Safe Diving Practice?

[pasley]

Another diver and I were discussing some recent dives of his and wanted to get your thoughts. He was kind enogh to e-mail me his dive profile for the dives for the sake of this discussion and for me to post on this board.

All dives were done on plain air.

First Dive: Saturday at 8:36 p.m. to 9:33 pm 57:40 minutes 46 feet for with an average depth of 34 feet. Temp max depth 63Suunto degrees

Surface Interval 11:44 hrs

Second Dive: Sunday Yukon 9:18 a.m. to 9:46 am 28:40 minutes 96 feet average depth 64 feet Temp max depth 59 Suunto Degrees. Computer went into mandatory 5 minute stop mode during this dive, but dropped the requirement as diver ascended from depth to 30 feet. Dive profile Yukon attached.

Surface interval 1:09 hrs

Third dive: Ruby E 10:58 a.m. to 11:22 a.m. 26:20 minutes 80 Feet average depth 62 feet temp max depth 55 Suunto degrees. Diver Attention was on at start of dive. Dive profile Ruby E attached.

Only one member that we are aware of in Sundays dives had dove on Saturday.

We were not sure what the diver attention symbol meant, so we asked SUUNTO directly. There reply was:
"The Attention Symbol means that microbubbling is peaking, and it is advised to wait for it to disappear before you do another dive. As you know, microbubbling usually peaks about 5min – 10min after the dive and the levels drop within a couple of hours or so. The triangle comes on 5min after almost any dive, the severity of microbubling (according to the RGBM algorithm) determines how long it is on.

If you are diving with the Vytec the RGBM 50 setting is also displayed using the same warning triangle to remind that you are using a more liberal (risky) setting.”

I felt his dive profile was not as conservative as it should be for a male age 43. So our debate is:
Does the dive from Saturday night factor into Sunday’s dive planning?
Does the dive on the Ruby E (Third dive) pose an increased risk for DCI?
How long of a SI should these divers have had between the Yukon and the Ruby E dive?
A member of this dive team does not have a computer and did not consult his dive tables. What are your thoughts on his dive profile?

Doc, not sure where to put this, but since the question is centered on DCI risk, I thought here. but fell free to reposition as you deem appropriate to another forum.

 

[Saturation]

I felt his dive profile was not as conservative as it should be for a male age 43. So our debate is:
Does the dive from Saturday night factor into Sunday’s dive planning?

Hi Pasley:

Yes. For true bubble model mechanics, as much as 5 days after the last dive. For practicality, most dives are noticeably limited by 3 hours of the last dive. In Suunto-RGBM, inert gas loads are tracked for 99 hours.

Does the dive on the Ruby E (Third dive) pose an increased risk for DCI?

Yes, in that it is greater than waiting for the WARNING sign to dissappear before the dive. HOWEVER, the Suunto-RGBM is very conservative at the default setting. Further, Suunto-RGBM will heavily reduce bottom time for that dive because of diver diving with WARNING on at this time.

How long of a SI should these divers have had between the Yukon and the Ruby E dive?

In Suunto-RGBM, its happiest at least at 1 hour. When the 'warning' sign appears it often requires 2.5 hours. You can run the simulation mode and keep adding SIT, and it will tell you when the bottom time for your dive is nearly the same as a bottom time for say a 12 hour SIT, that is, waiting longer makes little difference .. practically speaking.

You can certainly dive before 1 hour, and the Suunto will heavily penalize that dive. Its general more aggressive and less safe to dive within 1 hour for a prior dive deeper than 30'. The risk is greatest the sooner one dives after the prior dive ... its akin to a yoyo dive.

As for whether its truly analyzing microbubble related issues, that's another very long story. Suffice to say, Its established that normal sized bubbling is greatest after a dive during the 1st hour SIT, and drops very quickly soon after. It suggests inert gas loads are still quite high, and whatever bubbles that exits are largest at this time.

There is always a residual N2 time to consider after a dive and its often near minimal by about 3 hours SIT between dives.

A member of this dive team does not have a computer and did not consult his dive tables. What are your thoughts on his dive profile?

Assuming he dives with your group but without his own computer and thus relies on your computers for tracking? This is unwise, generally. If he sticks to the group tightly, the profiles will be nearly identical. However, divers in a group have slightly varying profiles, and while this is commonly not an issue, events can arise that could make results differ quite a bit ... for example if diver without a computer gets into the water first, comes out later, doesn't stick close to the group and dives all over the place, does other dives without the group etc.,

I have dove those wrecks many time when I was in San Diego. Vis can be good, but it was always cold. Your profiles are not aggressive but more typical, and having a conservative computer to use adds another margin of safety.

 

[pasley]

Thank you for your detailed response. It is along the same lines as my thoughts (though more eloquently stated, and articulated) that the previous nights diving counted and that his profile was "pushing it".

 

[Saturation]

Thank you for your detailed response. It is along the same lines as my thoughts (though more eloquently stated, and articulated) that the previous nights diving counted and that his profile was "pushing it".

Very welcome Pasley. I tried to be as factual as possible. If it doesn't sound straightforward its because it isn't. To do that I would have to inject more of my personal risk values into my statements.

Age is a risk factor for bends, but fitness is a more important marker than chronological age. Being in your 40s does not put one in the higher risk category if one is fit.

The WARNING sign in the Suunto is very conservative compared to the majority of computers [they use Spencer and Powell's tables, our own Dr. Deco] or Buhlmann [mostly Uwatecs.]

Reading your tissue graphs and report, you folks did a dive within reasonable risk, that's what the Suunto insures you do, if you follow its recommendations.

P.S. If most folks publish their profiles as you did, life would be much easier and more precise in deciphering issues in water! Kudos for keeping your profiles. Please keep it up.

Enjoy diving San Diego ... and just follow what the Suunto says and you should be fine.

 

[pasley]

Thanks again. It is actually a dive partner of mine’s profiles. I discussed the dive with him while we were making the dive on Saturday night and he said they were going to do 3 dives in 4 hours the following day. I suggested they re-evaluate that plan as I thought it too aggressive. After the dive he mentioned the attention symbol on his profile and we continued to discuss it.

He was of the opinion that the night before did not factor in, I thought it did. I wrote to SUUNTO for clarification as to what the diver attention symbol meant. We further discussed it and thought it would be a good topic for the board as an educational tool. So he kindly e-mailed me his profile.

I always print out my profiles after the dive and evaluate them for lessons I can learn for the next dive. I also agree that if you are going to ask a question about a dive you have done, it is good to post the full information.

It is good to hear that fitness is an offset to age. I am 50 and reasonable shape (2 miles in 14:30), beach dive at least once a week, which almost always involves a long walk, usually down and up a hill (cliff), sometimes there are even stairs, when we are lucky, to get to the water.

I dive a SUUNTO exactly because it is very conservative. For a man of 50 or even my dive buddy of 43, I think conservative is in order. I originally bought an Oceanic Data Pro because of its large numbers. I had an “underserved” hit at dive 12 and discovered it is a more liberal computer. So I moved to the SUUNTO.

 

[rcohn]

I don't pay too much attention to the diver attention symbol after I did the series of dives in this old post and had the DA symbol present after an hour surface interval.

From an old post of mine: http://www.scubaboard.com/showpost.php?p=140961&postcount=10

Ralph

 

[Dr Deco]

Hello melvin:

Does the dive from Saturday night factor into Sunday’s dive planning?

Certainly the gas loads will be a factor, although the nitrogen probably completely off gases by Sunday morning. In my research experience, bubbles will not persist that long in the body. The primary generator of micronuclei is physical activity. This position is different from that in the RGBM where nuclei are generated by random processes and have a certain regeneration time. I do not find that this accords with my research at NASA.

Age and DCS

It is our feeling at NASA that physical fitness is the real determining factor rather than age, per se. We are not alone in this assessment.

The Microbubble Symbol

This is put into the computer as a simple add on. It indicates, to me, that the dive posses a moderate degree of gas loading and not necessarily that bubbles are present. You would need to measure them, but they could well be there.

Gas Loading

To me, the increased gas loads would indicate that care should be taken post dive. As readers of this FORUM would recognize, in these circumstances, I would advocate that time be spent at the surface (before boarding, the “hidden stop.”) In addition, not climbing up the boat ladder with full gear (being assisted instead), and not carrying heavy gear during the post dive hour or two would all reduce the possibility of tissue bubble formation as well as arterialization from a Valsalva-like maneuver.

Dr Deco :doctor:

Readers, please note the next class in Decompression Physiology :1book:
http://wrigley.usc.edu/hyperbaric/advdeco.htm

 

[MonkSeal]

Diver Attention was on at start of dive.

I noticed that two profiles contain SLOW alarm which means that diver exceeded maximum ascent speed. This will always raise "Diver Attention" mark and in reality it will increase bubbling.

 

[Diver0001]

....snip....
centered on DCI risk, I thought here. but fell free to reposition as you deem appropriate to another forum.

I noticed on the 2nd dive that he made a quick ascent and a 3 min stop and still had 97% on the NDL. Was he maybe over the NDL before the ascent started? Looks like he might have been. If it were me I would have done that ascent differently. More slowly, with a deep stop and with a longer safety stop. IN fact, I think looking at these three profiles that his ascent could be slower across the board.

The profiles don't look too crazy to me other than that. The computer was probably moaning about the zig-zag in the last profile.

R..