Oxygen use while breatholding?

[donmoore]

I recently took an Oxygen administration class and CPR with first aid and one of the things they repeated often is we inhale air with approximately 21% oxygen and exhale 14% . So basically we only use 33% of the available oxygen. They say this in the context of artificial respiration, but use it in other contexts as well. One thing I questioned, is how does the time the air is in the breathing cavities effect the amount of oxygen absorbed?

It seems to me that in a CPR situation where the air is only in the provider's lungs for 2 seconds, absorption would not be much (probably less than 33%), but in a breathhold it would be much more than 33%. Does anyone know anything about this? What about the air in the breathing outside of the lungs and their alveoli, such as the throat? Will it circulate down into the lungs so the alveoli can draw oxygen from it? Maybe that is what contractions help do, because I usually feel better after having one.
don

[bobbybuttr]

Interesting questions Don. I don't know the answers, but I look forward to hearing from someone who does.
Bobby

[Bill]

Don
Until you get a better answer, let me talk about my understanding based on answers from medical folk over the years. Some of this is bound to be false info.
The old figures were inhale 20% O2 and exhale 15%. The body regulates the rate and depth of inhalations depending on O2 required and blood saturation stays near 100%. At rest I seem to exchange less than one litre, 8 times per minute. Climbing a hill results in 3-4 litres, 20 times a minute. Unless you are trained for it, when the O2 inhaled drops much below 10% you will black out. I'm guessing that your 21% in and 14% out will keep the blood fully saturated. If you exchange 5 litres, you only have to breath once per minute at rest.
Any dead space would be subtracted from the air exchanged by a factor of almost two. Think of a snorkel, the air that goes deepest into your lungs is only 14% to start with.
Contractions are interesting. The body is trying to do something but I think O2 use is slow enough that diffusion wouldn't allow O2 to stay in one place.
Please refer to my second sentence again.
Aloha
Bill

[choppiewater]

Hello,

After reading this post I have been thinking about ways to test this idea. At work we have some Nitrox (O2) sniffers. What I was thinking was to first do a baseline reading of one deep inhale followed by an immediate deep exhale into a big bouncy balloon which is rubber band tied to the intake of the sniffer. then start doing breath-hold of increasing duration and see if there is any significant change from the bassline reading. I really don't know what i will find but if anyone else has a sniffer and is bored too. . .

earlier today, i just blew into it once, right into the intake, slowly, like a relatively deep exhale which took about, say 15 seconds, and at the end it had moved from 21% down to 12%, rather linearly through the exhalation's duration. don't know what to think about it though. i'd figure if i blew it into the balloon a few times, the sniffer would take an average.

will post my findings when i get a chance.

does anyone find this design problematic?

-aloha,
mark