A study published this week in The Lancet medical journal is the first to properly investigate whether the technique improves the lives of children with the incurable disability.

"This is one of a long succession of alleged treatments for cerebral palsy that have come and gone, and this was by far the best researched," said Dr. Peter Rosenbaum, a cerebral palsy expert who was not involved in the study.

Children given slightly pressurized air improved just as much as those treated in high-pressure oxygen chambers, the study found.

Though most experts said they thought the findings proved high-pressure treatment was useless, proponents said the improvement in the comparison group means even slightly pressurized air helps.

Cerebral palsy is a collection of diverse syndromes characterized by movement disorders and is caused by brain damage before, during or just after birth. It affects two in every 1,000 babies in the industrialized world, and is sometimes caused when not enough oxygen gets to the brain.

"The logic that we can repair brain impairment caused by oxygen deprivation by supplying more oxygen after the damage has been done is just crazy," said Rosenbaum, chair of the childhood research center at McMaster University in Hamilton, Ontario.

"The underlying brain damage is permanent, and neither improves nor worsens," Rosenbaum said.

Experts say that in the early years physiotherapy and drugs can help children improve their motor function. As the child grows, the acquisition of skills slows and therapy is geared toward preventing deterioration, experts say.

High-pressure, or hyperbaric, oxygen is usually used to treat carbon monoxide poisoning, some infectious diseases and to protect bones before radiation therapy.

Its use in cerebral palsy has spread as testimonials of successful treatment circulated among families of stricken children.

"It's hard to know the exact number, but there are many centers doing it. It's a big business in the United States, and there are also centers in the U.K. and Canada," said the study's leader, Dr. Jean-Paul Collet, a professor of clinical research at McGill University in Montreal. "This is a classic situation of people in a desperate situation. They are ready to try anything."

Collet's study involved 111 children with cerebral palsy age 3 to 12. Half were given high-pressure pure oxygen and half got air pressurized to the lowest pressure that can be felt. Parents did not know which treatment their children were getting.

The children got 40 daily sessions over eight weeks and were tested after 20 sessions, after their last treatment and three months later.

The two groups' test scores improved by the same amount and the changes persisted three months after the treatment. The greatest improvements were seen in the children who started with low scores.

Even the slightly pressurized air increased the concentration of oxygen in the blood. The normal level is 100 milliliters of mercury. Slightly pressurized air pushed that up to 148 milliliters, while the high-pressure oxygen increased it to 1,230 milliliters.

Collet said the findings don't mean extra oxygen goes to the brain, but that it can't be ruled out.

"An increase to 148 may be enough to have an effect on motor function, but we'd have to compare improvements with (unpressurized) air to see if that's the case," he said.