P02 of 3.0 in a Hyperbaric Chamber?

debajo agua · Jun 8, 2012

After a recent visit to a Hyperbaric Chamber, I noted that ppO2 of 3.0 were acceptable. I was taken back, because in my Nitrox training, I was taught that anything above a ppO2 of 1.6 was taking a big chance, and from the other material I've read, I was under the impression that a ppO2 greater than 2.0 will almost assuredly send someone into convulsions/seizures. I understand the concept of how serious a seizure is underwater and the need for big safety margins; however, a ppO2 of 3.0 is twice of what I was taught was considered safe (1.4). I'm basically asking two questions:

1. Did the agencies that offer Nitrox certs. factor into their curriculum, huge safety margins, and in reality, the average human can take much higher levels of ppO2 before a risk of a convulsion?

2. If the answer to question one is yes, then 3.0 being acceptable in a hyperbaric chamber obviously has ppO2 safety buffer as well (lawyers

), just what kind of ppO2 levels can the human body tolerate?

BTW, I'm in no way advocating exceeding any agencies recommend ppO2 levels for diving mixed air. I'm curious about the buffers and what has been deemed safe for me.

rongoodman · Jun 8, 2012

The problem with seizures caused by an elevated ppO2 isn't the seizure, but being underwater when it occurs, and subsequently drowning. In a chamber, of course, this isn't an issue. As for how high a ppO2 which can be tolerated, it varies from person to person, and even from day to day. As Clint Eastwood once said, "Do you feel lucky?" There was a case a few years ago of a cave diver seizing and dying on a ppO2 of 1.4, and other reports of divers tolerating levels far above those considering safe today. The duration of the exposure factors in too. Add elevated CO2 levels into the mix, and it becomes even more unpredictable.

debajo agua · Jun 8, 2012

rongoodman:
There was a case a few years ago of a cave diver seizing and dying on a ppO2 of 1.4,

Interesting... I'd like to read the investigation reported.

I understand what you are saying. Many factors come into play and human sensitivity varies. The numbers come from somewhere. I'm currently reading Deco for Divers and I might have jumped the gun on this before it was covered.

rongoodman · Jun 8, 2012

debajo agua:
Interesting... I'd like to see the report on that investigation.

Ihttp://www.divers4life.com/TheCrack.html

cool_hardware52 · Jun 8, 2012

debajo agua:
After a recent visit to a Hyperbaric Chamber, I noted that ppO2 of 3.0 were acceptable. I was taken back, because in my Nitrox training, I was taught that anything above a ppO2 of 1.6 was taking a big chance, and from the other material I've read, I was under the impression that a ppO2 greater than 2.0 will almost assuredly send someone into convulsions/seizures. I understand the concept of how serious a seizure is underwater and the need for big safety margins; however, a ppO2 of 3.0 is twice of what I was taught was considered safe (1.4). I'm basically asking two questions:

1. Did the agencies that offer Nitrox certs. factor into their curriculum, huge safety margins, and in reality, the average human can take much higher levels of ppO2 before a risk of a convulsion?

2. If the answer to question one is yes, then 3.0 being acceptable in a hyperbaric chamber obviously has ppO2 safety buffer as well (lawyers ), just what kind of ppO2 levels can the human body tolerate?

BTW, I'm in no way advocating exceeding any agencies recommend ppO2 levels for diving mixed air. I'm curious about the buffers and what has been deemed safe for me.

I recently had the "opportunity" for a Navy Table 6 chamber ride. 60 ft depth on 100% 02 for about 4 hours followed by a slow ascent. There were air breaks, but most of the time it was under a hood sealed at the neck breathing 100% O2. PPO2 of 2.8. For ~4 hours. I never experienced any of the VENTID-C symptoms in the chamber.

Does that mean 2.8 PPO2 is ok for me? On another day, in the water, with different work loads, fatique, hydration, etc. it could be a very bad thing. As others have noted having a seizure in a nice dry chamber with medical attendants is very different from having one under water.

Much of diving is risk management, and very little is black and white. Following well tested deco tables simply reduces the risk of getting bent. Observing the max PPO2 of 1.6 and observing the NOAA exposure tables simply reduces the risk of a seizure. Bad outcomes remain non zero even for those that do not exceed these widely adopted recommendations.

In that setting one can expect a large element of conservationism, as much remains unknown and perhaps unknowable.

Tobin

P02 of 3.0 in a Hyperbaric Chamber?

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debajo agua

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