Rollie:
Rebreathers kill and will continue to kill.
Rollie, aside from being off the topic your post shows that you're unshadowed by any know-how.
What an idiotic comment to make, especially when the corpse to be recovered stems from an open circuit diver.
Kim:
I suppose it might possibly be helpful for people who dive to 270m - otherwise I don't see the point. I don't think it should be shown, who can it really help?
Actually, there is a bit of information on the original tape that is quite important for any diver.
Dave Shaw can be heard hyperventilating and breathing very shallow.
In the posted copy that I saw this couldn't be heard, but Don Shirley's voice-over described it.
As has been posted earlier in this thread, hypercapnia is the most likely reason for Dave's death.
While hypercapnia (CO2 poisoning) gets more often than not related to rebreathers, where the breathing gas gets recirculated in the loop, it can be a danger to every diver. Even free divers.
The bottom line is the CO2 content in the diver's body, nowhere else!
Carbon Dioxide is a product of the body's metabolism, hence it occurs in everyone.
The higher our metabolism, the higher our CO2 production, it's that simple. When the CO2 level rises, we breath harder (deeper) and faster to vent it from the body. The problem is when we start breathing very fast and shallow (hyperventillating) as the CO2 doesn't get sufficiently vented. The rise in CO2 will eventually lead to unconciousness (and underwater likely drowning).
Improper breathing patterns, such as breath holding and skip breathing can lead to that, no matter what the activity or what equipment is used. Free diving requires you to hold your breath.
Deep diving, on any equipment, leads to higher work of breathing due to gas density.
Poor performing breathing equipment with high WOB does the same.
High WOB translates into higher breathing effort and hence increased CO2 production.
When using a rebreather, any rebreather, the addition of the scrubber which is supposed to remove the CO2 from the loop is added to the equation. But no matter how well the scrubber is designed, and how well it performs, when the diver doesn't vent his lungs there is nothing or little to scrub.
For the group of people that analyzed the accident it was as much part of their investigation as the equipment analysis, and gave clues to the what, when and how it happened.
Do I think the video needs to be shown to bring the dangers of hypercapnia across?
Of course not. Any OW diver
should know this. But in the end the decision to make the video available to the public lies with the family and team members of Dave Shaw. I for one respect their decision, and I'm sure it wasn't made lightly.
It places the ball in our court, we can choose to watch it (for whatever reason) or not.
It's a grim video, even without the original soudtrack.
