Raising the Dead: Nightline Fri

[scubert]

Did anyone see this segment on Nightline?

One of the last bits was the video recovered from a diver (David Shaw) attempting a body recovery at 880'+ as he seized and died...

All you see is his view, as the camera was mounted on his helmet, so you see his hands and his task of attempting to recover the other diver.  That, along with the audio which only records his breathing and the bubbles was enough to give me the chills.

One of the most terrifying things I've ever seen, and a very tragic story.

[Omicron]

I didn't see that special, but I have seen that video segment from a different show.  As you said, it's a terrifying film.  Not how I want to think about my demise....

[drifter1430]

Is the video on the net someplace?

[WIdiver_Paul]

is all I could find. Horrible. One senses the confusion, narcosis and sense of impending doom from the last 2 minutes. We can almost guarantee he was hallucinating heavily or experiencing extreme tunnelvision. My condolenses to his family and wife for such a needless death. Hindsight illustrates the face of the first departed diver as the Grim Reaper. Still can't believe this was ever attempted without a full face mask. Or perhaps a time-delayed cartridge style lift bag would have been a wiser option for the corpse.

Just shows the importance of the first rule of recovery: don't risk your own life to retrieve a body...

A good post-mortem analysis , (hypercapnia=BAD)

My only other comment is they wouldn't  let commercial divers do dives like this past the age of 40, and Shaw was 51 and no shining example of top physical fitness. Very, very bad idea.

[schultz]

Here's a write-up from Outside magazine:

[Omicron]

This is a video interview w/ some footage...



This is a website that has some writeups by Dave Shaw himself...very interesting reading.

[ethanb]

Dr. Clarke of the Navy's Experimental Diving Unit gave an excellent talk at the 2005 NSS-CDS Workshop about the accident.  I looked for a copy of his presentation online and can't find it, so this is from memory.  The main point of his talk was that Shaw died from excessive CO[sub]2[/sub], most likely due to the high work of breathing (WOB) diving (and working) at such a depth.  The Mk15.5 rebreather he was using was intended to have a maximum depth of 200-300 ft (I don't remember exactly) and the designers never conceived that it would be used at nearly 900 ft.  At these depths, breathing gas has a density nearly 30 times what it would be on the surface.  Compounding the problem was the fact that Shaw used fine-grain (8-12 mesh) CO[sub]2[/sub] absorbent material in his scrubber canister, instead of the standard (4-8 mesh) material.  While using the finer grain material increases the surface area, improving scrubber life and efficiency and reducing inspired CO[sub]2[/sub] levels, it also further increases the WOB.  Higher WOB leads to shallower breathing, which means that the lungs can't efficiently exchange CO[sub]2[/sub].  Very high WOB can lead to extremely high levels of dissolved CO[sub]2[/sub] in the blood (even if the inspired gas has no CO[sub]2[/sub]) and this can lead to death.

Dr. Clarke's talk included some quotes from Shaw about why he chose to use the finer grained scrubber material.  The one quote I remember was along the lines of "For deep dives, I always use the highest quality fine-grained scrubber material to get the longest canister life."  While that true, perhaps Shaw did not fully consider the negative impact this would have on WOB.

Dr. Clarke also analyzed the grain size distribution of various scrubber materials and concluded that the material size distribution can vary widely.  This is bad, as it leads to tighter packing of the scrubber, increasing WOB. 

In any case, it's a very sad story (my thinking is it was a huge waste just to recover a body), but death can be the price one pays for being the first, for exploring and pushing the limits of human existence.  I'm just glad there are other people out there who want to do it. 

Ethan

[Vtach]

I think that anyone pushing these sort of limits has an understanding of what MAY happen but it is still no less a tragedy especially when it's someting relatively simple that snowballed into a lethal event (which sounds like a common thread in many diving accidents).  It's an even bigger tragedy if no one learns anything from this unfortunate event. 

My first thought about this was, "DAMN, 880ft!"  But watching that video made me really think.  You can plainly see how a relatively simple task can turn into catastrophe.  Task loading, anxiety, respiratory rate, heart rate, oxygen demand, work of breathing, CO2 retention.....  This is an event that could happen to any diver.  Diver at 100 feet with low vis, add 1 poorly functioning regulator, add some tunnel vision, add some narcosis, throw in some exercise and VOILA! CO2 retention, now where it goes from here depends on the diver.  Now obviously 880 ft (27.6 ATA of pressure) will create a much quicker physiological response to this than 100ft (4 ATA) will, but if left to progress, the results will be similar. 

For those deep air divers (been there, done that, no more), I remember reading an abstract that described how our airway anatomy is unable to adequately hyperventilate partial pressures of air (21/79) over 7 ATA due to the density of the gas at those PP's.  So, no problem when things are going well and you have a normal respiratory rate, but start to work a bit and you could find yourself following the same track.  I looked for the link but couldn't find it. 

Here's another good one for those who like "technical" reading, enjoy.

[Omicron]

I was thinking of that same abstract when I first heard about this and read up on it....of course, I can't find it now anymore either.