windapp
Contributor
All good answers. Just one thing to add. You never dive for long enough to get pulmonary toxicity which is the primary concern with 100% O2 in a hospital setting.
Nitrox's O2 toxicity VS O2 in hospitals
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KD8NPB
Contributor
Henry's Law.
Utilizing NOAA 1 (EAN32) at 130 ft results in a ppO2 of 1.6.
The easy way to think of this, is your body is ingassing 160% o2...you are supersaturating with O2.
The same holds true for nitrogen as well. On the surface, your ppN2 is 0.79. At 66 ft, your ppN2 is 2.37. You are slowly supersaturating with N2. Since the number is greater than 1.0, your body will begin ingassing nitrogen until your body is at equilibrium with the surrounding environment. This is the basis around how diving tables are formed.
The ppN2 is less than 1.0 above 30 ft, which is why some dive tables show an infinite dive time in the 0 to 30 ft region... Your body cannot become supersaturated with nitrogen, thus, you will never be required to stop to allow your body to reach equilibrium to the surrounding pressure. The slightly elevated partial pressure of oxygen helps too, but that is another chapter on dive physiology altogether.
Utilizing NOAA 1 (EAN32) at 130 ft results in a ppO2 of 1.6.
The easy way to think of this, is your body is ingassing 160% o2...you are supersaturating with O2.
The same holds true for nitrogen as well. On the surface, your ppN2 is 0.79. At 66 ft, your ppN2 is 2.37. You are slowly supersaturating with N2. Since the number is greater than 1.0, your body will begin ingassing nitrogen until your body is at equilibrium with the surrounding environment. This is the basis around how diving tables are formed.
The ppN2 is less than 1.0 above 30 ft, which is why some dive tables show an infinite dive time in the 0 to 30 ft region... Your body cannot become supersaturated with nitrogen, thus, you will never be required to stop to allow your body to reach equilibrium to the surrounding pressure. The slightly elevated partial pressure of oxygen helps too, but that is another chapter on dive physiology altogether.
So what about the same pp of 02 but in a chamber VS water. Will the effects of O2 toxicity be the same? There was a previous poster that said water might have a bigger effect on how the body gets 02 toxicity and it might actually be worse.
windapp
Contributor
ppN2 is 1.0 at 8.77 ft. You are correct that you would have an infinite dive time with a ppN2 of 1.0, but no specifically because it is 1.0 atm.
In the case of nitrogen, you are ongassing as long as the level in your tissues is less than the level you are breathing, so at 8.77 feet, you will definitely be on-gassing nitrogen initially as your tissues will start out with a ppN2 of of 0.79.
---------- Post added March 7th, 2013 at 02:15 PM ----------
I have never seen anything suggesting that O2 toxicity is different in the water. However, if you have a seizure in the water, you die. If you have a seizure in the chamber, you live.
windapp
Contributor
Where did you get this info? My understanding is that the incidence of CNS oxygen toxicity while diving is so low that there wouldn't be any way to actually do a statistical comparison.
There are a few differences here. Most often you are not breathing 100% O2 in a hospital. You may have a mask on but your likely mixing regular air with a little 100% O2. That's why if your suffering from a DCS hit you want that O2 delivery system cranked up to 15 lpm.
Also when diving your breathing that O2 at depth and under pressure so the PP is greater then at sea level.
The chambers will also take air breaks when doing DCS treatments. I can't remember the exact numbers but the standard Navy treatments is something like 20 minutes on O2 then 5 minutes off. Again those numbers may be wrong but it gives you an idea.
Seizing in a chamber or elsewhere in a hospital is not as life threatening as it is when underwater.
Also when diving your breathing that O2 at depth and under pressure so the PP is greater then at sea level.
The chambers will also take air breaks when doing DCS treatments. I can't remember the exact numbers but the standard Navy treatments is something like 20 minutes on O2 then 5 minutes off. Again those numbers may be wrong but it gives you an idea.
Seizing in a chamber or elsewhere in a hospital is not as life threatening as it is when underwater.
Just my 2 cents. The main concern for diving is CNS also called Paul Bert effect which is mainly caused from O2 breathed at more than 1.6 Bar for a short period of time while in Hospital the main concern is Pulmonary Toxicity also called lorrain smith effect that is caused by breathing O2 with a PPO2 higher than 0.5 but during a long period of time. These two limits are followed on a dive planning in order to allow a proper recompression treatment without causing more damage. This is clearly reflected for instance in the NOAA Exposure Limits table.
Took me a while to find the reference: http://www.scubaboard.com/forums/ma...y/440726-oxygen-toxicity-limits-symptoms.html
Hey, but what would the US Navy know about diving
Took me a while to find the reference: http://www.scubaboard.com/forums/ma...y/440726-oxygen-toxicity-limits-symptoms.html
Hey, but what would the US Navy know about diving
Thank you! your post appeared just before I was about to search for the same thing.
For those wishing to save some reading time, here is the relevant paragraph:
Check out this post as well: http://www.scubaboard.com/forums/technical-diving-specialties/448341-air-breaks-cns.html#post6666201
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