Free diving, tank sharing fatality - Australia

[Sam Miller III]

@Kris Kippax
Stated;

All I can say is anyone that is considering serious freediving, do your self a favour and get some professional training. Do not take advice from people off this forum.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Thanks' for the warning-- does that include YOU ?

An old broken down California spear fisherman /free diver who is slow walking.slow talking, and slow thinking wants to know ?
SDM

@Marie13 CE

 

[chris kippax]

@Kris Kippax
Stated;

All I can say is anyone that is considering serious freediving, do your self a favour and get some professional training. Do not take advice from people off this forum.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Thanks' for the warning-- does that include YOU ?

An old broken down California spear fisherman /free diver who is slow walking.slow talking, and slow thinking wants to know ?
SDM

@Marie13 CE

Most definitely

 

[Duke Dive Medicine]

It would depend on depth whether you could breath out to clear the reg, the article does not specify depth. At one ATM I can, because I forgot to put the reg in my mouth and got over 30' down before I realized I should do something about it, funny story but longer. Deeper than say 100' you would lower the CO2 concentration by 2/3, then going directly to the surface should not increase the CO2 significantly as the work load should be small and exhaling on the way up should also decrease concentration.

Took me, probably a post too long, but may be @Duke Dive Medicine could sort this out for us, if we ask nice. Please.


Bob

@Bob DBF , just catching up after the weekend, sorry. It looks like shallow water blackout is pretty well addressed elsewhere in the thread. FWIW though, there are two mechanisms. The first is related to depth and the drop in ambient pressure on ascent. The gas pressure in the lungs of a free diver is equivalent to the ambient pressure. So, the gas pressure in the alveoli, and consequently the partial pressures of both oxygen and nitrogen, increase on descent. A free diver at depth is consuming oxygen from his/her lungs, but usually (hopefully!) still has a high enough partial pressure of oxygen in his/her alveoli to maintain consciousness and function at depth. On ascent, however, the alveolar pO2 drops as a function of the ambient pressure. If the diver consumes enough oxygen at depth, the alveolar pO2 can drop to the point where he/she loses consciousness abruptly while ascending. The second mechanism is simple hypoxia, usually related to improper pre-breathing/excessive hyperventilation and is the classic "shallow water blackout" where the alveolar/blood pO2 drops enough for the swimmer to lose consciousness before his/her CO2 level rises to the point where he/she is driven to surface and breathe. Re whether a free diver's lungs would expand with an inhalation of compressed air at depth, yes, they would. The lungs are compressed in a free diver on descent, and the diaphragm moves up as that happens. As soon as the free diver takes a breath of compressed air at depth, the lungs expand to normal size with normal diaphragmatic movement.

Best regards,
DDM

 

[dmaziuk]

FWIW the phrase "sharing oxygen with a female scuba diver friend" appears in only one of several original news sources. That was the story picked by MSN, of course.

 

[Bob DBF]

The lungs are compressed in a free diver on descent, and the diaphragm moves up as that happens. As soon as the free diver takes a breath of compressed air at depth, the lungs expand to normal size with normal diaphragmatic movement.

The question from that point is what is the effect of breathing off the regulator and ascending directly to the surface as described in the article. Is the air breathed under pressure enough to to eliminate the chance of SWBO in that case, or is a "it depends" situation, and what mechanism would it depend upon?

just catching up after the weekend, sorry.

No worries, I figured you would respond when you got a chance, and I appreciate the expertise you share on the board.


Thanks

Bob

 

[Duke Dive Medicine]

The question from that point is what is the effect of breathing off the regulator and ascending directly to the surface as described in the article. Is the air breathed under pressure enough to to eliminate the chance of SWBO in that case, or is a "it depends" situation, and what mechanism would it depend upon?



No worries, I figured you would respond when you got a chance, and I appreciate the expertise you share on the board.


Thanks

Bob

Hi Bob,

The diver would have had a lungful of fresh air at ambient pressure, which should have been more than enough O2 to eliminate the chance of hypoxemic blackout, especially if he ascended directly to the surface afterward. The air would also have been low in CO2, which would have pulled CO2 from his body into his lungs and reduced the chance of a hypercapnic event. At the risk of speculating based only on the media report linked in the original post, I think it's much more likely that the free diver in this case suffered pulmonary barotrauma. It doesn't take much of a decrease in ambient pressure with concomitant increase in lung volume to cause that - even if he was venting air, if he was maintaining full lung volume on ascent, a wave going overhead could have done it.

Best regards,
DDM

 

[Dan]

I think it's much more likely that the free diver in this case suffered pulmonary barotrauma. It doesn't take much of a decrease in ambient pressure with concomitant increase in lung volume to cause that - even if he was venting air, if he was maintaining full lung volume on ascent, a wave going overhead could have done it.

How about if he did CESA?

 

[yle]

1 bar = 14.5 psi. 0.3 bar = 4.35 psi.

lol... dangit.

Thanks. My brain needs to be recalibrated frequently.

 

[Duke Dive Medicine]

How about if he did CESA?

He might have been doing one, but if it's not done absolutely correctly it can result in AGE. There are/were recompression chambers at the top of the Navy's Free Ascent Training (FAT) towers for that reason, and they stopped training with actual CESAs before I went to dive school in 1989. Again, it doesn't take much.

Best regards,
DDM

 

[John the Pom]

Hi Bob,

...snip... At the risk of speculating based only on the media report linked in the original post, I think it's much more likely that the free diver in this case suffered pulmonary barotrauma. It doesn't take much of a decrease in ambient pressure with concomitant increase in lung volume to cause that - even if he was venting air, if he was maintaining full lung volume on ascent, a wave going overhead could have done it.

Best regards,
DDM

That's why mixing free diving and scuba seems like a bad idea. As soon as you take that first breath of compressed air, you have to switch from a breath-hold, free diving mindset to a scuba mindset.