It's said you lose consciousness on emptying lungs and breathing inert gas. But on emptying lungs and holding breath, you don't lose consciousness?!

[G50]

With the inert gas method (using say nitrogen or helium), it is claimed that when you completely empty your lungs, and then breathe in a lungful of inert gas, you lose consciousness almost immediately on inhaling the gas.

However, if you completely empty your lungs and just hold your breath, you do not lose consciousness. In fact I can completely empty my lungs, and quite comfortably hold my breath for about 40 seconds, without any hint of passing out or losing consciousness. Presumably this is because I have sufficient oxygen bound to the haemoglobin in my blood to last for 40 seconds without any issues.

So I don't quite understand how in the inert gas method, people lose consciousness very quickly after the first inhalation of the inert gas.

 

[edu0z]

With the inert gas method (using say nitrogen or helium), it is claimed that when you completely empty your lungs, and then breathe in a lungful of inert gas, you lose consciousness almost immediately on inhaling the gas.

However, if you completely empty your lungs and just hold your breath, you do not lose consciousness. In fact I can completely empty my lungs, and quite comfortably hold my breath for about 40 seconds, without any hint of passing out or losing consciousness. Presumably this is because I have sufficient oxygen bound to the haemoglobin in my blood to last for 40 seconds without any issues.

So I don't quite understand how in the inert gas method, people lose consciousness very quickly after the first inhalation of the inert gas.

This is explained because the lungs are not designed to know how much oxygen is left in them, but rather to detect high concentrations of carbon dioxide. When you feel like you are drowning and need to breathe, it is not because you are running out of oxygen, it is because your lungs have gone on alert because they are filling with carbon dioxide. That is why when you replace oxygen with an inert gas and the lungs do not detect carbon dioxide, you pass out without feeling a sensation of drowning. It's not that you lose consciousness instantly, it's more that you pass out without feeling anything once enough oxygen for the body to function as it should runs out. (or something like that, you can do some easy research on the internet but that's basically it)

 

[Svenhog]

The explanation for this is that you don't empty your lungs completely, there's still some air left. This air contains oxygen, which is why you don't become unconcious directly. When filling your lungs with inert gas, all oxygen is removed.

 

[PreCambrianBliss]

it is claimed that when you completely empty your lungs, and then breathe in a lungful of inert gas, you lose consciousness almost immediately on inhaling the gas.

Where have you heard that? I don't think that's true. Even if you fully expel all the air from your lungs, you will still have a significant amount of oxygen in your bloodstream still circulating, I'd guess you would remain conscious for about 30 seconds. This would be true whether or not you're breathing inert gas, it's just much more uncomfortable not to. When you cut off circulation to your head via hanging, you lose consciousness much faster because you instantly prevent your brain from receiving oxygen, even if there's still some in your lungs and/or blood.

 

[Dying Knight]

With the inert gas method (using say nitrogen or helium), it is claimed that when you completely empty your lungs, and then breathe in a lungful of inert gas, you lose consciousness almost immediately on inhaling the gas.

Passing out may happen in a few seconds.

However, if you completely empty your lungs and just hold your breath, you do not lose consciousness. In fact I can completely empty my lungs, and quite comfortably hold my breath for about 40 seconds, without any hint of passing out or losing consciousness.

It's difficult to tell why it worked so for you, since you didn't describe the exact procedure of displacing oxygen from your lungs and the characteristics of your asphyxiant gas.

The explanation for this is that you don't empty your lungs completely, there's still some air left. This air contains oxygen, which is why you don't become unconcious directly. When filling your lungs with inert gas, all oxygen is removed.

Displacing all oxygen from the lungs is unnecessary for passing out, even breathing with air that contains less than 6% of oxygen causes rapid fainting

Effects of Oxygen Concentration

Concentration of Oxygen	Effect
18–21%	No discernible symptoms
11–18%	Reduction in physical and mental performance without appreciation
8–11%	Possible fainting in minutes with risk of death below 11%
6–8%	Fainting occurs after a short time
0–6%	Fainting occurs almost immediately

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6474450/

You can pass out after doing just a single deep exhale followed by a single deep inhale of an asphyxiant gas like the dude in the video below, because this may be enough to reduce the percent of oxygen in the lungs so it becomes below the critical threshold.

 

[Svenhog]

That's completely correct, the oxygen doesn't have to be 0 to pass out. My explanation was just a simplified way of explaining what is happening.

 

[G50]

Where have you heard that?

That you pass out and lose consciousness "almost immediately" on emptying your lungs of air, and taking a lungful of inert gas, I saw in a video demonstration of the inert gas method by Betty, from Exit International (the video entitled "Betty and the Helium Method"). This video is no longer online, but I downloaded a copy around 6 years ago. Obviously the helium method is a bit out of date now, since helium sold for party balloons is now mixed with oxygen, to prevent its suicide use. However, I believe the general technique will apply to other inert gases like nitrogen.

In the video, Betty explains that you prepare by placing the exit bag above your head, place the tube from the helium tank into the bag, and pre-fill the bag with helium (see screenshot from the video below). Then she says:

"It is simply a matter of fully exhaling, empty your lungs as much as you can, then hold your breath, and pull the bag full of helium down around your neck. Then take the biggest breath you can, filling your lungs with helium. The sudden replacement of the air in your lungs with helium leads to a precipitous drop in the level of dissolved oxygen in the blood that passes your lungs on its way to the brain, and consciousness is lost almost immediately, within a few breaths. Death follows a few minutes later. Remember it is important to be able to inhale and exhale deeply."

Screenshot From Video "Betty and the Helium Method" by Exit International


​

It's difficult to tell why it worked so for you, since you didn't describe the exact procedure of displacing oxygen from your lungs and the characteristics of your asphyxiant gas.

Thanks very much for your detailed post.

I was not using an asphyxiant gas, I was just emptying my lungs as much as I could, then closing my mouth and holding my breath, so that I am not taking in any more oxygen. But I find I can hold my breath for 40 seconds without experiencing any loss of consciousness, even when holding my breath with empty lungs.

Whereas if you see what I wrote just above, Betty from Exit International says if you empty your lungs and take in a large lungful of inert gas, "consciousness is lost almost immediately, within a few breaths".

So I am just wondering why consciousness is rapidly lost while you are breathing the inert gas, but is not lost when you hold you breath with empty lungs. But the explanation may be along the lines that Svenhog detailed:

The explanation for this is that you don't empty your lungs completely, there's still some air left. This air contains oxygen, which is why you don't become unconcious directly. When filling your lungs with inert gas, all oxygen is removed.

So maybe even when you empty your lungs as much as your can, there is still some air and oxygen left in the lungs. But when you start breathing the inert gas, perhaps this flushes out the last remaining bits of oxygen from the lungs, leading to rapid loss of consciousness.

 

[G50]

Looking into this further, it's probable that when the lungs are filled with inert gas, which means that there will be very low oxygen partial pressure in the lungs, that the oxygen bound to the haemoglobin in the blood is actually stripped off the haemoglobin, as the blood passes through the lungs, and that stripped off oxygen would then be expelled from the lungs.

This article says:

As the blood circulates to other body tissue in which the partial pressure of oxygen is less, the hemoglobin releases the oxygen into the tissue because the hemoglobin cannot maintain its full bound capacity of oxygen in the presence of lower oxygen partial pressures.

So that article suggests haemoglobin will lose the oxygen it is carrying when the blood passes through the lungs which contain an inert gas, because the partial pressure of oxygen in the lungs will be more or less zero. So this means breathing an inert gas not only deprives the blood of oxygen, but also strips oxygen from the haemoglobin as the blood passes through the lungs on the way to the brain. So this could explain why the inert gas method so quickly results in passing out and unconsciousness, because blood passing through the lungs and heading towards the brain may be stripped of its oxygen.

 

[Peaceful Departure]

If you hold your breath long enough, you will most definitely lose consciousness

 

[G50]

If you hold your breath long enough, you will most definitely lose consciousness

Yes sure, if you start with empty lungs and hold your breath, after a couple minutes say you may start to lose consciousness. Though you would probably not reach that far on your own, because no act of willpower will overcome the urge to breathe. But if for the sake of argument you were physically prevented from drawing breath, then I imagine you might start to lose consciousness after a few minutes, if you start with empty lungs.

But with the inert gas method, you lose consciousness within seconds, after just a few breaths of the inert gas. So clearly something special is happening when breathing inert gas, compared to when you just empty your lungs of air and then hold your breath. What could explain this rapid loss of consciousness with the inert gas?

I think that what I said just above might explain it: that having inert gas in your lungs actually strips away and expels the oxygen carried by the haemoglobin int the blood, because of the very low oxygen partial pressure in the lungs. So breathing an inert gas may actually pull out the oxygen from the blood passing through the lungs, causing unconsciousness to appear much more quickly.

This is why the inert gas method is good, because you become unconscious very quickly, and so there is no suffering.

 

[Dying Knight]

So maybe even when you empty your lungs as much as your can, there is still some air and oxygen left in the lungs.

Yes, there is residual volume. Lung volumes are well described here:

 

[TheRottingContinues]

When you manually exhale all you can and try to hold your breath, your body specifically does not let you pass out. I think it is a combination of both SI and biology. However, think of drowning; you need to totally empty your lungs and fill them with something else instead so that carbon dioxide doesn't build. With drowning, it's water, and with exit bag it's inert gas.

 

[Dying Knight]

When you manually exhale all you can and try to hold your breath, your body specifically does not let you pass out. I think it is a combination of both SI and biology.

You feel the urge to breathe when some critical concentration of CO2 is reached. It's possible to overcome this urge with strong will power. When concentration of O2 becomes low enough, CO2 doesn't cause the desire to breathe anymore, and your consciousness slowly fades out.

 

[G50]

Yes, there is residual volume. Lung volumes are well described here:

Very interesting video, thanks very much. It says at timecode 2:49 that after you have exhaled as much of air in your lungs as you can, there is still a residual amount of air left, which is about 1 litre in volume (corresponding to about 200 ml of oxygen gas, since oxygen is found at 21% in air).

However the amount of oxygen stored in the haemoglobin of the blood circulation is higher: there is around 1000 ml of oxygen gas bound to the haemoglobin in the blood (this is assuming 5 litres of blood in the body, and then using the info given here that 100 ml of blood has the capacity to bind 20.1 ml of oxygen).

Now it says here that "at rest a human consumes about 250 ml (about 15 cubic inches) of oxygen each minute". So that means a person has a few minutes of oxygen stored in their blood, and so would not normally pass out if their oxygen supply is cut off.

Thus the fact that you lose consciousness within seconds when breathing an inert gas suggests that the oxygen reservoir in the blood is not getting to the brain, otherwise you would not lose consciousness so quickly.

 

[Dying Knight]

However the amount of oxygen stored in the haemoglobin of the blood circulation is higher: there is around 1000 ml of oxygen gas bound to the haemoglobin in the blood (this is assuming 5 litres of blood in the body, and then using the info given here that 100 ml of blood has the capacity to bind 20.1 ml of oxygen).

Now it says here that "at rest a human consumes about 250 ml (about 15 cubic inches) of oxygen each minute". So that means a person has a few minutes of oxygen stored in their blood, and so would not normally pass out if their oxygen supply is cut off.

Low oxygen saturation of hemoglobin causes fainting. The threshold may be nearly 85% of max saturation.

 

[G50]

Low oxygen saturation of hemoglobin causes fainting. The threshold may be nearly 85% of max saturation.

Yes, once the haemoglobin oxygen saturation gets down to a certain point, you are going to pass out. I've taken my own oxygen saturation down to 65% during a test of a homemade debreather I've been trying to create. I did not feel anywhere near passing out at 65%; but once my oxygen saturation went below about 80%, I developed a really strong urge to stop breathing via the debreather, and to take off my face mask and breathe in some fresh air. I don't think this urge was due to CO2 buildup (as the CO2 scrubber removes the CO2), but may be due to the fact that your blood oxygen levels are low.

(This is the issue I have been having with my homemade debreather: once blood oxygen levels go below about 80%, it results in a very strong urge to take off the debreather face mask, and breathe fresh air. So as it stands, my debreather cannot be used, as the urge to breathe fresh air is very strong, and no sign of passing out even with blood oxygen levels down to 65%.)

 

[Dying Knight]

I wonder how precise those oximeters are. Maybe the indicated values like 65% and 80% are far from what is really delivered to the brain.

 

[G50]

I wonder how precise those oximeters are. Maybe the indicated values like 65% and 80% are far from what is really delivered to the brain.

Yes, that's what I thought, since the oximeter is connected to the finger, which measures the peripheral oxygen saturation, rather than the saturation in the blood vessels leading to the brain.

When I was testing my debreather, I saw that my finger oxygen saturation slowly went down to around 70% (it took about 5 minutes of debreather breathing to reach 70%). At that point I was feeling feeling a bit lightheaded, and with a strong compulsion to breathe fresh air (but with no sign of faintness or passing out). So I stopped the test, took off the debreather face mask, and started breathing fresh air. But over the next 30 seconds or so, even though I was breathing fresh air, the oximeter reading kept going down, reaching a low of about 65%, and then it started climbing again, and soon returned to around 98%.

 

[outrider567]

Yes, once the haemoglobin oxygen saturation gets down to a certain point, you are going to pass out. I've taken my own oxygen saturation down to 65% during a test of a homemade debreather I've been trying to create. I did not feel anywhere near passing out at 65%; but once my oxygen saturation went below about 80%, I developed a really strong urge to stop breathing via the debreather, and to take off my face mask and breathe in some fresh air. I don't think this urge was due to CO2 buildup (as the CO2 scrubber removes the CO2), but may be due to the fact that your blood oxygen levels are low.

(This is the issue I have been having with my homemade debreather: once blood oxygen levels go below about 80%, it results in a very strong urge to take off the debreather face mask, and breathe fresh air. So as it stands, my debreather cannot be used, as the urge to breathe fresh air is very strong, and no sign of passing out even with blood oxygen levels down to 65%.)

I got my Oxygen down to 46 but still didn't feel like fainting, and I had no desire to take off my Hood and breathe any air, because Nitrogen is just like breathing air anyway--I don't think one loses conciousness until the Oxygen level actually gets down to 25 or so