When testing my homemade debreather (made from a medical CO2 scrubber), I get oxygen starvation and strong desire to breathe fresh air at 5 mins

[G50]

I made my own debreather apparatus for about $30 using a readily-available medical CO2 scrubber cartridge/canister (the Spherasorb IS Can pictured below). This replaceable canister is intended for use with medical anaesthetic machines. The cartridge contains 1 kg of Spherasorb soda lime, which scrubs CO2 from the air passing through the cartridge. The cartridge has two air hole connectors on the top, sealed by a removable green plastic cover as shown in the picture. The air that goes into one of these holes gets passed through the soda lime granules, and then out of the other hole.

Spherasorb IS Can — CO2 Scrubber Cartridge
​

I connected a 22 mm anaesthesia tube to one of the two connectors on the canister, and attached an anaesthesia face mask to the end of this tube (anaesthesia masks work well, as they have a tight fit to the face, via an air cushioned surround which adapts to the face shape).

I then connected a 6 litre plastic bag to the other connector on the canister, via some more 22 mm tubing, to act as an air reservoir bag. So with this apparatus, when you breathe in or out through the face mask, your breath is passed through the soda lime cartridge, where the CO2 is scrubbed. This homemade debreather setup is pictured below.

My Homemade Debreather
​

However, when I tested this debreather using a pulse oximeter on my finger to monitor blood oxygen saturation, I found that after about 5 minutes of breathing through the face mask, as the oxygen levels went down inside the debreather, I had a strong desire to stop the test, take off the mask, and breathe fresh air. At the 5 minute point, I was also feeling mildly lightheaded, with a mild sense of panic, and a really intense desire to breathe some fresh air — a desire similar to how you feel when you have held your breath for a minute or so, and begin to get an intense compulsion to breathe in a gulp of fresh air.

So as it stands, my debreather experiment is a failure, as the intense compulsion to take in fresh air will prevent this method from working. I was expecting that I would begin to lose consciousness as the oxygen levels went down, but instead I maintained full consciousness, and had a strong compulsion to stop the test and breathe in fresh air.

During this test, I was holding the face mask to my face with my hand (it was not fastened to my face with a strap), so that if I did begin to lose consciousness, I would drop the mask, and consciousness would be regained as I started breathing fresh air.

Here are the measurements of my blood oxygen saturation while breathing through this debreather apparatus:

Time — Blood Oxygen Saturation

0 minutes — 98 Start of test.
1 minutes — 98
2 minutes — 97
3 minutes — 95
4 minutes — 87
5 minutes — 70 Stopped the test at 5 minutes, feeling lightheaded, and with a strong compulsion to breathe fresh air.


Why I am getting this intense desire to breathe fresh air, when I read that this desire is normally only caused by CO2 build up? Anyone have any ideas? I am removing the CO2 with the scrubber.

The only thing I can think of is that the 1 kg of soda lime within this cartridge is a bit lower than the typical amounts of soda lime used by divers in their rebreather apparatus (diver rebreather canisters typically contain about 2.4 kg of Spherasorb soda lime, according to this study). So maybe the CO2 removal is not that efficient, and I am getting some CO2 remaining.

There are reports of the debreather method working, so I must be doing something wrong.

 

[MBG]

How I hope they fix the R2D Rebreather lll….

 

[ClownWorld2023]

Did you confirm the CO2 was being removed by measuring it with a CO2 gas detector?

 

[G50]

Did you confirm the CO2 was being removed by measuring it with a CO2 gas detector?

That would be a very good idea, but unfortunately I do not have a CO2 meter (although they don't seem that expensive). But I did consider the possibility that my CO2 scrubber canister was not efficiently removing all the CO2, and that there might be some residual CO2 in the air reservoir bag of the debreather, and that it is this CO2 that is causing me to gasp for fresh air after about 4 minutes on the debreather.

However, I more-or-less ruled this possibility out by adding an electric air pump to my apparatus. I used an air pump which pumps 400 litres of air per minute (this air pump is designed to inflate lilos and other inflatables).

I used this air pump to circulate the air from the debreather air reservoir bag through the CO2 scrubber, and then back into the reservoir bag, at 400 litres per minute. This 400 litre per minute flow rate is much faster than the human breathing rate of 6 litres of air per minute, and thus because the air is being rushed through the CO2 scrubber at such increased speed, it should definitely remove all the CO2 from the air reservoir bag.

But even when using this air pump to turbo charge the CO2 scrubbing process, I still experienced a strong urge to breathe fresh air after around 4 minutes breathing through the debreather. So I don't think it is a CO2 buildup that is the issue, although to be sure, I would need to buy a CO2 meter.


My guess is that this is urge to breathe fresh air arises because when oxygen levels get low in the blood, you may automatically start gasping for air. I think a problem with debreathers might be that unlike the inert gas method, you do not lose consciousness immediately, so you are aware of the fact that you are short of oxygen, and that perhaps creates a strong craving to breathe fresh air.

I have argued in this thread that in the inert gas method, the reason you lose consciousness so quickly — within a few seconds of inhaling the inert gas into your lungs — is because in the lungs, this inert gas may actually suck the oxygen right out of the bloodstream (this suction due to having very low oxygen partial pressure in lungs filled with an inert gas).

The human blood carries around 1 litre of oxygen in the haemoglobin. But as this blood passes through lungs filled with an inert gas, I suspect the oxygen in the blood is stripped off the haemoglobin, and expelled from the lungs. And thus after the blood passes through the lungs and then goes to the brain, it has no oxygen in it. This I theorise is the reason the inert gas method produces a very rapid loss of consciousness within seconds.

You don't get this rapid lose of consciousness with the debreather, because oxygen levels go down slowly (it takes about 5 minutes to reach 70% oxygen saturation in the blood). So you are fully aware of the low oxygen level in your blood, at it makes you feel short of breath, and make you want to breath fresh air.

 

[ClownWorld2023]

My guess is that this is urge to breathe fresh air arises because when oxygen levels get low in the blood, you may automatically start gasping for air. I think a problem with debreathers might be that unlike the inert gas method, you do not lose consciousness immediately, so you are aware of the fact that you are short of oxygen, and that perhaps creates a strong craving to breathe fresh air.

I have argued in this thread that in the inert gas method, the reason you lose consciousness so quickly — within a few seconds of inhaling the inert gas into your lungs — is because in the lungs, this inert gas may actually suck the oxygen right out of the bloodstream (this suction due to having very low oxygen partial pressure in lungs filled with an inert gas).

I recall reading something about the brain being able to detect low oxygen levels and reacting in response.

 

[zel]

Why I am getting this intense desire to breathe fresh air, when I read that this desire is normally only caused by CO2 build up? Anyone have any ideas? I am removing the CO2 with the scrubber.

There are reports of the debreather method working, so I must be doing something wrong.

It's not that simple. There are two drives which provoke the instinct to breathe.

The primary and most immediate one in most people is the hypercapnic drive.
This is the one that you have heard about wherein a CO2 buildup in the blood is recognized by certain chemoreceptors. To make a long story short, this causes the panicky feeling of needing to breathe and the sensation of asphyxia.

However, we have a second drive called the hypoxic drive.
When the body has undergone mild and chronic hypercapnia, it will begin to adapt and use oxygen-sensitive chemoreceptors to regulate respirations. In layman's terms, if you have been mildly hypoxia for a while, your body learns to directly measure the O2 in the blood (rather than the CO2), and uses that to tell you when you need to breathe. This "transition" from the hypercapnic (high CO2) drive to the hypoxic (low O2) drive is most commonly seen in those with a history of COPD, but I might guess that if it's not a matter of equipment dysfunction, that it could be this.

I recall reading something about the brain being able to detect low oxygen levels and reacting in response.

Dangit, you beat me to it!

 

[G50]

However, we have a second drive called the hypoxic drive.
When the body has undergone mild and chronic hypercapnia, it will begin to adapt and use oxygen-sensitive chemoreceptors to regulate respirations. In layman's terms, if you have been mildly hypoxia for a while, your body learns to directly measure the O2 in the blood (rather than the CO2), and uses that to tell you when you need to breathe. This "transition" from the hypercapnic (high CO2) drive to the hypoxic (low O2) drive is most commonly seen in those with a history of COPD, but I might guess that if it's not a matter of equipment dysfunction, that it could be this.

Very interesting.

Although I am still at a loss to explain why my debreather does not work for me, due to the strong urge to breathe fresh air I get after about 4 minutes using the debreather. There are reports of debreathers working for people as an exit method (and from what I have read, when debreathers fail, it is just because the face mask was not sufficiently tight fitting, so that air and oxygen leaked in).

I do not have COPD. The illnesses I have are myalgic encephalomyelitis / chronic fatigue syndrome (ME/CFS), along with mild postural orthostatic tachycardia syndrome (POTS), irritable bowel syndrome (IBS), and several mental heath conditions including depression, generalised anxiety disorder, anhedonia, and a few others.

As far as I am aware, none of these conditions lead to elevated blood CO2.

 

[G50]

Just found out something interesting: the body's mechanism to detect and respond to low oxygen — the hypoxic ventilatory response — can be substantially inhibited by benzodiazepines (ref here), and also by ibuprofen (ref here).

So taking some benzos (if you can get hold of them) and some ibuprofen an hour or two before using the debreather might potentially prevent or reduce the feeling of oxygen starvation. I am going to test this out shortly.

Note that MAO inhibitor antidepressants appear to amplify the hypoxic ventilatory response (ref here).

 

[casual_existence]

I'm not well informed on this method but isn't there supposed to be two tubings one that goes exclusively in and another that goes exclusively out?

 

[G50]

I'm not well informed on this method but isn't there supposed to be two tubings one that goes exclusively in and another that goes exclusively out?

If you look at the debreather in the image below, there are two tubes running from the face mask to two soda lime canisters. It's possible these tubes might have one-way valves so that the air only runs in one direction, but I am not sure.





However, if you look at the debreather diagram in figure 1 on page 296 of this paper: "The debreather: A report on euthanasia and suicide assistance using adapted scuba technology", you see that it only has a single tube, and the setup is identical to my device. Figure 1 is shown below:

 

[casual_existence]

If you look at the debreather in the image below, there are two tubes running from the face mask to two soda lime canisters. It's possible these tubes might have one-way valves so that the air only runs in one direction, but I am not sure.


View attachment 124647


However, if you look at the debreather diagram in figure 1 on page 296 of this paper: "The debreather: A report on euthanasia and suicide assistance using adapted scuba technology", you see that it only has a single tube, and the setup is identical to my device. Figure 1 is shown below:


View attachment 124648

Okay so the only air you breathe is whatever was originally in your lungs?

 

[G50]

Okay so the only air you breathe is whatever was originally in your lungs?

That's right, and as you continue breathing this same volume of air in and out, its oxygen level gets less and less, as your body uses up the oxygen in this air. But the carbon dioxide you exhale is removed by the soda lime in the canister. So in the end, you are left with air without oxygen, which means only the nitrogen in the air remains. So in the end, you are breathing only nitrogen, which is an inert gas.

 

[casual_existence]

From what I've read apparently the hypoxic ventilatory response also happens at high altitudes. Presumably if you live in a low altitude this wouldn't happen? When I first started to look into suicide I saw this debreather thing but didn't really think about it much since inert gas is readily accessible in the US.
What's kinda strange is that these two methods are very similar in principle so why would you feel an urge to breathe?

 

[G50]

From what I've read apparently the hypoxic ventilatory response also happens at high altitudes. Presumably if you live in a low altitude this wouldn't happen? When I first started to look into suicide I saw this debreather thing but didn't really think about it much since inert gas is readily accessible in the US.
What's kinda strange is that these two methods are very similar in principle so why would you feel an urge to breathe?

Yes, that's what I was asking myself. The inert nitrogen gas method is generally promoted as a serene peaceful method, where people rapidly become unconscious.

And as you point out, the debreather method is very similar to the nitrogen method, since in effect with the debreather you end up breathing nitrogen gas after a few minutes, as the oxygen level diminishes. So why then did I feel a strong urge to breathe fresh air after a few minutes, when testing out the debreather method? It would be useful to compare to the nitrogen method, but I have not got access to a nitrogen gas cylinder, so I cannot check whether I might also get the same urge to breathe using the nitrogen method.

I guess it could be that some people are more prone to triggering the hypoxic ventilatory response when oxygen is low. I suffer from edgy nervousness and anxiety, so maybe I am more sensitive to low oxygen conditions?

I was recently reading this newspaper article about the fact that some US states are starting to experiment with the nitrogen method for state executions. The article ends with this:

By contrast, euthanasia guidelines produced by the American Veterinary Medical Association (AVMA), which represents 100,000 veterinarians in the US, reject nitrogen hypoxia for almost all mammals. The gas creates an environment devoid of oxygen that is "distressing for some species", it says.

So it seems some animals can become distressed under low oxygen levels. Maybe certain people also have issues with low oxygen, prompting this desire to breathe fresh air.

 

[MBG]

That would be a very good idea, but unfortunately I do not have a CO2 meter (although they don't seem that expensive). But I did consider the possibility that my CO2 scrubber canister was not efficiently removing all the CO2, and that there might be some residual CO2 in the air reservoir bag of the debreather, and that it is this CO2 that is causing me to gasp for fresh air after about 4 minutes on the debreather.

However, I more-or-less ruled this possibility out by adding an electric air pump to my apparatus. I used an air pump which pumps 400 litres of air per minute (this air pump is designed to inflate lilos and other inflatables).

I used this air pump to circulate the air from the debreather air reservoir bag through the CO2 scrubber, and then back into the reservoir bag, at 400 litres per minute. This 400 litre per minute flow rate is much faster than the human breathing rate of 6 litres of air per minute, and thus because the air is being rushed through the CO2 scrubber at such increased speed, it should definitely remove all the CO2 from the air reservoir bag.

But even when using this air pump to turbo charge the CO2 scrubbing process, I still experienced a strong urge to breathe fresh air after around 4 minutes breathing through the debreather. So I don't think it is a CO2 buildup that is the issue, although to be sure, I would need to buy a CO2 meter.


My guess is that this is urge to breathe fresh air arises because when oxygen levels get low in the blood, you may automatically start gasping for air. I think a problem with debreathers might be that unlike the inert gas method, you do not lose consciousness immediately, so you are aware of the fact that you are short of oxygen, and that perhaps creates a strong craving to breathe fresh air.

I have argued in this thread that in the inert gas method, the reason you lose consciousness so quickly — within a few seconds of inhaling the inert gas into your lungs — is because in the lungs, this inert gas may actually suck the oxygen right out of the bloodstream (this suction due to having very low oxygen partial pressure in lungs filled with an inert gas).

The human blood carries around 1 litre of oxygen in the haemoglobin. But as this blood passes through lungs filled with an inert gas, I suspect the oxygen in the blood is stripped off the haemoglobin, and expelled from the lungs. And thus after the blood passes through the lungs and then goes to the brain, it has no oxygen in it. This I theorise is the reason the inert gas method produces a very rapid loss of consciousness within seconds.

You don't get this rapid lose of consciousness with the debreather, because oxygen levels go down slowly (it takes about 5 minutes to reach 70% oxygen saturation in the blood). So you are fully aware of the low oxygen level in your blood, at it makes you feel short of breath, and make you want to breath fresh air.

How did you learn about lungs' reserve air and volume of oxygen dissolved in blood? Do you have sources to link or cite? I ask since inventor of the R2D Rebreather lll (Richard Avery as I recall) may read this and improve the device. That is in all our interests.

Do you have any other ideas or suggestions that could help them make a better product?

 

[G50]

How did you learn about lungs' reserve air and volume of oxygen dissolved in blood? Do you have sources to link or cite? I ask since inventor of the R2D Rebreather lll (Richard Avery as I recall) may read this and improve the device. That is in all our interests.

Do you have any other ideas or suggestions that could help them make a better product?

There is some discussion about the amount of oxygen in the blood (which is mainly attached to the haemoglobin of the red blood cells), and also the amount of lung reserve oxygen, in this thread: 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?!

In that thread it discusses that with the standard inert gas method, I think the inert gas may actually help suck out the oxygen from your red blood cells, so hastening the arrival unconscious. But you don't get that oxygen removal with the debreather method, because air expelled from your lungs goes back into the debreather reservoir bag, and is breathed back in again.


Regarding the sources you asked for:

In that thread, this post explains that even after you fully exhale, there is a residual amount of air left in the lungs, which is about 1 litre in volume (corresponding to about 200 ml of oxygen gas, since oxygen is found at 21% in air). That info comes from timecode 2:49 of this video.

I made a mistake in my post on another thread here when I said there was 1 litre of residual oxygen in the lungs when you fully exhale; in fact there is only 200 ml of residual oxygen in the lungs.

As for the amount of oxygen stored in the bloodstream, this post gives a reference, which I paste here: 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).

Thus in total, there is about 1200 ml of oxygen stored in the body, 1000 ml in the blood, and 200 in the lungs.


This stored oxygen I believe may be the part of the problem I have been running into when testing my homemade debreather. I think the stored oxygen may prevent you from losing consciousness quickly, and so you then become aware that you are short of oxygen, and start breathing more rapidly in a slightly panicky manner, because your body senses the low oxygen.

One possible solution to this panicky rapid breathing might be to take drugs which inhibit the hypoxic ventilatory response (HVR). The HVR increases your respiration rate when low oxygen is sensed in the body.

I read that certain drugs, especially benzodiazepines, but also to a lesser extent ibuprofen, can inhibit the HVR. References in this post above. So it's possible that if you took some benzodiazepines and ibuprofen say 2 hours before using the debreather, you might not get as much panicky rapid breathing.


The other solution might be to use a larger volume of inert gas (such as nitrogen) in your debreather reservoir bag. If you had a debreather reservoir bag with a volume of say 100 litres, then this brings the debreather method closer to the standard inert gas method with an exit bag over your head. This is because in a larger 100 litre debreather reservoir bag, the 1200 ml of oxygen in your body when expelled from your lungs will get diluted down in the 100 litre bag, so then you won't be breathing that oxygen back in again.

 

[MBG]

Thank you for the thoughtful reply. I hope Mr Avery sees it and makes adjustments to the device so that it may fulfill its promise.

Three things: (1) I thought the breathing reflex was driven by rising blood CO2 levels, not falling O2?

(2) Would adding back in a CO2 scrubber help?

(3) How many of the small, readily available and easily purchased nitrogen gas cartridges currently used by the device be required by a large reservoir bag device as you describe?

 

[G50]

(1) I thought the breathing reflex was driven by rising blood CO2 levels, not falling O2?

That's what I thought too, so I could not understand why I was getting these intense urges to breathe fresh are, and a panicky increased respiration rate, when testing out my homemade debreather, which contains a CO2 scrubber. But one person in this above post explained that while rising blood CO2 may be the main factor driving the breathing reflex, low O2 is also sensed by the body, and is an additional driving factor. This would make sense from my experience.

(2) Would adding back in a CO2 scrubber help?

In my own homemade debreather (pictured in the first post of this thread), I had a good CO2 scrubber, but it did not solve the problem of low oxygen.

(3) How many of the small, readily available and easily purchased nitrogen gas cartridges currently used by the device be required by a large reservoir bag device as you describe?

If those nitrogen cartridges contain 18 grams of nitrogen, then using this online gas volume calculator, that would equate to about 14.4 litres. So you would need 7 of these cartridges to obtain a volume of 100 litres.

All you would then need is a 100 litre plastic bag, connected to a good face mask. The face mask I used for my debreather are the anaesthesia face masks. These form a tight seal to the face, so a re good for this purpose. I think one would effectively be performing the inert gas method with such a large 100 litre volume of nitrogen.

Though I question whether even with the inert gas method, if you might still get this panicky desire to breathe fresh air. I would like to do a test run using a 100 litres of nitrogen, to see whether unconsciousness came quickly, or whether you get a desire to breathe fresh air. In a test run, one could hold the face mask to your mouth using your hand, so that if you did momentarily lose consciousness, your arm would drop and the mask would fall off your face, and then you would regain consciousness as you started breathing air.

 

[MatrixPrisoner]

You gotta find a way to be unconscious while all this happens. So that any autonomic survival instinct tendency is removed from the equation. Binge on sleeping pills and alcohol

 

[casual_existence]

You gotta find a way to be unconscious while all this happens. So that any autonomic survival instinct tendency is removed from the equation. Binge on sleeping pills and alcohol

If it's an autonomic response then it probably isn't enough to knock yourself out. An anesthetic would probably be better since even if the response is activated the body won't be able to respond.

 

[MatrixPrisoner]

If it's an autonomic response then it probably isn't enough to knock yourself out. An anesthetic would probably be better since even if the response is activated the body won't be able to respond.

I think being in deep sleep is enough to suspend the conscious survival instinct, because you see how many accidental CO deaths happen people while people are sleeping.

 

[G50]

Related thread:

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?!

 

[penguinl0v3s]

It's not that simple. There are two drives which provoke the instinct to breathe.

The primary and most immediate one in most people is the hypercapnic drive.
This is the one that you have heard about wherein a CO2 buildup in the blood is recognized by certain chemoreceptors. To make a long story short, this causes the panicky feeling of needing to breathe and the sensation of asphyxia.

However, we have a second drive called the hypoxic drive.
When the body has undergone mild and chronic hypercapnia, it will begin to adapt and use oxygen-sensitive chemoreceptors to regulate respirations. In layman's terms, if you have been mildly hypoxia for a while, your body learns to directly measure the O2 in the blood (rather than the CO2), and uses that to tell you when you need to breathe. This "transition" from the hypercapnic (high CO2) drive to the hypoxic (low O2) drive is most commonly seen in those with a history of COPD, but I might guess that if it's not a matter of equipment dysfunction, that it could be this.

Dangit, you beat me to it!

Woah, that's very cool. I didn't know it existed. Do you have a paper or research journal on it by chance? I would love to read more.