Mountain pass after diving

[TSandM]

This is an analogous question to the one about flying, but there probably aren't any data on it.

I drive to work over a mountain pass that reaches a peak elevation of 3022 feet. I have been using the 24 hour rule for multiple dives/multiple days, which has left me out of some good days of diving. Cabin pressures in airplanes, though, are significantly higher -- I believe about 8,000 feet. Are there any data that would permit me to shorten my interval, since my elevation gain is so much less?

 

[Diver0001]

There is a digital copy of the US Navy divers' handbook available on the internet. Aside from being an interesting read (in a geek diver kind of way) there are lots of little tid-bits in there about stuff like this. IIRC you'll be able to find a table (linked to the US Navy dive planner, I think) showing minimum surface intervals before ascending to various altitudes. Since you're doing your planning on a different table you can start with the Z group for working out your surface intervals.

Also, keep in mind that these tables were not meant for the cross-section individual and pad accordingly.

R..

 

[JeffG]

This is an analogous question to the one about flying, but there probably aren't any data on it.

I drive to work over a mountain pass that reaches a peak elevation of 3022 feet. I have been using the 24 hour rule for multiple dives/multiple days, which has left me out of some good days of diving. Cabin pressures in airplanes, though, are significantly higher -- I believe about 8,000 feet. Are there any data that would permit me to shorten my interval, since my elevation gain is so much less?

Yes, much better to wait 24 hrs than die a gross horrible death by being bent while driving over a 3000ft pass.

 

[scstjohn]

The following Hyperlink takes you to the altitude table we use in the Sierra Nevadas:

http://www.sierradive.com/Altitude.htm

Assuming that you are starting near sea level, going up to the 3,022 ft pass would add 8 pressure groups to your last dive. (2 pressure groups per 1000 feet, and conservatively use 4000 ft elevation for the pass).

 

[cal776]

I'd like to follow up with my own question.

My wife and I are considering diving with Parguera Divers in Puerto Rico next weekend. I have been told that on the drive back to San Juan the highest elevation is approximately 2000 feet. We would reach that elevation briefly approximately three hours after we finish the second of two dives (our only two dives on the trip). Can we safely make this drive without a significant risk of decompression sickness?

I should add that I realize it would be much safer to extend our interval before the return drive. However, we will only be in Puerto Rico for a few days and we will be hard pressed to see all the sights we would like to see even if we skip the diving.

 

[DandyDon]

I am sure he meant this this as a joke...

Yes, much better to wait 24 hrs than die a gross horrible death by being bent while driving over a 3000ft pass.

Being conservative and safe is certainly the way to go - but I have lived all of my long life at 3300 feet. You don't get nosebleeds here. With conservative diving, good hydration, longer safety stops, etc. there is little reason why you could not follow the guidelines given above.

 

[JeffG]

I am sure he meant this this as a joke...

Actually, I was being sarcastic.

 

[pasley]

Yes, much better to wait 24 hrs than die a gross horrible death by being bent while driving over a 3000ft pass.

I sense a tad bit of skepticism that it could happen.

Allow me to share a personal experience (first person account):

Two days after diving (40 feet, average depth 20 for 30 min, 2 hr surface interval, 40 feet average depth 15 feet, 30 minutes) I drove to Hemet California, elevation 1,400 feet from sea level to attend a meeting. The drive taking about just under 2 hours. I immediately turned around and in considerable discomfort drove back to sea level and the nearest decompression chamber. Two rides in the chamber over the next two days.

So yes, it can happen. It is possible to get bent (or at least aggravate the symptoms) from driving to altitude. Does it happen often? Probably not. Were there other factors? Yes almost certainly - I had been bent the week before and was not yet healed enough to go to that altitude. So this was really a continuation of the first bend. But the point is 1,400 feet of elevation was enough to trigger a reoccurrence that was actually more severe than the first. (And no in the 4 years and 200 dives since then I have not been bent again). In this case some minor nerve damage did result.

Second hand story: Dive buddies husband (who no longer dives) was bent. Unable to return to his home at 3,000 feet elevation for over 2 weeks. Every time he tried he had to turn around due to pain (got bent). Had to stay in a seaside motel.

Bottom line, can you get bent from a drive to 3,000? IMHO yes it is possible. Is it likely? IMHO no it is not. Should you leave the water and start your trip immediately? No, I would not recommend it. I would suggest it is probably a good idea to relax, enjoy a meal and some good conversation for a few hours before starting the trip over the hill. Give the body time to off gas for a while before starting the trip. Then I would observe the speed limit and not try to make the drive up the hill a speed contest. The longer you wait the better. I would also not dive aggressively and push the limits either with the slower drive allowing a better off gassing opportunity. The move nitrogen loading (or aggressive the diving) the longer I would suggest waiting. No flying (same as driving to 7,000- 8,000 feet) for 24 hours after diving is the recommended guideline from DAN. As has already been discussed you are changing pressure groups, so some caution is in order.

Disclaimer: Not a doctor, medically qualified person or even dive professional. The above is IMHO. Your results may vary.

 

[DandyDon]

Pasley, your contribution are generally some of the best on this board, but I question your summary here...

Bottom line, can you get bent from a drive to 3,000? IMHO yes.

In your case, you got bent the week before, aggravated that by diving again a week later - which is usually avoided in such cases isn't it, then it all peaked with your elevation change.

In the plan of the original poster, I really think that a diver would have to be already bent before ascending to elevation to take a hit on the ascent - as you were.

 

[TSandM]

Well, thank everybody for the information. As with everything else in this sport, it appears prudent to be cautious, but given the dives I do, I probably do not need to wait a full 24 hours to drive the pass, which means diving the afternoon before I leave is possible, which is what I wanted to figure out.