CO2 breath hold tolerance testing

[ADR]

I have been pondering on how to better measure CO2 tolerance and think the following method may be a way and tested it a little this morning. My motives for coming up with a test method is to then identify which method of CO2 training that we currently use best isolates CO2 training from hypoxic training and to find a way to gauge improvement accurately.

THE METHOD
•Inhaled air contains 79% Nitrogen and 21% Oxygen (ignoring trace gases)
•At the end of a breath hold the expired air will still contain 79% Nitrogen, some concentration of CO2 and a concentration of O2(less than 21%)
•An oxygen analyzer (you can make or buy these) will tell you the percentage of O2 and therefore the following equation will tell you the CO2

CO2 = 100 – 79(Nitrogen) – X(Oxygen)

If this is correct and you also have pulse oximeter (and I do ) then you can look for a method that gives you very high CO2 readings while maintaining an oxygen blood saturation above say 90%.(not hypoxic)

There are a number of assumptions in this method that could make all of this simply very poor science and I’m keen to hear what people have to say.

I tried two methods this morning just to see what CO2 readings I would get(without the pulse oximeter) and got the following results

1. PFI CO2 table (2min15) – CO2 after final breath hold 12.9%
2. 12 by 1min breath holds with 1 breath recoveries - CO2 after final breath hold 9.6%

....thoughts?

[cdavis]

Hats off to your logic, I love it. Roughly what does an 02 gas analyser cost?

Results seem a little surprising given my limited experiance. For example, I can't do 12 1 minute holds, 1 breath recovery, but a 2m15 PFI co2 table is no problem. Is there a huge individual variation or varabilty between tests or is there something other than co2 tolerance involved or ????.

Looking forward to other comments.

Connor

[ADR]

The 12 by one minute thing is not so hard if you do a slow(10-15sec) exhale/inhale. Are you doing the PFI CO2 tables that require 2 breath holds at the end of the sequence with only 15secs rest for each?

The analyzer itself is easy to build with parts from any electronics store (about $25). I have the plans if you want them. They are essentially the same as any scuba store uses for measuring nitrox/trimix. You plug it into O2 fuel cell and this bit will cost you about $90. Basically the the amount of O2 in the mix produces a voltage across the fuel cell that you can measure and given you can calibrate the thing to air at 20.9% you can then measure any exhaled sample. I'll take a pic of my unit tonight and add it to this thread if you want?

[Alexx]

Originally Posted by ADR

The analyzer itself is easy to build with parts from any electronics store (about $25). I have the plans if you want them.

That would be great Andy! Could you put it somewhere online, or should we PM you our e-mails?

[jome]

Correct me if I'm wrong, but it's not that straight forward.

If your RQ is less than 1.0 (which it most likely is), then as your o2 drops, less co2 is replacing it, so the total amount of gas is your lungs is decreasing.

Thus the % of N2 is increasing (as the total volume decreases but N2 remains constant) and the estimate is not very reliable.

Well, of course it does not matter, you don't have to know the ABSOLUTE values to be able to compare one performace to the other, you only need the difference. However interpersonal comparsions would be scetchy at best and of course, your own results as well depening on the conditions.

But if you know your RQ, at least within a reasonable margin, then you could get a reasonable estimate if you factor that in.

Also, in the beginning of the breath hold, unless you have hyperventilated very very hard, the air is most certainly not 79% Nitrogen and 21%.

[naiad]

I always use more volume of O2 than the amount of CO2 I produce - this must be true because I end up with less volume of air than I started off with. (Unless the CO2 is dissolved in blood etc.)

However, Andy's equation is useful to compare one performance to another. It certainly shows that the first table produces a higher CO2 level than the second one.

Lucia

[DeepThought]

CO2 is about 30 times more soulable in water than O2, I'm not sure how that translates to blood. On the other hand CO2's diffusion rate is slower than O2's - proportional to sqrt of molecular weight or something like that, so it takes more time to get rid of it.

This might suggest that your readings are lower than the amount of CO2 you should have produced.
On the other hand, I think I remember Eric F mentioning an exhaled volume of 10% CO2 on a breathold (measured with a more direct method I assume) is quite high.

Even if not calibrated properly, this kind of measuring might benefit you in finding which of your CO2 training routines exposes you to more CO2. Feel like comparing a few tables like those mentioned with apnea walking/stairwalking?

[naiad]

This is the thread Where Eric F mentions the 10% CO2...
Effects of high CO2

[ADR]

Here is a pic of my analyzer....still hunting through my docs for the plans

[ADR]

Here are some plans. They are a little different from the ones I used but essentially the same

The site listed in the plans sells kits or complete units if you don't want to source parts yourself.

[ADR]

Originally Posted by jome

Correct me if I'm wrong, but it's not that straight forward.

If your RQ is less than 1.0 (which it most likely is), then as your o2 drops, less co2 is replacing it, so the total amount of gas is your lungs is decreasing.

Thus the % of N2 is increasing (as the total volume decreases but N2 remains constant) and the estimate is not very reliable. .

Right you are , how is RQ measured?

Originally Posted by jome

Also, in the beginning of the breath hold, unless you have hyperventilated very very hard, the air is most certainly not 79% Nitrogen and 21%.

Dead air spaces do impact the inhaled lung percentages but air is still air and 21% before we inhale it. Essentially I just use it to calibrate the unit...which is fairly reliable if not exact.

[jimqpublic]

Curious question- how much oxygen remains in the exhaled air after a longish breath hold such as 4 minutes static or 2 minute dive?

Jim