I learned in biology that we have something called residual volume of air in our lungs. I saw a video on a sub showing the lack of oxygen through a burning fire. There were comments that if you went in that space you will pass out. There were stories about how a Chinese teacher passed out while tying his shoelace but students survived since they were standing up. Most humans can hold their breath for 10 seconds at least. So why is it that when you go into a tiny space with no oxygen but dense co2, you will pass out?
In: Biology
When you hold your breath, you’re holding that residual oxygen in your lungs. If you keep breathing, you’re releasing it. If you then take in a breath that contains no oxygen, you’re running out of oxygen dramatically faster than if you had just held it in.
I don’t think that is true as I have been in a vaccum before and I didn’t pass out. It is a common test in pulmonology offices, they suck the air out of the room and ask you to try to take a breath.
The panic attack I felt like I was having trying to breathe without any air was enough to make me pass out, but I did not.
This question depends on the composition of the air, and whether or not you are actually breathing.
Humans can hold their breath for a minute or two and use some of the oxygen that’s stored in the lungs, but if you’re in an environment filled with a neutral gas and continue to breathe, you won’t be able to use the oxygen in your lungs. For example if you walk into a nitrogen environment and keep breathing, you will exhale all of the oxygen that would be stored in your lungs if you held your breath. Additionally, the balance of oxygen between the blood and the lungs depends on the concentration difference between the two spaces. If you breathe in a nitrogen environment, oxygen will actually move out of your blood and into your lungs and then be exhaled.
For other situations such as CO2, it’s the CO2 that becomes the problem, not the lack of oxygen. Inhaling high concentrations of CO2 altars the pH of your blood and function of many proteins which can very rapidly lead to unconsciousness.
holding your breath does not stop blood flowing and if you had air in your lungs then you can hold your breath for as long as that air lasts and stay conscious. if you replace the air in your lungs with co2, then you will very quickly pass out. this is also why choke holds knock people unconscious. cutting off air to the lungs is inconvenient, cutting off blood to the brain is immediately dangerous.
For space in particular, you can’t hold your breath. Your lungs and throat are not able to hold on to much more than a 10th of an atmosphere of overpressure. And at that pressure, the gas exchange mechanism that normally gets oxygen from the lungs into the blood will work the other way.
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