No-Limits Question

[superhornet59]

Hey guys.. I just thought I'd throw this out there...

Many people out there have a static time of 6:30+ and there are a number of people who are into 8-9 minutes.

So how come everyones', including the top freedivers', no limits dives only last some 3 minutes? You aren't really doing a whole lot of work down there so I don't see where all the oxygen is being burned. I understand that we are reaching depths that are becoming dangerous (lung squeeze), but many divers still black out during near-record, and even much shorter, dives.

How come? Does this have something to do with high O2 concentrations at depth or something? I just don't understand why everyone's breath hold gets cut in in half when sitting on a sled instead of lying in a pool.

-Matt

 

[Kars]

Hi Superhornet,

Indeed like you've guessed there is much more to deep diving.
Narcosis, Co2, N2,
Decompression,
Equalisation,
Safety,
Logistics,
Materials.

I'm not sure about the O2 part, but I do know mr Herbert Nitch, the current World Record holder with 214m, did do a decompressionstop of close to a minute - in apnea- on his way up before surfacing at 4'23".

I'm sure other people can give more specific information what difficulties there are in No Limit's.

Love, Courage and Water,

Kars

 

[trux]

Well, aside from the mentioned aspects, and the stress of the performance, there is also another challenge that was discussed on the forum recently in another thread. After certain depth, the gas exchange in alveoli due to their collapse stops or is strongly limited, so in depth the freediver only uses oxygen stored in the blood. Oxygen (air) originally in lungs is used mostly in sinus and other cavities for compensation (or in case of Herbert Nitsch in his Coke bottle). In ascent, the freediver tries re-inhaling it, but there are certainly some losses, so I guess not 100% of the original volume can be reused in lungs again.

EDIT: this is the other thread I meant: http://forums.deeperblue.com/freedi...ts-gas-exchange-human-breath-hold-diving.html

 

[superhornet59]

That decompression stop isn't what you think. The deeper you go, the slower your lungs compress/expand (from 0-10 meters they shrink to half the volume. from 100-110 they only shrink by about 1/10th.) Therefore, traveling 4 m/s up is really no problem at very low depths.. but lets say you were doing 4 m/s at 10 to surface.. that meant your lungs would double in size in about 2.5 seconds. As you would imagine, that is *definitely* going to cause an embolism, even 1 m/s is the safety threshold. Therefore, at 40 meters Mr. Nitsch would begin a free immersion type surfacing (pulling on the rope, no fins). I imagine that burns oxygen, but really.. it isn't necessary to do it that way, if that was a big issue they would just design the sled to slow down so he wouldn't use his muscles.

There must be something else that's holding them back.. the 40 meters ascent problem is just too easy to solve.. it doesn't make sense.

I've also thought about equalization... but with fluid goggles and things like wet equalizing.. I don't imagine it makes a huge impact on amount O2 in your lungs.

-Matt

 

[superhornet59]

Well, aside from the mentioned aspects, and the stress of the performance, there is also another challenge that was discussed on the forum recently in another thread. After certain depth, the gas exchange in alveoli due to their collapse stops or is strongly limited, so in depth the freediver only uses oxygen stored in the blood. Oxygen (air) originally in lungs is used mostly in sinus and other cavities for compensation (or in case of Herbert Nitsch in his Coke bottle). In ascent, the freediver tries re-inhaling it, but there are certainly some losses, so I guess not 100% of the original volume can be reused in lungs again.

EDIT: this is the other thread I meant: http://forums.deeperblue.com/freedi...ts-gas-exchange-human-breath-hold-diving.html

Ahhh! that's gotta be it!

So in essence now, we just need to find a sled that can go faster at those depths.. bringing it back to the hydrodynamics problem i suppose

 

[trux]

Matt, both, embolism and DCS are an issue at freediving too, and at NLT dives the risk is higher, of course. I recommend you to look up DCS in the archieve - there are plenty of interesting discussions on that topic. One of the later thread is for example this one:http://forums.deeperblue.com/freediving-science/80117-free-diving-decompression-tables.html but there are more of them in the archieve. Tere are alos plenty of studies available on the web. Some of them are listed in the Apnea Media Base: dcs @ APNEA.cz

 

[trux]

Ahhh! that's gotta be it!

So in essence now, we just need to find a sled that can go faster at those depths.. bringing it back to the hydrodynamics problem i suppose

Well, I believe Herbert's sled is already capable to bring him to more than 300 m - at least that's the depth he plans to go with it. Originally it was planned for this year, I think, but I did not hear any updates on the project, so am sure if it still stands.

 

[superhornet59]

I read over that thread, but didn't make much sense of it.. so.. its possible that alveoli can collapse and you'd have to go back down? That doesn't make a lot of sense to me...

and wow... 300m.. that's a pretty ambitious jump!

 

[trux]

... its possible that alveoli can collapse and you'd have to go back down? That doesn't make a lot of sense to me...

How did you come to that conclusion exactly?

 

[trux]

and wow... 300m.. that's a pretty ambitious jump!

Actually he aims for 1000 feet (304.8 m). That was at least the plan in 2007 when he did his 214 m record, and it is still stated as the aim on his website. However, I believe he planned around 240 m in 2008 as an intermediate step (though, I may be wrong about the schedule). Hopefully we'll hear some news soon from Herbert, or see them on his website at herbertnitsch.com

 

[superhornet59]

I'm sorry, I misunderstood the what they were saying.

it sounds from the abstract that it is a modeling study. if so, it is not likely to take into account where the air is in the lungs, but assumes uniformity. During the descent the alveoli will have more air than the thorax, amd on the ascent the alveoli are likely to totally collapse as the air rises in the chest. If so, the start of the ascent will be the killer (just when you thought you were safe).

Anyone have access to the entire article?

Howard

that threw me into that direction, followed by

Even if the alveoli totally collapsed and gas exchange completely stopped, the blood would be almost fully oxygenated when that happens, giving the diver at least 3 minutes to 'go down and get back up' to a point where the alveoli are exchanging gas again.

I would imagine that total collapse and cessation of gas exchange might happen around 200m for a packing dive, which would give you 3 minutes to get to 300m and back again (=90 seconds to get down 100m, or 1.1m/s).

Which led me to believe they were talking about something like DCS... when you need to get back to a certain depth (or simulated depth, in a hyperbaric chamber) and then start going back up slower in order to save yourself.

So, my bad. But anyway, this whole thing is new to me... what happened to lung squeeze though? I thought divers were starting to cough up blood and whatnot.. how does Mr. Nitsch plan on suddenly going another 86 meters, beating the 'danger threshold' by almost a third? I also am new to this 'blowing into a bottle thing', how does that help in any way... don't you want to keep the air in your lungs, especially before you reach that point where oxygen exchange from air to blood stops?

 

[trux]

Well, you will find all details if you look it up in the archive, but briefly: Herbert blows out practically all his air into a bottle with open bottom, somewhere around 20 - 40 m deep, and he then reuses the air at bigger depth for equalizing sinus and ears. So I think he actually may already have violated the theory of Dr. Fitz-Clarke, because his lungs are pretty much empty and collapsed long before he reaches the maximal depth. Lung squeeze is avoided by good flexibility of diaphragm and especially by strong blood-shift (look up the term in the archive). Exhaling air has several advantages - besides easier equalizing, it avoids or reduces the risk of narcosis, the risk of O2 toxicity, and the risk of nitrogen saturation (and consequent DCS). It also improves diving reflex, and increases blood shift earlier in the dive.

 

[Kars]

Superhornet, I'm sorry to say but from your words and reactions I got the feeling that your understanding of decompression illness is not complete.

Decompression illness:
In short it's the result of ascending to quickly resulting in your nitrogen gas forming bubbles in the blood blocking the bloodstream causing injury. These nitrogen bubbles prevent O2 reaching the necessary tissues like the brain resulting in anything from tinkling fingers to death. Depending on time and depth different amounts of Nitrogen gets stored into the various bodily tissues, muscles, bone etc. This Nitrogen needs time to get back into the lungs. When the time is to short too much nitrogen stays in the blood, expends with the decreasing pressure, and will block arteries and vain, resulting in decompression illness, DCS, "the bens".

Read careful, things are sometimes more complex.

Yes Trux, I forgot the stress factor! - how could I ???
Well in my experience stress is a huge factor too, stress causes so many bodily reactions, and consumes very much oxygen.

About the equalisation bottle, from the dive-profile I think he exhales into the bottle at around 23m. Also Herbert's decent and ascend speeds are pretty fast.

The dive computers provided the dive profile with the depth, average descent speed (3.1m/s) and average ascent speed (4.0m/s). Nitsch went down to 214 meters in 1 minute 45 seconds, stayed there for three seconds, and came up to complete the dive in 4 minutes 24 seconds.

http://www.suunto.com/suunto/Worlds/diving/main/world_news.jsp?JSESSIONID=1GWNJt1d1Vvmlyyk1rgm6ytk7LLSKysZYhHKRJqCGfhsjd3Tj35F!504640094!NONE&CONTENT%3C%3Ecnt_id=10134198674734991&FOLDER%3C%3Efolder_id=9852723697949147&bmUID=1227734813725&PREV_CONTENT=/media/suunto/NewWorlds/Diving/content/News/News_index

Love, Courage and Water,

Kars

 

[superhornet59]

No no, don't get me wrong, I understand the physiology of DCS. I'm just saying, the rate with which you go up plays a role. If you ascend slowly like a free immersion style 'rope pull' then yes it is still quite possible to get DCS, but I'm saying an actual severe embolism (a relatively large bubble) will only occur if you rise very rapidly near the end (because that's when the rate of pressure change is highest).

When it comes to DCS I know more about it on the scuba side of things, but when it comes to freediving, its not so simple. I know there are some depths that cause no effects, some that will lead to DCS if done X number of times, and some that will immediately cause it after one dive. Herbert is obviously all the way into the third category with these dives, but I'm just saying that his DCS would be many times more severe if he did not ascend slower after a certain point. As you can see from his dive profile, that is very much the case, and there are no decompression stops, just a slow swim up.


Stress does also play a large part, but I imagine the good divers are able to nearly stress free. I recall the video of Tom Sietas when he found himself 121m under and his air bag would not deploy. He just sat there looking pretty calm for a good while before anyone came to help him.. I don't know how relaxed I'd be under those circumstances.


Anyway seeing as at that point the lungs are nearly collapsed and you could just fill your sinuses with sea water... what the next barrier? If not lung squeeze.. then what..? Narcosis is out because that only makes a difference based on concentration in the lungs.. which eventually will be nearly empty.

So.. are we now just looking for who can get the lowest, the fastest?

Crap... this is going to turn into Formula 1.. richest guy who can get the best equipment wins..

nooo.. this cannot be..

 

[Kars]

Hi Super Hornet, Speed is currently becoming the limiting factor, not really because of breathhold times, but rather because of DCS and Co2 and N2 Narcosis. Guilliaume Nery, the current Constant Weight World Record holder, 113m, did train especially in swimming faster to reclaim his world record. Dave Mullins who swims slower and has a vastly bigger lung capacity too, is running into the narcosis barrier too.
Sebastian's Murat's FRC - partially full lungs - approach may help in the CW category to lessen the N2 narcosis.

I hope Dave chimes in this thread and clarifies it a bit more, as I'm reaching the boundaries of what I know and have heard.

Oh and indeed with No Limits and Variable Weight is indeed an expensive endeavour when you want to have a decent amount of safety, and euh try to find a -200+ meter spot close to shore fit for freediving... - I would have to travel at least ~ 1400KM from the Netherlands to South France.

Love Courage and Water.

Kars

 

[efattah]

Sebastien Murat has done 9+ minute hangs on the sled at 15-30m depth. So the sled has nothing to do with limiting the breath hold, in fact it makes the breath-hold easier. Herbert himself told me that his 4'20"+ no-limits world record "didn't even feel like a 2 minute static...."

With such a long breath hold time, it is possible to do an enormously long decompression stop(s) on the ascent from a no-limits dive. Herbert could in theory do maybe 4 minutes of decompression resulting in an 8 minute dive. So I would say that DCS is still not the limit.

The limit right now is a combination of:
1) extreme debilitating narcosis
AND
2) extreme chest collapse, which can damage the trachea
AND
3) logistical/safety problems

 

[rxcnc2]

Sebastien Murat has done 9+ minute hangs on the sled at 15-30m depth.

Can you tell us more? I remember several years ago he announced a NLT record attempt of 200m (at the time it was around 170m I think) with a hand-operated recovery.. then nothing happened. To hear of 9' statics at depth is ... well... interesting.

The limit right now is a combination of:
1) extreme debilitating narcosis
AND
2) extreme chest collapse, which can damage the trachea
AND
3) logistical/safety problems

Naively I would have thought that equalisation is still a main factor, coke or not. Any clue what has held Herbert from his 1000 ft attempt so far?

 

[efattah]

Equalization is only a limit if you let it be. It is very simple to let the sinuses flood and then equalize. Water rushes into the eustachian tubes. I tried in at Dean's Blue Hole, it hurts a little when underwater, and it hurts a LOT when you get back to the surface. However you could easily do the same with sterile saline and it wouldn't hurt at all -- I've done it in Vancouver where the salinity is near physiological levels and it doesn't hurt. I'm sure Musimu did it on his 200m+ dives.

If you want to equalize with air, then it starts to get hard to go over 250m.

 

[rxcnc2]

It is very simple to let the sinuses flood and then equalize.

It might be simple, but I have often read about infections.

Anyway, what about Murat 9' at 30m? thanks.

 

[Stavros]

Hya All,
I find it quite strange discussing technical and scientific aspects of No-Limits diving when we have such a tiny sample of divers actually diving systematically in No-Limits to any respectable depths...say past 100 and not a huge crowd if we go to shallower depths.

We are looking at less than 10 people diving in NLT around the world and even they are not doing it systematically (except the late Loic :-( ).

I personally train for NLT and own all the equipment needed (special dive boat with high speed motorized counterballast, several sleds and a safety team trained to operate everything) and from my point of view the problems limiting divers are the following:

1) LOGISTICS - you need a lot of equipment and a lot of trained personnel to run a serious NLT dive (my normal CWT dives would require a buoy a rope and a safety diver - my normal NLT dive requires an 8m boat a counterballast preferably my motorised one and 4 trained safety divers)...As a result you end up doing very few build up/training dives as it is too damn hard to do more - remember Herbert building up to 214 in 10 days? Last year my build up to a NR dive of 125 included three dives: 85, 105, 125

2) Availability of depth and proper diving conditions - How easy is it to get 150m+ mooring depth in a protected location with easy access?

3) Fear of DCS - you might not get DCS but the fear of it is always something working on the back of your mind and stopping rapid progress.

4) Equalisation - everybody is doing their own thing - Mussimu equalises with water, Herbert uses a coke bottle, some people (including myseld) stick to a continuous mouthfill ... you don't get to do enough dives to really fine tune a specific technique

I thing the O2 factor is rarely a problem and I cannot really understand where you got the "fact" (in your first post) that athletes are BOing in NLT dives. I have never heard of BOs (after the Umberto - Pipin era) in NLT. I agree with the idea Eric posted that the dives as far as breathhold are a joke (my 125m took 3:00 and felt like a 30m CWT dive). If anything we might be looking at O2 toxicity at depth rather than running out of O2.

One other thing I found strange is that on the thread's first page you are using Herbert's 214m dive data as "STANDARD" - his ascent and descent speeds of 3-4m/s are anything but standard and were only achieved in that setup (which doesn't exist any more) which cost several 10,000s euros to build and run for the 15 days of the event...
I would suggest that 2-3m/s ascent and descent speeds are more realistic for the majority of sled setups (all 4-6 of them around the world)

Cheers Stavros