Human limits at depth

[mgmonk]

Now, feel free to move this post (books, tech, inst to inst.... I don't care), but I'd REALLY like to hear something from
1) divers that have the experience to comment
2) divers that know some of the people involved
3) divers that have extensive knowledge in human physiology

Without this turning into a bashing thread (I hope), I just finished two books that I feel many of you have read, probably. "Shadow Divers" and "Ocean Gladiator"

I'm not so much interested in what people think about the divers involved on a personal level, but I am VERY curious about what thresholds the human body can withstand.

DISCLAIMER---- I'm NOT advocating Deep Air or asking because I am going to read the replies and run out and test what I've read. I hope that I can get some insight without getting a bunch of inside jokes or one liners.

(Posting here requires a lot of backstory.... or maybe I'm sensitive. or both)

sooooo....

Whilst reading SD, I was pretty much amazed at some of the stuff these guys pulled off. I've read about a few of them before, and I thought it was a well told story. The dives seemed to fit within what I assumed I knew about the human body's tolerance to depth (regarding CNS O2 tox and N2 narc) on air. They found the U-boat at around 200ft/60+m, and even dove around it at 250ft/75+m. All of them experienced narcosis to varying degrees, and since they were dancing around the ppO2 limits, it's reasonable that none of them suffered.

Then I read Ellyatt's book ("Ocean Gladiator"), and he talks about doing SINGLE TANK air dives to 400ft/120+m and beyond. Granted, many of his stories don't end easy, but none of them end up in death.

Both books talk about the evolution of Tech diving, and both get into trimix and accelerated deco, but what I'm REALLY curious about is these extreme depths on air. I'm incredibly curious how sub-100m is done on a single tank of air. There just seem to be too many factors.

Anyway, maybe I'm that naive to buy into a bunch of brainwashing that I've been taught and do teach. Maybe the human body can withstand far more than it's given credit for, but aren't there points where the body just can't cope?

Or are there?

 

[String]

One word - luck.

If you push your luck sometimes you survive, sometimes you don't. For ever 10 successful single tank air dives there may well be 5 that weren't.

As for a single 120m dive and how its done - massively rapid descent, rapid ascent (ie bounce) get lucky with the deco, get lucky with the O2, get lucky with DCS and its fine. Ellyatt has done and continues to do a lot of very stupid stuff and so far in general he's been lucky (discounting the numerous chamber treatments etc)


Seat belts never used to be fitted on cars. Doesn't mean people should continue not to use them. Technology improves, knowledge improves, safety improves.

 

[TSandM]

IIRC, Sheck Exley told the story of some around 400 foot air dives he did in his youth . . . and I seem to recall a couple where people became unresponsive, and a couple of them were lost.

 

[scubadiver888]

I have not pushed the limits because that is just not me but I am curious about the guys who do air dives on a single tank to 200+ feet. I've read quite a few articles and interviews of these guys and I noticed something... they are basically doing a combination of extreme free diving and scuba diving. A lot of the techniques someone like William Trubridge will use to free dive to 75m+ have similarities in the stories I read from guys who dive 200+ feet on air.

One story I read of a group if guys diving to 300+ feet on AL80s sounds like they use the scuba gear to start down, they free dive from 100 feet down, they use the gear to stop descending, they give one kick to start back up. When they get back within recreational diving limits, they start using the scuba gear again.

The talk of mediation, being completely in touch with their body, the focus and concentration all remind me of articles I read on free diving. Maybe you want to look at something like Freediving Team - Vertical Blue Freediving Apnea Academy to see how William Trubridge went to 100m on a single breath.

 

[Slamfire]

I also think there has been shift or evolution of the collective human tolerance for risk in general. This has good (increased safety) and bad (less risk = less returns or advancements) consequences.

Think about Columbus trying to get funding for his expedition to the unknown in this day and age. He would have been drowned with arguments about the liabilities, lack of safety, etc. Note the audience reaction when Bill Stone says he wants to make a one way trip to the moon. The whole audience cracks up laughing because they think he's joking -- time stamp 15:11. In reality he was just saying that these kind of advancements require boldness.

 

[Insta-Gator]

I don't know, but seems awfully foolish to me. One of our fellow SB members has a tag line in his signature that reads something like: Skydiving doe not require a parachute, only if you intend to skydive twice is a parachute required. This fellow supposedly dove 318.25 meters (that's over 1,000 feet)

YouTube - World Record Dive 318,25 m

 

[mgmonk]

Maybe you want to look at something like Freediving Team - Vertical Blue Freediving Apnea Academy to see how William Trubridge went to 100m on a single breath.

intersting points. I've watched several Truebridge videos/interviews. The egypt blue hole diving puts me in a trance. It does seem like this bounce combo is getting to the heart me the matter. Mark talks about super fast decents followed by 'hitting the breaks' and then ascending quickly to rec limits where it's more like a 'traditional' scuba dive. Thanks for the fodder.

 

[uberdude]

IIRC, Sheck Exley told the story of some around 400 foot air dives he did in his youth . . . and I seem to recall a couple where people became unresponsive, and a couple of them were lost.

I just finished Caverns Measurelesss To Man Sheck Exley's autobiography a few days ago. Mgmonk you would definately like this!! TS your dead right about the depth. He actually went to 465ft on air and the people he was backing up were 15ft lower and died. Some one asked if he would consider breaking the record not under stress and just looked at them and said "you've gotta be kidding".

quoting directly from the book page 80-81
...at 440 ft I started having trouble with my distance vision, everything beyond ten ft degenerated into a silver-gray blur of pale light and shadows.A little deeper, and the tunnel vision began, a certain sign of oxygen toxicity. As I continued down, the tunnel quickly tightened, and a sparkling spot like a burning fuse appeared in the lower part of the port hole. Black out or convulsions was seconds away. I quickly opened the valve on my buoyancy compensator inflator fully and tried top read my depth gauge so I could plan my decompression if I lived that long. It seemed yards away in the tunnel of my vision,but it clearly showed 460ft. That meant the tips of my fins were hanging down below 465ft plus, only 15-20 ft from my friends. But it might as well been a mile.

This was an unplanned attempt to save 2 friends attempting a record. They died.

He regularly went to 300ft and deeper on air and talks about the narcosis. He also talks about minimizing black out where others did he didn't though experience and minimizing/slowing physical activity to prevent blacking out, it would appear he also had an excellent tolerance to narcosis. Diving between 200-300ft seemed to be a regular thing for him, and his diving buddies in the 60-70's.

Hope this helps

 

[drbill]

I've done a number of dives in the 180 to 200 ft range on air in a single HP120 (although I carried a pony which I only used once or twice). On at least one day I averaged 180 ft on three dives. I did all these solo because I didn't want to be (ir)responsible for anyone else's life but my own.

While I don't recommend such dives to anyone, I found that they did not affect me to the degree I would have expected based on my training and experience. I stress that I do not extrapolate my experiences to others. My experiences were entirely dependent on my personal reaction to both nitrogen and oxygen.

Only on one or two of these dives did I feel noticeably impaired by narcosis... which disappeared as I ascended into the 150-160 ft range. Today I can get noticeably narced at 110 ft. Why the difference? My assumption is that a few years ago when I was doing these dives, I normally dove 300-350 times a year and my body had probably built up a tolerance for nitrogen. Last year I did a mere 50 dives, spending far more time editing my accumulated video footage.

Today I would not even attempt a dive deeper than about 160 ft. If I do so in the future, it will be after re-conditioning myself through frequent and increasingly deeper dives. I have no specific reason to dive deep today (I was filming for an episode on "deep ecology" previously).

 

[Crowley]

I've never pushed the limits whilst I've been diving - this is how some people get their kicks from diving, which is fine, but I like tootling about with the fish in warm recreational waters. I know I've been Narced in 30 metres of water as a newbie.

BUT - there is still an old school "100 Club" here in the resort where I work - the members comprise instructors and guides who bounced down to 100 metres (during the surface interval whilst working, in some cases), but didn't always bounce back up. There were fatalities, and I know of at least one person who was severely crippled after a rapid ascent from 90 metres left him with decompression sickness that badly damaged his spinal chord. If people persist in balthering on about how cool it is I tell them to look for Yuri Lipski on YouTube (died filming his own computer at 100metres in the Dahab Blue Hole).

With proper training and equipment, then yes, by all means, but past a certain depth then the body simply cannot tolerate the overloading of gas. Air becomes toxic at around 60 metres (pp02 1.4ata at 57 metres, 1.6ata at 67m) and yes, there is a time delay associated with that but past 1.6ata it is a matter of luck. There are some who will insist that 2.0ata is safe, and yes it is - just not for everybody.

I think diving science has improved in leaps and bounds over the last twenty years and we have the capability to dive deep and regularly and this kind of diving is no longer the providence of an elite few. The extreme depths - well, some people are driven to push limits whatever activity that is, from diving to driving fast to eating a world record breaking amount of chillis.

All gases are narcotic to some degree and Helium causes High Pressure Nervous Syndrome at extreme depth - over 200 metres - and carbon dioxide buildup is so great that any increase in physical activity can quickly prove fatal.

As Dr. Bill says - he and many others have done successful single tank air dives to 60 metres and beyond, but at this sort of depth the margin for error becomes a lot more slender. With the technical know-how we have developed over the last decades, the single tank deep air diving is just not necessary and possibly a bit silly.

(ramble over)

Dive safe

C.