CNS not important anymore?

[kensuf]

In contrast, a recreational diver including the technical diver goes nowhere near the exertion level of combat swimmer. This probably explains why the USM or NOAA CNS tables may not reflect the true risk parameters.

In contrast, most recreational divers including technical divers, lack the fitness level of combat swimmers. Apples, oranges.

 

[old frogman]

In contrast, most recreational divers including technical divers, lack the fitness level of combat swimmers. Apples, oranges.

I agree. Therefore, I would leave it to the individual to decide on the CNS O2 toxicity strategy. Based on the context of the dive, situational conditions, individual fitness and technical capability. It is essentially a personal risk management decision.

 

[Agro]

OMG, still more questions than answers........

 

[JMarc]

OMG, still more questions than answers.

That avoid the common illusion that a simple and easy answer exist.

 

[OMyMyOHellYes]

Who sais so?

I think that was @nadwidny

 

[old frogman]

OMG, still more questions than answers........

There is no precise answer to managing CNS oxygen toxicity. The British (John Haldane) during WW2 did numerous experiments. He came to the conclusion that if you exceeded 2 ATMs (30ft) absolute pressure on 100% oxygen the risk for convulsions was unacceptable. After the war the USN EDU did more experiments and developed their oxygen exposure table which can be found today in the USN dive manual (available free on the internet). Later NOAA developed oxygen exposure table for mixed gas rebreather diving for their divers which is more conservative than the USN table.

Some divers on this thread have stated that if they are not exerting themselves, they can exceed the NOAA O2 time limits by up to 300%.

Looking at the French Naval combat swimmers experience, the clear parameters for oxygen tolerance appears to be physical fitness which generally enables you to exert yourself for up to 3 hours at a depth of 6 to 7 metres underwater on 100% oxygen.

Military and commercial divers at rest in a recompression chamber routinely breathe 100% oxygen at 3 ATMS (60 feet) absolute pressure.

In the end it is up to the individual to decide how much risk he/she is prepared to take based on their fitness and existing dive situational parameters.

There is a book "Chamber Divers" by Rachel Lance Ph D (biomedical engineer with USN) which details the experiments by the British during WW2. It may give you some answers.

 

[Dr Simon Mitchell]

There was a panel discussing this at the last AAUS symposium. I posted a followup on a different thread (below). I'm not sure when the official consensus statement will be coming out, but the decimation of NOAA probably isn't helping things.

Hello,

I was one of the panellists at the AAUS/NOAA workshop, and I am responsible for writing up the findings. The relevant material has been compiled and the new recommendation will be published in the September issue of Diving and Hyperbaric Medicine.

Most of the points made here are valid and will be reflected in the workshop's findings.

What we have done is derive a new evidence-based limit for an inspired PO2 of 1.3 atm (and by default, anything less than that too). I wish to emphasise that we could not simply publish a new set of guesses to replace the old guesses. Accordingly, we have compiled sufficient evidence based on real human exposures in test dive programs to make us comfortable with recommending a substantial modification to the NOAA limit for 1.3. You won't have to wait much longer for this to be released and I will notify on this board when it is published.

Simon M

 

[crofrog]

Hello,

I was one of the panellists at the AAUS/NOAA workshop, and I am responsible for writing up the findings. The relevant material has been compiled and the new recommendation will be published in the September issue of Diving and Hyperbaric Medicine.

Most of the points made here are valid and will be reflected in the workshop's findings.

What we have done is derive a new evidence-based limit for an inspired PO2 of 1.3 atm (and by default, anything less than that too). I wish to emphasise that we could not simply publish a new set of guesses to replace the old guesses. Accordingly, we have compiled sufficient evidence based on real human exposures in test dive programs to make us comfortable with recommending a substantial modification to the NOAA limit for 1.3. You won't have to wait much longer for this to be released and I will notify on this board when it is published.

Simon M

Thank you for what you do to push the science forward.

 

[Agro]

Hello,

I was one of the panellists at the AAUS/NOAA workshop, and I am responsible for writing up the findings. The relevant material has been compiled and the new recommendation will be published in the September issue of Diving and Hyperbaric Medicine.

Most of the points made here are valid and will be reflected in the workshop's findings.

What we have done is derive a new evidence-based limit for an inspired PO2 of 1.3 atm (and by default, anything less than that too). I wish to emphasise that we could not simply publish a new set of guesses to replace the old guesses. Accordingly, we have compiled sufficient evidence based on real human exposures in test dive programs to make us comfortable with recommending a substantial modification to the NOAA limit for 1.3. You won't have to wait much longer for this to be released and I will notify on this board when it is published.

Simon M

Great, thanks a lot.

1.3 is one thing. Will you also tell us about CNS limits?