cozumel accident 9/4/11, THE FACTS

[Thalassamania]

The smart money insists that it is best to be on a boat, breathe o2 and transport as quickly as possible to a chamber.

 

[cenotist]

The smart money insists that it is best to be on a boat, breathe o2 and transport as quickly as possible to a chamber.

I agree, but when this "as quickly as possible" is in a unknown and vague future? Sorry, I am trying to act as a devils’ advocate.

 

[Thalassamania]

The big problem here was the split duty between the injured divers and those who were still underwater. It does not sound like there was an planned out recall signal.

But consider the problem if you are four days from helo evac in the North Sea. That's a whole 'nother story.

 

[fdog]

Heart-burn...yes, I'd want at least triple that deco time. And deeper stops.

But I'm conservative, which the USN tables are not.



....in any case, if I woke up at 400' without a bouquet of bottles around me, I'd probabally die of fright without even having to make the ascent...


All the best, James

 

[Blue Sparkle]

A question on the deco/ascent schedule that Thalassamania mentioned: Was this for 300' (mentioned in a prior "schedule") or for the 400+' that Opal and Gabi went to? If it was for 300', how would another 120' or so change that?

 

[Thalassamania]

I'm fairly conservative too, and so are the Navy tables. Given my age and level of fitness I'd prefer to shape my curve a bit differently, but I also realize that at 75 fpm down (4 minutes to 300 ft) and 30 fpm up to 20 fsw (about 9 minutes and 20 seconds), about all that I'm messing with are really, really, fast tissues that should be damn near clear when I hit the 20 foot stop. The problem on this dive (for the divers) was, I feel, the blown ascent rate, lots of people find it hard to slow to even 60 fpm when they're OOA.

 

[nauticab]

The smart money insists that it is best to be on a boat, breathe o2 and transport as quickly as possible to a chamber.

yes, but imagine her state of utmost panic, intense pain, and desperation, not to mention of the known fact that the others were bent too. the other diver was her boyfriend. gabi went after her when she jumped back in the water. heath followed suit (i assume) due to his feelings for her.

and yes, the time of the dive, although not 100% clear, was mid-late morning. after most boats went out, but before surface intervals.

 

[Thalassamania]

I'm not saying it was easy. There were plenty of mistakes to go around, e.g., you try (within the bounds of the law) to never let the injured party make decisions, like returning to the water.

We game these sorts of issues before most cruises so that we have dealt with the critical issues and documented them, long before any emergency actually occurs, but I don't suspect that dive ops in Coz run things quite the way the National Science Foundation does in the USofA.

There is a whole section on this question in the "Final Report of The Workshop on Scientific Shipboard Diving Safety." which includes recommendations like: "In-water, oxygen decompression or the use of NITROX should be evaluated as techniques capable of providing greater safety margins. "

 

[boulderjohn]

A question on the deco/ascent schedule that Thalassamania mentioned: Was this for 300' (mentioned in a prior "schedule") or for the 400+' that Opal and Gabi went to? If it was for 300', how would another 120' or so change that?

This is what V-Planner gives me for a dive to 400 feet with the fewest amount of minutes it will allow for the descent plus bottom time:

Decompression model: VPM - B

DIVE PLAN
Surface interval = 1 day 0 hr 0 min.
Elevation = 1ft (c)
Conservatism = + 2

Dec to 200ft (4) Air 50ft/min descent.
Dec to 400ft (7) Air 60ft/min descent.
Level 400ft 0:40 (8) Air 2.75 ppO2, 400ft ead
Asc to 200ft (14) Air -30ft/min ascent.
Asc to 130ft (17) Air -30ft/min ascent.
Stop at 130ft 1:00 (18) Air 1.04 ppO2, 130ft ead
Stop at 120ft 1:00 (19) Air 0.97 ppO2, 120ft ead
Stop at 110ft 1:00 (20) Air 0.91 ppO2, 110ft ead
Stop at 100ft 2:00 (22) Air 0.85 ppO2, 100ft ead
Stop at 90ft 1:00 (23) Air 0.78 ppO2, 90ft ead
Stop at 80ft 2:00 (25) Air 0.72 ppO2, 80ft ead
Stop at 70ft 2:00 (27) Air 0.65 ppO2, 70ft ead
Stop at 60ft 3:00 (30) Air 0.59 ppO2, 60ft ead
Stop at 50ft 4:00 (34) Air 0.53 ppO2, 50ft ead
Stop at 40ft 4:00 (38) Air 0.46 ppO2, 40ft ead
Stop at 30ft 7:00 (45) Air 0.40 ppO2, 30ft ead
Stop at 20ft 25:00 (70) Air 0.34 ppO2, 20ft ead
Surface (70) Air -30ft/min ascent.

Off gassing starts at 180.7ft

OTU's this dive: 44
CNS Total: 766.9%

156.3 cu ft Air
156.3 cu ft TOTAL

​

Notice that it requires almost exactly twice as much gas as they had.

V-Planner and the U.S. Navy tables, which I do not have, apparently disagree significantly.

 

[Blue Sparkle]

I'm fairly conservative too, and so are the Navy tables. Given my age and level of fitness I'd prefer to shape my curve a bit differently, but I also realize that at 75 fpm down (4 minutes to 300 ft) and 39 fpm up to 20 fsw (about 9 minutes and 20 seconds), about all that I'm messing with are really, really, fast tissues that should be damn near clear when I hit the 20 foot stop. The problem on this dive (for the divers) was, I feel, the blown ascent rate, lots of people find it hard to slow to even 60 fpm when they're OOA.

Thalassamania, I wonder if you would answer a question I have. (I asked it just a bit earlier but the thread is moving along fairly quickly so you may not have seen it.)

Since the actual dive here was to around 400' or a bit more (they were supposed to stop at 320' but Opal kept on going to or past 400'; Gabi chased after her), how would that change the deco picture from the 300' that (I think) you are talking about?

Thanks,
Blue Sparkle

PS: Thanks boulderjohn, I think we were posting at the same time. Am I reading that correctly to be close to 1 hour of deco/stops on your schedule? I'm curious how the Navy tables will compare.