increased PO2 at depth

[cruiser]

Hey Cruiser:

Are you Nitrox Certified? I looked at your Public Profile, but it is not listed. Review Boyles Law of compressed gases at depth. With Nitrox, you do uptake more O2 than typical air (79%N - 21%O2). But your body metabolizes SOME of this. That is why we have an MOD (Max Operatating Depth) for the different percentages of enriched O2 we breathe. All Nitrox computers have a CNS Clock (Central Nervous System Clock) to monitor the extra O2 breathed. Before I list a few other things, let me know if you are Nitrox Certified. If you are, reviewing your text will help you.

Safe diving to you.

NC--

Yes, I am nitrox certified, and dive nitrox when on dive vacations. At CocoView in Roatan, and in Aruba, I do a lot of shore diving and watch my CNS clock. My max has been 88% on a given day. Also, I have my dive computer set for 1.2 PO2 because I dive solo mostly and am more comfortable with 1.2 than 1.4. So at EAN32 my MOD at 1.2 is 90 feet, at EAN34 my MOD is 83 feet. I don't generally dive below 50 feet so these MOD's are more than enough for me. The more I think about it, though, the more questions that kept popping up so thought I would post here Especially in light of the fact that at 4 atmospheres the air is being delivered at the ambient pressure; it just seemed like there would be unused O2, I just didn't have an idea of how much O2 was going unused.

 

[cruiser]

I don't recall having this effect. But remember as mentioned above, you have 2 gases affecting your body under pressure. You have the oxygen. The effects of increased oxygen should not be much until you start to deal with oxygen toxicity.

Pat--I haven't had this effect either, and wondered about it. Although when I took the nitrox class, increased oxygen was promoted as one of the advantages of diving nitrox, having more energy because of the extra oxygen in the mix. Now I'm thinking the benefit of increased oxygen is that it decreases the nitrogen.

The other thing you have is the increased nitrogen.

When you dive with nitrox, the increased oxygen probably has almost no effect unless you go deep enough to get into oxygen toxicity.

But when you dive at depth, you have increased nitrogen uptake and the narcotic effects of nitrogen under pressure.

The deepest I've dove is 136 feet in Cozumel, Santa Rosa wall. I was a very new diver, fascinated with all the marine life and was at 136 feet on air before I knew it. The DM was banging on his tank from above, telling me to ascend. He was on nitrox so wasn't as deep as I was. Thinking back, I don't recall feeling narced, but I wasn't performing tasks under water either, which is where impairment shows up.

 

[Dr Deco]

Hello cruiser:

The lungs are underutilized – at rest. The system has developed such that the lungs will work successfully during exercise. This is especially so during exertion such as running to escape prey. This is true for all mammals of which humans are an example.

The other responders have given nice answers that I will not repeat.

Dr Deco :doctor:

 

[NC Wreck Diver]

NC--

Yes, I am nitrox certified, and dive nitrox when on dive vacations. At CocoView in Roatan, and in Aruba, I do a lot of shore diving and watch my CNS clock. My max has been 88% on a given day. Also, I have my dive computer set for 1.2 PO2 because I dive solo mostly and am more comfortable with 1.2 than 1.4. So at EAN32 my MOD at 1.2 is 90 feet, at EAN34 my MOD is 83 feet. I don't generally dive below 50 feet so these MOD's are more than enough for me. The more I think about it, though, the more questions that kept popping up so thought I would post here Especially in light of the fact that at 4 atmospheres the air is being delivered at the ambient pressure; it just seemed like there would be unused O2, I just didn't have an idea of how much O2 was going unused.

Hi Cruiser:

OK, maybe reviewing your Nitrox text will answer a few questions for you. Let's talk about the O2 that we breathe out. If we didn't exhale a good amount of O2, CPR would be worthless (at the surface, of course). Think about it (all surface conditions), compressions are extremely important, but the O2 that you put into a victim is needed to oxygenate their blood. This is what I was taught in Rescue, years ago. I am not an EMT. I can deliver pure O2 to a breathing victim, but only an EMT is trained to use a demand regulator to a person not breathing. Not me. So, I take the pure O2, breathe it in myself, and deliver it to a victim. It's ramping up the O2 that is not being used in my own system.

So to get back to diving, we typically breathe in air at 21%, and exhale about 15-16%. Please don't quote me on these exhale percentages, I have to go look them up again. But our bodies use a fair amount less than the 21% we breathe in. So equate this to the questions that you are asking, and you can understand some of the points being made by other divers posts. You are right on about CCR (rebreathers), and the small tanks of 100% O2 and Diluent that they carry, along with the scrubbing particulate to absorb the CO2. Hope this helps, along with the other divers posts.

Safe diving to you

 

[cruiser]

Hi Cruiser:

OK, maybe reviewing your Nitrox text will answer a few questions for you. Let's talk about the O2 that we breathe out. If we didn't exhale a good amount of O2, CPR would be worthless (at the surface, of course). Think about it (all surface conditions), compressions are extremely important, but the O2 that you put into a victim is needed to oxygenate their blood. This is what I was taught in Rescue, years ago. I am not an EMT. I can deliver pure O2 to a breathing victim, but only an EMT is trained to use a demand regulator to a person not breathing. Not me. So, I take the pure O2, breathe it in myself, and deliver it to a victim. It's ramping up the O2 that is not being used in my own system.

So to get back to diving, we typically breathe in air at 21%, and exhale about 15-16%. Please don't quote me on these exhale percentages, I have to go look them up again. But our bodies use a fair amount less than the 21% we breathe in. So equate this to the questions that you are asking, and you can understand some of the points being made by other divers posts. You are right on about CCR (rebreathers), and the small tanks of 100% O2 and Diluent that they carry, along with the scrubbing particulate to absorb the CO2. Hope this helps, along with the other divers posts.

Safe diving to you

Very helpful, thanks. My nitrox book gives basic info, but was lacking on the why's and that's what I found I had further questions on

 

[DocVikingo]

Is it also placebo to feel more energized after diving enriched air nitrox?

Hi Cruiser,

Although a number of divers claim to "feel more energized after diving enriched air nitrox," there is no compelling evidence that EAN reduces fatigue.

Regards,

DocVikingo

 

[DocVikingo]

So to get back to diving, we typically breathe in air at 21%, and exhale about 15-16%. Please don't quote me on these exhale percentages, I have to go look them up again.

Hi NC Wreck Diver,

15% plus/minus 1% is an accurate figure.

Regards,

DocVikingo

 

[NC Wreck Diver]

Hi Cruiser,

Although a number of divers claim to "feel more energized after diving enriched air nitrox," there is no compelling evidence that EAN reduces fatigue.

Regards,

DocVikingo

+1 on your comment DocVikingo............My buddies would swear by it. But I didn't see the difference. I think they just got better sleep the night before a dive and laid off the six-packs. I was always the designated driver..........

 

[Peter Guy]

Cruiser asked

So the N2 keeps being absorbed until the blood is saturated or you start to ascend?

Short answer -- yes.

Longer answer -- ALL gasses will continue to be absorbed by the various body tissues (not only blood!) until the tissues reach equilibrium with the partial pressure of the gas(ses) surrounding the tissues. When you start to ascend ambient pressure decreases, thus the pressure of the gasses entering your lungs decreases (therefore fewer total molecules). As the pressure decreases, the gasses in your tissues will continue to achieve equilibrium with the partial pressure of the gasses surrounding the tissues. Since the surrounding pressure is now less, the gasses will start to flow out of the tissues. [Note -- this is the simplistic description!]

As a practical matter, the only way we can get the gasses out of our body is the same way they get into our body -- through our lungs which means the blood stream is the prime transporter to, and from, all the tissues.

And just maybe, if the difference between the partial pressure in the tissue and the partial pressure in the lungs is too great, bubbles will be created. But don't quote me on that!

 

[DCBC]

And if we are processing all these extra molecules, wouldn't that indicate that our alveoli are woefully underutilized at the surface?

You've already had some great answers. In summary, regardless of depth, O2 is consumed by the body by molecule, but a volume of gas is required to wash-off the CO2. In open-circuit, much of the O2 is lost through expiration. A closed-circuit rebreather can deliver a much larger duration of breathing mixture to the diver because the dillutent is a filler gas used to wash out the CO2, the CO2 is absorbed by the absorbant and oxygen is consumed and nothing is lost to the environment.