helium before diving

[badgers]

what would happen if I were to breathe 50% oxygen and 50% helium for 2 hours before diving with 29% nitrox to a depth of 130 feet?
bottom time 15 minutes?

just wondering
thanks

 

[Packhorse]

You would get a squeeky voice.

 

[Rick Murchison]

You'd have thrown away $50 worth of Helium, and $10 worth of Oxygen.
(Your nitrogen absorption would "catch up" very quickly; while theoretically you'd have given youreslf a bit of an edge by flushing your system of nitrogen before the dive, it really ain't enough to spit at. A waste of money)
Rick

 

[do it easy]

In theory, you would get rid of some of the nitrogen out of your body. How much is another question.

I believe the astronauts do something similar when they go on space walks, although they breathe pure oxygen beforehand and the pressure difference is reversed. OK, maybe they do the complete opposite. At any rate, when they leave the shuttle/space station in their space suit, they are at reduced pressure and would be at risk of getting bent (in space!) if they had a "normal" amount of nitrogen in their body.

I'm not an astronaut, but this is my understanding from watching TV, mostly the Simpsons and 24.

 

[badgers]

thanks

 

[fppf]

Do It Easy
You are very correct.
The shuttle's cabin pressure is 1 ATA with a 20% O2 80% N2 mix.
Before suiting up for an EVA they breath 100% O2 for a few hours to off gas, its basiclly doing deco. The EVA suits are at .34 ATA, they would get bent if they did not off gas before hand. Also because the pressure is so low they breath 100 % O2 during the EVA, even then there PPO2 is only .34 ATA.

They also are on 100% O2 during launch and reentree, incase there is a sudden loss of cabin pressure.

 

[Rick Murchison]

... from watching TV, mostly the Simpsons and 24....

I don't believe I'd have admitted that!
Rick

 

[h90]

I don't believe I'd have admitted that!
Rick

Considering the knowlege from the Simpsons, it might bring an benefit if we can vacuum ourself somehow with a vacuumcleaner to get rid of the n2. (I not yet finish with the drawings of my 02 vaccumcamber....

 

[Dr Deco]

Hello readers:


Helium and Oxygen

You would not gain much by breathing these gases. If you were to do this, eliminating the helium and breathing only oxygen would be better. Helium contributes to bubble growth just like nitrogen.

Even pure oxygen will not gain much for you as a diver. At pressure, you gain nitrogen quickly.


Astronauts

Hypobaric (altitude) exposure is a different matter. When going to altitude, you need to eliminate the nitrogen stored in your tissues; you are also breathing oxygen at altitude. With oxygen in the mask, you will have no inert gas uptake.

Astronauts prebreathe oxygen before EVA [extravehicular activity] because the pressure in the suit is 4.3 psi - equivalent to 30,000 feet.

The current prebreathe procedure at NASA is one I helped develop when I was at the Johnson Space Center.


Dr Deco :doctor:

 

[h90]

If I understand it right (sorry in advance for my english):

Considering I have no N2 in my body (and for the making the example easier my body is just blood).

If I get now 2.4 bar N2 (approx 30 meter). The rate of absorbation will be very high on the beginning and will slope in a round curve, thouching zero at infinity.

While the N2 level will start at 0 will increase fast to close to the maximal amount for that pp but getting it at infinity.

So when I start with 0 N2 (instead of my normal amount) I only safe that amount at the highest rate of adsorbation, so it is a minimal benefit.

Hope that english is understandable.....
Do you agree with my thoughts?
Michael

Hello readers:


Helium and Oxygen

You would not gain much by breathing these gases. If you were to do this, eliminating the helium and breathing only oxygen would be better. Helium contributes to bubble growth just like nitrogen.

Even pure oxygen will not gain much for you as a diver. At pressure, you gain nitrogen quickly.


Astronauts

Hypobaric (altitude) exposure is a different matter. When going to altitude, you need to eliminate the nitrogen stored in your tissues; you are also breathing oxygen at altitude. With oxygen in the mask, you will have no inert gas uptake.

Astronauts prebreathe oxygen before EVA [extravehicular activity] because the pressure in the suit is 4.3 psi - equivalent to 30,000 feet.

The current prebreathe procedure at NASA is one I helped develop when I was at the Johnson Space Center.


Dr Deco :doctor: