Why scuba diver can't share gas with freediver?

[dumpsterDiver]

How does one inhale? What makes it happen? Never having been presented with this problem before, I think that mechanism is an issue here.

You can lower the diaphragm, expand the chest, and raise the collarbone. These actions increase the size of the chest cavity, which causes air to come in through the mouth and nose. A free diver frequently does all three, at which point no more air can be inhaled because the chest cavity is already at maximum size.

When the diver descends, the gas within the lungs becomes more dense, causing the lungs to shrink. Does this cause the chest cavity to shrink as well? Descending also cases the air in the sinuses and middle ears to become more dense as well, but does that cause the skull to shrink?

I certainly have not tried it, but I would guess that a free diver who has descended with full lungs would be unable to inhale without first exhaling at least some of the air inhaled at the surface.

Wow,,, the chest of a freediver compresses a lot. You get very heavy when freediving. As an instructor you should know that the sinuses in the head are a rigid air space and a diver (freediver or scuba) will experience barotrauma if the internal and external pressure is not equalized.

Does the skull shrink? I will leave that one unanswered. Maybe it is a Halloween question?

An no a freediver does not have to exhale air from the surface in order to inhale at depth??? I don't even have a clue how you would come to that "guess"?

As I already described, take a deeeep breath from a scuba tank and start swimming down hard. After 20 or 30 feet, you will be able to inhale and inhale and inhale as you descend- completely analogous to being able to exhale and exhale and exhale when a scuba diver does a free ascent.

 

[Lost down under]

As I already described, take a deeeep breath from a scuba tank and start swimming down hard. After 20 or 30 feet, you will be able to inhale and inhale and inhale as you descend- completely analogous to being able to exhale and exhale and exhale when a scuba diver does a free ascent.

At 20-30 ft it's fine but around 150ft your getting into seriously dangerous territory, I wish I could talk about the science with confidence but I don't really understand the mechanics, something to do with at 50 odd meters the lungs take on alot more blood than they normally would protecting themselves from collapsing, this isn't always a good thing.

All theoretical of course, you'd have to be properly mad to be playing a clown at 50m.

 

[dumpsterDiver]

At 20-30 ft it's fine but around 150ft your getting into seriously dangerous territory, I wish I could talk about the science with confidence but I don't really understand the mechanics, something to do with at 50 odd meters the lungs take on alot more blood than they normally would protecting themselves from collapsing, this isn't always a good thing.

All theoretical of course, you'd have to be properly mad to be playing a clown at 50m.

Yes we already talked about that. There is so much incorrect information in this thread it is hard to sort out... At a "reasonable" depth a freediver can take a a hit from a regulator and just swim up, but that does NOT mean that it should be done.

 

[ican]

The reason for my post is not completely unfounded. I may be new to diving, but I'm not new to the science of compression or water. Here's my reasoning... At the surface, a free diver takes a breath of regular 1atm air. When he dives down to 150 feet, and decides he needs to take a breath on a Scuba tank from a rescue diver, it's not likely he's going to just take one breath. Even if it is only a single breath, he now has all the air he had from the surface in his blood vessels due to the compressive effect of depth, and takes another breath of compressed air. Unless he exhales all the way to the surface at this point, he has to keep breathing from the tank and stay with the scuba diver. Every breath he takes is now pumping nitrogen into the free diver's bloodstream, which wouldn't have been an issue had he just taken the surface breath, or the single breath at depth on the tank, then exhaled to the surface. But since the likelihood of a single breath is slim, he needs the same decompression stop that the scuba diver needs for that depth and time at that depth, or he risks getting bent, or a DCS issue.

In my initial post, I shouldn't have said it would be necessary on a single breath to stay with the diver the whole time on the ascent, but more than one breath, and the freediver is now a scuba diver sharing air, and has all the same responsibilities to prevent injury as any other scuba diver.

 

[captain]

Several years back at Vortex Springs while down at 60 feet I feel a tap on my shoulder. It was a free diver asking for a breath from my regulator, I handed it to him and he took a breath or two and swam off. After the dive I met him and found out he was a Navy diver from NEDU at Panama City and often begged air from divers.

 

[dumpsterDiver]

Freedivers do some weird things for "fun".. but this does address some of the questions in this thread.


[video=youtube_share;gg0fAIfgi5Q]http://youtu.be/gg0fAIfgi5Q[/video]

 

[Storker]

Freedivers do some weird things for "fun"..

They sure do. (Warning! The video in the link will definitely be NSFW in quite a few work environments!)

And despite the fact that she takes even several sips of compressed air while submerged, there's no indication of any "explosive decompression" going on...

 

[mrdre]

They sure do. (Warning! The video in the link will definitely be NSFW in quite a few work environments!)

And despite the fact that she takes even several sips of compressed air while submerged, there's no indication of any "explosive decompression" going on...

I was looking for exactly this video for 10 minutes just to post it here )

 

[Storker]

It is kinda like doing a scuba entry from an elevated tree stand using a rope swing, just because it might be fun and we can do it, doesn't mean we should do it..

Tree stand and rope swing? Bah.

[video=youtube;pQQb2FP1ewE]https://www.youtube.com/watch?v=pQQb2FP1ewE[/video]

(No, you wouldn't see me do that for a million dollars!)

 

[sphyrnidus]

It's a miracle I'm still alive. When we were young, 14-15 year old, back in the sixties, we used to do this all the time. I lived on curaçao and when we saw divers below when snorkeling (most friends of my parents) we swam down, took some breaths and exhaled all the way up. There was no deco chambers back then. For scuba training in 1968 we had to don and doff in the ocean at 30 ft! That was the normal procedure. As I helped the instructor every week till 1980, I did this hundreds of times to illustrate for the trainees what they had to do, see one, do one. And here I am today


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