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sasmedic · 22nd December 2007, 08:15

HI there

Firstly I do not know the sweetspot depth range for Rebreather's.

Secondly I must say the 330m OC record has not been accepted as a record as far as I know. There has been controversy about the dive as it was done only a few weeks or months after Nuno Gomes did his 318.25m dive in the Red Sea in 2005. It is easy to claim that a record has been set but to actually prove it is another!!

Based on Nuno's presentation on the record dive the HPNS seems to the big issue wrt going deeper on OC. Nuno planned to go deeper than the 315m tag he retrieved, but feared that he would not be able to retain his DV in his mouth due to the HPNS convulsions he had at that depth. Going deeper would thus depend on an individual's symptomatic onset of HPNS at a certain depth. What makes this area diffficult is the lack of scientific data available to do gas plannning as far as mixes according to certain depths are concerned and the associated deco profile for those gases. Everybody has their own idea of doing it and Nuno's outlook is to be as conservative as possible and has the mental strength (and strong will to survive - as he puts it) to sit under water for 14hours has worked so far.

The planned recovery dive of Dave Shaw had some criticism from international dive experts (presented at the DAN tech diving workshop 2006) that reviewed his rebreather after the fatal attempt as well as the camera footage that was strapped to his helmet. Apparently there was evidence of incorrect sorbent and packing of the scrubber that added to the CO2 toxicity. The work done at that depth by Shaw and getting entangled with out being able to free himself could not be adapted for by the Rebreather technology. And he planned this dive even after he had been treated for DCI on this first dive at Boesmangat in 2004.

When Shaw did not come up for his planned meet, the back up diver for Shaw dived beyond his planned 250m when his buddy inspiration's electronics imploded at about 280m. He then had to go onto OC for ascending and deco and then developed inner ear DCS, supposedly due to the isobaric counterdiffusion theory.

So it seems that for OC attempts the problem is of physiological and gas planning nature and on the Rebreather side it seems like it is the challenge to deal with emergencies that will require hard work as well as problems associated with bailing to OC when the scrubber time is overdue.

I also wondered if there is not a solution that could combine OC and Rebreather for deep attempts?

22nd December 2007, 08:15	#8 (permalink)
sasmedic New Member Current Rebreather/s: Dolphin Other Rebreather/s: Dolphin Join Date: Oct 2007 Location: South Africa Posts: 15	Re: Will OC records always be deeper? HI there Firstly I do not know the sweetspot depth range for Rebreather's. Secondly I must say the 330m OC record has not been accepted as a record as far as I know. There has been controversy about the dive as it was done only a few weeks or months after Nuno Gomes did his 318.25m dive in the Red Sea in 2005. It is easy to claim that a record has been set but to actually prove it is another!! Based on Nuno's presentation on the record dive the HPNS seems to the big issue wrt going deeper on OC. Nuno planned to go deeper than the 315m tag he retrieved, but feared that he would not be able to retain his DV in his mouth due to the HPNS convulsions he had at that depth. Going deeper would thus depend on an individual's symptomatic onset of HPNS at a certain depth. What makes this area diffficult is the lack of scientific data available to do gas plannning as far as mixes according to certain depths are concerned and the associated deco profile for those gases. Everybody has their own idea of doing it and Nuno's outlook is to be as conservative as possible and has the mental strength (and strong will to survive - as he puts it) to sit under water for 14hours has worked so far. The planned recovery dive of Dave Shaw had some criticism from international dive experts (presented at the DAN tech diving workshop 2006) that reviewed his rebreather after the fatal attempt as well as the camera footage that was strapped to his helmet. Apparently there was evidence of incorrect sorbent and packing of the scrubber that added to the CO2 toxicity. The work done at that depth by Shaw and getting entangled with out being able to free himself could not be adapted for by the Rebreather technology. And he planned this dive even after he had been treated for DCI on this first dive at Boesmangat in 2004. When Shaw did not come up for his planned meet, the back up diver for Shaw dived beyond his planned 250m when his buddy inspiration's electronics imploded at about 280m. He then had to go onto OC for ascending and deco and then developed inner ear DCS, supposedly due to the isobaric counterdiffusion theory. So it seems that for OC attempts the problem is of physiological and gas planning nature and on the Rebreather side it seems like it is the challenge to deal with emergencies that will require hard work as well as problems associated with bailing to OC when the scrubber time is overdue. I also wondered if there is not a solution that could combine OC and Rebreather for deep attempts? __________________ The best cure for fear is knowledge!!!
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