FPDocMatt
Contributor
Deep water blackout occurs as the surface is approached following a breathe-hold dive of over ten metres and typically involves deep, free-divers practicing dynamic apnoea depth diving usually at sea.[3] The immediate cause of deep water blackout is the rapid drop in the partial pressure of oxygen in the lungs on ascent.
Shallow water blackout only occurs where all phases of the dive have taken place in shallow water where depressurisation is not a factor and typically involves dynamic apnoea distance swimmers, usually in a swimming pool.[4] The primary mechanism for shallow water blackout is hypocapnia brought about by hyperventilation prior to the dive.
This confusion is exacerbated by the fact that in the case of deep water blackout hypocapnia may be involved even if ascent is the actual precipitator.
I'm starting a new thread because we kind of hijacked another thread with this discussion.
Can someone explain this to me? I'm a doctor and I don't understand it.
Hypoxia causing a blackout makes sense. So that explains deep-water blackout.
But why would hypocapnia (low carbon dioxide) cause a blackout? And why would it only occur when diving in shallow water?