Past NDL. And then this???

[BRT]

Isn't this kind of like telling someone to get a different doctor if they don't like the advice provided by the current doctor?

If someone doesn't like the advice provided by their current computer, they don't actually need to buy another computer. They can simply ignore the current computer... right? Essentially the same philosophy, but saves a good deal of money.

Stepfen, if I can offer one bit of advice that I didn't see addressed in any of the responses yet. Get in the habit of planning your dives, every dive. In this case, if you had spent 60 seconds with your buddy before that dive and compared the projected NDLs given by your computers for the next dive, you would have likely seen in advance a noticeable difference. You could then have discussed with your buddy how the two of you would handle the dive, and both of you would have been aware of the situation (i.e. that your NDL was going to be much less than his) before getting in the water.

When I become convinced the doctor I have is not giving me good advice I get a new doctor, Would you stick with one who was giving you very different advise than other doctors were giving your friends in very similar situations? Especially if they were getting good outcomes? Any time there was as wildly different opinion between doctors as there is between dive computers somebodies medical license should be looked at.

I don't want to ignore my doctor or my dive computer. I want both to give me reasonable solutions.

 

[KeithG]

I am not going to get into the ongoing algorithm debate. To @stepfen : this is a frequently discussed topic on SB that you jumped into with both feet. It is an interesting discussion and there is a lot of good info for a newish diver. But all the info can also be very confusing and sometimes seem contradictory (hence to SB debate).

If you can try switching Subsurface to VPM + 5 and see if the two "dives" are a closer match. If you do this let me know the result.

My version of Subsurface (i downloaded it a few days ago so it is the most recent) has VPM-B settings from +0 to +4 (I assume we should map them to levels 1 to 5?).

 

[stepfen]

The OP's profile said his training is both PADI and IANTD. I assume the PADI certification is OW. With the PADI OW course, you have the choice of taking the table version of the course or the computer version. Can you tell me. @stepfen, which version it was?

In the table version of the course, you do not learn much about computers; you learn how to use the tables, and you learn to use procedures in case you unintentionally go into deco, procedures that would have been completely inappropriate to this incident and that were not mentioned. In the computer version of the course, you learn to use the ascent rate prescribed by the computer, and you learn to follow the directives of the computer in case of an unintentional deco obligation.

I can't recall having an option but in any way I did the table version. Time to refresh my memory on the procedures.

 

[uncfnp]

My version of Subsurface (i downloaded it a few days ago so it is the most recent) has VPM-B settings from +0 to +4 (I assume we should map them to levels 1 to 5?).

The reason I made the suggestion is I dive recreationally with computers set for VPM +5 and Cressi SF 0 and they tend to match up fairly closely

 

[KeithG]

Here are the logs for all the dives of that trip in subsurface xml format. Please rename the file to NDL.xml before use (SB didn't let me upload XML directly).
Unfortunately they contain only ascent alarms (another annoyance of this particular computer but I leave that for another thread) and nothing about deco alarms or NDL values calculated by the computer. Cressi PC interface software shows NDL, deco alarms etc but I guess it may regenerate them offline from the log data on the PC.

Thanks for providing the file - I slurped it into my current version of Subsurface (I am new to Subsurface so it is interesting to get to play with some others data - I like the map stuff that shows up!).

These dive profiles / behaviour appear to be very aggressive to me - but I am not an algorithm / deco /subsurface expert so some of my opinions may be wrong?. But it will still be useful to discuss and learn from it.

1) The first red flag I saw was repeated sea-saw behaviour. In many (most / all?) of your dives you did one or more 10 to 25 foot dips. I have been told this seesaw behaviour is bad. I am unaware of how this affects various algorithms or nitrogen loading.

This is something worth discussing.

2) I tried 4 different algorithm settings in Subsurface and you went into deco in all of them except 1 (assuming my Subsuface-foo is working properly). The only non deco trip was a buhlmann 30/90 (which I claim matches my Uwatec Aladins) and it put you well under 10 minutes of NDL multiple times for extended duration's - especially the trouble dive (Jan 24th 2:37PM) in which my Aladin would have had you under 10 mins of NDL for around 20 minutes of the dive. As a warm water vacation diver this is not something I would do.

Algorithms tried:
VPM-B +0 - deco
VPM-B +4 - lots of deco
Buhlmann 30/70 - some deco
Buhlmann 30/90 - almost deco

Based upon my limited knowledge of Subsurface, these dives push the NDLS more aggressively than what I choose to dive when doing a LOB (or Bonaire) vacation.

 

[doctormike]

The thing about all the different algorithms for commercially available dive computers to be used in planning "recreational" dives, is that every one of them has an acceptably low rate of DCS. What is dangerous is guesstimating and blowing off deco because you think that your computer is too conservative, so you add a fudge factor.

Also, sawtooth profiles with extra ascents and descents are notorious for increasing the risk of DCS, even within NDLs. Ask me how I know...

 

[Dan]

Thanks for providing the file - I slurped it into my current version of Subsurface (I am new to Subsurface so it is interesting to get to play with some others data - I like the map stuff that shows up!).

These dive profiles / behaviour appear to be very aggressive to me - but I am not an algorithm / deco /subsurface expert so some of my opinions may be wrong?. But it will still be useful to discuss and learn from it.

1) The first red flag I saw was repeated sea-saw behaviour. In many (most / all?) of your dives you did one or more 10 to 25 foot dips. I have been told this seesaw behaviour is bad. I am unaware of how this affects various algorithms or nitrogen loading.

This is something worth discussing.

2) I tried 4 different algorithm settings in Subsurface and you went into deco in all of them except 1 (assuming my Subsuface-foo is working properly). The only non deco trip was a buhlmann 30/90 (which I claim matches my Uwatec Aladins) and it put you well under 10 minutes of NDL multiple times for extended duration's - especially the trouble dive (Jan 24th 2:37PM) in which my Aladin would have had you under 10 mins of NDL for around 20 minutes of the dive. As a warm water vacation diver this is not something I would do.

Algorithms tried:
VPM-B +0 - deco
VPM-B +4 - lots of deco
Buhlmann 30/70 - some deco
Buhlmann 30/90 - almost deco

Based upon my limited knowledge of Subsurface, these dives push the NDLS more aggressively than what I choose to dive when doing a LOB (or Bonaire) vacation.

How's the OP's ear doing after those yo-yo diving, I wonder?

 

[tursiops]

How's the OP's ear doing after those yo-yo diving, I wonder?

Probably just fine. 25ft excursions while at depth do not change the percentage pressure on the eardrums very much. The same excursions near the surface are problematic, as you allude.

 

[KeithG]

I am curious. From my dive computer / Subsurface tests I believe my Aladin runs a BuhlMann 30/90.

Is this considered aggressive?
For a vacation diver doing a week of 5 to 6 dives a day?

 

[KeithG]

How's the OP's ear doing after those yo-yo diving, I wonder?

They maybe just fine? I am not sure how equalization issues can be related to DCS issues?