padi teach hyperventilation but not to avoid skindiving after scuba?

[ballastbelly]

the padi ow has a few pages on skin diving and promotes hyperventillation to stay longer under water, it explains that skin diving is useful to scout out places to go scuba diving.

what i am surprised it did not mention was that deep breathhold dives after a scuba session increase risk DCS bubbling to almost an absolute certainty. i just stumbled on this by chance browsing through these forums & googled a bit about it. some recommend waiting a day after scuba at least. freediving before scuba is ok though.

the book explains avoiding air travel & high altitude driving, but not to avoid freediving? if the risk is scientifically established, thats quite an ommission

 

[Phantom Menace]

Back when I did my first PADI course (close to 30 years ago) they didn't say freediving after SCUBA was a bad thing to do but I am surprised they still have the same position.

At the freedive club I belong to we counsel people against going freediving after a SCUBA dive.

Also - the really deep freedivers only do one dive a day (and by deep I mean 80m plus divers).

---------- Post added June 30th, 2014 at 04:37 PM ----------

And PADI didn't teach hyperventilation back then

 

[Soggy_Diver]

Hi,

Just IMHO, but I have though the same thing about the risk of freediving after scuba.

Even if the freedives are shallow, pressure changes more quickly relative to depth at shallow depths than greater depths, so I avoid it altogether.

Freediving after scuba seems to me to be like "bubble pumping" or repeated "rapid ascents."

 

[Redshift]

You should also be surprised that it promotes hyperventilation!

 

[Tigerman]

I cant be assed to read the whole book again, but I DID just browse through the skindive bit and although that section does promote hyperventilation it does so SPECIFICALLY for skindiving and ONLY FEW BREATHS.

I wont look through the whole book for information about skindiving while saturated, but I know for certain it was mentioned in my OW course as one of those things that might not be a brilliant plan to do...


P.S. My book is old as I took my OW in 2006...

 

[Scott]

The old course materials did promote the use of hyperventilation, the new revised course does not.

 

[Redshift]

The old course materials did promote the use of hyperventilation, the new revised course does not.

Glad to know.

But indeed it should be mentioned that freediving after scuba diving may not be the best idea. Even free divers have a sort of decompression tables that set limits to dives and depths. There will be a small amount of absorbed gas during a free dive and if a scuba diver is close to the limit on some tissue, the free dive may be enough to cause problems.
Don't know if there are reported cases of such events though.

 

[Hawkwood]

the padi ow has a few pages on skin diving and promotes hyperventillation to stay longer under water...

They no longer do. Please tell me what edition of the manual you are reading?

 

[boulderjohn]

Before people get into a tizzy about this "failure," read this report from DAN's Alert Diver magazine.

Here is one section of it:

Does breath-hold diving after scuba diving increase the risk of DCS?

Wong: Breath-hold diving after scuba may increase the risk of DCS, but the evidence is scarce. The classic case was reported by Paulev, who experienced nausea, dizziness, belching, hip and knee pain, weakness, paresthesia and blurred vision after performing repetitive breath-hold dives to 66 feet for five hours. His breath-hold dives were preceded by a hyperbaric exposure as a chamber attendant for eight minutes at 66 feet.3 Three similar cases of DCS have been reported after divers were exposed to pressure in a hyperbaric chamber prior to breath-hold diving.

Pollock: Compressed-gas diving prior to freediving certainly increases the theoretical risk. High tissue concentrations of inert gas after compressed-gas dives could make the impact of the freediving important. While no experimental evidence exists, bubbles produced following the compressed-gas dive could migrate to more sensitive tissue when transiently compressed by the freedive. Similarly, the physiological stress of freediving could enhance pulmonary shunting, potentially increasing the risk or frequency of bubbles entering arterial circulation. The hazard might be greatest in the first part of the freedive when both bubble size and physical effort would be relatively high or at the end of the freedive if augmented shunting continued. Again, though, there is no evidence of these factors causing injury. Studying a relatively rare event like DCS is difficult; studying a second rare event on top of the first is much more difficult. - See more at: Alert Diver | Could Breath-Hold Diving after Scuba Cause Decompression Sickness?

In other words, the jury is still out on this issue.

About 8 years ago, IIRC, there was some evidence that doing a deep stop for a few minutes during ascent in a recreational dive followed by a very short safety stop was a good idea. One agency made that change as a part of its teaching, and some of its members on ScubaBoard were critical of PADI for not making that change. Well, subsequent research has not been very supportive of that change, and, once again, the jury is still out on the best ascent profile. Nothing is really clear. The agency that jumped in and made the change at the first opportunity no doubt felt like pioneers at the forefront of important change when they did it, but to my knowledge they are still the only ones holding to that change. Most agencies prefer to be sure something is true before changing official policies.

 

[Phantom Menace]

I am not a deep freediver (deepest I have been is 40m / 130 ft). Many of the deep freedivers recommend not doing more than one deep freedive each day to avoid DCS - recognising that the jury is out on repeated deep free dives and the likelyhood of DCS.

The deep guys do get nitrogen narcosis though.

Personally, I would avoid freediving after SCUBA - I don't want to become one of the reference cases ...

Also - hyperventilation is BAD. it increases the likelyhood of shallow water blackout (so yes, I am surprised that PADI ever taught it).