cozumel accident 9/4/11, THE FACTS

[Brules]

I posted the same question in the 60 page A&I thread and the summary was that it made it worse as instead of a true IWR - it counted as a second dive with more nitrogen loading heaped on what was already there. Unless she went to 100+' down, I think it may have done more harm than good.

 

[Thalassamania]

All things considered the incident was handled fairly well. The divers did not have a huge deco obligation, somewhere on the order of six to ten minutes at 20 feet. This could have been handled as omitted deco, if they had been able to make a normal 30 fpm ascent, were not symptomatic, and could return to the water within 5 minutes of surfacing. That would have meant about 15 minutes at 20 feet (or about 5 minutes if they'd taken oxygen back down). The problem was the speed of ascent and the fact that a diver was symptomatic ... normally this calls for pure oxygen, supine position and immediate transport to the nearest chamber. For recompression of a symptomatic diver you need to get deep enough to relieve pain and then come up with a treatment schedule to surface the patient ... not something I'd want to try, in the water, on the fly.

There are lots of, "if only ifs ..." here. To my way of thinking the biggest is, "if only if they'd hung some tanks with regs off at 30 feet."

I hope for the most complete recovery possible.

 

[cenotist]

Yes, Brules. I know the textbook answer to my question. But being at 30ft on o2, you are not taking in any nitrogen, and you keep the diameter of your nitrogen bubbles inside your tissues 24% less than at the surface, what means your off gassing is more efficient.

 

[Jax]

I have been below 100' but nowhere near 300'. One thing I have not been able to grasp well is the relative risks between 100' and 300' (or deeper). Yes I know there are variables but enough data should be available to give relative risks.

Knowing that the deeper you go, the risks increase, at some point you either stop or take extra precautions. My view expressed in the other thread is that barring proper gas mixture, they should have had larger tanks and a better site (sloping bottom instead of a wall).

Unfortunately, the bolded statement is not true.

While many agree that narcosis starts somewhere around 100', there are many that dive deep air to 180 and manage their narcosis, there are some that seem unaffected and others try to buddy-breath with a fish, and everyone's physiology, build, blood chemistry, and current state of fatigue, hydration, feeding, etc are so different that narcosis may appear at one depth one day and a different depth the other.

And some are narced above 100.

 

[Thalassamania]

Unfortunately, the bolded statement is not true.

While many agree that narcosis starts somewhere around 100', there are many that dive deep air to 180 and manage their narcosis, there are some that seem unaffected and others try to buddy-breath with a fish, and everyone's physiology, build, blood chemistry, and current state of fatigue, hydration, feeding, etc are so different that narcosis may appear at one depth one day and a different depth the other.

And some are narced above 100.

This is very true, on most days, under most conditions, I'm pretty good down to 190, but there have been occasional dives when, on the way down, I just stopped, ditched the original plan and either surfaced or made a shallower dive, that's just good sense.

When I've tried to preserve, I've almost always regretted it. Fortunately, since the ocean is pretty benign, it's always been something minor, for example an improperly tied bowline that did not hold, but on a bad day it could have been something much worse.

 

[Ron Lee]

The divers did not have a huge deco obligation, somewhere on the order of six to ten minutes at 20 feet. This could have been handled as omitted deco, if they had been able to make a normal 30 fpm ascent, were not symptomatic, and could return to the water within 5 minutes of surfacing. That would have meant about 15 minutes at 20 feet (or about 5 minutes if they'd taken oxygen back down). The problem was the speed of ascent and the fact that a diver was symptomatic ... normally this calls for pure oxygen, supine position and immediate transport to the nearest chamber.

Combine this with the following from Post 34 on the other A&I thread:

Dec to 200ft (4) Air 50ft/min descent.
Dec to 300ft (5) Air 60ft/min descent.
Level 300ft 2:20 (8) Air 2.12 ppO2, 300ft ead
Asc to 140ft (13) Air -30ft/min ascent.
Asc to 90ft (14) Air -30ft/min ascent.
Stop at 90ft 1:00 (16) Air 0.78 ppO2, 90ft ead
Stop at 80ft 2:00 (18) Air 0.72 ppO2, 80ft ead
Stop at 70ft 2:00 (20) Air 0.65 ppO2, 70ft ead
Stop at 60ft 1:00 (21) Air 0.59 ppO2, 60ft ead
Stop at 50ft 3:00 (24) Air 0.53 ppO2, 50ft ead
Stop at 40ft 3:00 (27) Air 0.46 ppO2, 40ft ead
Stop at 30ft 5:00 (32) Air 0.40 ppO2, 30ft ead
Stop at 20ft 6:00 (38) Air 0.34 ppO2, 20ft ead
Stop at 10ft 10:00 (48) Air 0.27 ppO2, 10ft ead
Surface (48) Air -30ft/min ascent.

The second quote was to 300'...not the actual 400'. I get about 33 minutes of stops. I have no way to determine which is "right" but if it were me, I would use the multi-stop ascent profile.

 

[cicopo]

By "rare hour" are we to read very early in the morning, or very late in the evening? If the latter, were all the social divers in the proper state of mind to carry out a safe dive?

It means that it was after the majority of dive boats had left the area for the reefs (mainly down south) and before they would return to the area. There's lots of boat traffic in that specific area from about 7:30 AM thru 10:00 AM , and then again after about 11:30 AM thru 1:00 PM when they return.

 

[Thalassamania]

Combine this with the following from Post 34 on the other A&I thread:



The second quote was to 300'...not the actual 400'. I get about 33 minutes of stops. I have no way to determine which is "right" but if it were me, I would use the multi-stop ascent profile.

That's all real purdy, might I suggest that the U.S. Navy Air Tables (Table 9-5) suggest an ascent at 30 fpm to 20 fsw with either 3 min. of oxygen or 6 min. of air, followed by a continued 30 fpm ascent to the surface would be adequate for a bounce to 300.

 

[annlaur]

But before my bedtime, let me throw one more stone into the water – how wrong it really was for Opal to jump back into the water? Maybe I put my reputation on line here, but in her place, knowing that I have to wait and not having problems with o2 CNS tox, I would probably jump in also. Only I would pack my o2, not air tank. There are many knowledgeable persons out there – maybe they have some idea about that?

Not a knowledgeable person by any means but maybe there was no regulator attached to the O2. I got bent once and put on O2, it was connected to a mask, not a reg. Not something that could be breathed off underwater. Wasn't on a boat, though (delayed symptoms, went to the dive op who put me on O2 while arranging for me to get to the chamber).
Don't know if O2 bottles on boats have masks or regs, but that could explain it.

 

[cenotist]

OK. Let me rephrase my question. After this extreme down-up dive and being bent, what does make more sense:
1. be on a boat, breath o2 and wait (slower off gassing, more pain, but more safe environment)
2. be at 20-30 ft in the water with o2 (faster off gassing, minimising the risk of thrombosis and other epiphenomenons, probably some less pain, but less safe environment)