Newbie Nitrox question; affects ventilatory rate?

[CODMAN]

Hi all, sorry for this newbie question that some might find stupid. I don't know much about Nitrox, so I'm asking this question out of curiosity... So please don't blast me... Educate me!

I know the basic benefits of Nitrox, but was wondering about another possible benefit...

Since Nitrox has More O2 in it than air, won't breathing it also increase the CO2 exchange with your blood, thus reducing CO2 levels of your blood more efficiently/faster? And since CO2 concentration of your blood, to the best of my knowledge, is what determines ventilatory rate (breathing frequency), wouldn't that help you breathe more slowly, especially if producing an effort? And if breathing more slowly, increase duration of your dive at a given depth (tank would last longer)?

In other words, wouldn't Nitrox help make your tank last a bit longer? Especially if you are a natural "Vacuum cleaner"? Or am I completely off track here?:shakehead :shakehead

I'm sure the Nitrox course (which I'll probably eventually take) would answer my questions, but I was curious about this, and my scientific brain wants the answer NOW!!! he he!

So, can anyone shed some light on this? Is it ludicrous?:shakehead Does it make sense?

Thanks for your input!

 

[SparticleBrane]

I think you're "complete off track" here.

 

[Daner]

Interesting theory however I would suspect that the affect CO2 levels in the blood have on air consumption is relatively small compared to the other contributors like, comfort level in the water/at various depths, activity level and concious underwater breathing habbits among others.

 

[dherbman]

I think you're "complete off track" here.

Care to elaborate?

I've read there is a slight benefit ro SAC realized with EAN.
http://www.scubaboard.com/showthread.php?t=32813

 

[CODMAN]

Thanks Dhberman for the link! I hadden't found that string; must have been looking for wrong terms...:lol:

So my ideas, and knowledge of physiology, weren't all that bad! But I've still got more important things to improve, like efficiency, breathing smootheness, etc... that will improve my bottom times more...

But at least my scientific curiosity is satisfied!

Thanks again!

 

[TSandM]

The determinants of arterial pCO2 (which is what the body regulates) are CO2 production rate, which is determined by metabolic rate, and minute ventilation, or the total VOLUME of air passing through the lungs. It is entirely independent of the ppO2 inspired. Your body produces CO2 through metabolism, and sets your respiratory rate and volume to keep the pCO2 at 40 torr.

Think about it -- if high pO2s dropped your pCO2, then the deep divers using hypoxic mixes would all be severely hypercarbic, which is quite dangerous. Luckily, the two things are not linked in the way you suggest.

 

[CODMAN]

Hmmmm...

Yeah, but to my knowledge (and correct me if I'm wrong), the exchange of O2 molecules between air and red blood cells is passive and directly related to the partial pressure difference and the fact that hemoglobin has a higher affinity for oxygen than for CO2, thus the exchange of 1 molecule of CO2 on the red blood cell for a "fresh" O2 molecule happens without any active transport mechanism. Thus increase the PO2 and you increase the CO2 exchange rate, thus diminishing your CO2 levels in your blood more with each breath of Nitrox than with regular air, and consequently reducing your ventilation rate...

OK, know this is what I remember from my university courses and I haven't been to look in my books for a while, so I might be wrong (or partly wrong) on this ...

And anyways, as I said above, I have more important things that I can improve on first! And I think, like others, the main interest in Nitrox is the nodeco time it allows, if ever that becomes a limiter for me!:lol: The question of bottom time was just a theoretical question I was thinking about...

Thanks for your insight!

 

[TheRedHead]

Helium is easier to breathe at depth so it may decrease the chance hypercapnia because you struggle less to breathe. Air feels so thick at 130 feet. Maybe Trimix is your answer, Codman.

 

[TSandM]

CO2 is carried in blood in three different ways. Most of it (about 80%–90%) is converted to bicarbonate ions HCO3− by the enzyme carbonic anhydrase in the red blood cells. 5%–10% is dissolved in the plasma and 5%–10% is bound to hemoglobin as carbamino compounds. The exact percentages vary depending whether it is arterial or venous blood.

The CO2 bound to hemoglobin does not bind to the same site as oxygen; rather it combines with the N-terminal groups on the four globin chains. However, because of allosteric effects on the hemoglobin molecule, the binding of CO2 does decrease the amount of oxygen that is bound for a given partial pressure of oxygen.

From Wikipedia

Thus there is not a one-to-one exchange of CO2 and O2. Although there are some interrelationships within the blood, mostly related to pH changes with rising or falling CO2 levels (Bohr effect), for all practical purposes FIO2 does not affect pCO2 until hypoxic drive kicks in (at very low pO2s).

 

[CODMAN]

And I stand corrected Ts! I need to go back to the books and refresh those principles a bit!

Thanks for your input!