Bends possible while flying 24 hrs after a dive?

[Charlie99]

Don Burke once bubbled...
Are you guys sure that's oxygen in those bottles you've been breathing from?

Nitrogen.... check. Oxygen ...... check. huh! Instead of N2 + O2, the label says "N2O" ..........hmmmm. Maybe that explains the giggles.

 

[Dr Deco]

Dear Scuba Board Readers:

A Few More Words - - - :grad:

This has been one of our more “fiery” threads, and it I clear that there is not a uniformity of opinion with the FAD issue. We see this variance all the time where a difference of opinion exists in what are the best nutrients to eat (diet), the best forms of medical and health care, etc. Likewise, there can be differences of opinion with respect to numerous practices regarding diving. DAN is just one organization between many doing research in barophysiology and diving. It was neither the first, the largest, nor the best (each laboratory group would consider itself “the best.”) It is probably the largest connected with problems for recreational divers, the group for whom it was founded. To my knowledge, it sets its own research agenda, designs its own experiments, and conducts them with funds generated by its members. This commentary is not meant to cast aspersions on DAN, but to place it in relationship to other agencies.

Research

Many agencies will have research proposals prepared and reviewed by outside scientists. This will allow various viewpoints to be expressed and possibly something might be added that was not thought of by the original writers of the research plan. [In some cases, a research plan that is rejected might not be funded by the agency for its own scientists.] I am not aware that any research plans are sent for review by DAN. I personally have never been asked to comment on or review any and I do not consider myself “awash at sea” where barophysiology is concerned.

Laboratories have studied the FAD question at the US Air Force, and NASA. Others have collected data from the diving world, e.g., Dr Wienke. Depending on your chosen conditions, you might get different answers.

An Example

Here is a simple example from everyday life on the time before flying. Suppose you wished to make a study on how long you should wait before going to the airport to go to a destination. Suppose also that you have only a certain limit to spend on this study and you plan to send observers to, say, ten airports. You will find

• what ten airports will be representative of the country - or should you take the worst cases;
• what days should we observe the security lines
• what times of day
• when questioning travelers, do we include how far you live from the airport?

These will yield different “safe” arrival times.

FAD Experiments :doctor:

FAD studies are just as complicated – more so. You are limited to the length of the dive days. It is costly to hold people for one week of diving to see what happens in a controlled setting. (Only the DSAT/PADI study did that, and it was costly.) Thus, you are limited in the number of dives. What physical activity is done while at depth? What activity is performed at the surface? When preparing for the “flight”, what physical activity is factored into the protocol. All of these are nuclei-generating events. Do the researchers themselves believe in the hypothesis of kinetic nucleiogenesis? If so, what aspects do they accept and what do they reject?

Bottom Line

The issue will take time to sort out and no one group will probably be responsible for the answer. DAN is, after all, not the final arbiter in all things diving.

Dr Deco :doctor:

 

[SeaJay]

Dr Deco once bubbled...
DAN is, after all, not the final arbiter in all things diving.

I couldn't agree more. The diver who's life is on the line is, in his own little microchasm. There is no other authority.

But the US Navy seems to think that DAN is at least capable. They're the one footing the bill this time, and they could have chosen any agency to do the research.

If the powers that be at the FAA still say, "24 hours," and the US Navy still says "24 hours," PADI still says, "24 hours," NAUI still says, "24 hours," SSI still says, "24 hours," and YMCA still says, "24 hours"... But BRW says, "Naaaaah... 15 should be good," guess who I'm going to believe?

Think about this for a moment... Think about how much the US Navy would LOVE to be able to move their SEAL team all over the globe, just a few hours after diving... Think about what sort of strategic advantage that could have. Do you not think that they would do it, if they could? Do you not think that they'd skip the big bill that DAN is charging them to do the research? (The current study is paid for by the USN.)

...But once again, I'll point out that NONE of that matters... NONE of that was my point. I'll explain it for the third time, just in case y'all missed it the first two times:

You are recommending a practice which is unsupported by facts. I would recommend that you refrain until the facts are in.

To my knowledge, it sets its own research agenda, designs its own experiments, and conducts them with funds generated by its members.

Nope. US Navy this time. Do I sound like a broken record yet?

 

[Scuba]

Good points Dr Deco, as well as others.

One of the problems in using a study to derive generalized guidelines, such as the FAD one being conducted by DAN, is inherent in the limited representative pool and variables being considered from a much larger existing whole. Aside from the analytical methods used, as Dr Deco points out.

When this study is completed it will apparently result in new general guidelines which will receive wide circulation throughout the diving world. The specific parameters, subject constitution and analytical methods employed will receive a much narrower circulation. The specifics of the study generally have to be sought by interested parties as opposed to the mass media circulation of the new guidelines, which may or may not mention some of the defining parameters considered.

As useful as the general guidelines these studies provide are - and they are useful, of equal or even greater importance is for divers to at least become informed of some of the important determining factors utilized and considered in the study.

For example, subjects constitution, dive profiles, and environmental factors.

This knowledge is necessary in order for each diver to customize the generalized guidelines to him/her-self. When each diver compares his specific dive profile, number and sequence of dives, environmental conditions and physical condition to those sampled in deriving the guidelines, he will be in a position to more accurately apply the guidelines to himself, or deviate from such, whether in a conservative or liberal fashion. Obviously this requires a certain degree of subject knowledge.

Aside from what is probably a statistical anomoly, the person who may get DCS without prior diving, the conditions which elicit DCI are present before flying as some have pointed out. Some cases will result in hits wether the further stimulis of further decompression caused by flying is present or not. This is where each diver must use sound judgment in evaluating his condition, and not fall into the easy trap of fooling himself into believing that everything will be ok because he currently falls safely or close enough to the general guidelines. I'm repeating what others have already said here, but this is a point in which for one reason or another many rookies and old pro's easily succumb.

On a different note, Seajay, here is a particular definition of "fact" which I rather like. I think its applicable in this case.

from Webster's dictionary:

"a piece of information presented as having objective reality"

One quick question. What is the atmospheric pressure change from sea level to 8,000 ft altitute?

 

[Dr Deco]

Dear Scuba Board Readers:

Science and the Back Story :grad:

Thanks to SeaJay and Scuba for the comments. What I am trying to do in the FORUM is to illustrate the point that there are different ways of performing a study. The initial condition will determine to a large degree the result. What I try to do in the FORUM is to explain what might be unexplained unless the initial conditions are known.

As divers are becoming more knowledgeable, as individuals everywhere are becoming more knowledgeable, they are questioning the basis of research work where it impacts on their lives. I hope that this FORUM assists in that interpretation.

"The more you know, the longer you live.":mean:

Dr Deco :doctor:

 

[crispos]

OK, I refuse to let this thread die.....who thinks I get DCS with this air/dive/air plan:

Fly to San Andres Island, Colombia, from Toronto, 5 hour direct flight, arriving 4:30pm
Next morning, 9:30 Am, dive a 60 foot profile, for say, 40 minutes.

At 5:00 pm, get in a domestic airline plane (do they have pressurized cabins - probably an old 727), and fly to Bogota over the Sierra, about 1000 km away (2 hour flight time). Arrive at 7pm. Bogota is at 9000 ft above sea level. STAY at this altitude for one week.

Let's see someone pop that into their DCS computer program.

 

[BigJetDriver]

Just as a point of information, we should all realize that aircraft have lots of holes in them, some more than others. The only way we keep any of them pressurized is to pump more air INTO them than the amount leaking OUT of them.

With modern, new generation aircraft, one could literally stand in the aisle and fire a whole magazine of forty-five caliber rounds through the skin without causing any depressurization of the aircraft! Gert Frobe would NOT fly down the aisle and out through the hole, a la James Bond. (Please note: I am in NO way recommending this as an activity for anyone to try!!! I do practically live in these darn things!)

An older aircraft, like a B-727, has less capable air conditioning and pressurization units (which we call "packs") than the current generation of aircraft. The older aircraft will just naturally have more leaks in it. As a consequence, one will probably find a cabin altitude in the 8,000 ft range, possibly somewhat higher.

Just FYI. Cheers!

 

[pasley]

Not first hand information.

I dive occasionaly with a lady whose husband got bent while flying comercial after waiting 24 hours before flying. He no longer dives and most likely has some other issues.

Background: Diver had been bent more than once before and had taken several years off diving.

The Event: Trip to Hawaii, he snorkled while wife dived. Gave into temtation and did some dives. I don't recall how many or to what depth, but I believe them to have been shallow and all within limits. To their knowledge, as I remember it, he was not bent before he got on the plane. It is possible he had symptoms and was in denial, but given his previous history, I would guess he would be very sensitive to symptoms and get treated.

He was decompressed stateside. Spend about a week in a motel at sea level because he lives in the mountains. When he tried to go home, he became symptomatic. Hence a week at the sea.

Of course it is always possible that I am remembering it all wrong.

AS to the studies being done, I wonder about one thing - would the results of the study be different if done on divers who actually got wet, and were swimming about? Would the "exersise" in the water affect the outcome of the test and the amount of bubble formation? I don't know anythiing about science, but was just curious.

 

[Dr Deco]

Hello pasley:

There are various factors that will influence the outcome of a laboratory test of DCS risk. Simple immersion in the water will affect the blood flow and influence the outcome. In some tests, having the subjects lie at least partially recumbent compensates the lack of immersion.

Exercise is a large factor, both while on the bottom and follow pressure exposure. In all tests, the subjects are never asked to move heavy objects (e.g., scuba tanks) around the laboratory. This exercise would put you at risk above the tested limits of the table if you did it on your own.

Dr Deco :doctor:

 

[adder70]

BigJetDriver69 once bubbled...


With modern, new generation aircraft, one could literally stand in the aisle and fire a whole magazine of forty-five caliber rounds through the skin without causing any depressurization of the aircraft! Gert Frobe would NOT fly down the aisle and out through the hole, a la James Bond. (Please note: I am in NO way recommending this as an activity for anyone to try!!! I do practically live in these darn things!)

Just FYI. Cheers!

Darn! :croctears <returns gun to safe>
:getsome: :mgun: