Past NDL. And then this???

[Dan]

DevonDiver has already pointed out, multiple times, that you can't compare the results of a dive using VPM or Buhlmann in Subsurface to that of a dive computer using a adaptive algorithm like RGBM. VPM/Buhlmann completely ignores many of the data artefacts that RGBM uses to significantly affect its result.

Compound these over multiple days, with multiple dives/day, and you get this result.

Both SUUNTO & Cressi use RGBM according to @DevonDiver. But that's not what I was wanting to show. I want to compare my ascent rate compared to OP's. You can see that his ascent ft/min slope is less steep than mine. What I learnt here is that you will get penalized if you ascent too slow.

 

[RainPilot]

So your reason for why is because that is the setting on your computer? Do you adjust it based your profiles for a given set of di ves? Maybe to make it more or less conservative, depending on how many dives you are doing? Do you leave it constant?

The rec diving I do is very low aggression levels. Warm water, no hard work at the bottom and so on.

If I had a day where I needed some extra padding I would drop to a Med conservative setting for sure.

In tech mode I'm using 50/70

 

[KeithG]

Both SUUNTO & Cressi use RGBM according to @DevonDiver. But that's not what I was wanting to show. I want to compare my ascent rate compared to OP's. You can see that his ascent ft/min slope is less steep than mine. What I learnt here is that you will get penalized if you ascent too slow.

I am not sure that I would draw the same interpretation. This was not a issue of slow ascent, it was an issue of practically no ascent while already in deco.

The OP went into deco and then remained deep enough to accummulate a much larger deco obligation. Instead of making an immediate safe ascent he continued the dive "a bit shallower" for the next 20 minutes. He was not really ascending to deal with the deco. He was continuing the dive and building more deco.

So I would not consider his behaviour as a "slow ascent", it was a continuation of a deco dive.

If the OP had started this ascent with 40 minutes of NDL there would have been no issue.

 

[Dan G]

He spent 35 minutes hanging at 10 feet and the computer didn't clear. That's insane. I have no idea what algorithm the Cressi Leonardo uses, but it is obviously not an effective tool for any dive involving even minimal deco (unless it can be set in a depth gauge mode to use with a pre-written plan).

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I think this is an important point. From what I can gather, many many computers are really designed to just be recreational computers. They do not like going into deco and react very differently than, say, a Sherwood reacts in the same situation.

The computer gave the OP a chance to ascend and be done with the dive in 7 mins. He ignored this and racked up a huge obligation. One way to look at it is this: the computer decides that the diver needs to sit out for a while (because it's initial direction was ignored) so it gives a deco obligation that will leads to the computer freezing him out of dives for a period of time. Sort of a, "I told you to go up and you ignored me. Now go to your room."

 

[Miyaru]

...
The symptoms he describes (joint pain) are not sub-clinical.... they are clinical. They may have led to a DCS diagnosis.
...

No not joint pain, but pain in the deltoid muscle. First two times it was just annoying and resolved after 15 minutes. Next day it was on both sides and severe, completely resolved after 30 minutes. Doctor later concluded that the combination of cold water and exercise (getting into the rib) probably caused some stress, likely not DCS. However, he advised me to stick with GF high of 75 since that seems to work better for me.

Point is, shifting 5% can make a big difference. It's no problem to change the setting in your computer, but you can't change the way your body reacts.

 

[KeithG]

I think this is an important point. From what I can gather, many many computers are really designed to just be recreational computers. They do not like going into deco and react very differently than, say, a Sherwood reacts in the same situation.

The computer gave the OP a chance to ascend and be done with the dive in 7 mins. He ignored this and racked up a huge obligation. One way to look at it is this: the computer decides that the diver needs to sit out for a while (because it's initial direction was ignored) so it gives a deco obligation that will leads to the computer freezing him out of dives for a period of time. Sort of a, "I told you to go up and you ignored me. Now go to your room."

I also would not interpret this as a "recreational" computer trying to "discipline" a diver.

This is a situation of a dive computer running its decompression algorithm and calculating that a diver has racked up a large 35 minute deco obligation.

The computer reacted correctly. The diver incurred deco, the computer told them about it and provided all the information required to clear the deco obligation.

Is there such a thing as a "recreational" computer? That does not handle deco? I have an air only dive computer from the 1990s and it handles deco just fine.

 

[Dan G]

I also would not interpret this as a "recreational" computer trying to "discipline" a diver.

This is a situation of a dive computer running its decompression algorithm and calculating that a diver has racked up a large 35 minute deco obligation.

The computer reacted correctly. The diver incurred deco, the computer told them about it and provided all the information required to clear the deco obligation.

Is there such a thing as a "recreational" computer? That does not handle deco? I have an air only dive computer from the 1990s and it handles deco just fine.

I'm not suggesting that the computer reacted incorrectly. In fact, quite the opposite.

 

[w3dge]

I also would not interpret this as a "recreational" computer trying to "discipline" a diver.

This is a situation of a dive computer running its decompression algorithm and calculating that a diver has racked up a large 35 minute deco obligation.

The computer reacted correctly. The diver incurred deco, the computer told them about it and provided all the information required to clear the deco obligation.

Is there such a thing as a "recreational" computer? That does not handle deco? I have an air only dive computer from the 1990s and it handles deco just fine.

I think the discussion was born because the profile given by the OP's DC varies significantly to that predicted by something like subsurface.

 

[DevonDiver]

.Is there such a thing as a "recreational" computer? That does not handle deco?

I think there's an important distinction between computers that implement algorithms which:

1) Are intended to best facilitate no-stop diving within typical recreational parameters (multi-day repetitive diving in shallow water with minimal surface interval). That also provide emergency decompression should the no-stop limits be accidentally exceeded. Emergency decompression may prioritise simplicity over efficiency, and may favor shallow deco stops where recreational divers will use least gas and can easily CESA etc if gas were fully consumed while attempting the deco.

Basically, KISS deco to get muppets safely out of the water when they screw up...

2) Are intended to best facilitate technical decompression diving, where dive repetition, surface intervals and other factors are subservient to the dive undertaken (not vice versa). Decompression is planned and calculated for optimal efficiency with an assumption that complex ascent plans are fine, comprehensive gas planning has occurred and there are no issues on that basis.

Basically, complex deco to get highly supersaturation saturated divers to the surface with a reasonable degree of confidence.

 

[Neilwood]

One of the problems with RGBM is that it is a proprietary algorithym (in this model of dive computer anyway) and therefore trying to model its behaviour on another program such as Subsurface is fraught with issues. The implementation of RGBM on the Cressi is not designed for decompression diving (it is stated quite a few times in their manual that it is for sport diving only etc) so should only be for "emergency deco"

One of the big issues is that the computer provided the deco information but the OP did not know how to behave in relation to it so instead of making a reasonably quick ascent, he chose to ascend slowly therefore racking up further deco. If he had ascended as soon as deco was apparent and at a normal rate it is entirely possible that his deco obligation would have been minimal or cleared on the way up.