Technical Freediving: Are Breathhold Divers Ready To Mix It Up? - DeeperBlue.com

[johndiver999]

Being ignorant is a bit different than changing the laws of physics. Pulmonary barotrauma and DCS odds do not go down with rapid accents from breathing compressed gas at depth.

The chance of DCS might not necessarily go up if you are comparing air versus nitrox for the "freediver".

 

[CuzzA]

Not sure who's being ignorant but it is a long bow to draw to poo poo something you have not been trained in/experienced.
What if Krack has devised a procedure to control these risks? I certainly don't know if he has or not. He may make a 20ft stop on ascent and exhale??

You are right. I am not trained to mix scuba and freediving. I'm unaware of any agency that advocates that practice. The issue is not what Krack does, the issue is writing an article that could be viewed as normalizing it for Joe Blow or some kid who would really love to shoot that big carbo sitting at 150 ft. and figures he could just do a breath up at 50 and get the fish, but doesn't exhale at the right depth and pops his lung, or even begins his exhale at the right depth, but runs out of gas and blacks out.

The beauty of technical scuba diving is there are gate keepers. You're not just going to walk into a shop and get a trimix fill and a bottle of o2. This helps prevent accidents and a black eye on our sport. There wouldn't be gate keepers for so called "technical freediving." Most divers do both and/or can easily access a scuba tank.

Keep in mind my goal is to bring out discussion. Devil's advocate is welcomed.

 

[CuzzA]

The chance of DCS might not necessarily go up if you are comparing air versus nitrox for the "freediver".

For pre breathing on the surface, I agree.

But here's a snip from the article. Keep in mind most freedivers will do a bunch of dives throughout the day.

Fattah has even investigated exhaling at the surface, taking a single kick to negative buoyancy, and then breathing nitrox at 15 m/50 ft, thus eliminating most of his CO2 load, which is typically generated in the first part of the dive, and then continuing his descent. Note that a breath from a regulator at 15 m/50 ft, that is 2.5 ATA gives the diver 2.5 breaths of air. “It gives you a huge advantage, with all that oxygen and little CO2. Someone in top shape could easily do a 10-minute dive” he said.

Clearly, the reclusive Fattah, who has an unorthodox approach to diving is not shy about his views. “I’m an advocate of nitrox. It adds a dramatic safety factor and practically eliminates surprise blackouts. I have had close calls with air but none on nitrox, not even close,” he said.
​

There's nothing clarified here. Kick to 50ft. and then start breathing nitrox. Well, for how long? One breath? A few minutes? What computer is going to keep track of nitrogen loading for this type of diving? Do 50 of those dives over the course of a few hours and you may get bent.

There's another issue with his statement regarding blackouts. No doubt if you do the same profiles as you would normally you would be reducing the chances of blackouts, but in the same quote he's talking about the benefits of extending the dives. The extended dive could very well put you back into the same or greater blackout risk. If you increase your o2 by 2.5 ata's, but extend your dive by 2.5 times, did you really increase your safety factor? Especially since you now have to start exhaling at 50 ft. rather than at or near the surface.

 

[johndiver999]

I thought the article was really interesting. I was very surprised that they seemed to imply that nitrox reduces narcosis relative to air. I can't imagine being able to dive to a wreck as 130 ft for 6 minutes (on a scooter).

I think some of the safety concerns need to be put into the "freedive perspective". Some of these people are doing over 330 ft on one breath while alone for almost the entire dive. Remembering to exhale when your lungs feel full does not really sound all that hard to me in comparison- especially if you set a computer alarm for the initiation of exhalation depth perhaps?

The oxygen toxicity with breath up of rich mix seems scary to me, but anecdotal evidence will generate answers as to what is reasonable and what is not.

And if you read the article, they are saying that the chance for low oxygen black out is really eliminated because the pain caused by the Co2 build up will force the ascent and termination of the breathhold. So they are arguing that low oxygen will no longer be the limiting factor. So the longer dive will be safer .. they say,

 

[CuzzA]

I thought the article was really interesting. I was very surprised that they seemed to imply that nitrox reduces narcosis relative to air.

I caught that error too.

 

[John C. Ratliff]

For pre breathing on the surface, I agree.

But here's a snip from the article. Keep in mind most freedivers will do a bunch of dives throughout the day.

Fattah has even investigated exhaling at the surface, taking a single kick to negative buoyancy, and then breathing nitrox at 15 m/50 ft, thus eliminating most of his CO2 load, which is typically generated in the first part of the dive, and then continuing his descent. Note that a breath from a regulator at 15 m/50 ft, that is 2.5 ATA gives the diver 2.5 breaths of air. “It gives you a huge advantage, with all that oxygen and little CO2. Someone in top shape could easily do a 10-minute dive” he said.

Clearly, the reclusive Fattah, who has an unorthodox approach to diving is not shy about his views. “I’m an advocate of nitrox. It adds a dramatic safety factor and practically eliminates surprise blackouts. I have had close calls with air but none on nitrox, not even close,” he said.
​

There's nothing clarified here. Kick to 50ft. and then start breathing nitrox. Well, for how long? One breath? A few minutes? What computer is going to keep track of nitrogen loading for this type of diving? Do 50 of those dives over the course of a few hours and you may get bent.

There's another issue with his statement regarding blackouts. No doubt if you do the same profiles as you would normally you would be reducing the chances of blackouts, but in the same quote he's talking about the benefits of extending the dives. The extended dive could very well put you back into the same or greater blackout risk. If you increase your o2 by 2.5 ata's, but extend your dive by 2.5 times, did you really increase your safety factor? Especially since you now have to start exhaling at 50 ft. rather than at or near the surface.

This discussion seems to leave out one very important hazard, and that is shallow water blackout caused by anoxia. Remember, it is not oxygen deprivation that signals the diver to breath. The "must breath" signal comes from a buildup of carbon dioxide. Under this scenario, starting with almost no CO2 at depth, it is possible to swim around for extended times until oxygen becomes too low upon ascent, with reductions of ppO2 with decreasing pressure, and the result is blackout.

SeaRat

 

[Bob DBF]

The "must breath" signal comes from a buildup of carbon dioxide. Under this scenario, starting with almost no CO2 at depth, it is possible to swim around for extended times until oxygen becomes too low upon ascent, with reductions of ppO2 with decreasing pressure, and the result is blackout.

From my read, his theory is that when breathing Nitrox, say 50%, it's a numbers game and the CO2 buildup will send you up, and the higher initial O2 content will not deplete enough to result in a blackout. It's a bit too vague to get me to try it out, besides I've already got a system that works for me, and I'm getting too old to change.

Unfortunately, the article is more theory rather than research on what the mix, profile, and time is going to give what results, which is the important part if one wants to try his diving style, or to understand why, and if, it will work for everyone.

I do think they should have repeated the "don't try this at home" warnings more often.



Bob

 

[John C. Ratliff]

From my read, his theory is that when breathing Nitrox, say 50%, it's a numbers game and the CO2 buildup will send you up, and the higher initial O2 content will not deplete enough to result in a blackout. It's a bit too vague to get me to try it out, besides I've already got a system that works for me, and I'm getting too old to change.

Unfortunately, the article is more theory rather than research on what the mix, profile, and time is going to give what results, which is the important part if one wants to try his diving style, or to understand why, and if, it will work for everyone.

I do think they should have repeated the "don't try this at home" warnings more often.



Bob

Bob,

There's is a problem with the thinking here:

By pre-breathing nitrox, for example, a nitrox mix somewhere between 32% and 50% oxygen, in conjunction with hyperventilation, which decreases the partial pressure of carbon dioxide (PCO2), the diver has additional oxygen to facilitate respiration during the dive; decreased nitrogen, which reduces inert gas loading, and therefore decreases decompression stress and also potential nitrogen narcosis, and decreased carbon dioxide which drives the urge to breathe. As a result, the diver will be able to dive longer before hypoxia and or hypercapnia mandate ascent.
From the above link.

The problem is that hypoxia has no warning sign, and even if hypercapnia (too much carbon dioxide) doesn't trigger a "must breath" reaction, the amount of oxygen, while sufficient for consciousness at depth because of the higher partial pressure, may not be just under the surface, especially with extended time at depth. The article, as written, implies that hypoxia has warning signs. This concept needs a lot more physiological research before becoming a Course, but unfortunately they will probably lay go ahead with it as if it is proven and accepted. People may die because of this concept. The comparisons to technical diving are very strained.

SeaRat

 

[Bob DBF]

This concept needs a lot more physiological research before becoming a Course, but unfortunately they will probably lay go ahead with it as if it is proven and accepted. People may die because of this concept. The comparisons to technical diving are very strained.

I'm in agreement that it's not ready for prime time. A clearer scientific explanation would help as well.




Bob

 

[seeker242]

Anyway, there's a number of other issues here

Theres also a number of issues diving to 250' on scuba. Probably why it's called technical freediving.

here's nothing clarified here. Kick to 50ft. and then start breathing nitrox. Well, for how long? One breath? A few minutes? What computer is going to keep track of nitrogen loading for this type of diving? Do 50 of those dives over the course of a few hours and you may get bent.

What makes you think that would not be covered in the training?