Dives and dive time

[boulderjohn]

Conclusion. Spinal DCS hits nearly 117 divers per year in France (if I extrapolate from the sample) so that's what I call "far from uncommon".

Maybe I missed it, but I don't see any way to determine how this number relates to how close it is to uncommon. How many total dives were needed to come to a total of 117 hits? If that number is high, then 117 could be a very small percentage.

I think the fact that we are talking about CMAS as the primary agency may well be important. As you indicate, it's training is different from most other agencies. I cannot speak with authority on the differences, but I believe it includes decompression diving at the basic level. I will be happy to be corrected on this point.

 

[boulderjohn]

You and I must have a different concept of the 'direct ascent to the surface'. I seem to recall my PADI instructor defining a direct ascent as one in which one doesn't stop. But I could be wrong, and I suppose that's neither here nor there anyway.

In the PADI system, bottom time ends when the diver begins the direct ascent to the surface. This can be easily misunderstood. If I am diving at 70 feet and determine that it is time to end the dive, my bottom time ends when I begin that ascent. If I choose to do a safety stop, that is part of the ascent, not the bottom time. You can see that if you look at the graphical system used to calculate pressure groups, etc. You input depth, bottom time, and (separately), the safety stop if you did one.

I have no problem with mandatory stops. I personally make stops on all NDL dives. My complaint is with the mandatory stop within the context of PADI's dive system, a fundamental concept of which is the CESA.

CESA is emphasized in the opinion of many at the detriment of proper gas planning and/or buddy skills, but its viability is contradicted by a mandatory stop (plainly stated: if you have to stop, you can't CESA).

CESAs are not a part of a dive plan. It is a way to get to the surface if you have a real screw up and went OOA without a buddy nearby. You don't think about mandatory stops when you are trying to reach the surface while out of air. You get to the surface and deal with any DCS issues that may have arisen from that emergency ascent later.

(In my course, which admittedly is a single data point, we spent probably twice as much time practicing CESA as we did sharing gas).

That should only be true if the instructor violated standards or if your class had an unusually difficult time completing the CESAs to standards.

On the other hand, I agree that more time should be spent on gas management and air sharing practice than happens in a typical course.

 

[hg frogman]

Maybe I missed it, but I don't see any way to determine how this number relates to how close it is to uncommon. How many total dives were needed to come to a total of 117 hits? If that number is high, then 117 could be a very small percentage.

I think the fact that we are talking about CMAS as the primary agency may well be important. As you indicate, it's training is different from most other agencies. I cannot speak with authority on the differences, but I believe it includes decompression diving at the basic level. I will be happy to be corrected on this point.

There are less than 100,000 divers in France. If 100 or 200 of them are hit by spinal DCS, that means that more than 1/1000 or 2/1000 of the French divers are hit (every year). For me this number is high (especially given that 30% of these people never completely recover). Others may find it low.

CMAS basic level (CMAS* diver) is grossly akin Open Water (no deco) but a bit easier (in France). The next level (CMAS**) is deco diving (air only, also for deco): down to 20 meters without direct supervision, down to 40 meters with direct supervision. CMAS** diver is quite hard training, not unlike Rescue Diver (assuming you're not considering that Rescue Diver is a walk in the park).

As I said, a lot of dives in France are mild deco dives (but only 2 dives a day with long SI, 4 hours or more) with the deco also on air. That's different from the very short and shallow repetitive resort dives that are common in other areas. But the OP's profiles weren't so shallow and short, in my opinion they were stretching towards the danger zone regarding DCS.

 

[Ontwreckdiver]

For some reason I was unable to access the official PADI list of expelled dive organizations, but perhaps you will be able to get into it by going to the PADI web site and following the site map through Quality Management to that list.

When I went to Aruba, I chose not to use Mermaid because of the presence on that list. PADI does not routinely expel dive shops from their organization.

I have been to Aruba 5 times and there are 2 or 3 good dive operators that don't run cattle boats and cater to cruise ships. Just do a search on Mermaid divers and you will find that they have had a few issues. Here's one CDNN :: Mermaid Divers Dive Boat Hits, Critically Injures Customer

 

[boulderjohn]

I have been to Aruba 5 times and there are 2 or 3 good dive operators that don't run cattle boats and cater to cruise ships. Just do a search on Mermaid divers and you will find that they have had a few issues. Here's one CDNN :: Mermaid Divers Dive Boat Hits, Critically Injures Customer

...and this happened long after they were expelled from PADI.

 

[mikecotrone]

Wow i just read all 14 pages of this marathon thread. I feel like awards should be given out for those who complete it start to finish

 

[tstormdiver]

CESAs are not a part of a dive plan. It is a way to get to the surface if you have a real screw up and went OOA without a buddy nearby. You don't think about mandatory stops when you are trying to reach the surface while out of air. You get to the surface and deal with any DCS issues that may have arisen from that emergency ascent later.

On the other hand, I agree that more time should be spent on gas management and air sharing practice than happens in a typical course.

I agree100%. When I teach Open Water Students, I give them a heirarcy of ways to get to the surface starting with the most desirable to least desirable coming from the standpoint of DCS risk.
1. A normal ascent, no faster than 30ft/ min & preferably a safety stop at 15ft for 3-5 min. (especially for dives over 30 ft in depth) done with proper gas planning & gauge monitoring.
2. An alternate air shaing ascent once again, no faster than 30ft/ min & preferably with a safety stop of 15ft for 3- 5 min. especially for depths greater than 30 ft.
3. A Controlled Emergency Swimming ascent directly to the surface, ready to ditch the weight system, if needed, but still at a rate of no more than 30ft/ min., when a buddy can not be found (which, with proper buddy skills & awareness shouldn't happen, but occasionally still does). Typically done when air supply is critically low or in an OOA situation in shallow water where the diver has ability to make it to the surface at the prescribed rate. This does expose the diver to a slightly higher risk of DCS than the first 2 options.
4. A Buoyant Emergency Ascent (ditching the weight system) directly to the surface. Done when OOA & the diver can not find their buddy & the diver needs to ascend faster than the prescribed rate, usually due to depth. I emphasize that this technique should only be used as an absolute last resort, as this technique can potentially expose the diver to an even greater risk of DCS. DCS may be a survivable situation, drowning most often, is not.

I do emphasize gas planning & managment to my students during my classes, but also realize that most divers are humans & as humans we can make mistakes. I try to give them the options they have & the potential risks involved with each option.

 

[dpaustex]

With the original info posted, I agree with other posters. Without knowing specifics of your overall profile (the average means nothing, really), and the actual time at each depth, you really can't comment.

But based upon the additional info about the operator, and still other comments, it is hard to say what the dive operator was doing. I've never had an operator complain about doing a safety stop, and once I had to do it longer because I did stay deeper, longer, than anyone else on a second dive, and almost went into deco (taking too many pix).

There are also other variables of computer settings (many types let you adjust your "aggressiveness profile", by adding a factor to the internal algorithms. No one can really make a valid comment about using tables, because tables assume you're diving a square profile, which isn't really logical or normal (except for researchers working a dig, at depth).

As with others, when doing a wall dive that has a runout at about 15-20 feet, it is quite common to spend your "safety stop time" simply perusing the top lip of the reef. There is no relation of the name safety "stop" to actually stop what you're doing. IMHO, you are actually off-gassing faster if you are at safety stop depth and actually moving, as your blood is circulating faster, and hence off-gassing more quickly (off-gassing is the whole point).

But all-in-all, you did what is right. As a diver, you are responsible for you.

 

[Blackwood]

CESAs are not a part of a dive plan. It is a way to get to the surface if you have a real screw up and went OOA without a buddy nearby. You don't think about mandatory stops when you are trying to reach the surface while out of air. You get to the surface and deal with any DCS issues that may have arisen from that emergency ascent later.

I agree100%.
3. A Controlled Emergency Swimming ascent directly to the surface, ready to ditch the weight system, if needed, but still at a rate of no more than 30ft/ min.

Why 30fpm if we no longer care about the table instructions?

I agree with John and Andy about the efficacy of stops. What I don't like is the mixed bag. Follow these instructions and you'll never get into a situation where you can't CESA. Oh and BTW if you have to CESA, you may be unable to follow the full instruction set.

I was taught that a basic purpose of PADI's dive system is to guarantee that, barring medical issues or entanglements, a diver can always safely CESA. This is accomplished by *drummroll* The Table *horns blowing and angels floating*.

It's not mandatory stops. It's the time/depth and the ascent rate (60fpm).

Yes, there's gray, there's a variety of physiology, there's what you ate or drank that morning, etc.. So there are no guarantees. So add padding. Cut back on the NDL numbers. Cut down on the ascent rate (e.g. to 30fpm). But by adding mandatory stops into a no-stop table, you've violated the above basic purpose. Does that mean Joe Diver is going to try and make an OOG safety stop and end up drowning? No, I hope not.

I doubt you folks will see it my way, and I doubt I'll see it your way, but I enjoy the discussion, so thanks.

 

[Elvistheking]

There are also other variables of computer settings (many types let you adjust your "aggressiveness profile", by adding a factor to the internal algorithms. No one can really make a valid comment about using tables, because tables assume you're diving a square profile, which isn't really logical or normal (except for researchers working a dig, at depth).

Or a wreck dive or a scallop drift or a deep'ish reef from a boat..............