Driving over altitude after diving - best practices?

[Mateo1147]

I have been lurking very intently on this thread. I regularly dive two or three dives in a day and drive over Stevens pass, elev. 4,050 ish' to get home with no I'll effects. My home is at 2,650' here in beautiful Eastern Washington. The one time nitrogen got the better of me I knew before getting above 200'. It would be nice to see more definative information about this topic.

[CaptnJack]

For instance, if I go from 6000ft to 13000ft prior to the dive in the space of, say, 4 hours, what is my residual nitrogen loading? Specifically, how should I adjust my dive plan to compensate?

Nothing IMO. On the actual dive your tissue will have a tiny amount of "pre-loaded" inert gas. That is just before you descend you will still have a slight overpressure gradient in your longer tissues and this in theory could reduce your allowable no-deco time. But in practice it won't make a bit of difference. 4 hours is actually a fairly long surface interval after all. All of your controlling tissues will be at ambient and you can just plan the dive as you wish for the applicable altitude.

[60south]

I'll be returning to Colorado later this summer. This is a bummer, of course, because the diving there is basically mud puddles.

However, I am interested in some rather extreme altitude diving (13000ft +). My concern is not so much ascending after the dive, rather acclimatization beforehand.

For instance, if I go from 6000ft to 13000ft prior to the dive in the space of, say, 4 hours, what is my residual nitrogen loading? Specifically, how should I adjust my dive plan to compensate?

Anyone have any insight into this kind of scenario?

[CaptnJack]

It's not really possible to do a "Navy" Profile at Edmonds. Its just not. For one you'd need to swim out on the surface to the furthest point of the reef, drop down, stay out there, and then do a 60 fpm ascent from that max depth (which I don't even think is 40ft). Nobody does that and forcing an actual Edmonds profile into the navy tables is inappropriate.

I would have no qualms about flying after diving at Edmonds, nevermind driving over the pass which is a couple thousand feet lower. I flew after this 32% profile without any hesitation too, 1:40 mins at an average depth of 85ft on 32%. Deco is not rocket science, and flying or driving to altitude after diving is just another form of deco.

Ginnie profile.pdf

(46.91 KiB) Downloaded 50 times

Of course people have been bent after the most benign profiles without any altitude at all, so the only way to absolutely be sure you won't ever get bent is to avoid diving altogether. That said, getting bent is not really that death defying, its basically just another type of sports injury and fortunately its generally 100% fixable.

[Gregp]

Here's a theoretical dive the would violate a safe ascent to 3000ft after diving at sea level using the USN tables (rev 6):

40' dive for 60 min gives a G repetitive group.
Followed by a SI of 60 min gives a F repetitive group.
If we did a following dive at 40', this give a Residual Nitrogen Time (RNT) of 55 min.

40' dive for 40 min gives a total of 95 mins (40+55=95), which is a J repetitive group.
J is higher than G so we calculate based on J.
If we want to ascend to 3000 ft, table 9-6 tells us we need to wait 2hr,25min.

If the second dive was instead 40' for 60 min, this would be a total of 115 mins (60+55=115), which is a L repetitive group.
L is higher than G so we calculate based on L.
If we want to ascend to 3000 ft, table 9-6 tells us we need to wait 5hr,2min.

The USN tables indicate that it's possible that a diver at EUP could get bent going over the snoqualmie pass with an elevation of 3000' if they don't wait long enough. Sure, the slow ascent may help decrease the likelihood of DCS, but the risk could still be there especially if the diver had a runaway ascent or some other circumstances that increases their likelihood of getting "hit".

[Gregp]

Dr. Edmond Kay MD has done a nice job of consolidating and simplifying the information. Though for some of us who want to drive over passes at specific elevations following diving, it leaves some unanswered questions.

I completed a few literature searches in hyperbaric medicine with ascent to altitude and there are some studies where this type of information is available. Many of the studies are consolidated and explained in Flying After Recreational Diving Workshop Proceedings May 2, 2002 by Divers Alert Network. If you are a DAN member, you can obtain a copy for reading.

In addition, the US Navy Diving Manual 2008 rev. 6, has a section (Chapter 9, Section 14) on "Ascent To Altitude After Diving/Flying After Diving." You can google it or see the pertinent pages attached. Use the USN diving tables (9-7 and 9-8) in the manual to calculate your group designation after your dives, and then use table 9-6 to determine the required surface interval before ascending. Note that you will use your highest repetitive group designation from the previous 24-hr period to determine the wait period, and don't forget to add the residual nitrogen time on as needed.

I would be interested in seeing data from those who dive and drive up to altitude and how that correlates with the USN dive table recommendations. If anyone has information on their dive profiles, residual groups, ascent amount, surface intervals, and any outcomes, please share it. Note that the USN manual of revision 6 is a little different than revision 5, so if you are posting your profile utilizing this, please specify the revision you're using.

Disclaimer: by no means does this information make any guarantees that you will not get bent following the USN guidelines. Please be cautious and obtain the correct education before ascending to altitude following diving.

[Waynne Fowler]

I don't think anyone can give you a definitive answer. The best that can be done is to tell you anecdotal stories and give opinions.
We all know or know of, folks that have done the trip/ or we've done similar trips ourselves *I have without incident, dove and gone over several passes on many different occasions*
There's probably too many variables to take into account. Can you do it... of course you can. You may be fine, you may not. One day you may do it without a problem, the next day you may get bent.
What are the odd's??? No one knows for sure. Even a guess is..... well..... just a guess.

[LCF]

Well, if you are at 30 feet, 17%, if my math is right, would be about 10 feet. If you can't safely go up ten feet in three hours, you had problems long before you got there.

[60south]

But if you think of the entire atmosphere of the planet as being the same as 33 feet of salt water, driving over a 5,000' pass is kind of like ascending an additional 2 or 3 feet.

Ah geeze. Now you made me do it. 5.6 ft.

pressure @ sea level (14.7 psi) - 5000ft (12.2 psi) = 2.5 psi.
ratio: 2.5/14.7 = 0.17 or 17%. 0.17 * 33 ft = 5.6 ft.

But the percentage pressure change is a better measure than the depth difference. If you think of ascending the same distance during a dive, from, say, from 66 fsw to 60 fsw, your pressure difference (absolute) is only only about 6%. So as your total pressure decreases, the percentage change becomes greater -- which is, of course, why deco stops are closer together as you approach the surface.

[Joshua Smith]

It's a funny puzzle. But if you think of the entire atmosphere of the planet as being the same as 33 feet of salt water, driving over a 5,000' pass is kind of like ascending an additional 2 or 3 feet. (too lazy to do the real math, but I'm sure someone will correct me even though I'm close enough). I tend to think that if that kind of pressure change is enough to cause a hit, you were probably already bent, or really close to it. Just my opinion. If you want to be really safe, wait 24 hours before climbing a flight of stairs. And if you want to be ultra-safe, don't dive.

[DanClements]

We dive with some folks out of tri-cities, and they regularly head back over Stevens or Snoqualomie after diving on this side of the Cascades without waiting. After packing up and driving it is probably two hours after exiting the water.

In Baja, we regularly drive from Cabo Pulmo to La Paz over a 3,500' pass without incident. Depth max about 60' on transit day. Again, after packing up and driving it is about a two hour surface interval. Dive computer indicates we are OK (Galileo Sol).

On the other hand, three years ago after a great few days at Rendezvous on Barkley Sound one of our Canadian friends got bent on his trip back to Victoria after driving over a low (> 2,000') pass and had to be flown (helicopter) to Vancouver for treatment. He figured he had a 3.5-4 hour surface interval.

Probably a lot of variables, but a two hour lag to 3,500' after two dives to a maximum depth of about 60' has worked out for us. That would work for a Snoqualomie to Blewett approach to Leavenworth.

[LCF]

I have to say that I seriously wonder about the diagnosis of DCS in someone who had been diving at Edmonds. The problem with DCS is that there is no definitive diagnostic test for it -- it is always diagnosed from symptoms and history. And it is almost always better to have a liberal view of what might be DCS and treat where unnecessary, than to dismiss symptoms and not treat what is actually DCS.

[oldsalt]

A local dive magazine posted an article in which a diver from across the mountains got bent returning home after two dives at EUP. This surprised me since Edmonds is a shallow dive, essentially an extended safety stop. The precise answer does not exist since personal differences and complicating factors abound. Everyone I know who got bent had either dived the identical profile before without problem or was diving with a partner who didn't experience difficulties. Precautions are usually simple, if inconvenient.
-Curt

[Joshua Smith]

Personally, I pay no attention to altitude gain after diving- including flying. One exception for me might be the "week of 3 dives a day using a liberal computer algorithm," because those folks seem to be the ones who get bent when they fly.

[60south]

After doing a lot of diving in Colorado, perhaps I'm just more cautious. There you can go from 5000' to 11000' within an hour.

I think my car got DCS a few times...

[YellowEye]

Hi
I had a co-worker who used to dive, who said he got bent by driving over the pass after diving.
I don't know the details of his profile though, other than it was after some dives in the San Juans. I think they were clamming. I'd suggest playing it a bit safe!

[CaptnJack]

This question has reliably come up year after year (here and on places like SB) for at least the past decade. So far I don't recall anyone getting bent who wasn't already dicey/symptomatic before they even started driving.

I'd drive over the pass without hesitation, the ascent rate is ridiculously slow and you aren't even staying at altitude. I would think a little harder about hiking to Camp Muir immediately after diving. If you do enough deco you can definitely fly after diving (8,000ft cabin pressure or even less depending on the plane).

[coulterboy]

When I dove the Silo, I drove back immediately after the dry Silo tour which we did about an hour after the dive. Got back to Edmonds a few hours without any issues.

[Desert Diver]

I don't pretend to know the truth and I'm not very conservative about such things but remember that you are completely saturated at 14.7 lb pressure and at 4000 feet you are at 12.7 lb, only 86% of the pressure at sea level. Probably won't make a difference. Anybody know of any cases where the symptoms started on a pass?

[LCF]

There is no science behind it, but I more or less take Jeremy's approach.

It takes me an hour to drive from my house to the top of Snoqualmie Pass, at 3000 feet. It took me at least a half hour to 45 minutes to get out of the water, debrief the dive, get out of all the gear and get it in the car. It's a minimum of a half hour from the dive site to my house, and even dumping gear on the driveway, it will take me a minimum of a half hour at the house before I'm on the road (usually more than that). In practice, moving as fast as possible, it would be probably three hours from the water's edge to 3000 feet. That is a VERY slow ascent rate! So not only is the pressure change minimal, but it's being done very slowly -- as opposed to an airplane, which goes from sea level to 8000 feet in a couple of minutes.

I simply do not worry about drives over our mountains. I might think a little harder about driving to the top of Haleakala if I'd done a couple of very deep dives in the morning.

[Jeremy]

"But I came out clean!" I'd think just as my eyes blew up and my blood boiled...

[60south]

We know 33ft is the equivalent of 1atm. How many feet of water is 4000 ft equivalent to? Around four feet of water. If you are going to get bent by the equivalent of a four foot change in water depth you were doing some far more aggressive deco diving than I've ever done. Drive over the pass worry free imo..

Careful. By that reasoning, if I haven't been diving, I should be able to drive over a pass from sea level (1 atm) to outer space (0 atm) with no ill effects, so long as I stay within the NDLs for a 1 atm pressure difference.

Just sayin'.

[Jeremy]

If you come out of the water clean you can fly or drive over a pass immediately imo..

I plan to dive Chelan, the Missile Silo, and Clear Lake this weekend with no regard for the passes. I'll report back if I get bent.

I hope you don't find your opinion is wrong

Thanks bro, I need all the sympathy I can get...

So the guideline above says after a single stress free dive wait eight hours before going over Stevens Pass (as an example). We know 33ft is the equivalent of 1atm. How many feet of water is 4000 ft equivalent to? Around four feet of water. If you are going to get bent by the equivalent of a four foot change in water depth you were doing some far more aggressive deco diving than I've ever done. Drive over the pass worry free imo..

(BTW, this assumes you are doing deep stops along a min-deco ascent profile...not the PADI 60 ft per minute from 130 and do a 3 min safety stop at 15 ft aka the "bend and mend" method)

[Desert Diver]

If you come out of the water clean you can fly or drive over a pass immediately imo..

I plan to dive Chelan, the Missile Silo, and Clear Lake this weekend with no regard for the passes. I'll report back if I get bent.

I hope you don't find your opinion is wrong

[Jeremy]

If you come out of the water clean you can fly or drive over a pass immediately imo..

I plan to dive Chelan, the Missile Silo, and Clear Lake this weekend with no regard for the passes. I'll report back if I get bent.