It's a scenario straight out of Gray's Anatomy a paramedic or doctor plops a mask over the face of a person struggling to breathe and begins dispensing pure oxygen.

Yet growing research suggests that inhaling straight oxygen can actually harm the brain. For the first time, a new UCLA brain-imaging study reveals why. Published in the May 22 edition of Public Library of Science (PLoS) Medicine, the findings fly in the face of national guidelines for medical practice and recommend a new approach adding carbon dioxide to the gas mix to preserve brain function in patients.

"For decades, the medical community has championed 100 percent oxygen as the gold standard for resuscitation. But no one has reported what happens inside our brains when we inhale pure oxygen," explained Ronald Harper, distinguished professor of neurobiology at the David Geffen School of Medicine at UCLA. "What we discovered adds to a compelling body of evidence for modifying a widely practiced standard of care in the United States."

Harper's team used functional magnetic resonance imaging (fMRI) to capture detailed pictures of what occurs inside the human brain during two different breathing scenarios. The technique detects subtle increases in blood flow triggered by the activation of different parts of the brain, causing these regions to glow or "light up" on the color scan.

The researchers scanned the brains of 14 healthy children, ages 8 15, as they inhaled 100 percent oxygen through a mouthpiece, and monitored their breathing and heart rates. After waiting eight minutes for the youngsters' breathing to return to normal, the team added 5 percent carbon dioxide to the gas mixture and repeated the scan.

A comparison of the two scans revealed dramatic differences.

"When the children inhaled pure oxygen, their breathing quickened, resulting in the rapid exhalation of carbon dioxide from their bodies," said coauthor Paul Ma
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Contact: Elaine Schmidt
eschmidt@mednet.ucla.edu
310-794-2272
University of California - Los Angeles
21-May-2007