Nitrox's O2 toxicity VS O2 in hospitals

[JonOh]

So I was wondering why patients breathing 100% 02 in hospitals do not suffer from O2 toxicity. Any ideas?

 

[rongoodman]

They don't suffer CNS toxicity because even at 100%, they're only breathing 1 ATA of O2, well below the safe limit. They will suffer pulmonary effects if kept for too long on higher concentrations, which are avoided whenever possible.

 

[TreyR]

They don't suffer CNS toxicity because even at 100%, they're only breathing 1 ATA of O2, well below the safe limit. They will suffer pulmonary effects if kept for too long on higher concentrations, which are avoided whenever possible.

What he said....

 

[raftingtigger]

Who says that 100% O2 use in hospitals doesn't carry oxygen toxicity risks? Increased O2 concentrations in neonates certainly has its risks. Medical oxygen is a drug and it is dosed as such. While I don't practice critical care medicine, 100% O2 use is rare. Just because you see a mask on a patient doesn't mean they are getting 100% O2. Even the non-rebreather masks can only deliver about 80% O2.

There are 2 major differences between medical oxygen use and diving use. Medical oxygen is used for long periods of time, often measured in days rather than minutes. Diving oxygen is used at higher than normal atmospheric pressures, but for much shorter periods of time.

If you use a 'safe' level of oxygen, say 1.4 atm, for diving then 100% O2 at sea level (by definition 1.0 atm) is less oxygen than what is considered safe for diving.

 

[HJeffreyM]

Because they are breathing that O2 at sea level (1ATA) or less. As you know from your Nitrox class (right?) there are two kinds of Ox-tox: 1) Central nervious system, which is a function of O2 partial pressure at depth, and 2) Tissue which takes a lot longer but does occur faster with rising O2 partial pressure.

Tissue ox tox would take a long, long time at sea level and is virtually unheard of in clinical settings.

 

[boulderjohn]

What everyone else said is true, but to take it a little further....

It is my understanding that for reasons that no one understands, O2 toxicity happens in water differently than on land. When a person is on O2 under pressure in a recompression chamber, they apparently have to go much "deeper" to have the same effect that would happen on scuba.

 

[Paladin]

Jacques Cousteau did some work in the 1940s that indicated that O2 at 2 atmospheres can be lethal. When diving air, that same concentration of O2 is reached at around 330 FSW. It was at about this depth that one of JYC's associates died during early SCUBA depth experiments.

 

[JonOh]

What everyone else said is true, but to take it a little further....

It is my understanding that for reasons that no one understands, O2 toxicity happens in water differently than on land. When a person is on O2 under pressure in a recompression chamber, they apparently have to go much "deeper" to have the same effect that would happen on scuba.

I did see one picture online, black and white, of a few people in a decompression chamber breathing 40% 02 at over 200ft (I think, I can't find the picture again to verify)

 

[pocky21]

During my chamber ride, they periodically "flushed" the tube with air to manage the PO2. You can seize in a chamber just as you can underwater - the physics and physiology doesn't change, it's just managed somewhat easier in a clinical setting.

 

[rlynch]

Don't forget the mechanics were trying to avoid with o2 tox... Water. You can seize in 1 Ata it just takes longer but generally your fine. Pilots seize at height as well.

But at depth in water, we have WATER around us. So you seize, you breath water, and that's it, you die.

In a chamber at 200ft you seize, you breath ambient gas......it sucks... You probably won't die from drowning...

For a diver it's all about not breathing water, not how much O2 you can Stand.

Every calculation we make for a dive should be based on not reaching an O2 limit and seizing at depth....