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Large numbers of people who are prescribed oxygen because they get short of breath when they are active do not benefit from the therapy, according to a groundbreaking Canadian study.

"Many people receive oxygen to assist them when they are short of breath, but few of them see a sustaining benefit," Roger Goldstein, a respirologist at West Park Healthcare Centre in Toronto and senior author of the research, said in an interview.

He said the findings, if they are heeded in the real world, should dramatically alter the practice of routinely prescribing oxygen to people suffering from chronic obstructive pulmonary disorder.

This could result in substantial cost savings and remove a great deal of stigma from COPD sufferers who are self-conscious about carrying their oxygen tanks in public, Dr. Goldstein said.

More than 10,000 Canadians a year die of COPD, making it the country's fourth leading killer. But at least 750,000 more are living with the condition, a combination of several respiratory ailments including chronic bronchitis and emphysema.

COPD is characterized by shortness of breath, wheezing and coughing, and the symptoms grow progressively worse and more debilitating over time. There is no cure.

At least one-third of COPD sufferers use supplemental oxygen, including portable tanks.

The therapy is controversial and extremely expensive. U.S. Medicare, which provides free health care to seniors, spends more than $2.2-billion (U.S.) a year on oxygen therapy, while provincial health plans in Canada spend an estimated $200-million.

"We know that it's expensive, but we don't know if it's effective," Dr. Goldstein said.

To conduct the study, which is published in today's edition of the American Journal of Respiratory and Critical Care Medicine, researchers recruited 27 COPD patients and followed them during a 12-week period.

During that time they received, in two-week blocks, either oxygen or compressed air (as a placebo) in their tanks. They also underwent five-minute walk tests, and answered quality-of-life questionnaires.

In the end, there was virtually no difference in any of the measures whether they used oxygen or the placebo, strongly suggesting the oxygen provided little or no benefit.

There is no question that patients with severe COPD who have low oxygen levels at rest benefit greatly from oxygen therapy, Dr. Goldstein said. "For them, it's life-saving," he said, and most are tethered to oxygen tanks 24 hours a day.

But the majority of those prescribed oxygen use it only intermittently, primarily when they are active. Many people with COPD will, for example, use an oxygen tank only when they go to the mall.

These prescriptions have become routine based on research showing that patients do slightly better in laboratory-based exercise tests if they are using oxygen. But the new research strongly suggests that they don't need supplemental oxygen at all in the real world.

"The key is to give oxygen to those who really need it, but until now we couldn't really identify who they were," Dr. Goldstein said.

The result has been an "indiscriminate use of oxygen and an over-reliance on it by those who don't benefit," he said.

The patients in the study used their tanks, on average, only about 40 minutes a day. That underscores just how inactive many people with COPD become.

In a commentary also published in the respiratory journal, Robert Wise of the division of pulmonary medicine at Johns Hopkins University in Baltimore, Md., praised the methodology of the research and said the findings were enlightening for physicians who struggle daily to figure out how to best treat COPD sufferers.

"The findings ... challenge those of us who prescribe oxygen to explore the intricacies of real-world activity levels of our patients and how oxygen may benefit those individuals," he said.