Free Diving same day as Scuba?!

[BigJetDriver]

Uhh, WTF? :06:
From the rest of your post, it looks like you more or less know this. [edit: score one against me for not reading your post.. you don't seem to get this]

All of this was explicitly stated in his article. The article is quite appropriately titled "WHY We Do Not Bounce Dive After Diving in the WKPP" You may want to go back and read it. There are a few other articles on that web site, most of which contain some actually useful information. Whatever you think of GI, making stuff up about him doesn't help your cause.

Jonnythan,

No need for the bad attitude. This was an honest request for information, and an honest misconception on the part of one of our writers.

Comments such as your "WTF", and your last sentence are impolite, and not really required. An explanation, based on medical fact, would be more helpful.

As for good ole George, this, after all, is NOT the DIR forum.

Cheers, lad!

BJD :anakinpod

P.S.---As I pointed out earlier, I do have some standing on this issue, since I am a trained and certified Diver Medic Technician.

BJD :doctor:

 

[BigJetDriver]

dumb question:

what is DMT?

Andy,

No question is dumb if meant as a sincere request for information.

DMT stands for Diver Medic Technician. It is a paramedic level certification that involves hyperbaric work, as well as medicine. Typically, a DMT will operate in the "oil patch" as the eyes, ears, and hands of the company medical director, who will be a doctor on-shore.

I was trained at the University of Texas Medical Branch, Galveston, Texas, at their Hyperbaric Medicine Department. The Department Chair of Hyperbaric Medicine was the noted researcher Dr. Richard Mader. The Technical Director was Kevin Corson, an ex-Navy Diver Medic, and Commercial DMT Trainer. Both of these men, as well as the rest of the staff, were extremely demanding instructors, and fascinating to learn from. Since this was not the field in which I earn my living, I had to go to extreme lengths of effort and performance to be accepted by the other members of my class. This was only to be expected, since we had one active SEAL Team Medic, one doctor, and the rest of the folks were oil-patch medics by trade. Since I placed second in my class, behind the SEAL and ahead of the doctor, I feel as if I "made my bones" as they say.

I must admit, since we had class from 0730 to 1930 each day, sometimes later on lab days, and then it was time to study, I had a headache from start to finish, and it felt as if my hair was on fire the whole time. Still, it was truly worth it!

I realize that this was a bit of a lengthy answer, but I hope I have answered your question fully.

Cheers!

BJD :doctor:

 

[H2Andy]

excellent, thank you.

sounds like a lot of work, but very rewarding.

 

[Saturation]

Doc -can you comment on the discussion going on in this thread?

I can understand how bounce diving on scuba can cause problems as you're continue to introduce nitrogen under pressure into your system. But is there risk in free diving to normal snorkel depths?

Thanks

Marc

I'll fill in until Dr. D returns.

Yes, but the risk is greater the deeper one freedive and one's end-dive residual nitrogen. There is less risk of course, with nitrox or with triox after a dive.

Reason #1:

The greatest change in bubble diameter occurs in the shallow depths. Consider from surface at 1 ATA to 33' is 2 ATA, or a change of 50%. To 15' its 25%. To 66' its 75%.

At issue is bubbles formed during a dive; the first hour is when bubbling post-dive is greatest. If these bubbles have formed and one freedives, it will squeeze bubbles size down a bit, and may allow them to squeeze through the lungs into the arterial circulation. Once back on the surface, it re-expands, and now one can get bent or get AGE.

Reason #2:

Post dive, the inert gas loads are greatest until at least 1 hour post dive. You can measure this inert gas load via your residual nitrogen pressure group. Exertion or heavy swimming with create new bubble seeds or stimulate existing ones to grow, causing more bubbles.

Reason #3:

Unlike scuba, ascent rates in freediving are much faster. Add to it, mechanisms 1,2, and you have a formula for injury.

Conclusion:

Do not to freedive within 6 hours post dive, better 12 hours. Shorter time frames, 3 hours, only if one is at or beyond group A via PADI tables.

Personally, I would never free dive during an entire scuba trip. Its not worth getting bent for under any circumstances. You may snorkel, which does not require any diving.

 

[H2Andy]

this thread really belongs in Dive Medicine, but as Don wanted to expose (eek)
new divers to this issue, i've merged both threads here.

my apologies for any confusion

 

[BigJetDriver]

I'll fill in until Dr. D returns.

Conclusion:

Do not freedive within 6 hours post dive, even better 12 hours. Shorter time frames, 3 hours, only if one is at or beyond group A via PADI tables.

Personally, I would never free dive during an entire scuba trip. Its not worth getting bent under any circumstances. You may snorkel, which does not require any diving.

All,

There, folks, is the unadulterated word direct from (I hope you'll pardon me, Doc!) the horse's mouth!

Thank you, sir, for weighing in!

BJD :anakinpod

 

[DandyDon]

All,

There, folks, is the unadulterated word direct from (I hope you'll pardon me, Doc!) the horse's mouth!

Thank you, sir, for weighing in!

BJD :anakinpod

Yep - Roger that, except You're credentials are pretty impressive, too! Thanks for making the information available on your profile...

this thread really belongs in Dive Medicine, but as Don wanted to expose (eek)
new divers to this issue, i've merged both threads here.

my apologies for any confusion

Thanks for that. Hope this thread helps some members avoid the pain and other risks, even thought they're only somewhat possible.

don

 

[diverdoug57]

Yeah, I know better, but I don't remember where and when I learned. Is the prohibition not taught in OW...?

I recently hit the Key Largo wrecks with Mulit-card Newbie, several training cards but little ocean experience, and we had fun - learning from challenges and all. On day 2, after 2 dives on the Duane, I dropped him off at a Dolphin facility to snorkel, while I took a nap.

3 hours later over a late lunch, the conversation turned to how they'd told him to freedive to get the Dolphins to play, and he'd been down to 15 feet several times! I called DAN right away!! They told me to make sure he was hydrated and watch him for problems.

His only symptom was a headache, which dissappered with hydration, so he was fine in the long run, but that was close - I think. I know that he had to be loaded with Nitrogen even with Nitrox dives on the Duane, and that was way too soon to be shaking his blood gases up.

So, are instructors not covering this...?

If so, what needs to be done...?

thanks, don

I don't ever recall seeing this as an item in the OW Instructor manual. The hydration issue would be a concern, as already noted in one of the other posts. Nitrogen build up will not be increased from free diving since it is all surface air in the lungs. A rapid ascent might be a problem, but isn't likely.

Worse than the freediving, there are now advocates out there for doing shallow dives after deep dives because their computer "allows" it. :monkeydan

 

[DandyDon]

I don't ever recall seeing this as an item in the OW Instructor manual. The hydration issue would be a concern, as already noted in one of the other posts. Nitrogen build up will not be increased from free diving since it is all surface air in the lungs. A rapid ascent might be a problem, but isn't likely.

Thanks guy! with your credentials, that carries a lot of weight. Thanks for loading them in your Profile...

As suggested, I guess an instructor is hard pressed to cover everything important, and maybe this doesn't cause enough problems for the agencies to consider adding it, but then - as others mentioned, it would be good to warn newbies. The way I remember it is: "When you load up with N2, it's like a warm soft drink or beer loaded with CO2. You don't want to shake it, then remove the backpressure." Except, rather than wasting beverages, it's N2 bubbles in your circulatory system - blocking blood flow, which is certainly a bad thing!

Worse than the freediving, there are now advocates out there for doing shallow dives after deep dives because their computer "allows" it. :monkeydan

Huh?! Did you mistype that, or am I totally missing the problem? That's Scuba 101, isn't it?

thanks, don

 

[coberry7]

Good info here. I never even thought that free diving after scuba diving was an issue. Makes sense not to do it, after reading this thread, and I will include it in my classes from now on.

Someone mentioned that skin diving was not required in an OW course. In a PADI course, it is now required training, in confined water. I am not sure if it is required in OW.

I haven't looked, so I am not sure if the PADI instructor manual eschews free diving after breathing compressed gas.

Free diving before or after was never mentioned in my OW class, and I have never mentioned any safety issues in my classes. I will now.


Thank you SB and all posters on this thread. Good info.

Colin Berry