Blood O2

[DeepThought]

I've heard that if you admit into a hosiptall and they check your blood and discover it has a lower O2 percentage than 95% you'll be connected to a respirator, or given pure O2 or something like that.

I also heard that some freedivers get to as low as 85%.

If this is true, does anyone know to what blood O2 levels freedivers get, and after how much time/effort? and how can we make sure it is safe to get to those levels? or how frequent it's still healthy to get to those levels.

 

[efattah]

My sister is an M.D., she told me that doctors get very worried if SaO2 goes less than 80%.

Common understanding is that a hard apnea ends with true arterial blood around 50% saturated. The actual level depends on the hypoxia tolerance of the athlete.

Pulse oximeters (on the finger) will show much lower values. I have gotten mine down to 11% without a samba! (Other times I have sambas/BO at 25%).

When you look at true arterial O2 saturation, you can only stay conscious at < 60% if you have high CO2, which creates acidic blood and unloads the oxygen. So, in other words, if you put someone on the top of mount everest, then the thin air will put them at < 60% and they will black out (unless they are altitude adapted and hyperventilate). But, if you reach the same saturation with a long breath-hold, you can stay conscious because of the high CO2. This is why hyperventilating makes you black out at a higher saturation than otherwise.

The scientists who developed IHT (interval hypoxic training) say that at less than 80% saturation, you rapidly steal oxygen from your organs and tissues, and go into 'deep tissue hypoxia'. That is why when they train athletes with IHT, they tend to keep them above 80%. It is also known that athletes that exercise hard at altitude can get to 75% or less. As always, you must make it clear if you mean true arterial oxygen saturation, or fingertip/earlobe saturation as measured by a pulse oximeter, which always shows incorrectly low values during deep hypoxia due to the blood shift.


Eric Fattah
BC, Canada

 

[DeepThought]

10x Eric.

What about brain damage? stealing O2 from other tissues less worries me (should it worry me more?).
Is it possible to stay conscious while your brain is so O2 deprived that brain damage might occur?

What is the definition of brain damage do to hypoxia? braincell mortality?

 

[efattah]

Brain Damage

I read a whole book on brain hypoxia. It was very complicated!

I learned the following:
- Loss of consciousness occurs at the moment of 'anoxic depolarization', which is when the sodium and potassium channel 'pumps' in the brain fail (normally all processes are reversible until anoxic depolarization) except:
- Chronic extreme hypoxia (without loss of consciousness) can cause brain damage, which often happens to sea-level inhabitants who climb a mountain over 8500m (they experience extreme hypoxia, i.e. fading vision, for many hours or even days without a single moment of re-oxygenation)
- A short period (i.e. a few minutes) of extreme hypoxia (without loss of consciousness) is itself not damaging, but upon reoxygenation many free radicals (Reactive Oxygen Species = ROS) are formed, and if these are not neutralized (by rest & nutrition), then these can cause brain damage


So, the bottom line is that a short period of extreme hypoxia is not damaging if you rest enough after and have good nutrition (i.e. lots of antioxidants). But if you do it too often, or without proper nutrition, then you will notice your daily concentration starts to drop (from personal experience!)

An interesting idea is introduced in this book. The author says that if you completely strangle someone (cutting off all blood flow to the head), then the oxygen stored in the blood in the brain lasts for 1 second, the ATP lasts for 3 seconds, and the creatine phosphate lasts for 3 seconds, and glycolysis lasts for about 1/2 second, so you lose consciousness in about 7.5 seconds.


Eric Fattah
BC, Canada

 

[DeepThought]

Thanks Eric!!

An interesting idea is introduced in this book. The author says that if you completely strangle someone (cutting off all blood flow to the head), then the oxygen stored in the blood in the brain lasts for 1 second, the ATP lasts for 3 seconds, and the creatine phosphate lasts for 3 seconds, and glycolysis lasts for about 1/2 second, so you lose consciousness in about 7.5 seconds.

Useful information. :mute

- A short period (i.e. a few minutes) of extreme hypoxia (without loss of consciousness) is itself not damaging, but upon reoxygenation many free radicals (Reactive Oxygen Species = ROS) are formed, and if these are not neutralized (by rest & nutrition), then these can cause brain damage

At last!! being lazy had payed off!
Is ROS a type of free radiclas, or is a free radical?
What I tihnk I know about free radicals is that they are a molecule with a spare or a missing electron. And they are one of the reasons for limited life span, since they do long term cellular damage.
So... what did I miss?