Free-diving student blacks out training - Taiwan

[johndiver999]

Perhaps, but I can’t imagine it’s good for you either? To each their own, but way too risky to push well beyond your body’s inbuilt safety/warning systems for me.

Probably not good for you and supposedly the more times a diver BO, the more likely it is to happen again at a later time.

Not to be argumentative, but rather to clarify... freedivers are taught that the BO .. IS a safety system.

The Brain shuts down the musculature, most sensory input, suspends breathing, locks up the epiglottis to prevent drowning and goes into a sort of power saving mode, where sometimes there is some remaining vestiges of consciousness (e.g., sometimes the victim can still hear). Supposedly, this is not damaging to the brain/body.

If the brain does not detect that it is safe to resume breathing within about 30 seconds or so, then it will relax the throat, an involuntary inhalation will occur (of water or air depending on situation) and if water enters the lungs, the danger is exponentially higher. Anyway that is my recollection of the layman description of some of the physiology.

I've never blacked out and hope to avoid it, but have seen it at least once in the ocean.

 

[<*)))><]

Interesting read. Explains the attraction and dangers of freediving in laymens terms.

 

[Joneill]

Probably not good for you and supposedly the more times a diver BO, the more likely it is to happen again at a later time.

Not to be argumentative, but rather to clarify... freedivers are taught that the BO .. IS a safety system.

The Brain shuts down the musculature, most sensory input, suspends breathing, locks up the epiglottis to prevent drowning and goes into a sort of power saving mode, where sometimes there is some remaining vestiges of consciousness (e.g., sometimes the victim can still hear). Supposedly, this is not damaging to the brain/body.

If the brain does not detect that it is safe to resume breathing within about 30 seconds or so, then it will relax the throat, an involuntary inhalation will occur (of water or air depending on situation) and if water enters the lungs, the danger is exponentially higher. Anyway that is my recollection of the layman description of some of the physiology.

I've never blacked out and hope to avoid it, but have seen it at least once in the ocean.

Thanks for the detailed explanation on BO!

 

[rx7diver]

You win for using NATATORIUM. Thank you for teaching me a new word!

Well, I should have capitalized it, as it was the actual name of the (now gone) campus facility: MU in Brick and Mortar - Natatorium. (The institution now has a 50 meter pool, more befitting Div 1.)

rx7diver

 

[Nemrod]

A natatorium is a facility for swimming sports.

It is possible to blackout from breath holding in a swimming pool. Lifeguards are trained, supposedly, to recognize this. As a guard one of my two pool rescues was a black out by a fellow who was breath holding and swimming repeatedly the length of the pool. And then I noticed him sort of wander and then he was just floating face down.

And yes, if water hits the larynx (or as in my case gets aspirated into the lungs) it will close up and at which point you are and in this case me, was in a heap o'trouble, just saying.

 

[Trace Malinowski]

I blacked out in a pool at my college in 1991 or 1992. I was doing static on the bottom. My G-Shock showed 2:35 when I last glanced at it. I was thinking about what to eat for dinner.

A French freediver I was training with pulled me up. He put me in a cross-chest carry and held me so tight he left a handprint under my left arm. My lifeguard co-worker Maura did rescue breathing on me. She came in to relieve me so I could train. Blood gas analysis in the hospital showed low oxygen exchange because I was getting sick - bronchitis.

My 2nd blackout occurred after staying too long smiling and profiling for scuba divers at 95 feet for photos ops. I was solo diving. I retained the snorkel in my mouth and continue to do so to this day because of this incident. The technique for using the expansion method of clearing is very similar to hook breathing once you reach the surface. It involves a brief hold to rest creating positive pressure but in a prone resting position. I disagree with a vertical body position with the head out of the water. There have been no studies either way. I suggested DAN do studies but their consensus was it would be unethical to have human divers experiment with breathing techniques and recording blackouts.

If DAN doesn't want to do it, it shows how serious a blackout episode can be.

Anyway, I blacked out, the tube was cleared of water on ascent due to the expansion method, the tube remained in my mouth, and I was left floating on the surface in the resting position. A female scuba instructor noticed something wasn't right, swam over to me, and began tapping and talking to me which snapped me out of the event. I woke up and was surprised to be in the water rather than in bed or on a couch or something.

My third blackout occurred during an extended range freediving class I was teaching after a 5:30 static at depth, my student rescued me and performed Blow-Tap-Talk until I responded.

I now advocate for breath-hold times no longer than 1 minute. That is science and the recommendation of Capt. Dr. Frank Butler, Jr, USN (ret.). He was a UDT turned SEAL turned physician turned ophthalmologist who studied breath-hold diving because of special operations forces apnea deaths in training. Blood gas analysis of Japanese and Korean Ama freedivers show significant levels of hypoxia after 1 minute.

I suggest we remember the AMA - A Minute Always, no more.

 

[kensuf]

View attachment 750057


Interesting read. Explains the attraction and dangers of freediving in laymens terms.

It's a fantastic book on many levels. I want to go on a Honduran submarine ride.

 

[Vicko]

I passed out TWICE while training for apnoea in a diving pool. It is incredibly easy, as after some proper training, the CO2 build-up is minimised, and you reach the point of lacking oxygen way before you get a strong stimulus to breath.
Only untrained and unfit people get the stimulus before passing out.
However, if the apnoea instructor does his job properly, the passed-out diver is recovered and revived in a few seconds, with no real harm for his/her brains.
The situation can be much more dangerous in the sea, of course.
But also the pool can be quite dangerous and caused a number of deaths, if supervision is not strict and the recovery action is not super-fast.

The technique you are talking about is hyperventilation and it's effect is elimination of previously dissolved co2 in your bloodstream. It used to be very popular especially in Italy and France (I learned it from the old Dapiran videos).
It doesn't actually help with holding the breath longer, it just makes the contractions that let us know we need to breath come later then usual and it's extremely dangerous as you noticed.
When teaching proper breathing techniques now the first thing we explain is not to hyperventilate but breath in a more relaxed way that relives muscle tension and lowers the heartbeat, thus actually allowing you to hold the breath longer.

My 2nd blackout occurred after staying too long smiling and profiling for scuba divers at 95 feet for photos ops. I was solo diving. I retained the snorkel in my mouth and continue to do so to this day because of this incident. The technique for using the expansion method of clearing is very similar to hook breathing once you reach the surface. It involves a brief hold to rest creating positive pressure but in a prone resting position. I disagree with a vertical body position with the head out of the water. There have been no studies either way. I suggested DAN do studies but their consensus was it would be unethical to have human divers experiment with breathing techniques and recording blackouts.

If DAN doesn't want to do it, it shows how serious a blackout episode can be.

The other side of the medal is that with the snorkel in your mouth your airways remain open, and if you surface with the head tilted back you drown. Most of spearfisherman that drown are found with the snorkel in their mouth. Of course if you don't ascend vertically this becomes less of a problem, but that way you are not ascending directly and you are using more o2 as your muscles have to work against the drag of the water too.
Just as a side not, why do the static on the bottom?

 

[BoltSnap]

Most of spearfisherman that drown are found with the snorkel in their mouth.

The majority of them are also found with wetsuits on, the wetsuit killed them?

 

[Vicko]

The majority of them are also found with wetsuits on, the wetsuit killed them?

No, but when a number of my friends drown, and they drown while doing something that every single freediving agency agrees on being a bad idea, I tend to believe that the experts were right.
I know that spearfishing makes a lot of compromises between safety and effectiveness, but I personally prefer to ascend in the quickest and safest way possible.