Compressed air mid-freedive

[5ata]

I'm sorry, I've stayed out of this up till now, but I must point out that you can't have it both ways.

Then tell that to some of the top world champion freediving spearfishing competitors who had to be transported to the chamber while competing in the world spearfishing championships in Tahiti a few years back....

You can get bent while freediving... Read Fred Bove's article on the very subject - http://www.skin-diver.com/departments/scubamed/FreedivingCauseDCS.asp?theID=626

As I said - research before making a blanket statement...

 

[freediver]

The is a laryngospasm that takes place once the freediver blacks out that closes off the airway - it is a physiological response to prevent water from entering the lungs - Audry had actually tried to make her way up to the second safety diver - she had refused air from the bottom one, but she blacked out on her attempt to ascend and once that happend, there was no way to give her air due to the closing off of her airway. I had to go back through my notes from when it occurred and see what I had written along with my physiology information related to freediving. Bottom line - she blacked out and could not have been given air.

In addition, her lungs were filled with plasma as stated before due to MDR - combine the elements of her dive - she was dead once she blacked out.

Arm chair scuba divers can debate this until blue from hypoxia, the reality is, unless you freedive and experience the actual physiological sensations that occur, you are speculating without experience.

This is correct, a laryngospasm (vocal chords constrict) is a known response in drowning. Also, bear in mind that, at this depth, the diaphragm doesn't have the range it should and it is the primary muscle in respiration.

 

[Marlinspike]

Thanks 5ata. I think some people are just fixated on the gas physics of the hypothetical and forgetting that there are physiological issues as well.

~Marlinspike

 

[Dibblerr]

Dude if you want FACTS, the internet is GREAT place to go!

~Marlinspike

Not quite sure what to make of this

5ata - Post #60
Absolutely fantastic answer, explains very well why gas could not be given
Just wonder why we had to go through 50+ posts of O2, CO2, N2 loading, lung volumes, expanding gases and other ideas which contradict each other & do not make much sense when Post 60 gives such a straightforward answer.

I dont know the 1st thing about freediving and dont pretend to but do have my share of common sense.

Safe Free/Diving

 

[Marlinspike]

So first you are kicking 5ata calling him an armchair diver and now you finally agree he knew what he was talking about. Glad you came to your comon senses.

~Marlinspike

 

[5ata]

Dibblerr - human nature usually dictates that when one doesn't understand something, one makes an assumption based upon current information. The challenge is it took this long due to realizing on my part that scuba divers usually have no information regarding the full physiological responses that occur while freediving. I needed to step back and review what was written to realize that I was not imparting the other half of the equation - that of the physiological aspects. So for that - my Bad...

The great part about freediving is that all the technology is removed and you are left with what you are capable of - gimme a pair of composite long blades, my Cressi Minima mask, a simple J snorkel and a freedive wetsuit - and I'm a happy man..

 

[Dibblerr]

So first you are kicking 5ata calling him an armchair diver and now you finally agree he knew what he was talking about. Glad you came to your comon senses.

~Marlinspike

As you can see by my post count here and elsewhere, I dont post much on diving message boards as most of what I say usually gets taken the wrong way, much like real life really.
I do read an awful lot of content on them though and one common theme running though a lot of threads is people suggesting things as 'fact' and then when called seem to wriggle & back down. Initial postings on fizziology here suggested this might have been the case.

It wasnt my intention to call 5ata an Armchair diver however re-reading my post it did read as such.

We got the answer however it came about.

5ata: again excellent info from post 60+

Signing off on this one...

 

[Charlie99]

Nitrogen absorption doesn't take place because the freediver isn't exchanging air during their dive.....Nitrogen absorption doesn't take place because the freediver isn't exchanging air during their dive. They begin and end their dive with the same volume of air. Since respiration doesn't take place, there is no exchange of gases. No exchange of gases - no increase in nitrogen absorption.

Your statement that "Nitrogen absorption doesn't take place because the freediver isn't exchanging air during their dive.....since respiration doesn't take place, there is no exchange of gases... No Exchange of gases - no increase in nitrogen absorption" is the core difference in our understanding of the physics and physiology.

That statement is similar to a belief of some novice scuba divers that a heavy breather who breathes through a tank faster than another diver has been exposed to more nitrogen, so therefore the N2 loading of the heavily breathing diver is higher. As has been explained by various diving physicians, including Dr. Deco right here on Scubaboard, that belief is false.

The more generally accepted theory is that absorption from the lungs into the blood is determined by the partial pressure of N2 in the lungs. The fraction of N2 doesn't change dramatically during either breathing or breathholding. What does change is the ambient pressure due to depth. Everthing I have seen in decompression literature indicates that, in normal freediving depths, there is virtually no difference in N2 absorption between a freediver and a scuba diver diving the same profile. Obviously, there are many additional effects from doing extreme depths, but it appears that you and I differ in our understanding of what happens on even a 100' freedive.

Some day I'll get around to acquiring the freediving books you mentioned. I will be very surprised if they actually support what you have posted about nitrogen absorption in freedivers.

 

[5ata]

You're entitled to your position and I'm not going to try and convince you otherwise

 

[Thalassamania]

Then tell that to some of the top world champion freediving spearfishing competitors who had to be transported to the chamber while competing in the world spearfishing championships in Tahiti a few years back....

You can get bent while freediving... Read Fred Bove's article on the very subject …

As I said - research before making a blanket statement...

1) You stated that there was no gas exchange.

2) You that without gas exchange you can't get bent.

3) You now agree that free divers have been bent.

Ipso facto, you can't have it both ways.

Read and remember what you wrote before making a blanket statement ...

You don't need to take cyanide to understand (and explain to others) that it can kill you as it binds to the iron atom of the enzyme cytochrome c oxidase in the mitochondria of cells, this deactivating the enzyme and breaking the electron transport chain and rendering the cell no longer able use the oxygen which is available to it.

Similarly, you do not need to freedive to understand (and explain to others) what occurs. All that was being requested was that you provide such an explanation on an anatomical/physiological level. Rather, you obfusticated and hemmed and hawed, leaving those of us who do not know you with the feeling that you have no idea of what you are talking about. I, for one, will chalk it up to the obvious emotion of the moment.

Let’s start again, politely and rationally:

1) what is there, on an anatomical/physiological level, other than narcosis which we understand, to prevent a freediver at great depth from taking a breath of trimix?
2) if it is possible to take such a breath what, again on an anatomical/physiological level, prevents a free diver from making an exhaling ascent to the surface?
3) Of what use is a safety diver if he or she is not equipped for and can not provide emergency assistance?
4) What references can you supply to support your answers to these questions?