cozumel accident 9/4/11, THE FACTS

[cenotist]

The VPM - B model is not designed for this kind of dives.

 

[Crush]

How about some more facts-were they fit to dive?

 

[Thalassamania]

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.

400 feet could change it, I do not know by how much. If we compare v-planner to the Navy at 300 feet there's already quite a difference, I assume that they would diverge even more at 400.

 

[Reef_Haven]

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


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.

Just curious,
Are you not able to use the Config tab to adjust your dive parameters?
What would it look like if you increased you descent rate to 75, reduced your RMV to 0.4 and set your conservatism to Nominal?

 

[Blue Sparkle]

400 feet could change it, I do not know by how much. If we compare v-planner to the Navy at 300 feet there's already quite a difference, I assume that they would diverge even more at 400.

Hi and thanks for responding to my query. I guess what I'm wondering is, your earlier post made it sound as though their deco (or lack of it) was not that far off what would be necessary (according to Navy tables?), and I think you were using 300' as a max depth. I wondered what those same tables would show for, say, 420' in comparison (i.e. your table at 300' vs. your table at 420').

Thanks,
Blue Sparkle

 

[cenotist]

I can see, that Thalassamania is busy answering other subjects and is not falling into my trap of IWR. So I shall answer my hypothesis myself. Navy Dive Man rev6 says about o2 IWR:
- Descend to a depth of 30 feet with a standby diver.
- Remain at 30 feet, at rest, for 60 minutes for Type I symptoms and 90 minutes for Type II symptoms. Ascend to 20 feet even if symptoms are still present.
- Decompress to the surface by taking 60-minute stops at 20 feet and 10 feet.
- After surfacing, continue breathing 100 percent oxygen for an additional 3 hours.
- If symptoms persist or recur on the surface, arrange for transport to a recompression facility regardless of the delay.

But in a section 20 4.4.2 it says “In divers with severe Type II symptoms, or symptoms of arterial gas embolism (e.g., unconsciousness, paralysis, vertigo, respiratory distress (chokes), shock, etc.), the risk of increased harm to the diver from in-water recompression probably outweighs any anticipated benefit. Generally, these individuals should not be recompressed in the water, but should be kept at the surface on 100 percent oxygen, if available, and evacuated to a recompression facility regardless of the delay.”
So, IMO in the end it should be also the responsibility of other (sane) persons on boat to prevent people with severe Type II symptoms from jumping into water again.

 

[cenotist]

There is no point in analysing this dive with V-planner, which is using VPM - B model.
“The dive profile from a VPM-B profile is a one that includes both deep stops and modest amount of time in the shallow areas. The basic concept of a bubble model is to limit and control bubble growth and bubble sizes to smaller amounts through the ascent, thereby avoiding the damaging effects of any larger bubbles.”

PS! For addition to Navy tables, the RGBM is a model, what brings you up relatively fast (this actually was the idea of designing this model – to bring divers fast close to the surface, so they can be at the “accessible” depth).

 

[koyote1111]

With regard to Opal re-entering the water...

Have wondered if this was simply a desperate attempt to alleviate pain (while waiting for the boat to depart for shore)?? I am not sure if a depth of 30 ft. would alleviate the type of symptoms that she was having. However, do wonder if the intensity of pain was such that her action was more so an act of desperation. Extreme pain can certainly lead to desperation.

I have experienced DCS followed by 5 rides in the chamber. I understand that the initial "depth" for treatment was 60 ft. At that depth, most pain resolved (in my case). So...could she have felt relief from pain at 30 ft.?

 

[Blue Sparkle]

There just isn't a lot of boat traffic at the time of day this took place, with the possible exception of some small glass bottom tours.

I think people just aren't sure what time of day it did take place and would like to know. It was stated a bit vaguely in nauticab's report here in this "facts" thread - and her report was otherwise quite detailed so it kind of stood out. Unless I have forgotten something, we just know it was a time of little boat traffic. I would imagine that still could be any number of different time periods.

Maybe nauticab will come back and clarify; she has been very forthcoming.

 

[ianr33]

Just curious,
Are you not able to use the Config tab to adjust your dive parameters?
What would it look like if you increased you descent rate to 75, reduced your RMV to 0.4 and set your conservatism to Nominal?

With a descent rate of 100'/minute,ascent rate 60'/minute, nominal conservatism and a SAC of 0.4 the gas used is only 37.4 cu ft. for a bounce to 400 feet.

Do you feel lucky?

Obviously ,ascent and descent rates have a massive affect on the gas used.

(And I totally agree with cenotist that V-planner is not designed for idiocy like this)