Manual calculation for accelerated deco

[lowviz]

...//... As we see from these examples, the difference (across sea level and 2000m) in pressure drop gradient is steeper with approximation to the surface.
Hence, it would stand to reason that even from a pure dissolution perspective, deeper stops would be sensible compared to sea level diving on the same algorithm or ascend approach, as the gradient would reach a theoretical tissue group's M-value earlier in the ascend. ...

I think that I see your concern. (Please pardon me for speaking out of turn)

Yes, at altitude your stop sequence will become 'compressed' with respect to depth and you will have to add stops at the lower end of your schedule. These aren't really 'deep stops' (ala' Pyle) but rather necessary additional stops that you have to add to get you off the bottom properly.

 

[boulderjohn]

I think that I see your concern. (Please pardon me for speaking out of turn)

Yes, at altitude your stop sequence will become 'compressed' with respect to depth and you will have to add stops at the lower end of your schedule. These aren't really 'deep stops' (ala' Pyle) but rather necessary additional stops that you have to add to get you off the bottom properly.

I am absolutely baffled by this. I don't know what it means.

 

[victorzamora]

So one could argue that the results obtained from the NEDU study, that seem to indicate shallower stop emphasis, do not apply to RD.

That's BEEN argued through hundreds of pages and thousands of post in the recent past. Believers of VPM and/or UTD's RD have denied it. Others have accepted the findings and changed their diving. Others read it and then, essentially, ignored it. Rehashing it here is, I think, fairly pointless.​

 

[lowviz]

...//... Altitude stop depth (fsw) = Sea level stop depth (fsw) x (Atmospheric pressure at altitude / 1 ATA) ....

@boulderjohn

The result of this is that you will end up needing more stops when diving the same depth if at altitude. The stops will be more numerous and closer (with respect to depth) than an equivalent dive to the same depth at sea level...

 

[boulderjohn]

@boulderjohn

The result of this is that you will end up needing more stops when diving the same depth if at altitude. The stops will be more numerous and closer (with respect to depth) than an equivalent dive to the same depth at sea level...

Why? I see no reason for this.

Neither does any software program I know. Buhlmann doesn't do it. V-Planner doesn't do it.

Simon said you need to do longer shallow stops. That is what Buhlmann does when adjusting for altitude.

 

[Dan_P]

I think that I see your concern. (Please pardon me for speaking out of turn)

Yes, at altitude your stop sequence will become 'compressed' with respect to depth and you will have to add stops at the lower end of your schedule. These aren't really 'deep stops' (ala' Pyle) but rather necessary additional stops that you have to add to get you off the bottom properly.

Exactly.
While I don't actually practice compression of stop intervals, I think we're addressing the same logic here.

Granted, when I'm diving at altitude, I do shift the overall emphasis of my ascend upward with the extention of shallow stops - but I do find that the deeper stops that I carry over unadjusted from what my ascend profile would look like on a sea level dive, ressonate with the logic of reaching m-values earlier in the ascend on an altitude dive.

Of course, I have no way of knowing what the correct ratio between dissolution- and gas mechanics emphasis may be, but I feel that's best left for another discussion.
For now, this is purely to attempt to explain better my view that stopping deeper on altitude dives doesn't equal increased emphasis on deep stops.

 

[lowviz]

see below...

 

[lowviz]

Why? I see no reason for this.

Neither does any software program I know. Buhlmann doesn't do it. V-Planner doesn't do it.

Simon said you need to do longer shallow stops. That is what Buhlmann does when adjusting for altitude.

Calculate the stops for a dive to 40 meters at sea level.

Apply Dr. Mitchell's suggested correction to those stop depths at 0.5 ATM elevation.

You really plan to ascend from the bottom to the first calculated stop?

 

[Dr Simon Mitchell]

The support of all the anti-RD comments are essentially based on the NEDU deep stops study.

That is not correct. See this post. In particular, note the Spisni study which was a study of RD vs a shallower stop approach.

Simon M

 

[boulderjohn]

As it turns out, I happen to know something about a decompression dive at an altitude of 0.5 atmospheres. I know that it has never been done successfully. It has been attempted, but it was not successful. Curiously enough for this thread, it was attempted by two people from my old UTD group. One was paralyzed for 3 months, with that time spent in one of the world's foremost rehabilitation hospitals. As for the other, his body was never recovered.

I discussed that dive with someone who specializes in high altitude decompression--Dr. Richard Walker. He consults with NASA (and he believes every astronaut who ever flew the shuttle was bent to some degree), and he consults with the Pentagon for U2 flights (similar problems). He explained that as you get higher and higher in altitude, more and more factors come into play. For example, the incompressibility of water vapor droplets in your breathing becomes a factor. He said there are only about 6 people in the world with the expertise to plan such a dive. The decompression stop needs for a decompression dive at that altitude would be enormous.

My deepest diving to date has been at a bit over 10,000 feet, and even then I do not feel comfortable using normal diving procedures.