Surface oxygen and CNS O2 toxicity

[Superlyte27]

That's pretty interesting.
And shouldn't be the norm Rjack. When we treat in a chamber of course we know that an 02 hit is possible. So we look for signs of this. Often times there's a tech/tender in the chamber with the injured diver (on air) incase something does happen, like convulsions or unconsciousness. The tender/tech can remove the O2 to stop the convulsions.

The fact still remains, if you are bent, and at a facility administering hyperbaric medicine, you are going for a chamber ride, whether there is risk of O2 hit or not.

And commercial divers unfamiliar with CONVENTID went to the wrong school or slipped through the cracks.

 

[Duke Dive Medicine]

Thanks for bringing this up, maybe Duke Dive Medicine will comment on the far less serious consequenses of taking a 'hit' in a chamber.

There's no real physiologic reason to refuse to treat a diver with DCS who's been using nitrox. In fact, it could be said that doing so would constitute a "failure to treat". Though it might be theoretically possible for a diver to develop pulmonary oxygen toxicity during treatment following extended dives using hyperoxic mixes, the risk of not treating the diver exceeds the risk of pulmonary O2 toxicity.
We rarely see central nervous system O2 toxicity during treatment, even at O2 partial pressures exceeding 2.8 ATA (our deepest treatment using 100% O2 is 68 feet, used for gas gangrene). If we do, it's normally associated with hypoglycemia, which lowers the seizure threshold. Our procedure is simply to remove the patient from oxygen and wait for the seizure to subside. We can administer benzodiazepines such as lorazepam (Ativan) for severe tonic/clonic activity, and if the patient really needs the oxygen, we can use benzos or phenobarbital prophylactically.
Immersion greatly increases the risk of CNS O2 toxicity, which is why we see pO2 limits such as those discussed here. Obviously, a seizure underwater is a catastrophic event, especially if the diver isn't using a full face mask. Thanks to everyone for keeping the discussion interesting.

 

[Lobzilla]

Thanks Duke Diving Medicine for sharing the additional info about treatment regimens that are obviously not covered in the normal diver education. Please keep it coming.

From the initial report is was not quite clear whether the individuals in question refused O₂ inside or outside the chamber or both.

 

[MXGratefulDiver]

Thanks Duke Diving Medicine for sharing the additional info about treatment regimens that are obviously not covered in the normal diver education. Please keep it coming.

From the initial report is was not quite clear whether the individuals in question refused O₂ inside or outside the chamber or both.

In fact, these treatment regimens are covered in normal diver education, if the course is taught as intended.

The original post stated that both divers refused surface oxygen, which would imply outside the chamber, since hyperbaric treatment is administered under pressure (i.e. not at surface pressure).

I suspect a part of the confusion is due to the fact that O2 toxicity and DCS can both result in similar symptoms ...

... Bob (Grateful Diver)

 

[manni-yunk]

Thank you Duke Dive Medicine



This is one of the most interesting threads Ive read on SB in my short time here.

 

[Duke Dive Medicine]

"The original post stated that both divers refused surface oxygen, which would imply outside the chamber, since hyperbaric treatment is administered under pressure (i.e. not at surface pressure)."

Both divers refused surface oxygen aboard their dive boats. They were happy to get O2 once they came to us.

Update: Diver 1, the nitrox deco diver with the spinal cord DCS, is able to walk much better but is still not able to urinate. We are treating him again today with our clinical patients at 2 ATA. Diver 2, the diver with inner ear DCS, was discharged home after being tested in the ENT clinic. He has persistent vertigo and hearing loss. He lives out of state and will follow up with a hyperbaric clinic closer to home.

There are some morals here for all divers: if you think you may be bent, don't go diving again, especially in that river called Denial. Use as much surface O2 as somebody is willing to give you. Above all, seek treatment immediately, don't wait.

 

[Lobzilla]

In fact, these treatment regimens are covered in normal diver education, if the course is taught as intended.

I meant the supression of tonic/clonic response to the increased ppo2 which is clearly outside of the realm of scuba instruction.

The original post stated that both divers refused surface oxygen, which would imply outside the chamber, since hyperbaric treatment is administered under pressure (i.e. not at surface pressure).

Rather than speculating, I wanted to know exactly where the divers refused O₂ for the following reason: There are numerous stories that O₂ is administered in lieu of (or delaying) hyperbaric treatment by emergency room staff that is not familiar with DCS, its symptoms, and its consequences. Once the divers were at Duke that was obviously not a concern anymore but we did not know (until Duke Diving Medicine clarified) where exactly the divers balked at the use of O₂

 

[MXGratefulDiver]

There are some morals here for all divers: if you think you may be bent, don't go diving again, especially in that river called Denial. Use as much surface O2 as somebody is willing to give you. Above all, seek treatment immediately, don't wait.

This bears repeating ... and emphasizing ...

... Bob (Grateful Diver)

 

[Gdon]

Sorry. Typo. We go by the Navy Diving Manual, which says that working dives with a pO2 greater than 1.4 are not permitted. Thanks for catching that.

It appears that your FACEBOOK discussion posting still has the typo.
( http://www.facebook.com/topic.php?uid=334685176868&topic=14128 )
I know it confused the heck out of me when I read it there.
I suggest a correction on your Facebook WALL to help insure that those who already read the discussion on FB with the mention of a 1.2 max will see it. (Maybe also a clarification of the reported growing acceptance of a 1.2 max for some scenarios.)

thanks for the info too.

 

[Duke Dive Medicine]

Gdon: yes, it does, busy trying to keep up with other stuff here. Thanks for joining us on Facebook.