Study suggests problems with 'indiscriminate use of oxygen'

Sunday, August 26, 2007

TORONTO -- Prescribing ambulatory oxygen for COPD patients improves exercise performance but not their quality of life, unless they have resting hypoxemia, according to researchers in Toronto.

"Ambulatory oxygen therapy is routinely prescribed for those who do not meet criteria for mortality reduction," wrote Roger Goldstein, a professor of medicine and physical therapy at West Park Healthcare Centre in Toronto and lead author of the study.

The study suggests serious problems with the "indiscriminate use of oxygen" to improve breathing in patients with COPD without resting hypoxemia, Goldstein added.

The study indicates that generalized treatment of COPD patients with ambulatory oxygen may be an unnecessary, inconvenient and possibly even detrimental expense. The study appeared in the August issue of the American Journal of Respiratory and Critical Care Medicine, published by the American Thoracic Society.

For many patients, a diagnosis of COPD comes with a prescription for ambulatory oxygen, even when they do not meet the standard criteria for long-term oxygen treatment (LTOT), the researchers reported.

In 2002, Medicare paid $2.2 billion for home oxygen therapy.

The researchers conducted a series of double-blind trials where 27 COPD patients without resting hypoxemia underwent three pairs of two-week trials, using either oxygen or compressed air (as a placebo). At the end of each trial period, patients were assessed with the Chronic Respiratory Questionnaire (CRQ) and St. George's Respiratory Questionnaire (SGRQ), and given a timed walk test to assess their exercise performance. Neither the patients nor the assessors were aware of whether they had received oxygen or placebo during the trials.

As a group, the patients on oxygen showed improvement in the number of steps taken in the walk test, but no improvement in their breathing scores or on their questionnaires.

"Although ambulatory oxygen acutely improved constant power endurance and a standardized home walking test, very few patients experienced benefit from oxygen at home," wrote the researchers.

These results are consistent with those in previous studies, which have also found that improvements in exercise capacity and endurance do not translate into perceived benefits in breathing and quality of life. However, one investigation in patients who had completed a pulmonary rehabilitation program, did find differences in the CRQ, suggesting a benefit from oxygen to more active patients, the American Thoracic Society reported.

These findings raise important questions about identifying patients who stand to benefit from oxygen.

"One approach to the issue is to restrict oxygen use to patients who show benefit from (a blind) trial," the researchers suggest, noting that while the costs of such trials are not negligible, they are "considerably less than the cost of providing long-term ambulatory oxygen for patients who do not benefit from it."