Water entry with regulator in mouth can cause embolism?
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ScubaSarus
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I can see if you are bouyant and jump in and sink 5-10 feet and suddenly rise back up and accidently holding your breath or not getting the air out of you lungs fast enough. Swells could make the issue worse. But I know of not one case.
I don't think holding your breath would be a problem, you would actually have to inhale fully on the way down then bob to the surface. Even then a lung expansion issue is seriously unlikely even more unlikely is an embolism related to that.
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If memory serves (from my days at the National Underwater Accident Center) there were a few such cases, but it was hardly a leading cause of death. There are several variations on the theme, diver entering the water breathing off the regulator, managed to take a breath after having penetrated the water and embolised as he popped to the surface, similarly a diver fell off the ladder when exiting, with the same result and finally diver going put under large swells breathing off his regulator.
Up thorough the mid 1980s it was common to train divers to enter the water with their snorkel in their mouth and their hoses under their arm(s). As training was reduced, and instruction practices became sloppy, there were a number of accidents that I'd categorize as "lack of gear savy," in which overweighted divers jumped into the water (or fell off the ladder), and not having put air into their BC sunk, were unable to locate their regulator, and drowned. In response to these incidents those agencies who were advocating the abbreviated programs (18 hrs. vs 40 hrs.) adopted the regulator in the mouth solution.
Up thorough the mid 1980s it was common to train divers to enter the water with their snorkel in their mouth and their hoses under their arm(s). As training was reduced, and instruction practices became sloppy, there were a number of accidents that I'd categorize as "lack of gear savy," in which overweighted divers jumped into the water (or fell off the ladder), and not having put air into their BC sunk, were unable to locate their regulator, and drowned. In response to these incidents those agencies who were advocating the abbreviated programs (18 hrs. vs 40 hrs.) adopted the regulator in the mouth solution.
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RubberDucky
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The embolism would have to be due to lung overexpansion injury. One could posit a diver jumping into the water, breathing off a regulator, and then holding his breath while bobbing back up to the surface -- but you'd have to go down far enough to make expansion possible, and be there long enough to take a breath, and then go back up. I don't know about anybody else, but I have three kinds of entries -- shore entries, where I wade in (no risk there); boat entries where I go in with my wing inflated (where I hardly go underwater at ALL before I'm back on the surface, and it takes seconds at most) and boat entries where I go in negative, in which case I'd better darned well have a reg in my mouth, because I'm not planning on coming back up. None poses any risk of embolism that would worry me in the slightest.
AbyssalPlains
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Never heard of this, but I've heard of many, many drownings because divers NOT having their regs in their mouths at the surface.
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Which brings up the question, "should someone who requires a regulator in their mouth to survive, on the surface, be diving?"
This is a bit of a reach but here goes...
I have from time to time encountered regs coming in for service where the exhaust valve was effectively glued shut by salt, silt or other crud. In some cases I could not even exhale hard enough to dislodge it and had to take the tee apart to excavate the neglected valve from whatever was encasing it or gluing it to the rim.
So...I suspect it is possible that if a diver were to fail to test his or her second stage by breathing a few breaths with it before jumping off the boat that a significant depression of the purge valve on entry could cause the reg to purge with the air having no where to go but into the diver. With a tight enough bite on the moutpiece the reg would not pop out under the pressure and I suppose an over expansion injury could occur.
It is important to note that just jumping in would not do it, as the water pressure on the diaphragm would start the flow but it would immediately stop if the air was not leaving the second stage as the pressure would push the diaphragm back out and stop the flow. In effect this would require two failures - the stuck exhaust valve followed by some object impinging on the purge button during the entry.
Alternatively, if the diver were to jump in with the blocked exhaust valve, descend 4-5 feet during the entry, inhale at the low point of the descent and then pop to the surface, the blocked exhaust valve could prevent the diver from exhaling from his or her mouth - although exhaling through the nose is still an option and unless the mask were really tight, I can't imagine it creating enough exhalation resistance to cause an over expansion injury.
Also, if either of these events were to occur it is possible that the water in contact with the reg and the resulting dampness for a few minutes after surfacing and exiting the water could free the valve before any post accident analysis detected the fault.
So in short, it might be remotely possible, but only if the diver fails to check the reg to ensure the exhaust valve is functioning before doing a giant stride.
I have from time to time encountered regs coming in for service where the exhaust valve was effectively glued shut by salt, silt or other crud. In some cases I could not even exhale hard enough to dislodge it and had to take the tee apart to excavate the neglected valve from whatever was encasing it or gluing it to the rim.
So...I suspect it is possible that if a diver were to fail to test his or her second stage by breathing a few breaths with it before jumping off the boat that a significant depression of the purge valve on entry could cause the reg to purge with the air having no where to go but into the diver. With a tight enough bite on the moutpiece the reg would not pop out under the pressure and I suppose an over expansion injury could occur.
It is important to note that just jumping in would not do it, as the water pressure on the diaphragm would start the flow but it would immediately stop if the air was not leaving the second stage as the pressure would push the diaphragm back out and stop the flow. In effect this would require two failures - the stuck exhaust valve followed by some object impinging on the purge button during the entry.
Alternatively, if the diver were to jump in with the blocked exhaust valve, descend 4-5 feet during the entry, inhale at the low point of the descent and then pop to the surface, the blocked exhaust valve could prevent the diver from exhaling from his or her mouth - although exhaling through the nose is still an option and unless the mask were really tight, I can't imagine it creating enough exhalation resistance to cause an over expansion injury.
Also, if either of these events were to occur it is possible that the water in contact with the reg and the resulting dampness for a few minutes after surfacing and exiting the water could free the valve before any post accident analysis detected the fault.
So in short, it might be remotely possible, but only if the diver fails to check the reg to ensure the exhaust valve is functioning before doing a giant stride.
Thal, it would seem that the cause of the embolism is NOT having the reg in your mouth BUT violating "the rule" of "Never Hold Your Breath" while underwater. Or am I missing something here?
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