Doing the Deeper Dive Second.

[GrierHPharmD]

Thanks for your thoughtful comments, Mike. Scientific data is so often misquoted and misapplied when presented to the public that it often seems as if science wavers back and forth on issues such as reverse profiles. It's so tempting to read more into the results of a study than the original investigators intended.

For my 2 cents, I believe in sticking to my training, modifying it where it seems to be appropriate and conservative (adding a half-max depth 1 minute safety stop on deep dives, for example), and concentrating on keeping my ascent rates nice and slow.

Good luck and safe ascents,
Grier

 

[Mako Mark]

Interesting point Mark, when we do charters in Nanaimo we have to do Dodd Narrows when tide change allows it. It has a max depth of 75ft. If it is the first dive of the day often people will pass on the wreck (Saskatchewan 110') to avoid RP. We use nitrox and EAD profiles to prevent the RP.

cheers,

We have a situation where instructors do a two training dives at about 30-40 ft in the afternoon and then are asked to do two 45-55 ft night dive. I tell them not to quit their job over it but be extra conservative and make sure they have a computer with them.

None of them have got bent yet, although one lady instructor that did it for years got diabaticosteonecrosis in the shoulder.

 

[Scuba_Vixen]

BW has posted some good stuff here on the board about reverse dive profiles. they recieve thorough treatment in "Technical Diving in Depth" by BW.

The output of the reverse profile workshop have been misstated more than not. They decided that for non-stop dives withing recreational depths and deth differences of no more than 30 or 40 ft that the order didn't seem to matter much. That's often twisted to mean that reverse profiles are ok but that isn't what they said.

If doing the shallow dive first or the shallow part of a dive first was the way to go we would be able to do our decompression before the dive instead of after.

I think the operative words here are: "They decided that for non-stop dives within recreational depths and depth differences of no more than 30 or 40 ft, that the order didn't seem to matter much."

If your first dive is shallow 40' or 50' reef dive, then a second dive to a 110' wreck is probably not a good idea for no stop diving. If the first dive was an 80' wall dive, then that 110' wreck may not be such a bad second dive.

The thing to bear in mind is that the second dive's runtime is likely to be much shorter when it's close to or deeper than the first, even with a fairly long SI. You may want to make the dive you want to spend the most time on first, even if it's the shallower one of the two.

A slower than usual ascent with a couple pauses before the safety stop would also be a good recommendation when doing 2 similarly deep dives repetitively.


Darlene