Welcome to brain Stuff from house stuff works dot com, where smart happens him Marcial Brain with today's question, is it harmful to breathe on oxygen? You think, since we need oxygen to live, that it would be okay to breathe on oxygen, And it is okay for an hour maybe, But if you breathe on oxygen for more than an hour, it starts to cause big problems. So the short answer is pure oxygen is generally bad and sometimes toxic. To
understand why, you need to go a little deeper. Your lungs are basically a long series of tubes that branch out from your nose and mouth and end in little, thin walled air sex called a viola. I think of soap bubbles on the end of a straw and you'll understand a viola. Surrounding each aviolas are small, thin walled
blood vessels called pulmonary capillaries. Between the capillaries and the aviolas is a thin wall about point five microns thick, through which various gases in our case, oxygen, carbon dioxide, and nitrogen can pass. When you inhale, the aviol i fill with this air because the oxygen concentration is high in the aviola and low in the blood entering the
pulmonary capillaries. Oxygen diffuses from the air into the blood. Likewise, because the concentration of carbon dioxide is higher in the blood that's entering the capillaries than it is in the aviolar air, carbon dioxide passes from the blood to the avioli. The nitrogen concentration in the blood and in the aviolar air is about the same. The gases exchange across the aviol or wall, and the air inside the avoli becomes
depleted of oxygen and rich in carbon dioxide. When you exhale, you breathe out this carbon dioxide enriched oxygen pour air. Now what would happen if you breathe on oxygen? In guinea pigs exposed one oxygen at normal air pressure for forty eight hours, fluid accumulates in their lungs and epithelial cells lining the avola. In addition, the pulmonary capillaries get damaged.
A highly reactive form of oxygen called the oxygen free radical, which destroys proteins and membranes and the epithelial cells, probably causes this damage in humans, breathing one oxygen at normal pressure, the same kind of thing happens. First, fluid accumulates in the lungs that causes the gas flow across the aviol to slow down, meaning that the person has to breathe more to get enough oxygen. Then mucus starts to plug
up local areas of collapsed a viola. The oxygen trapped inside these plugged a viola gets absorbed into the blood and no gas is left to keep the plugged avio l a inflated, so they collapse. Mucus plugs are normal, but they're cleared by coughing, but coughing doesn't work when the avioli have collapsed. If avoli become plugged when breathing normal air, the nitrogen trapped inside the avial i keeps
them inflated and prevents this clogging from happening. The astronauts in the Gemini and Apollo programs breathed oxygen for up to two weeks with no problems, So what was going on there? That's because the pressure inside the capsule was reduced. Today astronauts who are using spacesuits are breathing pure oxygen as well, but the pressure inside their suits is also reduced to improve mobility. Do you have any ideas or suggestions for this podcast? If so, please send me an
email at podcast at how stuff works dot com. For more on this and thousands of other topics, go to how stuff works dot com and be sure to check out the brain stuff blog on the how stuff works dot com home page