I’m doing emergency rescue for work and learnt that inhaling a few times at below 10% oxengenated air will leave you pretty much immobile, but I can hold my breath for at least a minute, so shouldn’t I be able to go without 02 for a similar amount of time? Sorry if this is smoothbrained, I tried googling it and couldn’t find an answer for this specifically.
In: Biology
The other answers are mentioning that a single breath of normal air has enough oxygen for more than one breath, but that still doesn’t explain why you can get more than two or three times as long out of a held breath, and can get 10 or 20 times as long instead.
Your body doesn’t have a low-oxygen response. It has a high-CO2 response. When you hold your breath, CO2 begins building up in your blood, and within 10 seconds, your heart rate is already falling, the pathways to your limbs are constricting, the spleen is releasing extra red blood cells from storage to extract every last molecule of oxygen from your lungs, and everything in your body is focusing on the single goal of keeping oxygenated blood going to your brain. In fact, for at least a few moments, the oxygenation of your brain will *increase* compared to normal, so you don’t feel faint.
If you enter a low oxygen environment without realizing it, you’re able to keep expelling CO2. Your heart rate doesn’t change, your limbs remain equally oxygenated as your brain (dividing a very low supply), and your blood cell volume does not increase. Your brain’s oxygenation will drop fast, and that makes you faint.
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