Free Diving and DCS

[eyy]

Thanks for the input guys,

I was thinking more along the lines of the amount of N2 that we can hold in our lungs.

Is that enough to get bent on.

:idea:

Thanks

 

[cabrerad]

Eyy,


Since your original question concerned free diving on days you are not SCUBA diving, there should not be any problems with that. As for diving on days you dive, the consensus seems to be to wait a few hours before free diving. Some competition free (non SCUBA) divers have claimed they have been bent, but they also went down to 80 meters. I gather you probably don't dive that deep. Anyone else feel free to chime in.

 

[pescador775]

Originally posted by eyy
Thanks for the input guys,

I was thinking more along the lines of the amount of N2 that we can hold in our lungs.

Is that enough to get bent on.

:idea:

Thanks

The answer to your question is yes. I thought I made that clear, apologies.

At surface pressure the amount of dissolved nitrogen in the human body is about one liter. Borrowing from classical Haldanian theory and Henry's law, this amount can be doubled to about two liters without subsequently incurring DCS. However, the human lungs, when inflated to maximum, contain approx 4 liters of nitrogen. I think you get the picture.

For example, if you could freedive to depths of 100 feet or more, and hold your breath for 30 minutes, you would get the bends, in my opinion.

 

[Liquid]

I ahvent read all the answers, so what I am going to write here might have alreay been written by another, but anyway-

-Let's start with free diving in normal conditions (no prior scuba)- here there is absolutly no risk of DCS whatsoever for a very simple reason- the amount of niterogen in the lungs is not enough to creat DCS. That simple. That's also why whales, dolphines turtles and others do not get DCS.

-Scuba and free diving-Now here's a very risky combination-Free diving after scyba is extremly danegerous and unrecommended. I know of a few people that got DCS this way, one had explosive DCS and died on the spot ( a friend of mine witnesed it, horrible!). As for free diving BEFORE scuba- no problem here.

-Free diving a day after scuba diving-Here i belive that the best solution as to be sure you are clear of niterogen before attempting it. I guess that you have a dive computer-If the computer clears you for flying, it should be also enough for free diving (as long as it has been at least 12 hours since you SCUBA).

That's about it.

 

[pescador775]

That was enough. Heh, heh.

I've shown that the human lungs hold more than enough nitrogen to place a freediver at risk of bends, if he can hold his breath long enough and dive deep enough. To me, this was largely a theoretical issue but I realize now that it is important to address this old myth which is widely banded about, eg, that there is not enough N2 in a divers natural lung capacity to place one at risk.

The question of freediving and SCUBA is really a repeat of the controversy of whether it is better to dive deep and then shallow or dive shallow followed by deep dive. Recently, there has been some extra sauce added, namely the "sawtooth" theory.

The answer is that no one knows, that's why it's controversial. My view is that the two diving styles should be treated the same. That is, that the question is solely of nitrogen loading calculated as total bottom time less surface time.

Those who make a Scuba dive following on a period of free diving should have the forethought to estimate their repetitive group status as a result of any previous free diving. Same with the reverse situation. As a practical matter I believe that any freediving following on a Scuba dive should be restricted to 30 feet or less. As suggested by cablerad, a surface interval would seem to be a sensible precaution as well.

 

[eyy]

Thanks guys I appreciate the input.

I was thinking about the theoreticals I guess.

EYY

 

[Liquid]

Originally posted by pescador775
1)
The question of freediving and SCUBA is really a repeat of the controversy of whether it is better to dive deep and then shallow or dive shallow followed by deep dive. Recently, there has been some extra sauce added, namely the "sawtooth" theory.
2)
Those who make a Scuba dive following on a period of free diving should have the forethought to estimate their repetitive group status as a result of any previous free diving. Same with the reverse situation. As a practical matter I believe that any freediving following on a Scuba dive should be restricted to 30 feet or less. As suggested by cablerad, a surface interval would seem to be a sensible precaution as well. [/B]

1) Actualy- there's a solid answer to the shalow than deep/deep than shalow quesion-and it's Deep than shallow. why? for a very simple reason- The dive tables are based on calculations that one of their factors is that every dive is as deep as the last one or shalower, but never deeper. Do it otherwise, and you change the algorithm. I worked a bit with some formulas and saw how it affects the tissues.

2)FREE DIVING AFTER SCUBA IS EXTREMELY DANEGEROUS. it dose't matter if you rstrict yourself to 30', as this is the mest danegerouse area. Just imagine- you go out of a dive, you have some micro-bubbles and you start free-diving,wich couses the bubbles to shrink and expend very quickly, cousing buble to join bubble and aventualy forming bigger bubbles. A a surface interval is a must on these cases, you should treat it the same as going to an airpalne. free diving the day after, should pose no problems.

My 2 agorot .

 

[pescador775]

Just imagine- you go out of a dive, you have some micro-bubbles and you start free-diving,wich couses the bubbles to shrink and expend very quickly cousing buble to join bubbes aventualy forming bigger bubbles.

Thanks, but I'd rather not imagine things in lieu of evidence. You continue to present speculative theories published by others as facts.

 

[Liquid]

Originally posted by pescador775


Thanks, but I'd rather not imagine things in lieu of evidence. You continue to present speculative theories published by others as facts.

I have personally witnesed DCS due to free diving after scuba. A friend of mine witnesed a case of explosive DCS that was coused by it, with instant death. As for bubble mechanics-I'll be the first to admit that I am not exactly in the first line of researchers, but I do have some aquired knowledge in the subject, and have spoken to several specialists about it during my days as an instructor, and later. I have also worked on several RGBM-like algorithms, in which the size of bubble is a thing you can practically "see". Imagtine what you like, but do yourself a favour-dont free dive after scuba.

 

[pescador775]

You still haven't given any facts, only stories and speculation. As far as I know the only way that the bubble theory has been demonstrated in the laboratory is with sound waves or vibrating reeds. Thousands of cycles of compression and rarefaction are required to produce this effect, far more than the fifty or so up and down pressure excursions experienced by a free diver on a typical 4 hour swim.

It could be argued that human blood is fundamentally different in some way as to effect a different outcome but this is again, speculation. The points of contention might be the existence of "micro bodies" or surfactants. Indeed, researchers who have observed the bubble expansion under lab conditions state that the origin of the bubbles can be traced to dust motes or mineral inclusions in the test bath. The natural accumulation of gas around these tiny inclusions becomes a focus of expanding gas bubbles as the sound or vibrations are injected into the bath.

Right now, I am aware of only one reputable paper on the subject of biologics (other than test animals) and bubble trouble due to the "sawtooth" theory. This "surfaced" recently as a way of explaining beachings of whales at AUTEC. The hemmoraging and bubbles in the whales are thought to be related to water borne sound pulses from Navy undersea transmitters.