Sunday, June 12, 2011

Black-out & samba - what does it look like?

A lack of oxygen (hypoxia) is what causes a blackout. Oxygen partial pressure in the aterial blood is around 100 mmHg (13.3 kPa). When you hold you breath the partial pressure drops depending on your requirement. Labour under water chews it up fast. When arterial oxygen partial pressure falls to 40 mmHg (5.3 kPa) or less you are at the potentially lethal range and you need to breathe ASAP, even then there is a delay between the oxygen reaching our lungs, tranferring to the blood and being pumped up to you brain. This delay could be 7-20 seconds. Watch you divebuddy for a while after hard dives!

Typical breathhold profiles may look like this:

Time (min)  0   1.0  2.0  3.0  4.0  5.0  6.0  7.0

O2 mmHg  99  99  98   96    88   74   52   40 

Pulse bpm  65   65  67   68    61   47   41   37

Note the steep drops in both pulse and oxygen levels.

On longer holds you can clearly feel how you muscle reoxygenate.

So what does a black out look like -  here is an almost amusing samba (more like a breakdance).

1. The back-up to help the diver - you should have this in hard pool training, ideally in any breathhold pool training.
2. That he believes he was ok and still attempted to convince the judges that he was ok.
3. He got to 6 min 58 sec - not bad! A definite disqualification.
4. Note how he regains some control - enough to go through the surface protocol of removing mask and giving an OK sign. That was probably as the oxygen reached his brain.

1 comment:

Warrior Dash said...

I had to admit I laugh at that part where his about to black-out. My God, good thing that man his with covered the edge of the pool so he wouldn't hit his head.