The results appear in the April 15th issue of the American Journal of Respiratory and Critical Care Medicine, published by the American Thoracic Society.
Elizabeth A. Laude, Ph.D., of the University of Sheffield in the United Kingdom, and seven associates investigated the effects of varying oxygen and helium levels in the air breathed during exercise by 82 patients who had severe, but stable COPD.
The investigators tested four different gas mixtures with the patients: 72 percent helium and 28 percent oxygen (Heliox28); 79 percent helium and 21 percent oxygen (Heliox21); 72 percent nitrogen and 28 percent oxygen (Oxygen28); and 79 percent nitrogen and 21 percent oxygen (medical air).
"Patients walked significantly further while breathing Heliox 28 than with either Heliox 21 or Oxygen 28," said Dr. Laude.
By replacing the nitrogen with normal supplementary oxygen with lower density helium gas, the researchers hoped that they might reduce airway resistance and improve the participants' respiratory gas exchange.
"COPD is associated with impaired exercise capacity, which contributes significantly to a reduced quality of life in these patients," said Dr. Laude.
COPD results from persistent obstruction of the airways associated with either severe emphysema or chronic bronchitis. In emphysema, the tiny air sacs of the lung (alveoli) become enlarged and their walls are destroyed. In chronic bronchitis, the bronchial glands enlarge, causing a chronic cough and excess mucus. Ten to 15 percent of all smokers develop COPD as a result of irritants in tobacco that cause inflammation of the alveoli.