Thoughts on Bounce Dives

[Akimbo]

... One is that at 300 feet the dive shop owner was so narced that she continued downward, and the other is that she actually passed out and continued downward.

<snip>

Technical divers who routinely go to those depths do so with ample equipment, gas, and training to make the dives very safe...

"Very safe" is where we disagree. IMHO, you need a chamber onboard and people that can run it in order to make a 300' dive very safe -- or even reasonably safe. I can't comprehend how "technical divers" can ignore the very real possibility of getting bent. I've seen too many CNS hits from dives to these depths to even consider them with a chamber more than a few minutes away.

Granted, the tables we used were MUCH less evolved, but that doesn't make any difference in a forced omitted decompression event. I guess the plan is to just die in that case.

 

[Superlyte27]

&#8220;Very safe&#8221; is where we disagree. IMHO, you need a chamber onboard and people that can run it in order to make a 300' dive very safe &#8212; or even reasonably safe. I can&#8217;t comprehend how &#8220;technical divers&#8221; can ignore the very real possibility of getting bent. I&#8217;ve seen too many CNS hits from dives to these depths to even consider them with a chamber more than a few minutes away.

Granted, the tables we used were MUCH less evolved, but that doesn&#8217;t make any difference in a forced omitted decompression event. I guess the plan is to just die in that case.

"Very Safe"? perhaps not, but reasonably safe? Yeah. Here in Florida there's probably 20 dives per week to depths of 300'. The DCS incidence is pretty low, less than 1%. And those occurrences that I do know of are due to diver error; at least in the sample of data I'm using of about 20'ish divers who frequent 300'.

If we bring CNS hits into the above paragraph... I don't know of a single recent incident of CNS issue where appropriate gas was being used for the depth.

Now, I will say this...
Just last week I had spoken to some friends about attaining a chamber for our personal use.... Mainly because CNS concern is real when you're talking about 1000 CNS on a long dive. I'd rather tox at 20' in a chamber than in a cave. The HUGE problem with that is... I'm the only cave diver I know certified to operate it. So, it really doesn't help me.

 

[Akimbo]

&#8230; Now, I will say this...
Just last week I had spoken to some friends about attaining a chamber for our personal use.... Mainly because CNS concern is real when you're talking about 1000 CNS on a long dive. I'd rather tox at 20' in a chamber than in a cave. The HUGE problem with that is... I'm the only cave diver I know certified to operate it. So, it really doesn't help me.

This is the time to shop for a used chamber and compressors. As you know, the low price of oil is decimating a lot of companies that have to liquidate down to survival mode.

Have you considered using the chamber for training as an income source? I bet a lot of people would pay just to learn about Nitrogen Narcosis, let alone more advanced topics. Best of luck finding a good buy.

Edit: If it came down to it you could run the chamber yourself from the inside if you had dual controls. I know people who have done it and it sucks less than waiting for evacuation to a hospital where some non-hyperbaric doc wastes an hour or two looking for other medical causes before sending you someplace else that has a chamber.

 

[Centrals]

Edit: If it came down to it you could run the chamber yourself from the inside if you had dual controls. I know people who have done it and it sucks less than waiting for evacuation to a hospital where some non-hyperbaric doc wastes an hour or two looking for other medical causes before sending you someplace else that has a chamber.

1. Only a minute fraction of patients that were admitted to our local chamber are diving related. Our coastal water is pretty shallow so most local diving were well above 20m.
2. Couple of yrs ago, two HK divers were taken to a chamber in Philippines. Unfortunately the chamber was occupied for whatever reason. At the end both divers did not survive. However, I must emphasis that the delay in the treatment might not contribute to the demise of both divers. Chamber is NOT a magic bullet.

 

[REVAN]

It's generally accepted that at about 217 feet air becomes toxic. Go deeper on air and do so at your terminal peril. A fast descent to about 200 on air with controlled ascent using recreational limits is totally dooable on a normal size tank as a first dive (i.e. no residual Nitrogen). The risk in this dive is the narcosis that you WILL experience. Tunnel vision. Potentially magical thinking. Lack of focus. Now, on their own these things aren't that big of a deal and can be fun, but when you are dropping like a rock and supposed to be paying ABSOLUTE STRICK UNWAVERING attention to your depth gauge, narcosis can be deadly. In sum, don't bounce unless you go with an experienced diver who understands the physiology and has some emergency diving experience.

Without reference to personal beliefs vis a vis whether bounces are dumb... Thoughts or concerns of a technical nature would be great.

First, I'd like to emphasize the post by @dumpsterDiver. He had a lot of very good points that should be taken seriously.

I've done many short duration dives to a depth of around 200 ft on air. Reading your comments, I very much doubt that you have done anything similar.

First of all, doing any deep dive with a single tank (i.e., no redundancy) is risky and stupid, in my opinion.

Second, 218 ft on air is NOT poison. oxygen toxicity on your stated scenario is probably the least of your worries.

Third, leading people to believe that being accompanied by an experienced diver who has emergency experience is pretty silly, because if he is also diving on a single small tank at 200 ft - his ability to do much of anything to help is pretty damn limited.

Fourth, the misconception that you must concentrate on the depth guage is very, very bad advice. In fact, the exact depth is the least of your worries on such a dive. You need to be NOT focusing on ANYTHING and MUST be focusing on a lot of things simultaneously including: your exertion level, time, air pressure, dive buddy location and all the other things you are trying to accomplish during this bounce dive.

Fifth, you statement that tunnel vision alone is NOT that big of a deal is DEAD wrong as well.

So.. you got pretty much EVERYTHING wrong except for the statement that narcosis is dangerous at 200 on air.

Bounce diving on air to 200 ft is unwise and not recommended by any agency.

IF you are gonna do it, you need to slowly work up to it. Some people will NEVER, EVER be able to do it with any semblance of safety and self awareness. A lot better to find this out at 140 than 200 feet.

In any regard, you are going to be very, very hard pressed to find a responsible, experienced and a safety conscious mentor to accompany you on these sort of single tank, deep air bounces..

I'd like to add to this that I know where you can find a group of very experienced divers who can and would be willing to work with you toward doing bounce dives with minimal gear and on air to depths of around 200 ft, and do it with safety as a top concern. These people are called freedivers, and there are a lot of good ones in Canada who regularly and routinely bounce to 200 feet depth. My first thought is to contact Kirk Krack of PFI to get started. Other names that come to mind are Freedive Toronto, William Winram, and Eric Fattah. These are all Canadian assets that may be willing to help you find a viable path to achieve this goal if you are serious about it.

What you want to do can be done, and many others have achieved this. I have done many bounce dives to and beyond 200 feet in freediving competitions. The competitions provide an environment where you can do this with, what I think to be, acceptable risk. You need to connect with the right people and have the dedication to follow through and do it with the appropriate safeties in place, not as an ignorant diver seeing how far you can go without any training, preparation, or precautions aside from what you can get from free advice off the internet.

 

[Akimbo]

... At the end both divers did not survive. However, I must emphasis that the delay in the treatment might not contribute to the demise of both divers. Chamber is NOT a magic bullet.

Perhaps not magic, but amazingly effective when treatment is very prompt, as in within minutes of the onset of symptoms or surfacing from omitted decompression. Everyone walked away from chamber treatments that I have witnessed. I have little doubt that the outcomes would have been much different if the delay was hours instead of minutes.

 

[halocline]

It's generally accepted that at about 217 feet air becomes toxic. Go deeper on air and do so at your terminal peril. A fast descent to about 200 on air with controlled ascent using recreational limits is totally dooable on a normal size tank as a first dive (i.e. no residual Nitrogen). The risk in this dive is the narcosis that you WILL experience. Tunnel vision. Potentially magical thinking. Lack of focus. Now, on their own these things aren't that big of a deal and can be fun, but when you are dropping like a rock and supposed to be paying ABSOLUTE STRICK UNWAVERING attention to your depth gauge, narcosis can be deadly. In sum, don't bounce unless you go with an experienced diver who understands the physiology and has some emergency diving experience.

Without reference to personal beliefs vis a vis whether bounces are dumb... Thoughts or concerns of a technical nature would be great.

Go for it. I'll hold your beer!

 

[John C. Ratliff]

First, I'd like to emphasize the post by @dumpsterDiver. He had a lot of very good points that should be taken seriously.



I'd like to add to this that I know where you can find a group of very experienced divers who can and would be willing to work with you toward doing bounce dives with minimal gear and on air to depths of around 200 ft, and do it with safety as a top concern. These people are called freedivers, and there are a lot of good ones in Canada who regularly and routinely bounce to 200 feet depth. My first thought is to contact Kirk Krack of PFI to get started. Other names that come to mind are Freedive Toronto, William Winram, and Eric Fattah. These are all Canadian assets that may be willing to help you find a viable path to achieve this goal if you are serious about it.

What you want to do can be done, and many others have achieved this. I have done many bounce dives to and beyond 200 feet in freediving competitions. The competitions provide an environment where you can do this with, what I think to be, acceptable risk. You need to connect with the right people and have the dedication to follow through and do it with the appropriate safeties in place, not as an ignorant diver seeing how far you can go without any training, preparation, or precautions aside from what you can get from free advice off the internet.

REVAN,

Please read the following abstract from PubMed:

PLoS One. 2014 Aug 12;9(8):e105006. doi: 10.1371/journal.pone.0105006. eCollection 2014.

Brain damage in commercial breath-hold divers.

Kohshi K1, Tamaki H2, Lemaître F3, Okudera T4, I****ake T5, Denoble PJ6.
Author information



Abstract

BACKGROUND:

Acute decompression illness (DCI) involving the brain (Cerebral DCI) is one of the most serious forms of diving-related injuries which may leave residual brain damage. Cerebral DCI occurs in compressed air and in breath-hold divers, likewise. We conducted this study to investigate whether long-term breath-hold divers who may be exposed to repeated symptomatic and asymptomatic brain injuries, show brain damage on magnetic resonance imaging (MRI).
SUBJECTS AND METHODS:

Our study subjects were 12 commercial breath-hold divers (Ama) with long histories of diving work in a district of Japan. We obtained information on their diving practices and the presence or absence of medical problems, especially DCI events. All participants were examined with MRI to determine the prevalence of brain lesions.
RESULTS:

Out of 12 Ama divers (mean age: 54.9±5.1 years), four had histories of cerebral DCI events, and 11 divers demonstrated ischemic lesions of the brain on MRI studies. The lesions were situated in the cortical and/or subcortical area (9 cases), white matters (4 cases), the basal ganglia (4 cases), and the thalamus (1 case). Subdural fluid collections were seen in 2 cases.
CONCLUSION:

These results suggest that commercial breath-hold divers are at a risk of clinical or subclinical brain injury which may affect the long-term neuropsychological health of divers.
http://www.ncbi.nlm.nih.gov/pubmed/25115903

There are other stories and studies of decompression illness happening to U.S. Navy escape tank instructors from breath-hold diving. So don't be so sure that damage hasn't been done by these bounce dives from free diving. Here are some more links:

http://www.ncbi.nlm.nih.gov/pubmed/20737928

http://www.ncbi.nlm.nih.gov/pubmed/16967769

http://www.ncbi.nlm.nih.gov/pubmed/6535313

SeaRat

 

[danvolker]

OK, if I go from my 90 foot drops to 200 footers....I will just go up to 20 feet where I will grab an O2 bottle and do deco for 10 minutes....

Sperm whales coming up from a long deep dive....surface briefly, then drop down to 30 feet or so and languish about for 15 minutes or so, as a natural deco stop....or so I've heard

 

[Superlyte27]

Akimbo... what do you think I could get one for.

I'm seriously considering building one myself. We have the technology.