Helium-oxygen improves exercise tolerance in pts with COPD
Does a combination of helium and oxygen improve exercise capacity in patients with chronic obstructive lung disease?
Inhaling a combination of 72% helium and 28% oxygen during exertion increases the comfortable walking distance and reduces the perception of exertional difficulty in patients with stable chronic obstructive pulmonary disease (COPD). (LOE = 2b)
Laude EA, Duffy NC, Baveystock C, et al. The effect of helium and oxygen on exercise performance in chronic obstructive pulmonary disease: a randomized crossover trial. Am J Respir Crit Care Med 2006;173:865-870. [PMID:16439720]
Cross-over trial (randomized)
These researchers studied 82 patients with stable COPD who complained of exertional dyspnea. The patients were ex-smokers and continued their usual medication during the study. Over the course of several visits, each patient underwent various tests of exercise capacity and lung function before and after exposure to medical air (ambient air inspired via tubing), 1 of 2 concentrations of helium and oxygen (72%/28%; 79%/21%), or 1 of 2 concentrations of nitrogen and oxygen (72%/28%; 79%/21%). Additionally, the patients recorded their ratings of perceived exertion. Only 75 of the patients completed all phases of the study. Patients breathing medical air walked less distance than any of the other groups of patients. Among patients breathing various helium mixtures, there was no significant difference in patients' walking distance or in their rating of perceived exertion. On average, patients breathing 72% helium, however, were able to walk more than 130 meters farther than those breathing medical air and experienced significant improvement in their ratings of exertion (although the latter improvement was borderline clinically important). One fun method in this study: Blinding was maintained by having patients not talk during, and for 2 minutes after, the test to prevent anyone from hearing the estimated 2 octave rise in the voice. Finally, although this study addressed medically stable patients, a Cochrane review of 4 small studies in 2000 concluded that the evidence in support of helium-oxygen mixtures for acute exacerbations was inconclusive.
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