Panic!!!

[boulderjohn]

Stratification of gases in a scuba tank

First of all, it is impossible for me to guess how many times I have mixed gases. I have also taught gas blending courses.

When your first mix gases through partial pressure blending, you get stratification, with the stuff you put in last sitting on top of what as there first. When mixing nitrox or (especially) trimix), I don't even think of analyzing the gases until time has passed. If I need to analyze sooner, I agitate the tank by laying it on its side, picking it up, laying it down, etc. many times. With trimix, whenever possible I prefer to leave it for a day.

Please note: over time it becomes less stratified, not more stratified.

Right now I have a bunch of nitrox and trimix tanks in my garage that have been there for many moths because I have been laid up for health reasons. I guarantee you that if I were to go out analyze them right now, I would get the same results that are on the analysis sticker I put on many months (in some cases over a year) ago.

 

[lowwall]

Every time I see the title of this thread...

 

[boulderjohn]

About CESA:

Emergency ascent - Wikipedia

en.wikipedia.org

"This procedure is recommended for ascents where there is no decompression obligation, a free surface with little risk of entanglement, and the diver has sufficient breath hold capacity to easily reach the surface conscious.

I thought I would first point out a quote from the article you cited:

If exhalation is limited to relaxing and allowing the expanding gas to escape without effort, there should not be a feeling of running out of breath, as the air inhaled at depth expands during the ascent and the lung volume should remain nearly constant.[5]​

Please note that this contradicts your contention that CO2 buildup during the dive leads to diver panic.

Next, I found a quote following that which has me puzzled.

While in a practical sense there is little difference between a CESA and a "free ascent" (aka Emergency Swimming Ascent or ESA), the technical difference between the two is that in a CESA the regulator second stage is retained in the mouth and the diver exhales through it (in case gas becomes available due to the drop in ambient pressure) while in free ascent, the regulator is not retained or there is no regulator available, and the diver exhales directly into the water.[6]​

I have never heard of this differentiation, and I want to caution divers that they should always retain the regulator during an emergency ascent. If you were for some reason to inhale water during the ascent, that would start a reflex that would likely lead to drowning. Furthermore, something that has not been discussed here is that in an out of air situation, the tank is not actually out of air. The regulator does not have enough pressure to deliver air at the present depth because of the ambient pressure. When you get shallower, the regulator will be able to deliver some of the remaining air. Of course, that won't help you if you have discarded the regulator.

 

[CG43]

Hello

In addition to boulderjohn a calculation that shows how easy such an ascent can be.

The diver has a 10 l tank and breath in 50 m depths until the tank is empty .
The tank has now 10 l * 6bar/1bar = 60 l air .
The diver ascent from 50 m depths to 14 m with 18m/min. speed ( like littel bubbels) .
from 14m to 3m with 11m/min speed .

In 32m he toke his first breath of 3 l ; Runtime 1 min.
Now he has 60 l - (3 l * 4,2) = 47,4 L in his tank .

He ascents from 32 m to 14 m with 18 m/min . Now 14m depths : Runtime 2 min .

He breathes 6 l * 2,4 = 14,4 l . Now he has 47,4 - 14,4 = 33 l in his tank .
He ascents from 14m to 3 m in one minute . Runtime 3 min.

In 3m he can breath until tank pressure is 1,3 bar . ( 10 l *1,3) = 13 l in the tank .
The diver has (33 - 13) l = 20 l air he can breath from the tank .
Because the pressure is 1,3 bar he has (20 l / 1,3) = 15,4 l air for breathing in 3 m depths .
That's enouth for 1 min. safety stop . Runtime 4 min.

Everything easy , or not?
I tried this and yes it worked for me.
Every diver can train the ability to do so and no one but himself is to blame if he voluntarily renounces this piece of safety .
For me, freediving is an effective training to react sensibly and relaxed in LOA or OOA.
There may be others too i don't know .

 

[Goonzodiver]

Hello

In addition to boulderjohn a calculation that shows how easy such an ascent can be.

The diver has a 10 l tank and breath in 50 m depths until the tank is empty .
The tank has now 10 l * 6bar/1bar = 60 l air .
The diver ascent from 50 m depths to 14 m with 18m/min. speed ( like littel bubbels) .
from 14m to 3m with 11m/min speed .

In 32m he toke his first breath of 3 l ; Runtime 1 min.
Now he has 60 l - (3 l * 4,2) = 47,4 L in his tank .

He ascents from 32 m to 14 m with 18 m/min . Now 14m depths : Runtime 2 min .

He breathes 6 l * 2,4 = 14,4 l . Now he has 47,4 - 14,4 = 33 l in his tank .
He ascents from 14m to 3 m in one minute . Runtime 3 min.

In 3m he can breath until tank pressure is 1,3 bar . ( 10 l *1,3) = 13 l in the tank .
The diver has (33 - 13) l = 20 l air he can breath from the tank .
Because the pressure is 1,3 bar he has (20 l / 1,3) = 15,4 l air for breathing in 3 m depths .
That's enouth for 1 min. safety stop . Runtime 4 min.

Everything easy , or not?
I tried this and yes it worked for me.
Every diver can train the ability to do so and no one but himself is to blame if he voluntarily renounces this piece of safety .
For me, freediving is an effective training to react sensibly and relaxed in LOA or OOA.
There may be others too i don't know .

If I understand correctly your ascent begins with a CESA that lasts twice the limit for which PADI considers CESA safe (I recently spoke to a PADI instructor about this).
Then it is interrupted with a breath and then everything else.
You have successfully performed this ascent, but if I remember correctly you are also a freediver.
So I am left with the doubt of having grasped the message.
Do you think this aspect (freediving capability) is useful in this context?
If not in this context (CESA ascent following a failure of the breathing apparatus at 50m) , what other cases (you are talking about LOA or OOA, and in another comment you wrote "Nevertheless, many accidents would be preventable by apnea skills.") may exist?

[I didn't think it was possible to extract air from the tank below 8~10bar, but the rest of the reasoning doesn't change much.]

PS:
The moral for me is, if you are a solo diver you should not go to a depth from which you cannot manage a controlled emergency ascent [i.e. a CESA]. That this depth exists and varies from person to person I think is beyond doubt.

 

[CG43]

Hello Goonzodiver

At the time when I did these experiments, I was able to freedive 30 m deep and 4 minutes long breathholds on a good day . In this respect, I was well prepared and there were no difficulties.
Padi can only give procedures and limits for most divers. And that's what Padi does here is reasonable .

Since I didn't have a computer at that time, the ascent speed and thus also time is only approximate according to the then common method of small bubbles.
I took the breaths while swimming up. The used specified depth value is for the calculation.
First and only stop in 3 m .
The attempts I made was without BCD in warm water with little neoprene, and less lead.
CESA or buoyant emergency ascent, the difference would not have been very big,
I didn't drop any lead , but i would do if if is nessesary to come up without overexertion .

The reg. I used was a tuned Dräger Secor 200 UPSTREAM. It already works perfectly at 4 bar ip .
The lower the ip, the lower the cracking sucction.
With slow inhalation you can breathe down the tank to almost zero over ambient pressure ,
especially at shallow depths.
Since you use more air at great depths, you are forced to surface even earlier and the calcalation becomes even better.
By the way : The same applies to simple downstream regs .

The basic idea of this type of ascent is to breathe out of the tank first at a shallow depth, because this saves air.

Here is an another explanation why the exhalation of the air expanding during the ascent reduces the respiratory stimulus :
1.) The concentration of CO2 in the lungs does not change through exhalation
2.) The ambient pressure decreases during exhalation time .
3 With constant CO2 content and decreasing total pressure, the CO2 partial pressure decreases.

During this time, new CO2 is produced. Depending on the balance, the PPCO2 increases or decreases

 

[bshmerlie]

14 pages of answers to a topic about mask clearing and panic. wow. I just want to say something about handling yourself in stressful situations. Everyone is different. Repetition and training are the best methods to ensure you don't panic in various situations. Practice all the various skills you learned in your OW course and practice some more. The more you do something (ie diving) the more comfortable you will be handling various situations that may come up. BUT some people's personality are just more prone to panic than other people. So know yourself. Are you a high stress, high anxiety type of person? Do you get overstressed in common everyday situations at work or in your everyday life? Some people can handle stress better than others and some people are quick to panic. If you are the type of person who is quick to panic in a stressful situation than maybe diving is not the sport for you. Know yourself and be honest with yourself. Diving should be a relaxing a fun experience. If you are feeling anxiety or fear every time you go down. Then honestly it's probably best just to stick to snorkeling. Not everyone is meant to dive and that's Okay. There are a lot of other sports out there.

 

[Goonzodiver]

14 pages of answers to a topic about mask clearing and panic. wow. I just want to say something about handling yourself in stressful situations. Everyone is different. Repetition and training are the best methods to ensure you don't panic in various situations. Practice all the various skills you learned in your OW course and practice some more. The more you do something (ie diving) the more comfortable you will be handling various situations that may come up. BUT some people's personality are just more prone to panic than other people. So know yourself. Are you a high stress, high anxiety type of person? Do you get overstressed in common everyday situations at work or in your everyday life? Some people can handle stress better than others and some people are quick to panic. If you are the type of person who is quick to panic in a stressful situation than maybe diving is not the sport for you. Know yourself and be honest with yourself. Diving should be a relaxing a fun experience. If you are feeling anxiety or fear every time you go down. Then honestly it's probably best just to stick to snorkeling. Not everyone is meant to dive and that's Okay. There are a lot of other sports out there.

in reality most of these pages discuss aspects quite disconnected from the main theme.
I think it is because of me in fact if we went off topic and therefore I apologize to all readers..
However I am anxious, but anxiety CAN AND MUST BE CONTROLLED.
And I certainly won't give up going underwater!

 

[CG43]

Hello

Got me thinking, how often / common are panics? Does everyone have one at some point during their diving 'career'? What are peoples opinions?

I don't think we went out of topic .

A real or imagined danger is the mental prerequisite for panic.
The second prerequisite is the physical reaction to perceived danger, the fight/flight reaction.
These two components can reinforce each other and then cause panic .

Through mental or practical exercises of potentially dangerous situations, it is possible in many cases to interrupt this vicious circle. A second option is to work on the physical reactions .

Typical physical characteristics of panic are :
High heart rate
Skeletal muscles tensed (fight/flight)
Rapid breathing
Nervousness and restlessness

The typical physical characteristics in freediving are the opposite of this.
This breaks the vicious circle of panic, and also reduces O2 consumption and CO2 production..
If the diver succeeds in activating his freedive mode, he has a good remedy for panic and fear , which is applicable in many different cases. This is very helpful to successfully control anexia.