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.
During the exercise test, the gas mixtures were administered through face masks with a special valve for the incoming gas. An investigator carried a gas cylinder with the mixture while walking beside the patient.
Individuals with the worst lung function test results showed the greatest benefit from the special mixtures.
"Although the recent American Thoracic Society/European Respiratory guidelines had recognized COPD is a preventable and treatable condition, it is still regarded by many as one in which significant improvement is not possible," said Dr. Laude. "Our data shows this is not the case. The changes in endurance exercise and reductions in breathlessness we report while breathing increased inspired oxygen or heliox gas mixtures are substantial, being at least comparable to those achieved with current bronchodilator therapy, pulmonary rehabilitation or even lung volume reduction surgery."
In an editorial on the article in the same issue of the journal, Jadwiga A. Wedzicha, M.D., of University College London in the United Kingdom, tried to answer a fundamental question raised by the study. He wrote: "Can these findings be applied in clinical practice? The most promising use of Heliox mixtures would be as an adjunct of pulmonary rehabilitation in patients with severe COPD who are still disabled by dyspnea and are unable to achieve full benefits of training despite pharmacologic treatment and ambulatory oxygen therapy. Use of Heliox with rehabilitation needs to be tested in large controlled studies with appropriate outcome measures. Heliox is also easier for the patient to tolerate during exercise than noninvasive ventilation, but the two treatments will need formal comparisons. However, before any further development in Heliox therapy for COPD, improved methods of delivery of Heliox to the hospital clinic and community would need to be developed. Recent data shows that despite benefits in patients with COPD, compliance with ambulatory oxygen in the community is relatively poor."
Contact for research: E.A. Laude, M.D., Biomedical Sciences, University of Sheffield, Addison Building, Western Bank, Sheffield, S10 2TN United Kingdom
Phone: +0114 2222346
Contact for editorial: Jadwiga A. Wedzicha, M.D., University College London, Academic Unit of Respiratory Medicine, Royal Free Hosp/ Rowland Hill St, London NW3 2PF United Kingdom
Phone: +44 204317 7517