An ambulance is rushing you to the emergency room, and you’re losing consciousness. The medics grab a facemask and start feeding you a stream of pure oxygen... to cause damage to your brain? A new UCLA brain-imaging study is part of a growing body of research that suggests inhaling pure oxygen is bad for you. The researchers did MRI brain scans of 14 kids, age 8 to 15. In one test they were fed pure oxygen; in the second 95 percent oxygen and 5 percent carbon dioxide.
With pure oxygen the kids’ breathing quickened and blood vessels constricted, preventing oxygen from reaching the brain and heart. Then things got worse. The hypothalamus responded to the emergency signals the body was sending by dumping a massive flood of hormones and neurotransmitters into the bloodstream. Which interfered with the heart’s ability to pump blood and deliver oxygen - the worst thing in a crisis situation. But adding the little shot of carbon dioxide calmed the hypothalamus, the blood vessels relaxed and the surge of dangerous chemicals stopped. Because when it comes to oxygen, you can have too much of a good thing.