Prescribing ambulatory oxygen in patients with chronic obstructive pulmonary disease (COPD) improves exercise performance, but not the quality of their daily 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 S. Goldstein, M.B., Ch.B., Professor of Medicine and Physical Therapy at West Park Healthcare Centre in Toronto, lead author of the study. "[This study] suggests serious problems with the indiscriminate use of oxygen to relieve day-to-day dyspnea in patients with COPD without resting hypoxemia."
The study, which indicates that generalized treatment of COPD patients with ambulatory oxygen may be an unnecessary and inconvenient, and possibly even detrimental expense, appeared in the second issue for August 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). In 2002, Medicare paid $2.2 billion for home oxygen therapy.
The researchers conducted a series of double-blind N-of-1 trials wherein 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 dyspnea scores or on their questionnaires. When assessed as individuals who served as their own controls, four patients showed improvement in the dyspnea scores with oxygen, and only one was identified as a clear responder," whose overall scores and walk tests improved markedly on oxygen, and who requested early termination of the placebo phase of the trial during all three periods.
"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.