Anybody done an Emergency Ascent?

[Charlie99]

A bubble is a bubble nomatter who's body it is in. Physics is not going to change from one body to another.

As you get shallower the bubble will expand faster than at depth. One could, in theory, hold their breath from 600' to 500' without expansion problems. But from 10' to 0' could be fatal.

We seem to be talking past each other. Of course I agree that bubbles will expand faster when shallow. That's why I pointed out that during the last 33' of an ESA that you would have to exhale air equal to what was in your lungs at 33'.


My intent was to state that my experiences with ESA differed from your comments such as "It is surprising at how hard you exhale to do this safely" and "On Free assents your blowing fairly strong. On Buoyant assents you are actually yelling in the hoods mouthpiece."

My experience in more in line with glbirch's "Exhaling gently all the way of course".

Furthermore, my posts were an attempt to point out that, contrary to popular myth, you can simply keep your airway open and let the excess air effortlessly and automatically bubble out.

I will even go so far as to say that training that has people excessively exhaling, humming, yelling, etc. is improper.

Along the same lines is the frequent admonition to "never hold your breath", without explanation of what this really means. I have no concern at all about pausing my breathing at any point of the breath cycle provided my epiglottis is open and my airway is not otherwise obstructed.


Here is an interesting post of one of Scubaboard's medical moderators about a 5 minute free ascent from 30 meters at a Submarine Escape Training Tower.

 

[sea nmf]

On one of my first dry suit dives, my weight belt came off, and I wasn't quick enough to grab it (I know . . . .too much weight, over-inflated, etc).

I was at 50', inverted (not horizontal - I was trying to see something), and being in a big balloon, I went up feet first. It happened so fast I didn't think of "flaring" to slow down. But I did remember to say "aaaaahhhhhh" all the way up and not take a breath.

All was fine. So it can be done but it is not recommended. Situational awareness and all that.

 

[miketsp]

I accompanied a diver that panicked at 25m+ after having problems with the reg and shot for the surface before I could donate. I followed just a little slower and breathing regularly which was just as well as I was then able to assist.

 

[SueMermaid]

So.....if you dive within the NDL, you should, theoretically, be able to do an emergency ascent without killing yourself. Or did I learn something different? Is that not the whole purpose of the dive tables? Or am I missing the point altogether?

 

[Gary D.]

We seem to be talking past each other. Of course I agree that bubbles will expand faster when shallow. That's why I pointed out that during the last 33' of an ESA that you would have to exhale air equal to what was in your lungs at 33'.


My intent was to state that my experiences with ESA differed from your comments such as "It is surprising at how hard you exhale to do this safely" and "On Free assents your blowing fairly strong. On Buoyant assents you are actually yelling in the hoods mouthpiece."

My experience in more in line with glbirch's "Exhaling gently all the way of course".

Furthermore, my posts were an attempt to point out that, contrary to popular myth, you can simply keep your airway open and let the excess air effortlessly and automatically bubble out.

I will even go so far as to say that training that has people excessively exhaling, humming, yelling, etc. is improper.

Along the same lines is the frequent admonition to "never hold your breath", without explanation of what this really means. I have no concern at all about pausing my breathing at any point of the breath cycle provided my epiglottis is open and my airway is not otherwise obstructed.


Here is an interesting post of one of Scubaboard's medical moderators about a 5 minute free ascent from 30 meters at a Submarine Escape Training Tower.

Depending on the hood the speed of the assent can be fast enough where you do yell in it. I have hit the surface still yelling. As far as humming you can hum at any rate so it isn't wrong. What is wrong is excessive exhaling. We were tought the proper and improper rates prior to doing it.

Her is a couple of links.

http://www.subvetpaul.com/SB_Tank.htm

http://www.nr-1-book.com/NewFiles/EscapeTraining.html

http://www.divernet.com/technol/escap298.htm

http://www.royal-navy.mod.uk/static/pages/3940.html

The Royal Navy is close to our training but not exact. We didn't have the cable to ride and our tank in Pearl was larger.

Gary D.

 

[H2Andy]

So.....if you dive within the NDL, you should, theoretically, be able to do an emergency ascent without killing yourself. Or did I learn something different? Is that not the whole purpose of the dive tables? Or am I missing the point altogether?

yes and no. a slow ascent, even within NDL, is in fact
a rolling "decompression stop."

if you go up too fast, you have missed this "decompression
stop" and the risk is there for DCS, even if you were
within your NDL's before beginning the ascent.

however, the far greater risk is for pulmonary baurotrama, if you don't keep your airway open on the way up
to allow the expanding gas in your lungs to escape harmlessly.

 

[ShakaZulu]

So.....if you dive within the NDL, you should, theoretically, be able to do an emergency ascent without killing yourself. Or did I learn something different? Is that not the whole purpose of the dive tables? Or am I missing the point altogether?

You got it babe...............CESA - Controlled Emergency Swimming Ascend should really be your last option. That's why we have dive buddies right???

With regard to the question at hand, only during practise.......may the day never come.

 

[miketsp]

So.....if you dive within the NDL, you should, theoretically, be able to do an emergency ascent without killing yourself. Or did I learn something different? Is that not the whole purpose of the dive tables? Or am I missing the point altogether?

H2Andy's comment above is quite right. My dive tables show NDLs which are based on 9m/min ascents. These are rolling deco stops.
In the case of the CESA I mentioned above from 25m+ I believe we got away with it without any complications because it was right at the beginning of a dive. I spent less than 2 minutes at depth and the diver that did the CESA, less than 4.
If it had been at the end of the dive I doubt if I would put my own health at risk to accompany a diver doing a CESA.

 

[Doc Intrepid]

So.....if you dive within the NDL, you should, theoretically, be able to do an emergency ascent without killing yourself. Or did I learn something different? Is that not the whole purpose of the dive tables? Or am I missing the point altogether?

Agree with Charlie99 on all counts.

I've done two, both from between 100' and 110', about twenty years ago. The first one was quite deliberate, a rite of passage done with a graduating IDC course, in warm, very clear tropical ocean in the South Pacific.

The second one wasn't deliberate, and occurred in very cold, dark, fresh water off a wreck in Lake Michigan.

Both went well, relatively speaking. Short bottom times. At the time of the latter, however, I was grateful for having done the former. Many lessons learned that day. It certainly can be done but it helps if you're reasonably relaxed, swim up slowly, and - as Charlie99 notes - simply keep the airway open, blowing small bubbles, at a rate which sustains you all the way up. (And you do catch another breath or two off the reg at 30' and above, obviously keep the regulator in your mouth.)

 

[SueMermaid]

H2Andy's comment above is quite right.

Of course it is! Andy's always right!
Seriously, I agree too, I didn't mean popping to the surface like a cork, (my instructor pounded into us the soda-can principle), but a nice, calm, slow emergency descent on one (unheld!) breath.