Black outs in free diving

[Sandie7]

Sorry if this was posted before, but couldn't find in the "search".

What exactly happens when you black out doing free diving ?

thanks

 

[dumpsterDiver]

Sorry if this was posted before, but couldn't find in the "search".

What exactly happens when you black out doing free diving ?

thanks

If your buddy is trained and is watching you.. nothing.. If not, then you DIE (most often)..

 

[tbone1004]

google "shallow water blackout"

basically at depth you have a high enough PPO2 to sustain life, as you ascend, the PPO2 drops, sometimes to the point that it is not enough to sustain consciousness and you black out.

 

[Hickdive]

Er, you become unconscious and, if you're alone, you most likely drown.

A more technical explanation of why people black out when freediving;

At depth the oxygen in the lungs, although depleted, has a sufficiently high partial pressure to continue oxygenating the blood both carried combined with hemoglobin and dissolved in the plasma. As you ascend, the pp02 drops below what is needed for transfer across from lungs to blood and the level of oxygen in the blood drops below the point needed to sustain consciousness; so you pass out.

 

[dumpsterDiver]

google "shallow water blackout"

basically at depth you have a high enough PPO2 to sustain life, as you ascend, the PPO2 drops, sometimes to the point that it is not enough to sustain life and you black out.

Yes as the post below explains in better detail.. the oxygen level has not dropped below the level to sustain life - this type of over simplification could lead someone to suspect that a BO is fatal. A better explanation is that the oxygen tension is so low that the body shuts down a portion of the brain and consciousness is lost.

The brain (or the body) is not harmed by this process, and it is thought to be a mechanism to "protect" the brain and conserve oxygen levels. So the BO occurs when the oxygen pressure is too low to keep the diver awake and functioning.

If an oxygen supply is not quickly provided after a BO, then death will come soon.. It may seem to be a minor distinction, but a high percentage of freedivers have had a BO and the ones that survive are typically not harmed by the occurrence.

 

[Sandie7]

Thank you, all !

 

[tbone1004]

Yes as the post below explains in better detail.. the oxygen level has not dropped below the level to sustain life - this type of over simplification could lead someone to suspect that a BO is fatal. A better explanation is that the oxygen tension is so low that the body shuts down a portion of the brain and consciousness is lost.

The brain (or the body) is not harmed by this process, and it is thought to be a mechanism to "protect" the brain and conserve oxygen levels. So the BO occurs when the oxygen pressure is too low to keep the diver awake and functioning.

If an oxygen supply is not quickly provided after a BO, then death will come soon.. It may seem to be a minor distinction, but a high percentage of freedivers have had a BO and the ones that survive are typically not harmed by the occurrence.

could be both, but yes sustain consciousness would have been a better term. corrected above.

 

[Phantom Menace]

Not all black outs are related to Shallow Water Blackout - but many will be when diving deepish. Here is a summary of the physics of freediving. (Credit to Dumagat Freedive. I have nothing to do with them at all but like some of the simple info sheets they have put together).
Freediving Physics Simplified | Dumagat Freedive



It is possible to push yourself to the point of blackout in a pool hence breath hold training should never be undertaken alone and you should be confident that your buddy knows what to do in the event of a black out or "Loss of Motor Control" aka LMC or samba. A BO can sneak up on you so be careful!