If we assume that the altitude-adjusted NDL should keep us safe when ascending from a dive while at altitude, how is that different from surfacing at a lower altitude and then slowly ascending to a higher altitude?
Research shows that we form bubbles after surfacing from an NDL dive (even one shorter than the NDL time), but they do not seem to be an issue when staying at that depth. (Drs. Mitchell and Doolette, among others, have reported on this; sorry I don't have a specific reference on-hand. Google should point you toward some videos of their conference briefings.) The problem arises when you ascend to a higher altitude
after those bubbles have formed.
Admittedly, I'm filling in the gaps in your explanation (and thus could have misunderstood), but my understanding is that you want to use the NDL time at the altitude-equivalent depth. Then you feel you can immediately ascend to that altitude after the dive. After all, if you did the dive at that altitude, you'd get out of the water without issue, right? Unfortunately, those are two very different scenarios: subclinical bubbles (at altitude) vs subclinical bubbles followed by an ascent.
As an example, below is what that might look like, and you'll see it violates the NOAA/NAVY ascent to altitude tables. (These are the best source of ascent information/timelines that I know of. Certainly more precise than the rather vague DAN guidance of > 12 hrs for a single dive.)
Example: diving at sea level to 60 ft, then crossing a 4000 ft pass. I believe you're trying to plan with the altitude-equivalent depth (70 ft), which has an NDL time of 48 mins. After a 60 ft/48 minute dive at sea level, you are at Navy pressure group I. The Ascent Table for 4000 ft elevation gain from Group I
requires nearly 3 hours. You're definitely not able to go right away, which was the point of my initial response. (My apologies if I've misunderstood your intended approach. Please elaborate if so!)
