High PO2 levels for recompresion question

[WonderSlug]

Howdy

Im taking a NAUI Nitrox course and one of the tables in the book talks about the various levesl of PO2 with mixes and what they are used for.

One of the examples is a PO2 level of 3 for a 50/50 mix at 6 atm. It says this is used for recompresion treatment.

What i cant seem to get past is based on what im learning that this is a very CNS toxic O2 level.

Is the NAUI manual correct?

If it is how is this not toxic for the person being treated?

Thanks
-=WonderSlug

 

[Charlie99]

WonderSlug once bubbled...
Howdy

Im taking a NAUI Nitrox course and one of the tables in the book talks about the various levesl of PO2 with mixes and what they are used for.

One of the examples is a PO2 level of 3 for a 50/50 mix at 6 atm. It says this is used for recompresion treatment.

What i cant seem to get past is based on what im learning that this is a very CNS toxic O2 level.

Is the NAUI manual correct?

If it is how is this not toxic for the person being treated?

Thanks
-=WonderSlug

I don't know about 50/50 at 6atm, but a very standard treatment is 60' on 100% O2, which is a tad over 2.8ppO2. 5 minute air breaks every 20 or 25 minutes. Google on USN Treatment Table 6 for more detailed info.

Yes, there are some incidents of oxtox in the chamber, but not all that many, and convulsions in a chamber aren't all that dangerous.

Susceptibility to oxtox varies widely from individual and even for a single individual, it varies widely from day to day. That is why the US Navy no longer puts its divers through an oxtox test.


A convulsion underwater has a high probability of resulting in the death of the diver due to loss of reg and drowning. So considering the wide variation in onset of symptoms, it makes sense to use very large safety margins.

Remember that if you need to rescue someone that is below your MOD.

 

[BigJetDriver]

Charlie99 once bubbled....

(1)...a very standard treatment is 60' on 100% O2, which is a tad over 2.8 PPO2. Five (5) minute air breaks every 20 or 25 minutes. Yes, there are some incidents of oxtox in the chamber, but not all that many, and convulsions in a chamber aren't all that dangerous...(in the overall scheme of things!...Ed!)

NOTE: NAVY TREATMENT TABLE 6 SHOWS 20 MIN O2, THEN 5 MIN AIR, AND SO ON TO 1:15, WHEN BOTH INTERVALS GET LONGER. (Insert by Ed.)

(2) Susceptibility to oxtox varies widely from individual and even for a single individual, it varies widely from day to day. That is why the US Navy no longer puts its divers through an oxtox test.

(3) A convulsion underwater has a high probability of resulting in the death of the diver due to loss of reg and drowning. So considering the wide variation in onset of symptoms, it makes sense to use very large safety margins.

(4)Remember that, if you need to rescue someone who is below YOUR MOD! (Emphasis mine, Ed.) [/B]

These are all excellent points that Charlie has made and deserve special emphasis!

 

[Dr Deco]

Dear Readers:

High Pressure and DCS

High pressure (6 ATA fsw) has been generally employed to treat arterial gas embolisms. The concept is that the gas bubble is reduced in size, and it can pass through the capillary channels. The actual mechanism, I believe, is that the gas “bubble” (generally thought of as spherical) in the capillaries is “sausage shaped.” As the pressure is increased, the length of the bubble is reduced. Twice the pressure will reduce the length by one half. When a gas phase is lodged in a capillary, there are surface forces that retard is movement. Reducing the length is one method of allowing blood pressure to push it through. (Note that, except for “decreasing the size of the bubble,” this explanation is different than what is generally given.)

50/50

The increased pressure is good for contracting a bubble's length, but pure oxygen is toxic. Thus, a few decades ago, a plan was proposed to increase oxygen up to its usable maximum (3 ATA) and top it off with nitrogen to produce the final pressure of 6 ATA.

Dr Deco :doctor:

Readers, please note the next class in Decompression Physiology :grad:
http://wrigley.usc.edu/hyperbaric/advdeco.htm