How deep?

[Michael Kazma]

These questions are impossible to answer.

It all depends on the dive profile preformed. As a recreational diver it is always "possible" to make it to the surface with an ESA. If you will get bent, that is a different matter.

Technical divers do not have this "luxury". On a deep long dive running out of gas is just not an option and will most likely result in death.

The answer is...DO NOT RUN OUT OF GAS and ALWAYS DO NECESSARY DECO STOPS.

PS "make it to the surface without getting severely bent (as in requiring prompt medical treatment?) " Any symptoms of bends requires immediate medial attention.

 

[spector39]

Escape from submarines have been successfully made at depths of 300 feet.
AmericanHeritage.com / Why the Best Technology for Escaping from a Submarine Is No Technology
You have to remember to exhale all the way to the surface, but it can be done.

That was a great read. The storries of both the U-57 and the USS Tang are incredible!

 

[spector39]

I think i might have read this a little wrong. I was thinking buoyant ascent, and not CESA.

If you read the shark attack story by Bret Gilliam i think he did a nearly 400 foot free ascent. Though he was severely bent he did survive.

A great story but not for the faint at heart.

Shark Attack! | Divers' Blogs

I have read that story before. Very chilling tale to say the least. When I initially read it, I doubted it; I had no idea a 400 ft. ascent was possible. I guess he's living proof that it is, if what he says is indeed true.

 

[spector39]

This is taken from the article MaxBottomtime posted.

“We knew that a system of free escape would work. If you’re down three hundred feet, the air you fill your lungs with is compressed. It’s also richer in oxygen. As you rise toward the surface, and the pressure on your body decreases, the air in your lungs expands. If you blow the air out on the way up, your lungs remain the same, and you’ll have plenty of oxygen to keep you alive all the way to the top. In fact, you can never run out of air. There’s always a liter of air in your lungs that’s never expelled.”.

The trick was managing the rate of ascent. “You had to watch the bubbles,” Schlech noted. “If you stayed behind the bubbles, you were okay. If you found yourself catching up with them, you’d have to blow harder. If you were falling behind, you’d hold your breath

The bold part above is counter intuitive, at least to me. "Exhale the last breath I have??" Everyone knows what a normal breath feels like. And we all know that if we keep exhaling (above surface,) we'll eventually hit a point where we can't exhale anymore. But under pressure, you just keep on exhaling as the air expands while you ascend. I'd hate to have to go through it; it must be a very surreal experience. :buggy:

 

[knotical]

Hi spector,

A challenge with deeper CESAs is controlling how fast to exhale. It can be a bit disconcerting to have nearly empty lungs at depth. Assuming a constant rate of ascent, the relative decrease in ambient pressure is less when you are deep than when more shallow. That's why it's often said we are at greater risk of lung overexpansion at shallow depths.

In my only actual CESA (j-valve days), I kept the reg in my mouth and kept trying to breathe. I got very little air at depth, but more as I got shallower. The key was that I tried to inhale and to exhale normally. When exhaling, I eliminated the risk of injury. When inhaling, I got the comfort of more air. It was actually a pretty benign experience.

Good questions. Keep thinking. It can make you an even better diver.

k

 

[CamG]

Greetings Spector39 and what some awesome real emergency reports to answer your question. I think the key here is EMERGENCY.
We practice CESA's for those emergencies only and in OW.
With more advanced environments overhead or decompression obligations you are operating with a ceiling or no direct access to the surface. Which dictate more advanced dive planning and or GAS MANAGEMENT.

This gas planning was introduced to me at the OW level and as I have progressed into more advanced dives gotten more critical.
A really good friend once told me you only rise to the lowest level of your training!
Having witnessed free flows at the local quarry he is so very correct.
On one hand you have the trained diver who correctly handles the situation and the other you have those who panic and cause life threatening issues over a free flow!
Divers train so that the risks of the underwater environment are managed and stress levels are managed as well.

The afore mentioned ascent from the sub is amazing and even for military personal those service men and women had to be wound pretty tight for such a situation.
When that is the only way out we will only rise to the lowest level of our training!
I am very appreciative that this was shared, like Leadturn shared knowing that it can be done is a comfort that I hope I never have to use but if I do gives me hope!
If I was in the service and on a sub I would be training like a mad man for sure!

At what depth can you ascend and not become bent? Well it depends on the divers hydration levels, time at depth and max depth, and conservative dive planning.
There probably are many more but the bottom line if you are diving Padi RDP and avoiding close to manditory stop times the risks are managed pretty well.
But not totally, there are exceptions.
People have gotten bent on shallow reef dives of normal length.
It just depends on the diver on that day and what kind of night they had.
A female diver had been out drinking and was dehydrated before the dive.
She took a hit from that alone. A chamber was available and she was fine after treatment.
Two divers can do the same dive plan deco schedule and one get bent and the other be totally fine.
Proper hydration is a critical factor when diving and the #1 way to minimize the risk of decompression sickness while following a conservative dive plan.

My philosophy is to plan the dive, dive the plan ; mull over all the specific hazards of the environment and who is going along and readjust the plan accordingly.
Obviously this is a abbreviation and the gear scrutiny is a three step process.
I find it mentally prepares me and helps to keep me always anticipating failures and moving to solve issues at depth. Training levels and experience are key factors to determine how challenging to make a dive or not.

I hope this helps but it is a different direction to the questions you were asking.
This is just my opinion and based on my experience and training. This not intended to offend or preach to anyone but rather offer a perspective to ponder.

CamG Keep diving....Keep training....Keep learning!

 

[knowone]

Free diving is a grounding upon which scuba should be based.
Breathe from your BC.
Say ahhh.
The heart is not designed to pump froth.
All kings have beheaded some of their subjects.

 

[Garrobo]

A while back I hired a DM to go diving with me on a shallow reef to practice emergency ascents. The deepest I tried one from was around 30 feet. I at first tried a couple with the reg in my mouth but found this made it hard to control the exhale process. So I did a couple with no reg and found it much easier. On the 30 foot ascents I had to go to the reg because I couldn't ascend any further without taking a breath at around 10 feet. I had a full tank of air so didn't have any problems with supply. A younger, healthier person with better lung capacity capabilities shouldn't have any problems doing a 30 footer in my opinion.