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Diving Safety, Accidents and Incidents Post here to discuss accidents, incidents, ideas, gear, or anything else to improve spearfishing safety. Memorials and condolences threads should be placed in that separate forum.

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Old 03-27-2009, 03:30 PM   #31
Ray Odor
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Re: Three more blackouts!

Don’t be misled by all the scenes of divers going deep and blacking out on the way up. It seems like yesterday that our Tampa Trident Club was invited up to Silver Springs, in Ocala Florida, to take part in Argosy Magazines “ Under water Track Meet” in the early 70’s. Two tether balls were anchored 25 ft apart in 15 feet of crystal spring water. We competitors were lined up on the dock waiting our turn to compete. Eddie and I stood together, waiting our turn and watching our best free diver, Joe, hypervenalating to do his thing. All of a sudden, on his third pass, his body folded up on the bottom.
Eddie and I,both jumped at the same time, grabbed him, and swam him to the surface. We had just saved our buddies life, in a really “SHALLOW WATER” black out.
DO NOT: Think this has to be a deep water dive for it to happen.
DO NOT: Take too many deep breaths. One atmosphere, (14 ft) of water, can exert enough pressure to cause black out.
Test on dry land: Take ten deep breaths, then, have someone standing behind you, put their arms around you and squeeze your chest. Most people will black out. Now test 4 or 5 deep breaths, while exhaling as much CO2 as possible from each breath. This should be plenty for your deep dive.
You have just experienced “Shallow Water Blackout”
Good Diving and LOL.
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Old 03-27-2009, 10:48 PM   #32
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Re: Three more blackouts!

That video is sends chills up my spine, ray is 100 percent correct, it doesnt have to be deep, thanks terry and sheri for working to make our sport safer.
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Old 03-28-2009, 02:08 AM   #33
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Re: Three more blackouts!

Quote:
Originally Posted by Ray Odor View Post
DO NOT: Think this has to be a deep water dive for it to happen.
DO NOT: Take too many deep breaths. One atmosphere, (14 ft) of water, can exert enough pressure to cause black out.
Test on dry land: Take ten deep breaths, then, have someone standing behind you, put their arms around you and squeeze your chest. Most people will black out. Now test 4 or 5 deep breaths, while exhaling as much CO2 as possible from each breath. This should be plenty for your deep dive.
Ray, breathing deeply to remove CO2 is exactly what causes divers to black out. Unfortunately, there is no way of 'safely' removing CO2. The more you remove, the more comfortable you will be and the earlier you will black out, which is a bad combination. The 4-5 breaths you're advocating WILL in fact reduce time to blackout. Many people accept this tradeoff because of the increased comfort, which is fine, but I think it's quite important not to pretend that there is a line between 'safe' and 'dangerous'. All forced breathing reduces time to BO by some degree.

Also, to clarify something: a shallow water blackout is exactly the same as a normal surface blackout (e.g. in the pool), which is caused by cerebral hypoxia. The only difference is that the high partial pressure on the bottom temporarily protects the diver from losing consciousness. Then when they return to 1atm at the surface, they have to instantly pay back the extra time they got on the bottom. It is not that the "water exerts enough pressure to cause black out." Instead it is the end-of-dive reduction in water pressure that makes you pay back your effective oxygen debt. Your main point is right though: divers can BO at any depth, and if you push hard enough you can BO even before you ascend. The raised ppO2 will only delay BO for so long.

Last edited by Mullins; 03-28-2009 at 02:26 AM.
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Old 03-28-2009, 08:49 AM   #34
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Re: Three more blackouts!

Mullins, thanks for your much more technical,in depth, explanation.
We need to do anything we can to prevent this SWB from happening.
Ray
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Old 03-28-2009, 09:24 AM   #35
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Re: Three more blackouts!

Quote:
Originally Posted by Mullins View Post
Ray, breathing deeply to remove CO2 is exactly what causes divers to black out. Unfortunately, there is no way of 'safely' removing CO2. The more you remove, the more comfortable you will be and the earlier you will black out, which is a bad combination. The 4-5 breaths you're advocating WILL in fact reduce time to blackout. .
I don't understand this comment. Maybe I'm taking it out of context or you didn't choose your words carefully? Why would hyperventilation reduce "time to black out"? I thought hyperventilation would allow someone to more easily attain a breathhold duration that would cause a BO, but the effect would be that they would feel more comfortable due to the reduced CO2 levels for most, or all, of the breath hold?

I always thought that hyperventilation would not have a significant effect on maximum breathhold (that is, as long as you were willing to really suffer).
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Old 03-28-2009, 12:41 PM   #36
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Re: Three more blackouts!

i think hes just talking about purging some Co2(4 to 5 breaths) before a dive. You can blackout from having too much Co2.
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Old 03-28-2009, 06:45 PM   #37
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Re: Three more blackouts!

Hyperventilating (lowering CO2) has 2 main effects:

- you'll feel better because the lowered blood pH caused by high CO2 on a breathhold is the main trigger of the urge to breathe
- you'll black out earlier than you otherwise would, because the Bohr effect is negated

The Bohr effect is quite an important part of freedive physiology. On a normal dive (no hyperventilation), as CO2 rises and your blood becomes more acidic, haemoglobin binds less strongly to the oxygen that it carries. This makes it increasingly easy for your brain and other organs to take oxygen from the blood that flows through them. So you might finally blackout when you reach about 50% O2 saturation.

When you hyperventilate pH stays high and this does not happen. So when you reach, say, 60% O2 saturation, the haemoglobin is still binding tightly to the oxygen it carries and your brain can no longer extract enough oxygen to stay conscious.

The two effects of hyperventilation in combination (there are other more minor effects like increased heart rate) can cause real problems. Not only do you feel better, you blackout faster. Sometimes they can even overlap, and you black out before feeling any urge to breathe.

Unfortunately spearos usually only hear about the reduced urge to breathe. Freedivers on the other hand tend to push much harder, and end up finding out about the Bohr effect first-hand. If hyperventilating reduced the urge to breathe while having no other side-effects, all freedivers would do it. Instead, most now avoid any breathup at all, putting up with the discomfort of high CO2 in order to get the longest/deepest/furthest dive before BO.
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Old 03-28-2009, 09:02 PM   #38
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Re: Three more blackouts!

Thanks!
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Old 03-28-2009, 09:28 PM   #39
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Re: Three more blackouts!

I'd highly recommend reading as much published information as you can about freediving and black outs.

A good place to start would be the article from last fall by Neal Pollock, PhD from DAN. It's on the Dive Wise website. http://www.divewise.org/articles/pollock_bh_review.pdf

Julie has begun to collect blackout survival stories and memorials on the Dive Wise site. If you have a story others could learn from, please submit it.

Chad
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Old 04-07-2009, 01:32 AM   #40
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Re: Three more blackouts!

Thanks for doing this!
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Old 04-07-2009, 09:40 AM   #41
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Re: Three more blackouts!

Thanks for sharing Ray!
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Old 04-08-2009, 07:45 AM   #42
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Re: Three more blackouts!

Thanks Terry and Sheri. I'm going to share this w my buddies and especially my 10 year old grandson who is really getting into spearfishing.
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Old 04-08-2009, 11:29 AM   #43
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Re: Three more blackouts!

Great stuff guys. It is so easy for a great day to turn bad. If we follow the very simple basics Sheri mentions, and accept that we are not Aquaman, we should be fine.
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Old 06-16-2009, 07:00 PM   #44
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Re: Three more blackouts!

Thanks for the video. I showed my brothers this video to let them know the dangers of freediving.
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Old 07-29-2009, 06:26 PM   #45
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Re: Three more blackouts!

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Originally Posted by tmaas View Post
Three young freedivers blacked out within weeks of each other in two separate incidents. While they all survived, their mothers made a vow to publish their accidents so that other young freedivers might avoid this killer. Commissioned by these two mothers, Julie Richardson and Chirs Dimond, and with support from DAN, I filmed and produced this 6-minute video for You Tube. The primary goal of this spot is to alert new divers to the dangers of freediver blackout and how insidious it can be. Sheri Daye co-wrote and narrates this in-your-face video for young folks. Here is the link -- share it with a kid you love:
http://www.youtube.com/watch?v=PBnEIMTrgFk
Terry
Terry and Sheri, thank you for taking the time to produce this..... I have lost
18 friends in 30 years in Tahiti, USA and New Zealand many, were not kids.
All the best, Don

Last edited by Don Paul; 07-30-2009 at 12:14 AM.
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