Shallow Water Blackout

[Vorago]

To all you swimmers out there who like to swim underwater...

DO NOT HYPERVENTILATE BEFORE YOU SWIM UNDERWATER!!!


I broke my personal record of swimming under water this morning (35 meters)...turns out one of the worst things you can do is repeated deep breaths (hyperventilate) before you go under...which is what I have been doing.

Why? It reduces natural CO2 levels in the body that are responsible for your breathing reflex. If there's not enough CO2 in your body you could hit the point where you black out due to lack of O2 before the breathing reflex caused by rising CO2 levels kick in.

I feel like I've escaped death or something...

Just a heads up, that's all

[Relic]

Wow, we had a swimming pool when I was a kid and I used to do this all of the time. I never once passed out but maybe the gradual O2-starvation caused my brain to be as odd it is today?

[René_Julien]

Glad to hear you didn't drown.
Congrats on the record.


Where do you go diving?
Oh and by the way, you're nuts. It's to cold outside. (Yeah, yeah, I know it doesn't matter at 35m.)


By the way, does it also effect the O2 and CO2 levels in your blood? Or does that not matter in this case.

You mean it's not good because you have not enough CO2 in your longs. (?)

[Vorago]

Diving? Me? Hell no! I was at the Wezenberg swimming pool, aka de wiêzenbaarg...

What I mean is, hyperventilating reduces the natural CO2 levels in your blood. Therefore, if the body is swimming and turning O2 into CO2 the CO2 levels in your blood, these levels don't rise fast enough for your breathing reflex/urge to kick in. So you can hit the point where you're body passes out from oxygen starvation before you feel the urge to breath.

[René_Julien]

Ah, I misunderstood you. I thought you went down to 35m.

I should know this stuff because I once taken rescue lessons, initial diving and wild water kayak lessons.
But I suck at biology.
Good thing I'm not a professional lifeguard.

I once swam just over two lenghts under water. (regular pool lenghts: 25m).
It was about 60 meters. Training, control your swimming, etc. etc.
After the second turn underwater it got difficult for me.
I had lessons on this for about a year, two evenings a week.
They were organized by a kayak club, and teached by a professional fireman and lifeguard.

But that was back when I was athletic.
I'm to out of shape now.
I'd be glad if I could swim 10m under water now.

[Vorago]

And they never told you about this???

[René_Julien]

Originally Posted by Vorago

And they never told you about this???

I assume they told me this over and over again with illustrations and all.

But hey, I was a 15y old with a short atten

[Vorago]

tion span


Nicely done

[MakiSupaStar]

I've gone 125 meters underwater. I've also routinely free dive 35-40 feet. I've found that hyperventilating is not necessary. More important as just relaxing and slowing your heartbeat. I don't know the science behind it, but I've always felt that the more you do something the better you get at it.

[Blonde Bassist]

Originally Posted by MakiSupaStar

I've gone 125 meters underwater. I've also routinely free dive 35-40 feet. I've found that hyperventilating is not necessary. More important as just relaxing and slowing your heartbeat. I don't know the science behind it, but I've always felt that the more you do something the better you get at it.

thats exactly right, you'd be better off doing the complete opposite of hyperventilating, and slowing your breathing and heart rate down. Big deep breaths, eyes closed, gradually relax, then go for it. I've done a good 50-75 or more in my more athletic days. I'm a part-time lifeguard when i'm not gigging, and this does come up sometimes. although I've never actually seen anyone (apart from the swimming club, who know what they're doing) go more than about 15 metres underwater. The swimming club regularly do sets of around 12 or 16 lengths (33 metres each time) underwater one after another, they have some serious lung capacity.

[Stanley Design]

You're supposed to take 5 breaths with 10 second exhale before diving I'm told.

[Ericman197]

Just to let you dudes know, it doesn't matter how deeply you're breathing - you can still hyperventilate. You know how the doctor asks you to breathe in and out, deeply? Sometimes they'll break it up, because if they do a full and thorough lung exam, a patient could pass out from hyperventilating.

Another thing you guys might try (though you probably already know about it) is the diving reflex. Basically, you expose your face to cold water (it has to be well under 70 F to work). For some reason (I really have no idea lol) this stimulates the Vagus nerve to a bunch of things, including slowing your heartbeat (it also reduces your sensitivity to cold). Another random fact of the day is that stimulation of the Vagus nerve is also responsible for brainfreeze (cold stuff in your throat stimulates it, and it causes dilation of blood vessels in your brain to keep it warm... but this quick dilation causes a headache as well).

[Baryonyx]

Yeah, latent hypoxia is the last thing you want.