No Fly Time Calculation No computer

[Andy_W]

Just out of my curiousity...how do DAN or PADI or whichever agency get the figure of 18 hrs or 24 hrs. Don't flame me guys...

 

[Fordan]

Just out of my curiousity...how do DAN or PADI or whichever agency get the figure of 18 hrs or 24 hrs. Don't flame me guys...

Well, if I understand things correctly, the 1989 Undersea and Hyperbaric Medical Society (UHMS) Workshop on Flying After Diving issued the 12/24/48 hour recommendations, which is what I suspect many of the certification agencies are following.

DAN did a study from 1993 to 1998 simulating dives followed by simulated flight in their hyperbaric chamber (http://www.dan.org/research/projects/fad/index.asp), and held a Flying After Recreational Diving Workshop in 2002, where the consensus opinion was the 12/18 hour recommendation DAN uses today. (Workshop proceeding available to DAN members)

 

[miketsp]

You might review what DAN actually says. It changed a few years ago.

Most of the posters here seem to think they know more than DAN, tho? The DAN guidelines are really rather conservative. Read their Accident reports for the last few years - see if you find any hits while flying 18 hours after diving. Check our A&I forum. Check the ScubaDoc site. Find me a reason to skip that dive.

If a good dive is availble in the 18-24 hour range, I'm in. I will use Nitrox if available, but if not, I'm still in. Now if you're much older than me, you might want to be more conservative. I'm only 58-11/12.

I guess so. There is no reason for that 24 hour countdown timer to still be on computers, but it is - and most of those posting here are going by it, regardless of the facts.

You say look at the Accident reports and see if you find any hits while flying 18 hours after diving:
DAN Project dive exploration (since 1998): DAN has data for 382 flying after diving injury cases and for 245 injury-free controls. 53% of the injured cases waited less than 24 hrs before flying, while 76% of the controls waited more than 24 hrs. So unless I read this wrongly quite a high percentage waited more than 24hours and still had problems.

I tried to post this PDF but once again the system will not accept uploads.
http://www.nzunderwater.org.nz/Medical/me.flying.pdf

 

[BigBill]

I was told by an instructor on my last trip, 18 hours, but I normally go with the 24 hour rule - 24 hours after my last dive, and I think my computer has that same rule, although I haven't found documentation to support that (UWATEC SmartCom). I would much rather be safe, than sorry!

 

[Web Monkey]

I thought the DAN recommendation was 18 hrs for multiple NDL dives, and "substantially longer" for deco dives. Where does it say 24 hrs?

My DiveCon manual says 18 hours minimum, and 18-24 if you've done daily multiple dives.

Terry

 

[DandyDon]

You say look at the Accident reports and see if you find any hits while flying 18 hours after diving:
DAN Project dive exploration (since 1998): DAN has data for 382 flying after diving injury cases and for 245 injury-free controls. 53% of the injured cases waited less than 24 hrs before flying, while 76% of the controls waited more than 24 hrs. So unless I read this wrongly quite a high percentage waited more than 24hours and still had problems.

I tried to post this PDF but once again the system will not accept uploads.
http://www.nzunderwater.org.nz/Medical/me.flying.pdf

Thank you...! I will indeed read that later today. It is nice to have something more to look at. Based only on your statement for now, tho - the "controls" are not injured divers. That's but a group within a study. I'll read and see...

My DiveCon manual says 18 hours minimum, and 18-24 if you've done daily multiple dives.

Yeah, the agencies are going to be slow to change their manuals. DAN is the respected authority on the subject, so they have no need to.

 

[DandyDon]

You say look at the Accident reports and see if you find any hits while flying 18 hours after diving:
DAN Project dive exploration (since 1998): DAN has data for 382 flying after diving injury cases and for 245 injury-free controls. 53% of the injured cases waited less than 24 hrs before flying, while 76% of the controls waited more than 24 hrs. So unless I read this wrongly quite a high percentage waited more than 24hours and still had problems.

I tried to post this PDF but once again the system will not accept uploads.
http://www.nzunderwater.org.nz/Medical/me.flying.pdf

Thank you...! I will indeed read that later today. It is nice to have something more to look at. Based only on your statement for now, tho - the "controls" are not injured divers. That's but a group within a study. I'll read and see...

Yeah, the agencies are going to be slow to change their manuals. DAN is the respected authority on the subject, so they have no need to.

Okay, read over that article, which can be challenge...

(1) In the one study there, above the one you cited, they examined 278 injuries while diving. Over half of those had symptoms before flying and should have known better. It didn't say much more, but in other articles this study is cited as a reason for better diver education, less denial. Perhaps most or all really had symptoms before flying?

(2) In the study you cited, for 382 FAD injuries it only says that half waited less than 24 hours, half longer. They compared this to 245 divers in a control group, with 76% waiting more than 24 hours, but no injuries in the 24% who didn't. Really, this article only references these studies slightly, no detail. One might take from these references tho, that of the 382 injured, perhaps all that took hits had symptoms before flying? Hard to say. Of the controls, no symptoms, and no hits while flying.

(3) In the third study cited there, there we no hits in the controls that did single dives to depths less than 60 ft when they flew 12 hours later, no hits among those with repetitive dive who waited more than 17 hours to fly.

From many articles I have read, based on DAN and USNavy studies, it seems to be more a matter of the diver admitting symptoms and not flying. Again and again, 12hours seems to be relatively safe for single dives, 18 for multiple - aside form the "unexpected hits."

More and more, it seems to be a problem of real diver education, based on facts, which is why I am stay the course here. Of the divers above who said "24 Hours," none have given reason other than their computers said so. Where is the education in that?

When one considers how many divers fly every year, it is really a very rare problem. Wearing a seat belt in the van ride to the airport is probably much more important than waiting more than 18 hours.

 

[miketsp]

(1) In the one study there, above the one you cited, they examined 278 injuries while diving. Over half of those had symptoms before flying and should have known better. It didn't say much more, but in other articles this study is cited as a reason for better diver education, less denial. Perhaps most or all really had symptoms before flying?

The big problem is that once you have made the dive and then get get to the airport and at check-in you feel a twinge - now was it due to lugging those big suitcases and dive bags around or is it something more serious? At that point, not getting on the plane may be quite complicated - no hotel reservation in a tourist area, no seats available on next flights for maybe a week.
I've had a couple of false alarms on dive trips where muscle pains turned out to be just that. Muscle strains from manhandling heavy bags & gear in and out of boats.

From the cited report:
Remember, there are no guarantees. We know from the DAN injury reports (and the
NZUA Reports), some divers do still get 'bent' after a PFSI of longer than 24 hrs.

One of the other reports puts the probability of an incident at around 1% after 18hours. If I dive & fly 6-7 times / year, I don't really consider that good enough.

I'd really rather wait the full 24 hours whenever possible to give time for a more reliable decision as to whether I should get on the plane or not.

 

[DandyDon]

The big problem is that once you have made the dive and then get get to the airport and at check-in you feel a twinge - now was it due to lugging those big suitcases and dive bags around or is it something more serious? At that point, not getting on the plane may be quite complicated - no hotel reservation in a tourist area, no seats available on next flights for maybe a week.
I've had a couple of false alarms on dive trips where muscle pains turned out to be just that. Muscle strains from manhandling heavy bags & gear in and out of boats.

From the cited report:
Remember, there are no guarantees. We know from the DAN injury reports (and the
NZUA Reports), some divers do still get 'bent' after a PFSI of longer than 24 hrs.

I don't think that symptoms that develope only after a trip to the airport, a good 12 hours after diving at least before going, would be a concern. I think they would show up in the first few hours in virtually all cases - altho we can ignore them so easily.

One of the other reports puts the probability of an incident at around 1% after 18hours. If I dive & fly 6-7 times / year, I don't really consider that good enough.

I'd really like a link! That sounds many times higher than my understanding.

I'd really rather wait the full 24 hours whenever possible to give time for a more reliable decision as to whether I should get on the plane or not.

That si a fine personal decision, just not one to be made blindly based on out of date habits.

 

[miketsp]

..snip..
I'd really like a link! That sounds many times higher than my understanding.
..snip..

I have a link to one older DAN report that puts the figure at 1% at 12 hours after a single dive of 60ft 55mins.

http://www.diversalertnetwork.org/medical/articles/article.asp?articleid=20

"You could decide to wait for 12 hours before your flight, and have an estimated 1 percent risk of Definite DCS and approximately 2 percent risk of Ambiguous DCS."

Of course this is a little artificial since I've never gone out in a boat to do a single dive and 60ft is pretty shallow to load the slow compartments.

And as the report itself mentions "All of our exposures at present are dry, resting dives under carefully monitored conditions. In no way should these results be construed as guidelines at this point. Wet, working dives may give very different results."

If you consider a 2 tank outing that is worth doing, that normally means at least one deeper dive. Throw in a bit of tribonucleation hauling heavy equipment around if the weather gets rough and your safety margins disappear.

I remember seeing something about a prediction considering more realistic conditions but I'm pretty sure it was in a mag which means a search at home when I get some time.