Do you/would you fly with an 19hr surface interval?

[chrpai]

Brian2828: get out your table or dive computer, plan all the dives and see where your residual nitrogen is going to be at the end. Look at your final pressure group. When on vacation, I do not dive on the last day. If you take the advice of some people who push the limits and you get DCS, ask them if they will cover the thousands of dollars of treatment. Commercial aircraft are pressurized to apps 8000ft when at altitude. Do what you know is right based on the training you have received from your INSTRUCTORS.

Argument from authority doesn't work for me. There are many "right" things one can do and there are many things that are only "theory" and not "known".

Eitherway, your advice about pressure groups is of limited value. Consider a Z diver as a result of a dive to 130' and a Z diver as a result of a dive to 35'. That's going to have completly different nitrogen loading in your body and implications on time to fly.

 

[tracydr]

The DAN study was relatively thorough. It has been a number of years since I looked at it carefully, but as I recall I left it thinking that the 18 hour limit for multiple dives was conservative. Even with the length of time the diver plans to be in the water, if it were I doing the diving, I would follow the 18 hour rule without hesitation. And yes, 19 hours is more than 18 hours.

I agree. 19 hours is more than 18. Seems pretty simple. 6 conservative, 30 foot dives, although an unusual profile, doesn't seem like it would be a problem.
I have seen somebody who probably got DCS from flying too soon after diving. He dove an agressive profile the entire week before flying, with less than 12 hours before flying to Galapegos. Then started diving cold, difficult, 100 foot dives, 4 times a day in Galapegos. If I recall, he started complaining of a severe headache on the flight. It kept getting progressively worse, until we were way out at the furthest islands and ended up having to turn back to get him to a chamber.
He was an older guy 70s, which may have also contributed. He was doing deep, decompression dives commercially the day before flying!, So, serious dehydration and fatigue could have been another issue.
I think his experience had a lot of complicating factors. Age, fatigue, deeper/colder, more difficult dives and a long, hard day of flying.
Unfortunately, he wasn't honest about his dive profile prior to flying, so we were thinking that the headache started on the plane and was unrelated to diving. Sort of a red herring there. Please, people, if you have a medical professional ( or two) assessing you in an emergency, be honest!

 

[mdax]

I've posted this before...but it's good info for this discussion.
The noaa table is what I use. It says to use 8000' for commercial aircraft, which I'd use based on this paper discussing that the FAA sets a rule of no more than 8000' for passenger aircraft.
I believe the proper table for determining the designation groups used in the previously linked table is here

 

[-hh]

For those of you that have a problem with my post. I am not telling anybody what to do, only making a suggestion. If you want to dive any number of hours before flying because you are smarter than the table, computer, DAN, or you think you are just immune to any repercussions go ahead. I will be interested to read your post after you recover from DCS or whatever stupid ailment you had. I have been teaching for a few years so if you want to get into a discussion of dive theory and decompression models we can do that in a different thread. I simply stated that the op should refer back to his training and do what he knows to be right, instead of pushing the limits for one more dive and increasing his risk of injury.

See you in the ER

Argument from authority doesn't work for me. There are many "right" things one can do and there are many things that are only "theory" and not "known".

That's where I saw the logical fallacy creep in, be it intended or otherwise. Unfortunately, when it comes to the educational qualifications of Dive Instructors, the Agencies have set their standards very low ... not even a High School Diploma is required. Fortunately, there's a lot of Instructors who are vastly more educated - - but this is by coincidence from other personal life choices, so it can't be assumed.

Eitherway, your advice about pressure groups is of limited value. Consider a Z diver as a result of a dive to 130' and a Z diver as a result of a dive to 35'. That's going to have completly different nitrogen loading in your body and implications on time to fly.

IIRC, the PADI table that goes up to Z is running on a 1 hour controlling compartment. Here's the older PADI table that was based on the USN and 2hrs...and coincidentally, showing this to folks who insist that PADI never endorsed any Deco profiles is an extra bonus.

In any case, as the nature of the dive profiles change, the important take-away point is that so the controlling compartment will change too; for a series of very long & very shallow dives, it is going to be one of the long compartments which ends up being what determines how long the SI needs to be for a diver to 'completely' clear.

-hh


PS: when it comes to the question of DCS hits while flying, we do have to remember to discern out what can best be described as "Undeserved Hits" for which the normal statistics don't seem to apply. For example, literature proceedings mention a researcher (Mike Emmerman) who reportedly documented a hit that occurred at a whopping 41 hours after the dive.

 

[Rhone Man]

IIRC, the PADI table that goes up to Z is running on a 1 hour controlling compartment. Here's the older PADI table that was based on the USN and 2hrs...and coincidentally, showing this to folks who insist that PADI never endorsed any Deco profiles is an extra bonus.

Ah. the memories. If my recall is correct, that table used to provide for a recommending "time before flying" of 4 hours, or 12 hours if you had been engaging in decompression diving?

 

[mathauck0814]

+1 I wouldn't worry about it at all.

 

[DiveNav]

If I am not mistaken ... in the ZHL16C algorithm the slowest compartment has a half time of 635 minutes...... almost 11 hours

Albert (aka eDiver)

 

[-hh]

Ah. the memories. If my recall is correct, that table used to provide for a recommending "time before flying" of 4 hours, or 12 hours if you had been engaging in decompression diving?

Possibly on the first part, but I'd say definitely a no on the second part, since part of the way that the new PADI Table were developed, they carried the assumption/requirement of absolutely no decompression profiles, as well as the "WXYZ" rules.

At a presentation given in South Carolina by Peter Bennett, Bill Hamilton and Dick Clark, Al Wells' personal recollection was that it was Peter Bennett who said that the PADI RDP was a response to complaints from resort operators about long SI times. Of course, such 'accommodations' are hardly new. When Haldane tested his first tables on Admiralty divers from the HMS Spanker, he "rounded up" some depths to the nearest fathom, shortened deco stops because the divers were freezing trying to do the extended deco stops (which was unacceptable to both the divers and their supervisors), etc.

Personally, I had the good pleasure a few years ago of meeting one of Buhlmann's Swiss volunteer military divers; his particular claim to fame was that he was the first guy who got bent while driving home up into the Alps ...ie, altitude effects..after series of experimental dives.

All in all, it just goes to show us really all just how relatively recent this research has all been.


-hh

 

[GrumpyOldGuy]

What I don't understand is most divers will run right up to NDL on tables on a dive if they have enough air, day in and day out. Heck, they often go past the table NDL if they are on a computer since its averaging. They trust the tables are correct and have enough tolerance for the typical diver under normal conditions and are undergoing significantly more pressure differential.

Then they turn around and when the same agencies that publish the tables say 12 or 18 hours no-fly, they want to pad it more to make it safer.

 

[windapp]

Heck, they often go past the table NDL if they are on a computer since its averaging. QUOTE]

I just wanted to provide a minor clarification. Computers don't average anything. Computers track the nitrogen loading of several tissue compartments over time by monitoring depth an time. They then compare the loading of each compartment to the maximum tolerable pressure gradient at the surface (M0), and give the time required to reach the closest M0 value. This is an integration of an exponential decay equation, and averaging is definitely not a term to describe this process.

The reason why I wanted to provide this clarification is to avoid the risk of someone thinking that they could somehow average the table values when planning their dive profile.