removing carbon dioxide from inhaled air

When you remove the CO2 from inhaled air, you loose the impulse to breathe faster. You simply become light headed and eventually loose consciousness.
I saw Dr. Jonathan Miller do this in his series “the body in question”. He used a CO2 scrubber and a rebreather.
I am specifically looking a for a video clip of someone doing this same thing.

If you remove the CO2 from air, you breathe just fine. The sensors that detect CO2 buildup are in your brain and heart, not in your lungs, so the concentration of CO2 in inhaled air is largely irrelevant to maintaining consciousness. It is only the removal of oxygen that will cause a loss of consciousness.

The problem with rebreathers isn’t that they remove the C02 from inhaled air, it’s that they are a closed system that removes the CO2 from *exhaled *air. That means that after you have removed all the oxygen by breathing, you have a system full of nitrogen. Because the body is still able to expel carbon dioxide into a nitrogen atmosphere, you don’t realise that you are short of oxygen. You keep breathing normally despite not absorbing any oxygen, and eventually pass out.

Bear in mind that it was made over 40 years ago so the quality is not great. The part you want is about 43 minutes in.

As an aside rebreathers are interesting. In theory you can have one that allows you to spend DAYS underwater rather than an hour or a tiny fraction of an hour if you are deep if you use your typical scuba tank.

The other interesting thing about them is that the OXYGEN sensors are not particularly reliable. And even worse CO2 sensors are so bad I don’t even think they are ever used.

So, you have this device that’s great for diving. Except the O2 level might get too high because the sensor malfunctions and all of a sudden you have convulsions, likely without warning. Or the O2 level will get too low and you’ll pass out, likely without warning.

Neither one is a good thing while underwater doing a serious dive (which is why you’d be using a rebreather in the first place). Usually, most of the time when that happens the person dies.

That’s it!!! Fantastic!

I can’t speak to what’s in the brain and heart, but I can tell you that your lungs are definitely sensitive to CO2 concentration. The next time you and your friends swill a 2-liter bottle of carbonated soda, do this:

  1. exhale completely.
  2. wrap your lips around the mouth of the empty soda bottle.
  3. inhale the contents of the bottle, squeezing it as necessary to aid your inhalation.

With the soda having been recently removed from the bottle, there will still be a relatively high concentration of CO2 in there. When that ends up in your lungs, you will instantly feel like you’ve been holding your breath for two minutes.

Go one step further and seal a hunk of dry ice in a zip-loc bag. Just before the bag bursts due to buildup of pure gaseous CO2, open the bag and try to inhale deeply. I say “try” because you won’t be able to: it’ll hurt your lungs so much that you’ll start coughing violently.

I once thought it would be a good idea to suck that last bit of gas out of an inflatable life jacket. One that had been inflated by a CO2 cartridge.

Not a pleasant experience.

Isn’t this pretty much what the OP said? :confused:

I’m sure that inhaling very cold gas makes you cough. I’m not sure how that proves that lungs have CO2 sensors.

And, even if inhaling the gas from a soda bottle does make you feel breath-deprived, we still don’t know if that’s because there’s lots of CO2, or because there’s little oxygen.

The gas isn’t particularly cold. Yes, it’s in a ziploc bag with dry ice - but it’s a small piece of dry ice with relatively little surface area, and the ziploc bag itself has a lot of surface area; the temperature of the gaseous CO2 is relatively close to room temperature.

Try it, and you’ll know immediately that the reason you’re coughing has nothing to do with temperature.

We do know…because there are plenty of oxygen-free gases you can inhale that don’t cause irritation.

Here’s your next experiment:

  1. Obtain a helium-filled balloon.
  2. Lie down on a bed, couch, or other comfortable flat surface.
  3. Exhale as completely as you can, then inhale deeply from the balloon.
  4. Hold your breath.

Your lungs now have a very high concentration of helium, relatively little oxygen, and very little CO2. As you continue to hold your breath, the reason for step #2 will become obvious: you will soon (within 20 seconds) become hypoxic and dizzy, and if you continue to hold your breath you will lose consciousness - all without ever having experienced any particular urge to breathe (i.e. no lung irritation). If you do this experiment while standing or sitting, there’s a good chance you’ll get hurt when you pass out.

Point being that low O2 concentration does not drive the urge to breathe.

This isn’t rhetorical. I’ve done these things, and if you doubt what I’m saying, I invite you to try them for yourself.

I think the pain of breathing high concentrations of CO2 comes from carbonic acid being formed in your lungs.

DON’T DO THIS ALONE. Passing out, still with no particular urge to breathe, is not a recipe for a long life. Make sure you have someone present to revive you.


Why would there be a relatively high concentration of CO2? You have displaced the liquid that was in there with air from the atmosphere. Where did the excess CO2 come from? It can’t have come from carbonic acid in the water, because that had to be removed before any gas was allowed? So what was the carbon dioxide reservoir within the bottle that provided these elevated concentrations?

So you inhale a gas at -20oC, that forms carbonic acid when it contacts mucous membranes. And it hurts.

Who’da thunk it?

That may be. And trust me it IS fucking painful.

And for that matter I suggest nobody reading here do any of these mytbusterish experiments. Nothing like coughing till you strain a muscle or throw up and aspirate some of your own vomit or some such.

Having said that. You can breath an inert gas with no 02 or a very low 02 concentration. You will not have the urge to breath. You might feel a bit winded. You might get a bit light headed. Right before you pass out and die if someone isn’t there to save you.

But those are “mights”. Everything I’ve ever read on this kind of stuff basically says “low/no 02 you just drop dead without warning”

But, the point being, the LACK of 02 is NOT what is giving you the urge to breath. I’ll let you figure out what else it might be.

That question doesn’t need to be figured out. it has been comprehensively answered.

:rolleyes: Well, that settles that debate.

“carbonated soda” = “beverage with large quantities of dissolved carbon dioxide.” As you dispense fresh beverage from the bottle, substantial quantities of CO2 come out of solution, which leaves the bottle with an elevated concentration of CO2 after all the liquid is gone. It’s not pure CO2 (as in the dry-ice-in-a-ziploc-bag scenario), but it’s not pure air, either.

This works best at a party scene, where the bottle is emptied in the space of maybe 15 minutes. A bottle that has been opened/closed many times over the space of a week or so (with flat soda at the end) is one where most of the CO2 has escaped, and something closer to pure atmospheric air is left behind.

You should go back up and reread what I wrote above; it’s not that cold when you inhale it, and the sensation you feel is not the same as you get from walking outside on a very cold day.

Also, “carbonic acid hurts your mucous membranes” = “your lungs are sensitive to CO2 concentration,” which solidly negates your “Nope” above. It doesn’t matter whether the CO2 in your lungs comes from a ziploc bag, a soda bottle, or your own alveolar blood; the bottom line is that CO2 in your lungs, regardless of the source, causes discomfort and induces an urge to breathe.

Super-high concentrations of CO2 in the lungs (as when inhaling from a bag of dry ice) may hurt, but lower, painless concentrations (as when inhaling from a recently-emptied 2-liter soda bottle) do induce the exact same urge to breathe that a person experiences after holding their breath for a couple of minutes. I am speaking from direct, personal, repeatable experience here.

It may be that CO2 sensors in the heart/brain regulate breathing when a person is asleep (can an MD confirm this?), but the elevated CO2 concentrations achieved in the lungs when you hold your breath for an extended period produce sensations in the lungs that induce the urge to exhale and draw in fresh air.

I’ll agree with others here that the helium experiment and dry ice experiment are probably ill-advised, but inhaling from an emptied soda bottle is harmless and enlightening. I really recommend you try it instead of just typing “Nope.”

I try this all the time at our lab, where we have tanks of CO2 and the like, and Machine Elf is correct – the more CO2 I add to regular air that I breathe in, the worse the sensation of instant dyspnea is; it happens immediately with inhalation, without time for blood circulation. What’s the deal? Is that because the formation of carbonic acid on the lung tissue triggers the same feeling as having high blood CO2 concentration?

In a recent thread about the least-painful way to die of “natural” causes, KarlGauss made this post, which discusses the various causes for the sensation. I found it unsettling.