week-long dive profiles

[riddler]

I live in a land-locked state, so most of my diving is week-long or weekend trips to the Carribean.

When I first started diving, my mentor was the LDSO, who told me that a good dive profile for a week of diving is: Deepest dives at the beginning of the week (for instance, 100 feet on Monday), followed by successively shallower dives on subsequent days (80 feet on Tuesday), with the last days' diving being quite shallow and short (30 feet on Friday). This makes sense to me, as a way to take the highest nitrogen loading early, and spend the rest of the week taking on smaller amounts. By the off-gas day (Saturday), your body shouldn't have to do much work to off-gas to acceptable levels before flying home (Sunday).

I've overheard the new LDSO, on several occasions, telling customers and students something different when we prepare for trips. If there is a planned dive on our trip that is deeper than the customer has been before, he suggests doing not-so-deep dives first, to "build up to it". For instance, if a 100-foot dive is planned, he recommeds an 80-foot dive on Monday, followed by a 90-foot dive on Tuesday, and slowly approaching 100-feet by the end of the week.

I understand the new LDSO's point from a narcosis standpoint. My opinion is that deep dives should become deeper over multiple trips - for instance 80 feet at the beginning of this trip, so that divers have time to adjust to narcosis and understand it's effect on them. Next trip, try an 85-foot. Next trip, maybe 90. All after taking a deep-diving class, of course :05:

But I think the idea of "building up to" deep dives in one trip is counter-productive to a good week-long dive profile from the standpoint of DCS. If you do deeper dives over the course of a week, I think your nitrogen loading on the last day is going to be quite high and your body may not be able to off-gas as much before flying home.

Is either of these two theories correct? Or does it matter at all which way you go, from a DCS standpoint?

 

[miketsp]

Very few operators will take unknown clients out on a deep dive on the first day.
The first day of a trip is really for shakedown. Most people are tired from travelling. Many forget part of their kit or something has been damaged in transit.
In my experience the most challenging dives should be done on the 2nd or 3rd day.
From the DCS point of view, just avoid doing deep dives on the last day.

 

[ranger979]

I think you approach is a very good way to do it and would work well for people who make frequent trips. However, for someone who may not have the opportunity to do much travel it doesn't work as well. Especially if there is something in particular that you want to see that is deep. How many people are going to pass up what may be a once in a life time dive simply because it is deeper than they have dove before.

In those cases, I think gradually going deeper makes more since. Of course, ideally I believe that if you should get the experience for the type of dives you are planning on making before you go.

 

[riddler]

Very few operators will take unknown clients out on a deep dive on the first day.

Forget first day. I put that there for example purposes. On most of my trips, the first dive is checkout, the second dive may be the deep dive, but the deep dive is usually the second day.

The point of the question: is it better to do the deeper dives toward the beginning of the week, with successively shallower dives? Or is it the same from a DCS standpoint to "work up to" the deeper dives toward the end of the week?

If it doesn't make a difference, then I would guess that doing the deeper dives at the end is better from a narcosis standpoint.

 

[miketsp]

While the US Navy Manuals report that following a 1600 foot deep saturation dive, team members developed DCS four days later on a commercial air flight, I would just make sure that I don't do any deco dives in the 48 to 24 hour window before flying and no dives in the 24 to 0 hour window if I have been diving over multiple days.
So more than 48 hours before the flight I would arrange my dives in the most convenient order.
However, as you say I personally feel that my narcosis tolerance is higher if I work up to a deep dive over a couple of days. Say 25m on 1st day, 35m on 2nd day and anything else 3rd day on. It's probably just because my stress level is lower. That's just my experience. Not everybody agrees.