padi teach hyperventilation but not to avoid skindiving after scuba?

[boulderjohn]

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

Not too long ago a DAN study said that minor hyperventilation--like three breaths--was acceptable and not dangerous, especially for the everyday person doing minor free dives while snorkeling. As I was taught to teach that section, we were told to warn about shallow water blackout and explain why it happened. We then cautioned divers to use only a few breaths for that reason. We also differentiated between serious free diving and people going down 20 feet to take a look at the coral and then heading back up. The latter will never get shallow water blackout.

 

[Phantom Menace]

Fair enough BoulderJohn - limiting the breaths will make a difference.

One of the things we do in the club I belong to is practise a 3 part breath (i.e. think about filling the stomach, then chest then upper chest cavity/neck/shoulders) before a dive. It is interesting how much more air you can actually get in that way (without resorting to "packing" - which is a whole different topic). We also look at slowing our breathing down to a "5 seconds in, 10 seconds out" pace (i.e. 4 breaths per minute) for 2 or 3 minutes before a dive (and sometimes longer) to help with relaxation, slowing the heart down and getting in the right mindset for a long dive. This 5 sec in 10 sec out approach also helps avoid hyperventilation.

One thing I am concerned about is those on the border between shallow snorkelling (say less than 10m / 33 ft) and "free diving". There seems to be a growing number of people working their way deeper without the knowledge/awareness of the risks and support structure to manage those risks. Here in NZ at least I have quite often corrected trained OW, advanced higher level certified divers round the risk of SWB in particular. (it can sneak up on you without apparent warning).

 

[dumpsterDiver]

Not too long ago a DAN study said that minor hyperventilation--like three breaths--was acceptable and not dangerous, especially for the everyday person doing minor free dives while snorkeling. As I was taught to teach that section, we were told to warn about shallow water blackout and explain why it happened. We then cautioned divers to use only a few breaths for that reason. We also differentiated between serious free diving and people going down 20 feet to take a look at the coral and then heading back up. The latter will never get shallow water blackout.

People can black out in shallow water from pushing their oxygen level too low. Limiting breathhold diving to 20 feet (or any arbitrary depth limit) does not provide assurance that a black out or loss of motor control will not occur. Improper rest intervals on the surface and others factors like exertion can cause a BO. Also freediving after Scuba diving is not safe, regardless of what PADI says about it.

 

[ballastbelly]

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

mine is the 2010 2.11

 

[Hawkwood]

Thanks. That explains the reference to the hyperventilating breaths.

 

[FredinPH]

As a new member here and new to diving I have been studying potential hazards faced when snorkeling. I found a very informative and fairly current three part series on Shallow Water Blackout that also includes potential genetic predispositions to arrhythmia and sudden death that is particularly prevalent in young athletes' who are driven to push the limits as over achievers to include multiple college majors and competitive sports to include swimming. I found the information in the video's to be well researched and sound advice for avoiding Shallow Water Blackout and what to look for in those who might be predisposed to Sudden Death during extreme exertion - Long Q-T Syndrome and Rogue Gene RyR2. Of course someone needs to have an ECG to discover the Long QT Syndrome prior to an event.

Part 1 of 3 is available here:

Shallow Water Blackout Safety Part 1

I am a former Aeromedical Evacuation Officer - US Army with advanced medical training and experience flying Air Rescue in Washington State for three years where we found ourselves transporting divers suffering DCS, Nitrogen Narcosis and other injuries.

Based on the information in this thread I am interested in learning more about possible problems from free diving within a certain timeframe after Scuba.

From what I have read, dumpsterDiver is spot on.

 

[Redshift]

Interesting that DAN says there isn't much evidence. After my last post, and just by chance, when talking to a friend I was told of two cases where that happened. In one the diver had symptoms when free diving after scuba diving. OK, since there are cases of delayed symptoms of DCS we cannot state with 100% confidence that this was caused by the snorkelling. In the other case, de diver was doing a live aboard and decided not to do one of the dives. But divers later saw him free diving and going down to greet them. Once divers arrive to the boat after that dive, that free diver was already on oxygen.

 

[PeacockMantis]

Part 1 of 3 is available here:

Shallow Water Blackout Safety Part 1

Although the video gives some good information, coming to the conclusion that: "..., underwater swimming should be banned at all aquatic facilities". When it comes to underwater swimming for time or distance only 1 rule applies: Just don't do it" seems pretty stupid.

 

[drbill]

I experienced a very sad death here at the Casino Point Dive Park. A dive instructor was diving with his sister (an M.D.) and I believe a few students. Following their dives on SCUBA, he went out to retrieve his float by free diving... and blacked out on the bottom. When he was brought back to shore, his sister tried to revive him but was unable to. It was very sad to watch this play out. In all my years of SCUBA (and free) diving, I have never mixed the two.

 

[Arubandi07]

Although the video gives some good information, coming to the conclusion that: "..., underwater swimming should be banned at all aquatic facilities". When it comes to underwater swimming for time or distance only 1 rule applies: Just don't do it" seems pretty stupid.

Check again; I believe they're referring to UW swimming in conjunction with hyperventilation ...