Excessive MicroBubbles

[SM Diver]

Dear Dr. Powell:

I think I understand the physiology of what is going on in your attachment. It’s been a while since I took A&P in college, but the venules (tiny veins) carry waste product, including Nitrogen (I’m assuming only) out of the system. Apparently, from your attachment, microbubbles have a “clotting” effect, almost in a manner of the way fatty deposits can create arteriosclerosis. However, unlike arteriosclerosis, the microbubbles eventually clear themselves out, thus allowing the capillaries to fully function and carry nitrogen out of the body during off gassing.

The point of confusion in your attachment is there is no dive profile to reference it. For example, after the first dive, do I have the same “blockage” in the capillaries after a 21 ft. dive, as I would a 100 ft. dive? If so, how is that possible? There would be a whole lot more ongassing during a deeper dive.

And if the quantity of microbubbles is dependant on the dive profile, then I am wondering how, after only one dive, I had the dive alert symbol: Here is my first dive info:

SI: 43:20 hh/mm
Dive Time: 13:20 mm/ss
Max Depth: 24ft
Avg. Depth: 20 ft

When I did my SECOND dive, I had had a surface interval of 44 minutes, so how in the world after a 13 minute dive in 24 feet of water am I still getting a diver alert/microbubble warning? Granted, my SAC was very high that first dive (1.05), due to a strong current and aerobic sprint looking for the ledge (which I didn’t find that first dive, hence the short time), but am I supposed to wait an hour after one 13 minute 24 ft. dive?

Thank you very much for helping me understand this. It’s a little unnerving diving through alarms, but I’d look like the biggest idiot in the world telling friends after one 20 ft dive, “Sorry guys, go ahead, I have another hour before I can dive again.”

 

[Dr Deco]

Dear Scott:

Meters and Tissue Bubbles

I would likewise be upset if I thought that I was diving when my meter said that something was amiss. The fact of the matter is that I believe there is a big conservatism factor that the meter designer has built in. A problem here is not that you see through the specious reading, but that, in some cases, the device might actually shut down because of a “violation error.”

If the designer actually thought that the system was in a mode where a large gas phase had formed, you would be in a dangerous two-phases situation where the models break down. It does not appear that this occurred, but it is why deco meters go into their “violation” mode, lock out, and cannot be reset except for a long surface duration. Recompression or surface time is the only two ways to “reset” the system when excessive gas phase is present.

For a short time spent below the 30-foot NDL, I can not at all understand the limitation. If this was actually programmed to occur, then the designer was in error in his/her understanding of the physiology of decompression bubble formation in the time and depth range.

Explanation of the ATTACHMENT

The diagram is simply to indicate a generic profile that was severe enough to actually generate decompression bubbles. It was to illustrate what might be occurring in your tissues in a deep dive but certainly not in a short, shallow dive.

Dr Deco :doctor:

 

[SM Diver]

Once again, did three dives on Sunday and had the Diver Alert come on again, even after shallow dives of only 22 ft. It stayed on for an hour, before clearing for the next dive (I actually waited, although I'd only spent 23 minutes at 22 ft.).

I wrote Suunto a detailed email, asking about the alarm, and this is the reply, which I have just received via email (for whatever it's worth):

Short surface intervals, regardless of the depth, can cause the alert to appear. The alert is a recommendation to extend surface interval. You can still make the dive.

Regards,

Jim

 

[Genesis]

Two dives to about 60', on EANx32, and when I went to plan the second one it put up the attention symbol with my original intended surface interval - even though I had plenty of Nodeco time to make the second dive on the profile I intended.

First time I've run into that, but I had no violations of and kind on dive 1, so it appears that this is exactly what was going on.

 

[BRW]

Guys and Gals,

As the designer of the Suunto (RGBM) meter algorithm,
let me just add some observations and facts about
the Suunto RGBM series -- Vyper, Stinger, Cobra, etc --
as well as Plexus, Hydrospace, ABYSS, and soon -- and --.

1) -- SIs of less than 2 hrs, deeper than previous dive
beyond 60 fsw, multiday diving, and violated
ascent rates (faster than 30 fsw/min for more than
5 sec) get penalized on next dive -- reduced NDLs and
possible, but not probable deco.

2) -- all penalties fade away after 3 hrs or more SI,
(except very slight multday reduction in NDLs
increasing with day dive frequency -- but never
more than 4% after 7 days of diving)

3) -- these "corrections" are based on bubble mechanics
folded over data in maximum likelihood fit (modified
and/or Haldane folded RGBM)

4) -- Hydrospace Explorer computer does same for
mixed gas deco diving. Plexus, the same.

5) -- above RGBM "corrections" are the result of folding
full blown RGBM phase model over 1000s of basic
ZHL or USN or Spencer dives (the original meter
algorithms) and "adjusting M-values to fit RGBM
full up model. M-values are limiting critical tensions
(dissolved gas limit pts in hypothetical tissues)

6) -- full up RGBM meters are coming soon -- maybe DEMA.

7) -- so are other RGBM meters from other manufacturers.

8) -- ABYSS is a validated and tested (see earlier posts)
software product that offers the modified RGBM (above)
used in metyers that you now use, and the full up
iterative model (with natural deep stops) that you
you will find in meters soon.

Good diving,

Bruce Wienke

Program Manager Computational Physics
Counterterror and Countermeasures Dive Team Ldr

:mean:

 

[Genesis]

I got an odd one today.

I was on an 84 foot profile. Came over a ledge and there was a shark under it. I adjusted my buoyancy with my breathing pattern, popped up about 10', let the shark pass, and then dropped back down - all with no air added in my BC (it wasn't a very quick ascent or decent - I wasn't interested in attracting Jaws attention!)

Looked at the computer shortly thereafter and it had a STOP on it (in the NDL limit window!) I still had 17 minutes of NDL time left at that point - it was NOT showing "ASC TIME" or a ceiling. I thought perhaps the meter had broken, but the dive time continued to count up and the depth was still showing correctly and moving when I did up and down a bit, so I continued, using my watch as a backup.

We got to the "time" call by my watch and started ascending. The meter still said we had 8 minutes left.

We did a deep stop for 3 minutes at 40 feet (my usual - half depth, then another if the next half doesn't get us to 20 or shallower) and then came up to 15 feet for the usual safety stop. As we got to 19 feet I got the CEILING indicator (at 10') and ASC TIME with 4 minutes! It almost immediately (within 10 seconds or so) cleared and showed the 3 minute safety stop....

We sat out the stop and surfaced normally. I got the diver attention when it went into repetitive mode; it cleared an hour later and we went back in for Dive #2.

Looking at the profile on a download, it did flag a "SLOW" warning (I never saw or heard it - it must have been a VERY transient thing), but this was all of about a 6' ascent and decent, and wasn't done by kicking or adding BC air - it was all done while hanging and using nothing more than breathing mechanics!

Anyway, obviously the computer wasn't happy, but I thought it was an interesting datapoint....

 

[BRW]

Guys,

Knowof other reported ascent probs ala those on this
thread. Had a buddy with one while we were spearfishing
in Texas Gulf last weekend. Is in corelation coefficient
for ascent violations in meter program -- needs reduction.

No real problem and have suggested "quantitative"
amelioration of problem to Suunto directly. But annoying.

Thanks for all your comments

Bruce Wienke

Program Manager Computational Physics
Counterterror and Countermeasures Dive Team Ldr

 

[Genesis]

How do we find out when these kinds of things are fixed, and is there any kind of upgrade path? (I think I know the answer to THAT question )

Its the one thing that I find extremely annoying about the Vyper. Other than that, I love it - but those warnings, if they really don't mean anything, are a pretty severe annoyance.

A deep stop protocol (optional is even better; some people won't want it, but I'd use it) would be nice as well.

 

[SM Diver]

BRW once bubbled...
Guys and Gals,


1) -- SIs of less than 2 hrs, deeper than previous dive
beyond 60 fsw, multiday diving, and violated
ascent rates (faster than 30 fsw/min for more than
5 sec) get penalized on next dive -- reduced NDLs and
possible, but not probable deco.

Thanks for jumping in here, as I didn't think my reply from Suunto was especially helpful. As you saw, the reply was basically, "yeah, there's a warning, but you can dive anyway."

If that's the case, I can't understand why it would be there. Anyway, it appears from your reply that an SI of less than 2 hours can cause a Diver Alert. If that Dive Alert triangle, which is recommending a longer SI, is to be ignored, then why have it?

Apart from that, my compliments for any part you had in the manufacturing of an outstanding product line.

 

[Genesis]

If I get one, it typically clears after one hour or so. The exact time appears to depend on a lot of factors, not all of which I understand.

If I don't get one, and do another repetitive dive on less than an hour interval, I'm nearly guaranteed to get the warning when I get out on the SECOND dive....

(BTW, you CAN figure out how long it will take to clear, although the manual doesn't tell you how. Use the SIMPLAN feature, add in various SI times to the current SI, and see if it shows up. If its not there then at that total SI it will have cleared off. A short iterative process will tell you how long you must wait for the attention symbol to go away.)