Free diver drowns attempting anchor retrieval - Key Largo Florida

[afenner5]

Your explanation was amazing Doc thanks. Helps me understand what happened down there a little better.

---------- Post added December 4th, 2015 at 09:06 AM ----------

Unfortunately, what SHOULD have happened, that didn't apparently, was that his buddy should have been there watching for him the whole time underwater, ready to go down to get him the moment of any sign of trouble. Ideally, his buddy should have been going down to meet him underwater. A SWB with proper buddy safety should never cause anyone to die. A buddy should be able to easily retrieve an unconscious person from at least 10m. His inexperience with nitrox didn't cause this, not having a proper safety buddy there, doing what they are supposed to do, is why he died. Unless it was a deep water blackout, then maybe you can't say that.

But, according to Divewise, a freedive safety organization talking about blackouts: "Some survivors have described the experience as a beautiful way to die. No suffering, no warning, no clue death was near. It is this feature of freediver blackout that makes it so deadly."

So if it was a blackout, it's safe to say he didn't suffer at all.

I absolutely agree with you, there were 6 other adults, 3 of which were divers, the others could at least swim, they were completely irresponsible and apparently unreliable! I know its his fault also BC he was careless and he knew he shouldn't have jumped in without a buddy (he would tell me all the time) but I hold them responsible as well. Hope you guys see this and think twice before jumping in by yourself when diving ...even if its just a simple task ...like retrieving an anchor. Search & recovery , he did it all the time , he just got too comfortable, forgot to follow the rules.

---------- Post added December 4th, 2015 at 09:11 AM ----------

Also I'm glad to hear this about the shallow water blackout (which is the explanation the police department gave me) thinking of him suffering often keeps me up at night. (Which explains why i came upon this thread at 1 am , 3 months later) How much did he suffer? What were his last thoughts? Did he know he was about to die? That explanation gives me some peace ...so I'll go with that. Thanks.

 

[TotDoc]

Doc did a wonderful job of explaining gases, but maybe a little too in depth for some us farm boys. For a simpler view of SWB, I understand this I think...

On the dive, your body consumes available O2, converting it to CO2, which continues to happen even on ascent with CO2 collecting in your lungs - but as you approach the surface and the water pressure drops around 10-15 feet below, the Partial Pressure effect on your body is such that there is a higher ratio of O2 in your blood than in your lungs and Osmosis sends O2 back from your blood to the lungs, depriving the brain: ZZZZZZZZZZZZZZzzzzzzzzzzzzzzz

Is that off...??

Maybe I need to read Doc's post closer.

Yeah, a fair bit of the explanation was a bit in depth, and I skipped presenting the math for partial pressure calculations.
Here's the way simple explanation:
Shallow water blackout (a mechanism which you can actually accomplish WITHOUT being underwater, as it turns out...) is a result of having oxygen pressure in your body falling below the level to maintain consciousness (due to your body utilizing the oxygen and the fact that you are not breathing in any more), BEFORE the accumulation of CO2 in the body triggers your perceived need to breathe. You pass out before you realize you are too low on oxygen.
Deep water blackout involves an acceleration of this process - gasses under pressure have a stronger effect on the body. Having low oxygen levels at depth is not necessarily dangerous, because the oxygen's effect is intensified under pressure. Your body still uses the oxygen at depth, and can still use up enough oxygen to have you at a dangerously low level before CO2 accumulation triggers your perceived need to breathe. When you come up, and pressure around you drops, the effectiveness of the oxygen level in your body also drops. If you cross the threshold of what is needed to keep your brain awake, goodnight!

Here's a link to a video that shows just how insidious hypoxia (low oxygen levels) can be. Notice, the guy was dangerously low on oxygen (his lips and finger tips even turn blue during the video), yet he only has a minimal increase in his breathing rate. He is essentially doing a breath holding excercise while breathing here, as they blew all the oxygen out of the room. This demonstrates the mechanism for shallow water blackout, though. Oxygen levels are critically low, but since he is not accumulating CO2 because he is breathing throughout the exercise, he never perceives the fact that he is about to pass out.
Hypoxia: When the brain is deprived of adequate oxygen supply. [VIDEO]

 

[seeker242]

Yeah, a fair bit of the explanation was a bit in depth, and I skipped presenting the math for partial pressure calculations.
Here's the way simple explanation:
Shallow water blackout (a mechanism which you can actually accomplish WITHOUT being underwater, as it turns out...) is a result of having oxygen pressure in your body falling below the level to maintain consciousness (due to your body utilizing the oxygen and the fact that you are not breathing in any more), BEFORE the accumulation of CO2 in the body triggers your perceived need to breathe. You pass out before you realize you are too low on oxygen.
Deep water blackout involves an acceleration of this process - gasses under pressure have a stronger effect on the body. Having low oxygen levels at depth is not necessarily dangerous, because the oxygen's effect is intensified under pressure. Your body still uses the oxygen at depth, and can still use up enough oxygen to have you at a dangerously low level before CO2 accumulation triggers your perceived need to breathe. When you come up, and pressure around you drops, the effectiveness of the oxygen level in your body also drops. If you cross the threshold of what is needed to keep your brain awake, goodnight!

Here's a link to a video that shows just how insidious hypoxia (low oxygen levels) can be. Notice, the guy was dangerously low on oxygen (his lips and finger tips even turn blue during the video), yet he only has a minimal increase in his breathing rate. He is essentially doing a breath holding excercise while breathing here, as they blew all the oxygen out of the room. This demonstrates the mechanism for shallow water blackout, though. Oxygen levels are critically low, but since he is not accumulating CO2 because he is breathing throughout the exercise, he never perceives the fact that he is about to pass out.
Hypoxia: When the brain is deprived of adequate oxygen supply. [VIDEO]

Do you know if peripheral vasoconstriction has anything to do with it? I think I have read that the mammalian diving reflex causes increased and decreased peripheral vasoconstriction that is proportional to atmospheric pressure. So the deeper you go, the more constriction there is in the extremities, pushing more blood into the major organs like lungs, heart, brain, etc. and the process reverses itself coming shallower. Seems reasonable to say that this would further contribute to the loss of O2 to the brain simply because there is less blood going to the brain than there was when you were deeper. Although, I don't know how significant that effect would be.

 

[TotDoc]

Well, the mammalian diving reflex does cause vasoconstriction (closing off) of peripheral blood vessels to maximize circulation to critical organs, but it seems unlikely to me that it would play a really significant role in freediving blackout - at least in regards to decreased blood flow to the brain. The only way I could see that vasoconstriction would play a role is that if it is reversing as someone comes up (which I'm not sure it does, since it is also triggered by cold water on the face, and the effects tend to persist while submerged) then it MIGHT result in increasing oxygen demand as you ascend, as previously unperfused tissues are now receiving blood flow again and would be snatching up oxygen from the blood. That would result in a more rapid development of significant hypoxia. I don't think it would be an issue that too little blood flow would be going to the brain, though, since I have never seen anything about relative peripheral vasodilation occurring. If you are simply returning to normal surface circulation, you would have plenty of blood circulating to the brain to keep things running - you just need that blood to be containing oxygen so you stay conscious.

 

[CuzzA]

Really glad to see a thread develop with so much good information; hate that it came at the expense of someone's life.

Here's some videos of survivors so others can see how real and dangerous it is and why you have to have a buddy watching you IN the water with gear ON. You also have to know your limits.

[video=youtube;lP_9aWr4pJU]https://www.youtube.com/watch?app=desktop&persist_app=1&v=lP_9aWr4pJU[/video]

[video=youtube;wwLCoufAfdY]https://www.youtube.com/watch?v=wwLCoufAfdY&app=desktop[/video]

[video=youtube;VlGKJn1BfhU]https://www.youtube.com/watch?v=VlGKJn1BfhU&app=desktop[/video]

 

[fiduce]

Just like the doc said: the three tank dives he made that day had raised his nitrogen burden (tissue saturation) to a high level and the first freedive sink he did, especially when he quickly came back up from 50', triggered a DCS that made him collapse during the second sink.

 

[dumpsterDiver]

Just like the doc said: the three tank dives he made that day had raised his nitrogen burden (tissue saturation) to a high level and the first freedive sink he did, especially when he quickly came back up from 50', triggered a DCS that made him collapse during the second sink.

Ahhhhh.. No..

 

[seeker242]

Really glad to see a thread develop with so much good information; hate that it came at the expense of someone's life.

Here's some videos of survivors so others can see how real and dangerous it is and why you have to have a buddy watching you IN the water with gear ON. You also have to know your limits.

[video=youtube;lP_9aWr4pJU][/video]

[video=youtube;wwLCoufAfdY][/video]

[video=youtube;VlGKJn1BfhU][/video]

That 2nd video looks like an example of how to be a bad buddy...Letting the guy sink again after he passes out...

 

[CuzzA]

Fixed my links. DCS was not the cause of death, nor was that ever reported.