Looking for a more aggressive computer algorithm.

[scubadada]

Thank you for all the reasonable responses.

We are both nitrox certified. However, nitrox is not always an option. It simply isn't available, at any price, let alone what I consider a reasonable rate to pay.

I am not interested in pursuing technical training at this point. I know how to comply with my computer's deco if necessary, but I do not plan my dive with deco in mind. Additionally, liveaboards and dive boats that I usually dive with have some rather harsh rules about going into deco on their watch. I don't mind, it's their boat.

I will look into the information presented. Thank you.

Wijbrandus,

If you're willing to consider buying a new computer for the more liberal algorithm, I would think you would be willing to shell out the additional cash for nitrox whenever it is available. The extra NDL time with nitrox at the intermediate depths you describe are quite substantial.

The Pelagic Pressure Systems DSAT algorithm (Oceanic, Aeris, others) and the Cochran algorithm are considered among the most liberal whereas the Suunto algorithm is among, if not the most conservative.

The second algorithm included in the Oceanic Dual Algorithm computers, Z+, is a Buhlman ZHL-16C, and is more conservative than the DSAT algorithm. I assume this is for folks that want a more conservative algorithm for themselves or to more closely match their buddy's computer.

Good diving, Craig

 

[redacted]

You mean that adding a deco stop is safer than using a more liberal algorithm to allow you dive without the stop? Finding a computer that allows your dive does nothing to the dive or its safety. Adding a stop gives time for your tissues to outgas nitrogen and should make DCS less likely.

If you accept the premise of decompression theory that a slower ascent and shorter dive time gives a greater margin of safety, it follows that a more conservative computer is safer. If you don't accept that then why follow any algorithm at all, just stay down as long as you like and pop up to the surface.

Adam

I mean that idea that "more conservative" commercially available computers (algorithms) have any better a safety record than there "more liberal" competitors. But, now that you mention it, any empirical evidence that adding deco stops above and beyond those recommended by any credible algorithm actually produces a measurable safety improvement. It may just be a mater of more is not going to be worse, but it has no effect on actual results.

 

[redacted]

If you want longer bottom times, just get some advance/tech training and start doing planned deco dives, that is much, MUCH safer than pushing your dive computer to the max NDC dives.

Once again, clearly an alternative. Particularly attractive in that it opens up the opportunity for much more bottom time than switching to a "more liberal" computer and following those NDLs. But, where do you find any evidence that is "much MUCH safer"; or for that matter, any measurable bit safer???

 

[Hatul]

I mean that idea that "more conservative" commercially available computers (algorithms) have any better a safety record than there "more liberal" competitors. But, now that you mention it, any empirical evidence that adding deco stops above and beyond those recommended by any credible algorithm actually produces a measurable safety improvement. It may just be a mater of more is not going to be worse, but it has no effect on actual results.

How would you conduct such a study to collect empirical evidence? You would need one group to dive with one algorithm and another to do the same dive with a second algorithm and see which has more bent divers? It's an almost impossible study to do.

You could look at divers who are bent after following different computers but how would you correct for all the confounding factors, such as different dive profiles, age, hydration, health etc.

There was an imaging study years ago (I believe it was MRI) of spinal cords of asymptomatic divers that found lesions in the spinal cord. There is also possibility of bone and eye damage from diving.

see Long-term Effects of Sport Diving

I assume you don't smoke, wear a seat belt and take care of yourself, why take extra risks in diving.

Adam

 

[redacted]

How would you conduct such a study to collect empirical evidence? You would need one group to dive with one algorithm and another to do the same dive with a second algorithm and see which has more bent divers? It's an almost impossible study to do.

You could look at divers who are bent after following different computers but how would you correct for all the confounding factors, such as different dive profiles, age, hydration, health etc.

There was an imaging study years ago (I believe it was MRI) of spinal cords of asymptomatic divers that found lesions in the spinal cord. There is also possibility of bone and eye damage from diving.

see Long-term Effects of Sport Diving

I assume you don't smoke, wear a seat belt and take care of yourself, why take extra risks in diving.

Adam

I agree that such a study would be difficult, particularly when any difference that might exist must be very small. I suppose it could look a precursors to DCS like bubble formation and extrapolate any observed differences. Or it could look at accident stats but any difference in computer algorithms would probably be lost in more common contributing factors like ascent rate and hydration.

The point is, there really is no good reason to believe there is a safety difference (risk). Unlike smoking, the use of seatbelts, and exercise; where the differences (risks) have been statistically demonstrated.

 

[Hatul]

I agree that such a study would be difficult, particularly when any difference that might exist must be very small. I suppose it could look a precursors to DCS like bubble formation and extrapolate any observed differences. Or it could look at accident stats but any difference in computer algorithms would probably be lost in more common contributing factors like ascent rate and hydration.

The point is, there really is no good reason to believe there is a safety difference (risk). Unlike smoking, the use of seatbelts, and exercise; where the differences (risks) have been statistically demonstrated.

If you're set on getting a liberal computer, ScubaDiving.com | Scuba Diving Magazine has a few good articles about the algorithms each computer uses and how liberal/conservative it is.

Dive Computer Secrets Revealed | Scuba Diving Magazine
Dive Computers | Scuba Diving Magazine

look through those articles.

Adam

 

[gcbryan]

What was the surface interval & depth again?

5 day surface interval, nominal conservative setting for 100 fsw.

Deco of 1:20 at 20 fsw and 4:00 at 10 fsw.

 

[Kern]

5 day surface interval, nominal conservative setting for 100 fsw.

Deco of 1:20 at 20 fsw and 4:00 at 10 fsw.

For a clean getaway after a run time of about 27 minutes.

Alternatively, I do 19 minutes BT, take 3 minutes to ascend to 5 mts where I do a 3 minute safety stop. Run time 25 minutes.

Original Navy tables have 19 minute BT well within NDLs, modified Navy (doppler based) for sport divers & Padi tables put it at the edge if not over ( I'm converting from metric, so some rounding errors).

So, not the most aggressive, but not as conservative as I imagined prior to using it on NDL dives.

 

[fnfalman]

For those who claim that liberal algorithm computers (ala Pelagic Systems) are less safe than computers using more conservative algorithms, do you have any research or empirical data to prove this assertion?

If Haldanean algorithm is too "dangerous" then why is it still being used by various dive computer designers? Why would any company want to put out a product that might hurt or kill the end user and risk loss of sales/law suits/governmental wrath? That makes zero business sense.

 

[Hatul]

For those who claim that liberal algorithm computers (ala Pelagic Systems) are less safe than computers using more conservative algorithms, do you have any research or empirical data to prove this assertion?

If Haldanean algorithm is too "dangerous" then why is it still being used by various dive computer designers? Why would any company want to put out a product that might hurt or kill the end user and risk loss of sales/law suits/governmental wrath? That makes zero business sense.

I don't think it's possible to get such data to compare different computers, unless perhaps you want to torture hundreds of mice for such experiments.

Nor am I saying any computer is dangerous. There is enough safety margin or people would be getting bent using them. But the margin of safety must be greater with a more conservative algorithm. It has to be, because your dive time is shorter and/or it prescribes a deco stop slowing ascent. Decreasing dive time and/or slowing ascent has to increase safety margin with respect to DCS at least.

Anther issue as that article I linked pointed out, there may be injury over years of diving that may be very subtle and we're not aware of, a bit like the boxer suffering from boxer's dementia after years of fighting. There was at least one study that found spinal-cord lesions in asymptomatic divers. In my mind it's better to err on the side of caution.

Adam