freediving after a scubadive

[oceanic]

Do you guys know if there is any type of danger in freeding after scuba?

If I were to do a 90 foot scuba dive and decod. properly and waited a two hour interval before freediving. and I mean a couple of 60 feet freedives instead of the useal 2nd shallow scubadive.


I did that once before and someone told me that it could be dangerous. Do to some residual nitrogen.

Thanks.

 

[Beaky]

As I understand it, with the added nitrogen in the body, you would have to limit your ascent rate while freediving, the same way you do in scuba. This would obwiously limit the depth you could freedive to, because of the long ascent times involved.

Actually, a too fast descent might be bad too, I'm not sure. It all has something to do with the nitrogen forming bubbles which cut of circulation.

It would be great if someone with a good understanding of this could comment, since I have heard many different versions on how long you need to wait after scuba diving! My PADI instructor was petrified that I would freedive the day after I did scuba (which I choose to ignore)!

The rule of thumb though, seems to be that you shouldn't freedive the same day as you have done scuba. (But freediving before scuba is ok).

Another sollution is to skip the scuba part altogether, and you don't have to worry about it!

// Johnny

 

[Bernt]

My understanding is that the effects of freediving both before or after tank diving is still largely an uncharted territory scientifically. It seems fair to assume however, that one may shake a few nitrogen bubbles together and loose freediving shortly after a decompression dive at least. But there is after my knowledge little research documenting adverse effects of a post dive freedive. Better safe than sorry though

 

[fpernett]

Don´t

Originally posted by Beaky

Another sollution is to skip the scuba part altogether, and you don't have to worry about it!

// Johnny

That is a good advice.
My advice is that you shouldn´t freedive after a SCUBA dive. How long? That will depend on the SCUBA dive profile. Isn´t the same surface interval for a 60 feet/20 min dive than a 260 feet/30 min with decompression.
There is no way to compare SCUBA and Freedive tables so you should follow your SCUBA table and apply the same rule as for flying. For a "normal" SCUBA dive I´ll wait at least one day. It will be more difficult to give you a good advice on a technical dive.
Dr. Lanphier studies was on DCS in freedivers, and remember that Haldane get "bent" from freediving. The recommendation is to keep the surface interval twice the inmersion time. If your freedive inmersion lasts 4 minutes, your surface interval should be 8 minutes to keep you away from bends. But nothing is 100% sure.
So keep it conservative

 

[jvoets]

For normal scuba dives, wait at least 12 hours.
That's the time it takes to clean out your slow tissue (with half times of 2 hours).
If you've done very deep, cold or hard work dives, I'd double that to 24 hours to be on the safe side.

I've been doing shallow freedives (10m max) a few hours after doing 15-20m scuba dives before I heard of the dangers attached. Probably you'll be very conservative with the 12 hours rule, but better to be safe than sorry.
I will be sticking to that now I know that it is dangerous to freedive right after scuba (because of the ascent rate and recompression of bubbles).

You're better off switching the order. Do your freedives first and have a scuba dive as desert.

 

[Erik]

Here's what's happening in your body after any scubadive:
The remaining gasses in your blood and tissues are coming out of solution, turning into micro-bubbles, the bubbles are attracted to each other and they become bigger. If you now go freediving, the bubbles that are on the venuous side of your circulatory system can be immediately be compressed small enough to pass your lungs. As soon as you ascend, these bubbles can now expand and get into your nevous system and brain.
I will speculate that Benjamin Franz was "hit" like this, even though he was only freediving. Too many deep sled rides over a short period of time, and that's the result.
Cheers,
Erik Y.

 

[icarus pacific]

I agree completely and also have to go that route re: Ben's hit.