Preventing Shallow Water blackout?

[VikingDives]

The OP was asking about how to prevent it. I'll concede that I've never seen SWB in a snorkler, but most of my experience is in the pool teaching the (dreadful) PADI snorkeling portion of confined water.

Even there, the instruction is to have 1 up and 1 down... There's no way to know if it is going to happen to you, and there's no way to innoculate yourself.

There's a lot of good info here:

Shallow Water Blackout Prevention

www.shallowwaterblackoutprevention.org

 

[dmaziuk]

I'm curious what led to the swimming pool deaths. The fact that they occurred in swimming pools doesn't preclude extreme behavior, like hyperventilating and attempting 7 minute static apnea.

There's two mechanisms both called "SWBO": one is basically running out of oxygen. That's what presumably happens in the swimming pools: "presumably" because by the time the victim is pulled out, they've drowned, and that's the official cause of death. "Extreme behaviour" is typically involved, though it doesn't have to be 7-minute breathholds -- doing fast laps underwater at the end of the workout when you've already built up significant "oxygen debt", can be enough. (There is a speculation that swimmers may continue to swim on "autopilot" for a bit after blacking out, that doesn't help either.)

The other mechanism is the rapid PPO2 drop when coming up from depth -- typically combined with oxygen debt accrued during the dive. That happens to freedivers doing deep dives. There you have the safety diver who can actually watch them blacking out so there's no "presumably" there.

Neither of those is likely to happen to an average snorkeler: they're neither pushing 30-second hundreds underwater, nor diving to significant depths.

U.S. swimming pools ban long breath-holding after deaths

A U.S. Navy SEAL hopeful and his friend, an off-duty lifeguard, were barreling through underwater drills in a pool just 3.5 feet (1 meter) deep. No one realized anything was wrong until their limp, unconscious bodies were noticed beneath the surface.

www.reuters.com

 

[Eric Sedletzky]

During my ab diving days I was told to keep my dives to a minute and a half max. I always paid attention to the first wave of spasms of C02 buildup telling me breathe idiot!
Most of my dives were probably about 45 seconds to one minute, and max depths to 30 to 35 feet. Most dives were in the 10 to 15 foot range because that’s where most of the abalone were.
The other rules were, never hyperventilate which is different from “breathing up”, and after surfacing from a dive breathe until you are re-oxygenated (at least a couple minutes).
The worst thing a freediver can do is come up after a dive and immediately begin hyperventilating trying blow off C02 to get back down without properly re-oxygenating. You will begin to spasm due to excess C02, not because of a lack of oxygen, so if you blow off all your C02 and still don’t have enough O2 in your blood you’re not going to get the signal before you’re in trouble. And if you’re coming up from deep, the re-expansion of your lungs will pull remaining oxygen out of your brain which is double trouble and it will be lights out.

 

[Seahuntjerry]

Suggest Best to do a pulse check immediately also!
Aha Instructor trainer faculty retired Paramedic
52 years of teaching and 60 years of diving experience.

 

[John C. Ratliff]

I have written about SWB and on several occasions discussed it here on ScubaBoard. Someone above asked how SWB can occur in a swimming pool. Here's what I wrote:

Shallow water blackout is a name for a disease which can effect all breath hold divers. It is potentially deadly, and is also known as an expert’s disease, for it most often effects those who have a great deal of experience. However, it can effect anyone, diver or underwater swimmer, who stays underwater too long. It usually effects those who try various techniques to extend their breath hold diving time, who dive repeatedly or who compete or try to set underwater distance records.
This has happened to me in a high school swim team breath-holding contest between me
and my good friend, Tommy Lengyl. His Mom was our coach, and I was determined to beat his swim of four, 20-yard length of the pool. I hyperventilated until I could "see stars," than took a deep breath and dove into the pool from the shallow end. I swam underwater swimming a modified breast stroke. At the third turn, I felt some urge to breath but suppressed it. Then I came to the fourth turn, and told myself I would turn, take one stroke underwater, surface and swim to the side of the pool. I did that; the trouble is that I remember nothing from the time I pushed off that fourth turn, until I was at the edge of the pool breathing deeply. I am thoroughly convinced that had I not told myself to surface and swim to the side of the pool, I would have swam underwater until I died (that's how it happens sometimes, as documented in physiology journals I read in the 1970s at Oregon State University)...

I'm trying to attach the full discussion with the charts I developed here too.

SeaRat