Blacking out while diving

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harmonised

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What can cause a diver to blackout? I have been reading somewhere that it can happen in shallow water and deep water, and it's one of the the major reasons why you should never dive alone. Is blacking out a major concern for a diver?


thanks in advance
 
People often speak of shallow water blackout as a hazard for free divers (not on scuba). You posted in Basic Scuba Discussions, so are you asking about scuba divers?

If so, there are a range of possible causes. Medical issues such as epilepsy come to mind.

Richard.
 
People often speak of shallow water blackout as a hazard for free divers (not on scuba). You posted in Basic Scuba Discussions, so are you asking about scuba divers?

If so, there are a range of possible causes. Medical issues such as epilepsy come to mind.

Richard.

Yes, I am referring specifically to scuba, but I think they were referring to free diving like you say, so not a major risk to scuba divers?
 
What can cause a diver to blackout? I have been reading somewhere that it can happen in shallow water and deep water, and it's one of the the major reasons why you should never dive alone. Is blacking out a major concern for a diver?

It's not a problem for SCUBA unless you have other problems such as physical, medications or chose your breathing gas poorly.

If you black out at other times, you shouldn't be diving.

flots
 
It's not a problem for SCUBA unless you have other problems such as physical, medications or chose your breathing gas poorly.

If you black out at other times, you shouldn't be diving.

flots

No never have blacked out, I saw a discussion on this on another board, but they were talking about free diving. I didn't realize it until drrich2 pointed it out to me.
 
I have fallen asleep, clipped off at deco. Dzat count?
 
There is no gear-related reason why one would black out if they were scuba diving with an open-circuit system (i.e., compressed air) provided that the gas mix they are breathing is appropriate for the depth. Breathing the wrong gas mix for the depth can cause blackout or seizures. If you are diving recreationally and within your limits with a standard gas (e.g., air, EAN 32, etc) you should be fine.

There have been a few cases where scuba divers have died while diving closed-circuit systems (i.e., rebreathers) in which case the incident was death by drowning following passing out because of equipment malfunction - in most cases the CO2 was being scrubbed, but there was insufficient oxygen being injected into the circuit leading to a blackout.
 
Let's start with a more specific definition of "blacking out." Medically the patient will lose consciousness. The definition is important because the two basic systems involve are the nervous system and the cardiac system.

One reason, but more uncommon, for a person to pass out is a seizure. So air contamination from carbon monoxide poisoning may be a very rare cause but not out of the realm of it can happen. Oxygen toxicity from overly enriched Nitrox could be another. Patient's with primary seizure disorders however are not medically cleared for scuba and wouldn't be diving unless they lied on their medical form.

The most common types of passing out are from cardiac issues. For otherwise physically fit divers of any age there is minimal to no risk. For diver's over the age of 50 with concurrent conditions like high blood pressure and high cholesterol there is a possibility of a heart attack leading to passing out. It is unlikely that a diver would have a fatal irregular heart beat out of the blue. Almost always their is a prior history of heart disease such as a heart attack that would put that diver at risk. Unless they lied about that too then they would not have been cleared to dive for at least 6 months after their heart attack and not until they have had a full cardiac evaluation.

Blacking out from free diving involves a phenomenon where you override the normal desire to breath and hold your breath until you pass out. Since one of the cardinal rules of diving is never hold your breath this shouldn't EVER be the cause of someone blacking out while diving. If you do hold your breath you would suffer barotrauma to the lungs and could pass out from the internal damage it caused while ascending.
 
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