit from the coils procedure.

The coils trial isn't studying costs. 'In the long run the hope is this could be more cost-effective,' says Dr. Sciurba, by reducing hospitalization costs, complications and readmissions. A PneumRx spokeswoman says the coils procedure in Europe costs $15,000. 'We aren't yet far enough along in the U.S. market to have a valid comparison,' she says.

Experts have had mixed results with other nonsurgical techniques, such as chemical sealants and steam to destroy the diseased part of the lung. In another current clinical trial, researchers are guiding a small, umbrella-shaped valve into the airways that redirects air from less healthy to more healthy parts of the lung while letting trapped air escape. An earlier trial of the valves ended without meeting the requirements for Food & Drug Administration approval, but Redmond, Wash., device maker Spiration Inc., is funding a new trial to determine if the procedure can help reduce over-inflation of the lung and improve overall lung function and quality of life.

D. Kyle Hogarth, director of bronchoscopy and assistant professor of medicine at the University of Chicago who is leading an arm of the valve study there, says a possible risk to the use of any device is infection from foreign bodies inserted into the lung. While coils aren't designed to be removed, valves could be removed if necessary, he says. Because emphysema can affect individual patients' lungs differently, in the future, patients may end up qualifying for both coils and valves, 'to treat different types of abnormalities and breathing problems,' Dr. Hogarth says.