Question on Shallow Water Blackout

[Bajura Bob]

Been spearfishing (free diving) for about 30 years, mostly self taught. Usually dive at depths 30-60 feet, but will go to spots in the 80+ range at times. I don't push myself on dives and have a comfortable downtime of 2-3 minutes. QUESTION: For those that have survived a shallow water blackout episode (or know someone), did any of these occur during a non-stressed dive where the diver was not pushing his limit?

By the way, I'm new onboard. I do my diving on Puerto Rico's Wild West.

 

[Pastor]

Welcome to the forum Bob, I have moved this thread to the freediving section, you'll get more answers there/here

 

[efattah]

I had a big samba during a fun, submaximal dive in 2002. The dive was to only one third of my max depth, for only half of my normal dive time. The samba/BO was caused by a hard previous dive, with too short of a recovery in between. Doing a harder dive and then taking a short recovery, and diving soon after, is the best way to meet the grim reaper. If you make a dive you feel really stressed you out (low O2, or acid buildup, fear, etc.), then I recommend resting motionless for at least 7-8 minutes on the surface.

 

[naiad]

Yes, it can happen. Many factors can contribute to the risk of blackout, and pushing the limit is just one of them. I have blacked out in pool training and did not feel I was pushing the limit. I have done the same time and more many times now without blacking out, so it must have been caused by other factors.

 

[trux]

Exactly as Erik and Naiad wrote - there are far too many factors playing a role at a blackout, and even more at the depressurizing blackout (usually called SWB). Besides the acid lactic build-up from previous dives, these other factors (among others) may have a great effect: hyperventilation, mind focus to a certain task (shooting a fish, reaching certain point, ascent,...), physical effort at depth, ascent speed, fatigue, disease, food, hydration, diet, medicaments, drugs, atmospheric pressure, temperature,... Especially those factors having influence on the blood pH (hyperventilation, diet, ...) may change your usual perception of the urge to surface, so when the depressurizing effect suddenly increases the hypoxemia, you may blackout without any warning even if you did not think you were pushing the limits.

 

[Bill]

"I don't push myself on dives and have a comfortable downtime of 2-3 minutes. QUESTION: For those that have survived a shallow water blackout episode (or know someone), did any of these occur during a non-stressed dive where the diver was not pushing his limit?"
Hi Bob
Question for you: When do you black out? Better yet, how much 'buffer' between your usual dive and black out? Are you sure? Would you bet your life on it?
I discovered the probable scenario of a few funny dives I'd had, about thirty years after the dives, when I took my first course on free diving. It looks like I had at least two black outs while spearfishing. Turns out that you can do a surface black out and the memory loss is long enough that you don't remember being in trouble. My last black out was a dynamic. At 70% of plan, the last memory was that everything was going great but, not to extend the dive. I came up at planned distance, but not for long.
Be careful out there and you'll be able to dive another 30 years.

 

[naiad]

A very scary story about this.
http://forums.deeperblue.net/freediving-stories/74732-lessons-learned-swb-story.html

 

[harbour seal]

two more accounts of surviving shallow water blackouts:

http://forums.deeperblue.net/freedi...ntimate-account-our-most-dangerous-enemy.html

http://forums.deeperblue.net/safety/66420-my-shallow-water-blackout-nightmare.html

both are scary, but make for excellent threads.

cheers,
sean
vancouver, canada

 

[Bajura Bob]

THANKS TO ALL. In light of all I've read, I'm amazed that I haven't had SWB. I estimate that I've done tens of thousands of dives 40+ feet during my 30 years of spearfishing. I never had free diving training. Ironically, it was diving efficiency that probably lead to my becoming a "safer" diver. I figured out that a relaxed dive increased bottom time, that not getting excited or fighting a fish on the bottom could prevent a scary ascent wondering if I'd run out of air. Perhaps what helped most was the realization that moving very slowly at all times (the hunter's stealth) increased the chances for seeing and attracting game fish. It does scare me to think that there was a time (20's - 30's) that I often dove in the 80+ range and did push my limits. I guess it scares me even more to think that it's possible to have SWB during dives where one does not hyperventilate, stays at comfortable depths and ascends before any urgency to breath. Quite a dilemna as diving with a buddy is no guarrantee of safety. As most my spearfishing buddies realize, it is very easy to become separated when chasing fish.

Any doctors out there that can comment on the possiblity of a SWB alert device in the future?

Good luck diving, amigos. Bajura Bob

 

[Stavros]

T Quite a dilemna as diving with a buddy is no guarrantee of safety. As most my spearfishing buddies realize, it is very easy to become separated when chasing fish.

Bob - diving with a buddy is a guarante for safe spearfishing... as long as the buddy safeties and doesn't spearfish while you are diving... its not nuclear science just common sense. As long as both you and your buddy realise that there is a real risk of dying if you spearfish alone then becoming separated while spearfishing is not that easy any more

Cheers and have many safe dives

Stavros