Driving up the Mountain?

[ScubaSky]

I was taught and teach my students that they should not dive at a certain altitude, then drive their car over any summits or mountains that are at a higher altitude, in order to avoid decompression Sickness.

Now I understand the theory of nitrogen coming out of solution due to decrease pressure during the altitude climb. But if my rough calculations are correct it takes appox. 2000 ft. of Air to equal just over 2 ft. of water. if you follow the 30 ft. per minute ascent rate that means you would have to climb or swim the distances faster than 4 seconds?

I am guessing that there is something that I am Missing in the whole picture of this caution.

 

[Dr Deco]

Hi ScubaSky:

This is sort of the “shadow world” of diving. Not a lot of study has gone into this in the laboratory. If someone where to ask me, which I guess you did, I would respond by saying that a large part of the difference between diving and crossing the mountains involves this question of microbubbles.

In the diving situation, the nuclei are reduced (usually) during the buoyant, in-water phase of the dive. These microbubbles are regenerated (or enlarged) when you climb onto the boat. An individual who is completing the diving for the day will be packing gear and such and will possibly generate even more microbubbles. If we now couple that with an ascent over the mountain (or in an airplane), these nuclei can expand even more (by Boyle’s law expansion), the Laplace pressure (from surface tension) is reduced more when the bubble expands, more nitrogen diffuses in and a possible case of DCS results.

Thus our difference lies in nuclei generation and in a reduction in pressure. One must consider the two phases (dissolve nitrogen and gaseous nitrogen) to view the problem. A simple Haldane (all nitrogen in the dissolved phase) will not provide the mechanism.

Dr Deco :doctor:

 

[ScubaSky]

If I understand you correctly, the main concern is not in the disolved nitrogen coming out of solution. But the Micro bubbles becoming large enough to cause problems through out the body due to the reduced pressure at altitude?

These microbubbles are also the concern when exerting your self or excercising after a dive?

 

[Dr Deco]

ScubaSky:

It is a little of each. The nitrgen does come out of solution but it enters the bubbles formed by the diver during the post-dive period.

This happen on level ground (exertion) but it can be made worse by an ascent to altitude.

Dr D

 

[mania]

As far as I know inside the plane the atmosphere pressure is equal to 2000 meters above the sea level. So if I have to have a 24 hours break between the last dive and the flight the similar rule should apply to going to the mountains of at least such altitude. But I'm not sure if I think properly
Mania

 

[DeepTechScuba]

The NOAA Diving Manual has an Ascent To Altitude After Diving chart. It lists altitudes and the amount of time you must wait, given your U.S. Navy repetitive dive letter group, before you may safely ascend to that altitude.

 

[MikeFerrara]

DeepTechScuba once bubbled...
The NOAA Diving Manual has an Ascent To Altitude After Diving chart. It lists altitudes and the amount of time you must wait, given your U.S. Navy repetitive dive letter group, before you may safely ascend to that altitude.

Yes. This is something that BRW addresses pretty well in his book. In a Haldanian model it's a matter of not pushing any compartment beyond it's critical tension (M value). Of course this only addresses disolved gas.

 

[DeepTechScuba]

Dr Deco, it doesn't seem like you have ever crossed any mountains after diving. Is that because there are no mountains in Texas?

 

[Dr Deco]

I simply have never crossed any mountains shortly following a dive. This was true even when I lived in Seattle. It can get you into trouble (crossing, that is, not living in Seattle).

Dr D
=-)

 

[grouchyturtle]

If crossing a mounatain, how much af a difference in altitude does it take before there is any real risk?

I did a bike trip a few years ago out by ScubaSky. And could see how crossing one of those mountain passes out there would present a risk.

But is for example: diving at Dutch in PA and then driving to say Scranton, going to be that much of a greater risk?

Also, where can I find a copy of that Ascent To Altitude After Diving chart?