Quote:
Originally Posted by fleshy
Shallow water blackout short and simply is this. Not blacking out from lack of oxygen, blacking out from having to much CO2 in your blood. It happens the most with younger and middle experience ranged divers because they are pusing their limits. Building up more CO2 in their systems than they are used to, and at the same time taking lots of fast repitition dives. Best way to avoid SWB, is to have good breaks between dives.
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Sorry, fleshy, but this is a completely wrong statement. Shallow water blackout (as commonly understood), or depressurizing blackout (as sometimes referred to) happens when the oxygen level drops suddenly during the ascent due to the fastly decreasing PAO2 (partial alveolar oxygen pressure). Due to the expaning lungs during the ascent, the PAO2 drops below the level of PaO2 (partial arterial oxygen pressure) or even PvO2 (partial venous oxygen pressure), so the diffusion through the aleolar wall decrease, halts, or even reverses (sucking out the oxygen from the blood back to the lungs).
The SWB often happens after self induced hypocapnia (low level of CO2) through hyperventialation. The low CO2 level suppresses urge to breath, and decreases tolerance to hypoxemia.
