Diving after flying

[Hawk]

Could it be that you had altitude training as part of your certification and are mistaking the procedures for diving at altitude after coming from a low elevation? There are waiting periods involved here. I am just guessing since we had high altitude training as part of our OW course. Here anything that you dive is considered high altitude and requires special considerations and conservative planning.




Later, Hawk.

 

[The Iceni]

Hi all,

I hope you don't mind me adding by tuppence-worth to this discussion.

I look at it like this. The pressure changes experienced in flying are the same as would be experienced during a brief period on the surface following an infinitely long stauration dive at about 10 feet and a subsequent return to that depth. This is because civilian aircraft cabins are pressurised to the equivalent of about 6-8,000 feet or 0.7 bar, I believe, giving approximately the same pressure drop.

Micronuclei are certain to form (particularly in the slower tissues) during the ascent, particularly in fast jets but, of course, the "victim" returns to his saturation depth after his flight. It therefore occurs to me that the longer the flight the more micro-nuclei form but on the other hand after an extended period all the bodies tissues will, of course, equalise with cabin pressure to a new, lower state of saturation.

Not forgetting the problems of dehydration, fatigue, and hypoglycaemia etc. this suggests to me that long-haul flights should be safer than short flights in an unpressurised light aircraft, the most hazardous flights being middle distance.

I suspect G forces must also play their part.

For what its worth diving following a flight could be looked upon as in-water recompression but I certainly think one would be very, very wise to delay one's diving after flying. The question is for how long?

On the other hand, I have often wondered whether Jet-lag was a form of cerbral DCI?

I am not pretending I know the answers here, only asking once again.


Paul

 

[Liquid]

Hm.

Ok, First I'm no doctor, and never studied this specific aspect thoroughly, but I am an experienced instructor, and from my experience, and knowledge-

There is absolutly no reason you shouldn't dive after a flight, if you feel completly ok (meaning, that you ate and drank well on the flight and are not tiered).

You can actualy sky-dive into a dive (and I know people that do it).

As far as I know, in a certain way, diving after flying is safer than diving after not flying, for the reason, that becouse you were at lower pressure, you have less dissolved niterogen in the blood than you would normaly have.

The issue reminds me a certain question I ask my students, after I teach than that if they dive in altitudes, they need to use special tables- I ask them what happens if they dive at the dead sea (altitude of about minus 400 meters), should they use a different table? Usualy they mix up a bit, but through my leading they come to the answer that you dont, since using the same regular tables there is safer than usual. Only problem, is u need about 40 lbs more than in sea.

Another matter here is the pressures difference:
decreasing pressure from 1 bar to 0.7 bar is not enough to pose any kind of threat, the differencial is just to small.

I'll have to mention here, that I have never before though about the bubble nuclei formed in the flight, and that I need to give this matter some further thought, but for the time being, my opinion is that the amout of niterogen in the blood is already reduced enough to more than compensate for the formed nuclei.

 

[Lost Yooper]

Well, I wouldn't go sky diving afterwards, but that's about it. I've been told that the cabins are pressurized to 3000' -- maybe I'm wrong.

I wouldn't personally worry about it unless I had a precondition that would subject me to getting bent in the first place (PFO, shunt, overweight, bad dive, bad deco profile/precedures, etc.).

I really liked your answer, LD.

Take care.

Mike

 

[roakey]

Originally posted by Lost Yooper
Well, I wouldn't go sky diving afterwards, but that's about it. I've been told that the cabins are pressurized to 3000' -- maybe I'm wrong.

Mike,

I flew with a guy that had an altimeter on his watch and set it correctly before takeoff. We saw 6-8k feet throughout the flight, except near the end where they slowly pressurized the cabin to ambient so the descent wouldn't be hard on folks.

Roak

Ps. United flight from Colorado Springs (6k') to San Francisco (0'). Sample of one, so take it for what it's worth

 

[donooo]

This is not a clear thought but,,,,,,,, while looking at driving to altitude after diving I wandered in to the Cochran Commander dive computer. It is always on and collecting data on atmospheric pressure. If you were to fly/drive from altitude to sea level to dive with a friend that also had a Cochran the data would be different at the start. This might be Centrall Wahington to Seattle or Yuma to SD. It is keeping track of pressure /time relationships. If your computer thinks it is different, then your body might also. This seemed the best computer for looking at flying /driving to altitude problems.

O, and I read an article also that said not to dive after flying. Might of been a past Dive Training. Might of been the article on altitude diving.

good luck don O

 

[Deepy]

If you fly, there is a greater risk of emboly. Some people died after long flights. So far as I know the ground for this are the bubbles in the tissues of your leg if you are sitting for hours. This may have an impact on diving after flying too.

 

[BillP]

Hi Deepy:

I believe what you are referring to is a pulmonary embolus due to a deep venous thrombosis. When your legs are dependent (hanging down) and still for long periods- like on a long flight- the blood in the veins can clot. Those blood clots can break off and travel to your lungs obstructing blood vessels. It is unrelated to gas bubbles or diving.

For more on the topic, go to:

http://ohp.ksc.nasa.gov/alerts/dvt.html

HTH,

Bill

 

[The Iceni]

Well spotted roakey!

Civilian cabin pressure is indeed set between 6-8K feet, not 16K as I originally posted (In fact the pp O2 at an altitudes above 16k feet is too hypoxic to support conciousness and portable oxygen is needed by mountaineers).

I have now corrected the error but would still appreciate some views on my hypothesis about jet lag. Is there any evidence at all from aviation/space medicine on the formation of bubbles/micronucleii during a longish aircraft flight?

 

[Dr Deco]

Dear Paul:

I would be very surprised if 8,000 feet of altitude would produce tissue bubbles. Not only is the pressure change small, but also the passengers are seated. It has been known since the Second World War that the seated posture is protective against DCS in comparison to standing. This would give an added measure of resistance to microbubble formation.

As far as I know, jet lag is a phenomenon encountered when several time zones are crossed and the biorhythm is shifted. If one makes a long flight within a time zone (or two), such as a flight from New York to Rio de Janeiro, the jet lag is not encountered.

Dr Deco :doctor: