Apr. 27, 1998 By Melanie Fridl Ross
GAINESVILLE, Fla.---University of Florida researchers are testing whether exercise can help alleviate shortness of breath in lung disease patients.
The respiratory muscles in patients with chronic obstructive pulmonary disease - which includes several conditions characterized by obstructed air flow, such as emphysema -- often do not adequately generate the forces required to breathe effectively. The problem is compounded by the medications used to treat the disease, such as corticosteroids, which sometimes further weaken these muscles.
Eventually, patients may require supplemental oxygen or have to depend on mechanical respiratory assistance. The end result? Their quality of life declines as the disease progresses.
"It's very common to see patients with lung disease who have levels of oxygen in their blood high enough that the body doesn't sense a problem, yet the individual is limited by shortness of breath," said Danny Martin, an associate professor of physical therapy at UF's College of Health Professions. "Part of the reason they are experiencing that sensation is the breathing muscles are weakened by disease and the side effects of the medicine used to treat the disease. The brain interprets the sum of all these things as shortness of breath."
Martin is part of an interdisciplinary research team that includes study investigators Dr. Eloise Harman, professor and chief of pulmonary medicine at UF, and Paul Davenport, who holds a joint appointment as a professor of physiological science at UF's College of Veterinary Medicine and the College of Medicine.
Because emphysema and chronic bronchitis frequently co-exist, health professionals prefer the term chronic obstructive pulmonary disease, or COPD. Nearly 16 million Americans battle the disease, the fourth leading cause of death, according to the American Lung Association. Each year, COPD kills more than 96,000 Americans.
About 80 to 90 percent of COPD cases are caused by cigarette smoking; a smoker is 10 times more likely than a nonsmoker to die of the disease. Frequent lung infections and exposure to certain industrial pollutants also are culprits.
Emphysema is characterized by irreversible damage to the tiny air sacs in the lungs. The walls between the air sacs lose their ability to stretch and recoil, and weaken and break. As the lungs become less elastic, air becomes trapped in the sacs, impeding the exchange of oxygen and carbon dioxide. Symptoms include cough, shortness of breath and a limited exercise tolerance.
UF researchers are setting out to determine whether a person's ability to breathe can be improved by strengthening the respiratory muscles involved in breathing. About 60 COPD patients who typically experience shortness of breath during exercise will undergo a unique exercise training program five days a week for six weeks at Shands hospital at UF. They will be compared to a group of patients who do not undergo exercise training.
Researchers will evaluate changes in exercise tolerance while patients undergo treadmill walking tests as well as a series of daily exercises in which they breathe against a spring-loaded valve that provides varying degrees of resistance. Participants also will complete paper tests designed to assess their quality of life.
The maximum amount of pressure participants can generate during the breathing test is determined by having them breathe in as hard as they can on the valve; they will be trained at 60 to 80 percent of that capacity and take a total of 24 breaths over a 10-minute period of time. Researchers will then test participants' sensitivity to changes in their breathing load.
"It's kind of like sucking a milkshake through a straw, when you have to pull hard on something to breathe in," Davenport said. "We have ways of varying that resistance that allows us to measure how sensitive a person is to those loads."
The breathing exercises are akin to doing a few repetitions of a very heavy weight rather than many repetitions of a very light weight.
"It's kind of like lifting weights with your diaphragm," Davenport said. "If you strengthen the respiratory muscles, we theorize that the individual's perception of their shortness of breath will be diminished in much the same way that your perception of how hard it is to lift a 20-pound dumbbell changes after you've been lifting a 10-pound weight. If you're doing weight training, for example, and you go to lift a piano, it feels a lot lighter if you've been doing weight training than if you haven't.
"That scenario is similar to the shortness of breath caused by muscle weakness," he said. "We can't reduce the pressure or the force that the muscles of breathing have to generate in COPD because of the disease, but we may be able to make the muscles stronger so any given level of exertion will feel lighter or easier to them, because of the complex way the brain interprets data coming from the rest of the body.
"UF researchers already have shown that doing the breathing exercises once or twice a day increases respiratory strength in normal subjects more than half the time, Davenport said.
"If you strengthen that pump, our hypothesis is that the sense of breathlessness will decrease and help these patients tolerate exercise better, and their quality of life will increase," he said.
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