Underwater Swim Training- Shallow Water Blackout

[Rooster59]

This is kinda scuba as it's training related. If you are training yourself for an underwater swimming requirement, understand what shallow water blackout is.

Dartmouth Swimmer Died Trying to Do 4 Laps Without Breathing

This guy lived:
Darren Harrity — Shallow Water Blackout Prevention

Same guy now:
Coast Guard swimmer rides a rip tide to conserve energy in daring nighttime rescue that saved 4 | OregonLive.com

 

[dumpsterDiver]

Technically, shallow water BO does not result from breathhold swimming in shallow water.

Shallow water BO is a loss of consciousness which results from a drop in oxygen pressure in the brain as a breathold diver ascends from deeper water into shallow water (or more commonly actually reaches the surface).

However, breathold practice in water should never be done without adequate supervision - even if the water is shallow. A few years ago a world record holder died in a shallow pool alone- presumably while training alone.

 

[dmaziuk]

Dartmouth Swimmer Died Trying to Do 4 Laps Without Breathing

Official story is that 15m rule in swimming was introduced because of the "unfair advantage" of the underwater dolphin kick. A few unofficial versions quote near-drownings when people tried doing it for the entire 100 and found out the hard way you can't hold your breath for a minute and swim at the competition speeds at the same time. The rule -- and the stories -- have been around for 50+ years so it's not exactly news.

And as DD said it's not SWBO, just the regular garden variety oxygen deprivation.

 

[TMHeimer]

We just had a local pool death. Someone practising underwater swimming. Only detail given was due to "distress". Perhaps a heart attack?

 

[John C. Ratliff]

Technically, shallow water BO does not result from breathhold swimming in shallow water.

Shallow water BO is a loss of consciousness which results from a drop in oxygen pressure in the brain as a breathold diver ascends from deeper water into shallow water (or more commonly actually reaches the surface).

However, breathold practice in water should never be done without adequate supervision - even if the water is shallow. A few years ago a world record holder died in a shallow pool alone- presumably while training alone.

Actually, DumpsterDiver, that's not quite correct. There are two mechanisms for SWB. I have done some writing about this over the years, but have never published it. You can see what I've written below. Here is a brief quote from the below paper:

This can happen in two ways. One is on a shallow dive, when the diver experiences the urge to breath and, with the lowered percentage of CO2 from hyperventilation, stays underwater until he blacks out (represented in Graph I). The other way happens on deeper dives, those deeper than 33 feet (10 meters). This is taravana, the feared disease of the South Seas. The diver hyperventilates, as before, then dives deep. As (s)he dives the pressure increases, and the partial pressure of oxygen also increases. The diver pushes himself to stay somewhat longer than he normally would, and is finally forced to the surface. As he does, the pressure decreases and the partial pressure of oxygen also decreases in the lungs. But the partial pressure of oxygen in the blood remains high, since it is almost a closed system. However at the lungs, oxygen, because of the higher partial pressure in the blood, passes back into the lungs and is lost for metabolic purposes. Couple this to another phenomena, than the body has a higher tolerance to higher percentages of CO2 when exercising which allows the diver to stay down even longer before the urge to breath is felt, and the result is catastrophic: acute hypoxia and unconsciousness. Brain damage is imminent if the diver isn’t resuscitated immediately because the brain is already depleted of oxygen. This condition is depicted in Graph II.

SeaRat

 

[John C. Ratliff]

Official story is that 15m rule in swimming was introduced because of the "unfair advantage" of the underwater dolphin kick. A few unofficial versions quote near-drownings when people tried doing it for the entire 100 and found out the hard way you can't hold your breath for a minute and swim at the competition speeds at the same time. The rule -- and the stories -- have been around for 50+ years so it's not exactly news.

And as DD said it's not SWBO, just the regular garden variety oxygen deprivation.

No, it is SWB. (See the paper I enclosed above.)

Concerning the "15m rule," I have not heard of that rule. However, as the former Finswimming Director for the Underwater Society of America, and having access to the rules for Finswimming competition worldwide, the competitive limit for breath holding under CMAS rules is 50m. Using a monofin, the world record is somewhere less than 16 seconds for 50m underwater breath-hold men's swim.

 

[tursiops]

There are two mechanisms for SWB. I have done some writing about this over the years, but have never published it. You can see what I've written below.

With all due respect, writing something does not make it true. Publishing it does not make it true, either, if by publishing you mean printing it somewhere or putting in on a website. You get a little closer to "truth" if the publishing involves peer review.

I'm not saying what you said is untrue. What I'm saying is that simply writing it down does not make it factual.

 

[TONY CHANEY]

I totally disagree with Ratliff stated.

I believe that SWB is based on another point of view and I will not go to great depths to explain it but:
Since the number one mechanism that controls the respiratory system (in most people) is the increase in CO2 (hypercapnia). Some people hyperventilate on the surface to "blow" off CO2 thus decreasing their drive to take a breath. Now the second mechanism that controls the respiratory system (again in most people) is the lack of oxygen (hypoxia). Both chemicals are picked up by chemoreceptors in the brain and heart but, these chemoreceptors (in most people) are more sensitive to CO2 than O2. When a swimmer blows off CO2 then they reply upon the hypoxic drive to signal them to breathe. The downside to this method is that, sometimes, by the time the signal is addressed the swimmer's oxygen is so low that they have depleted their oxygen to the point that they blackout at the surface. Now you have either a death or a person with an anoxic brain injury. I can provide rescue breaths, intubation, life support, etc to bring back someone with a very high PaCO2 level but not a super low PaO2 level. OBTW, as CO2 increases the pH decreases (respiratory acidosis) and can be tolerated to the lowest level I have ever seen someone come back from 6.9 whereas the normal range is 7.35-7.45.

Please read this: https://www.swimmingworldmagazine.com/news/shallow-water-blackout-the-silent-killer-of-swimmers/

 

[dumpsterDiver]

Actually, DumpsterDiver, that's not quite correct. There are two mechanisms for SWB. I have done some writing about this over the years, but have never published it. You can see what I've written below. Here is a brief quote from the below paper:


SeaRat

John:

Wikipedia seems to contradict your definition of Taravana.

And shallow water blackout is generally used to describe a BO caused by a diver ascending from a significant depth into shallow water. A diver who stays shallow and just blacks out while swimming is .... not sure what they call that.. hypoxia?


https://en.wikipedia.org/wiki/Taravana

 

[Steve_C]

Channeling my inner tursiops I will point out that Wikipedia is not always right either. Often is, but not always. Not agreeing or disagreeing with anybody, just noting.