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Herbert Nitsch Recovering Well after achieving World Record depth

Thread Status: Hello , There was no answer in this thread for more than 60 days.
It can take a long time to get an up-to-date response or contact with relevant users.
It would be a bizarre change, and is only half serious - but I suspect effective in reducing DCS with only a relatively small logistical increase.

I think that bubble formation / off gassing at 30m could be a very practical standard/ruled depth - the incremental change in size of bubbles up to that point is much smaller per 10m etc. And is not so deep that you are potentially complicating things further.
 
If you could be 100% sure that the diver is completely OK when ending the dive at 30m depth this could be safe. But I don`t like the the idea. I just feel it`s not freediving anymore. But the thing that makes it a really, really bad idea is that if something goes wrong, you have a disaster. A BO at 30m and the need for deco is a bad situation. That`s why I think recompression in the water is a bad idea.
 

Did Sebastian go to 249m as well?

And, any news on how Herbert is doing? The blog has not been updated in over a week.
 
 
As the procedure for extremely deep dives changes, so too does the motivation. We wanted to know how deep a person could dive while holding their breath. If you do a no-limits dive to 300m and stop at 30m on the ascent, in fact you are accomplishing a remarkable thing. Because, if the diver did anything useful at that depth (300m), then that would make this style of diving way better than a scuba dive to the same depth, (a 300m scuba dive would last around 10 hours with zero bottom time). Even if the freediver did 20 minutes of deco from 30m to the surface, the dive would only last 25 minutes instead of 10 hours, FOR THE SAME AMOUNT OF TIME ON THE BOTTOM.

The question may change to something more practical; what is the fastest and most cost effective way to perform useful work at a depth of 300-350m?

I have already conceived of a modified 'hybrid' dive where the diver hyperventilates for ages, then uses a 'spare air' containing 100% O2, and while at the bottom at 60-90m, the diver 'packs' one tiny gulp of O2 every minute. No O2 toxicity would occur since O2 would be ingested at the rate it is consumed. CO2 would accumulate but the dive could last up to 15 minutes. Nitrogen loading would be minimal since there is a finite amount of nitrogen in the lungs. This style of diving would be way faster and cheaper than a scuba dive. More commercially viable in many cases. The depth would only be limited by CO2 narcosis.
 
I have also heard many versions about what depth O2 becomes toxic. I can`t tell you what`s right or wrong but I can tell you what the Norwegian tables say. When it comes to the surface recompression (ODO2) a standard table says breathing O2 at 12m for about 20min for one period.
What you say about absolute depth of 12m and not more than 10min does not compare to the Norwegian Tables. In fact if there is suspicion of air-embolism, They do like this: Straight to 18m, breathe 100% O2 for 20min, then 5 min normal air. Then they do this two more times (total: 3x20min at 18m) and go to a shallower depth. My friend that is a chamber operator in the navy and also in the hospital said that when they treat certain bacterious infections (not related to diving) they can do as much as 90min on 100% O2 at 20m!! (Please pardon my english when it comes to medical terms...)
B-J
 
B-J said:
I have also heard many versions about what depth O2 becomes toxic. I can`t tell you what`s right or wrong but I can tell you what the Norwegian tables say.
Click to expand...
Guess there would be a great deal of difference between the tables for surface recompression and chamber treatments scenarios (both under medical supervision) and recommended safe limits for diving with pure Oxygen (guess 12m/10min. would be the old US Navy model?), which would be much more conservative as predisposition to acute O2 poisoning can be very individual and may have other risk factors involved (including CO2 build up?). Guess there might be an individual test carried out for saturation divers to find out their sensitivity. After all, breath hold diving to 300m isn’t the standard recommended diving scenari oeither (yet).
 

This very interesting and perhaps a way for some top level divers to make a little income I imagine the navy has done some work with this or may be in the future; a spearo (and very solid freediver) I know out here just went into the SEAL program. I hope I get to pick his brain at some point in the future. What you are describing of course would take world class training and discipline. In the interest of risk management you want to monitor not only time and HR but I would think blood O2 sat and CO2 levels which if understand correctly potentially would be higher than any current type of freediving. Is there a noninvasive way to measure these levels underwater (although for military and commercial application I imagine subcutaneous nano devices would be well within reason). What research has been done in regards to diving after hyperventilating with pure O2? To start a dive with a lungful of pure O2 would be toxic wouldn't it since above a certain partial pressure O2 becomes fatally toxic, and a diver of that caliber would have loads of O2 left even after several minutes (then you need stops on the way down).
 

Signs of O2 toxicity for humans:

K = t2*(PO2/101.3)*c

where,
t is the exposure time
PO2 is the oxygen pressure
K is the cumulative oxygen toxicity index.
c = 6.76

Symptom may appear when K reaches a threshold value Kc = 2.31 X 10(8) (Arieli et al. J Appl Physiol 2002; 92:248-56)

The parameters c and ln(Kc) in the power equation are linearly related to metabolic rate (M) and inspired CO2 (Arieli. Aviat Space Environ Med. 2003 74(6 Pt 1):638-42). The mean time to CNS oxygen toxicity (tc(M)) as a function of metabolic rate may be calculated for humans as follows (according to Arieli 2003):

tc(M) = [(e(-2.85 M + 31.8))/(PO2/101.3)(-7.45 M + 39.6)]0.5

where,
M is metabolic rate in units of resting metabolic rate. It is safe to assume that M is reduced below basal levels during diving (in some dives/divers) suggesting that O2 toxicity is better tolerated during apnea, O2 stores aside.

But you also need to know PCO2
PCO2 is dependent on tissue temperature and M


Starting to get complicated and impractical. Therefore, you need empirical evidence to come to any reasonable conclusion, anything else is just unsubstantiated theories.
 
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