After dive : brief altitude commute

[hedonist222]

Hello everyone

I dive 5 dives over the weekend. 3 on day one, and 2 on day two.
Regular air. Not nitrox.

Generally the dives are scheduled with deepest first then shallower & shallower.
Surface interval between dives is between 60 to 75 minutes.
Usual first/deepeat dive is no more than 20m/60 ft.

Then surface interval.
Next two dives are generally shallower but no shallower than 10m/30ft.

Second day (two dives) is generally the same.


My question now is :

On day two, about 90 minutes after my second/lsst dive, I need to drive through and up the mountains.

The total distance is 30km/20 miles.

Elevation peaks at 2.5km/8200 feet.

Average altitude I guess would be about 1.8km/6000 feet.

Should I do this?

Drive the 30km/20mi of approx avg altitude of 1.8km/6000 feet.
Frankly, lve done this 5 times over the past 5 weekends.
Did not even think about it because I thought maximum altitude was 800 meters/2600 feet.

Till today. Today I mentioned the route to a fellow commuter and he casually mentioned that, although he's also done it, he's apprehensive about the altitude exposure.

That's when I decided to check altitude as I drive through and recorded the altitude as above.
What do you guys think?
I really appreciate your input.
Thank you.

 

[Jcp2]

You’ve not indicated how much time each dive lasts, but I’m assuming that they are long enough to load significant amount of nitrogen in your body. Based on limited data, DAN recommendation is 18 hours surface interval before flying commercially or ascending to 6000-8000 feet, as the atmospheric pressures are similar.

Flying After Diving: How Long Do Scuba Divers Have to Wait?

 

[Storker]

Our national tables give guidelines for ascending to altitude and flying after diving. For ascending to altitudes above 1250 msl you should follow the guidelines for flying after diving, and both your average and max altitude is above that.

Now, it's a mite complicated to translate the guidelines to something comparable to other tables since different tables use different pressure group designations and different slowest tissue compartments, but I'll try to translate our pressure group designations to bottom times for a single dive to 18m

15min bottom time: No waiting
20 min bottom time: Wait 2 hrs
30 min bottom time: Wait 5 hrs
35 min bottom time: Wait 7 hrs
40 min bottom time: Wait 9 hrs
45 min bottom time: Wait 11 hrs
50 min bottom time: Wait 13 hrs
55 min bottom time: Wait 14 hrs
60 min bottom time: Wait 16 hrs

You can calculate your final pressure group, compare it to your pressure group after a single dive with the bottom times I've quoted and get a half-decent idea about where you are. But be aware that your slow tissues will be more saturated after repetitive dives, so what you get here is a best case scenario.

Me, I'd probably avoid driving to those elevations you mention after a diving schedule like what you're talking about. At least if I don't have access to a tank of 100% to get me some sur-d first

 

[loosenit2]

Because you have not given us bottom times for your dives it is not possible to calculate. The attached guide is a handy reference to keep with you. It is the NOAA ascent to altitude table. You use the highest pressure group you have attained in the last 24 hours to determine your wait time to ascend. (note that NOAA pressure groups may be different than your agencies tables).

I have also attached an article that shows the process in more detail using the U.S. Navy Dive tables.

If you are like most divers this process is not easy to do if you are relying on a computer rather than calculating your PG using a table as computers don't give you a pressure group. If you are relying on a computer you have to default to the DAN/Agency recommended no-fly times unless your computer has an ascent to altitude feature, especially because you are peaking at 8200 ft which is a similar to the altitude in a cabin while flying (6000-8000 ft).

There are arguments that a driving ascent to altitude is the same as a decompression schedule and thus you decompress as you drive depending on the rate of ascent and the times involved. Others on the board may be able to calculate that for you; but this has not been systematically studied in any way.

I'm glad you have been ok doing this the last 5 weekends but there are a lot of factors that can affect DCS. Hydration, age, alcohol use etc. You may be fine 100 times and then one weekend go on a bender before diving or be dehydrated and that will be the time you have a problem.

 

[Searcaigh]

@Corrupted_Diver

Where are you diving on the east coast of UAE?

When we usually dive from Fujairah (FIMC) we take the highway over the mountains to join the Sharjah-Kalba Road. Maximum altitude of the road is 466m / 1,529ft.

If you are diving further north from Dibba and take the truck road over towards Ras Al Khaimah, I don't think the road is higher than about 270m / 886ft.

I have driven these roads hundreds of times over the past 22 years along with many other divers including those doing reasonably deep deco diving, (>70m), and I've never heard of anyone having DCS issues from driving over these routes.

Personally I usually dive Nitrox, (but for years only used air), and post dive, generally relax a bit, have lunch etc., before driving back to Dubai, although a few times I have driven straight home after dives as I've had to be back for some appointment, and never had issues or anyone traveling with me.

 

[hedonist222]

You’ve not indicated how much time each dive lasts, but I’m assuming that they are long enough to load significant amount of nitrogen in your body. Based on limited data, DAN recommendation is 18 hours surface interval before flying commercially or ascending to 6000-8000 feet, as the atmospheric pressures are similar.

Flying After Diving: How Long Do Scuba Divers Have to Wait?

Each dive is no more than 50 minutes.
Generally dive 1 is the deepest dive - so either 50 minutes or slightly less.

Our national tables give guidelines for ascending to altitude and flying after diving. For ascending to altitudes above 1250 msl you should follow the guidelines for flying after diving, and both your average and max altitude is above that.

Now, it's a mite complicated to translate the guidelines to something comparable to other tables since different tables use different pressure group designations and different slowest tissue compartments, but I'll try to translate our pressure group designations to bottom times for a single dive to 18m

15min bottom time: No waiting
20 min bottom time: Wait 2 hrs
30 min bottom time: Wait 5 hrs
35 min bottom time: Wait 7 hrs
40 min bottom time: Wait 9 hrs
45 min bottom time: Wait 11 hrs
50 min bottom time: Wait 13 hrs
55 min bottom time: Wait 14 hrs
60 min bottom time: Wait 16 hrs

You can calculate your final pressure group, compare it to your pressure group after a single dive with the bottom times I've quoted and get a half-decent idea about where you are. But be aware that your slow tissues will be more saturated after repetitive dives, so what you get here is a best case scenario.

Me, I'd probably avoid driving to those elevations you mention after a diving schedule like what you're talking about. At least if I don't have access to a tank of 100% to get me some sur-d first

Thank you

Because you have not given us bottom times for your dives it is not possible to calculate. The attached guide is a handy reference to keep with you. It is the NOAA ascent to altitude table. You use the highest pressure group you have attained in the last 24 hours to determine your wait time to ascend. (note that NOAA pressure groups may be different than your agencies tables).

I have also attached an article that shows the process in more detail using the U.S. Navy Dive tables.

If you are like most divers this process is not easy to do if you are relying on a computer rather than calculating your PG using a table as computers don't give you a pressure group. If you are relying on a computer you have to default to the DAN/Agency recommended no-fly times unless your computer has an ascent to altitude feature, especially because you are peaking at 8200 ft which is a similar to the altitude in a cabin while flying (6000-8000 ft).

There are arguments that a driving ascent to altitude is the same as a decompression schedule and thus you decompress as you drive depending on the rate of ascent and the times involved. Others on the board may be able to calculate that for you; but this has not been systematically studied in any way.

I'm glad you have been ok doing this the last 5 weekends but there are a lot of factors that can affect DCS. Hydration, age, alcohol use etc. You may be fine 100 times and then one weekend go on a bender before diving or be dehydrated and that will be the time you have a problem.

@Corrupted_Diver


Bottom time would be , roughly:

dive 1, day 1 : 50 mins
dive 2, day 1: 50 mins
dive 3, day 1: 50 mins
Dive 4, day 2: 50 mins
Dive 5, day 2: 50 mins

Some weekends, dive 1 and 3 are 20 minutes but generally as above.

Thank you. I realize the scenario is not as straightforward as tables.




Where are you diving on the east coast of UAE?

When we usually dive from Fujairah (FIMC) we take the highway over the mountains to join the Sharjah-Kalba Road. Maximum altitude of the road is 466m / 1,529ft.

If you are diving further north from Dibba and take the truck road over towards Ras Al Khaimah, I don't think the road is higher than about 270m / 886ft.

I have driven these roads hundreds of times over the past 22 years along with many other divers including those doing reasonably deep deco diving, (>70m), and I've never heard of anyone having DCS issues from driving over these routes.

Personally I usually dive Nitrox, (but for years only used air), and post dive, generally relax a bit, have lunch etc., before driving back to Dubai, although a few times I have driven straight home after dives as I've had to be back for some appointment, and never had issues or anyone traveling with me.

Alaqqah beach.

I am referring to the new Khor Fakkan highway. It opened up 2 months ago.
You get on 611 from Dubai, then right before the Aldhaid highway, you take the exist towards Khor Fakkan. AKA Khor Fakkan highway.

Ruler of Sharjah launches transport and heritage projects on emirate's east coast

 

[Searcaigh]

I am referring to the new Khor Fakkan highway. It opened up 2 months ago.

I'd check the altitude of the road with a GPS.

Looking at Google Earth very few of the mountains around there exceed 1,000m on the peaks, and I understand that the road uses tunnels therefore at a lower altitude.

I might look at using this road the next time I dive at Sandy Beach.

 

[hedonist222]

I'd check the altitude of the road with a GPS.

Looking at Google Earth very few of the mountains around there exceed 1,000m on the peaks, and I understand that the road uses tunnels therefore at a lower altitude.

I might look at using this road the next time I dive at Sandy Beach.

You're right, based on a few topographic maps online, those mountains don't speak over 1000 meters/ 3600 feet.

I used my car's built-in altitude gauge to observe.
To check if it was working, it did gradually come down from 2200 meters to 3 meters.
So I assumed it was working.
If it uses satellites to estimate altitude, it may have malfunctioning because I was in and out of tunnels - as tunnels impede satellite reception.

 

[hedonist222]

The misreading in altitude changes the whole dynamic of this thread.

I would now say that it peaks at 600meters / 2,000 feet.

Therefore I don't think I should be concerned about dcs from altitude.

Thanks everyone.

 

[Storker]

Therefore I don't think I should be concerned about dcs from altitude.

Whether or not you should be worried is something only you can decide, but to again quote our national tables:

Ascend to 250-600 msl
18m/50min: No waiting
15m/90min: Wait 3h
Higher pressure groups: Wait 7h

Ascend to 600-1000 msl
18m/45min: No waiting
18m/55min: Wait 3h
Higher pressure groups: Wait 9h

Ascend to 1000-1200 msl
18m/40min: No waiting
18m/50min: Wait 3h
Higher pressure groups: Wait 11h

If you ascend to no more than 600 msl, one single no-stop dive to 18m or more won't call for any waiting time before ascending, but if you stay shallower for a longer time you might be recommended to wait before ascending to just 250 msl. That means that your slower tissues come into play even for rather moderate ascents, and if you dive multiple dives, you'll load your slower tissues quite noticeably.

You may well be just fine and again, it's your own decision to make, but if you get a hit on your way home after a diving schedule like the one you're describing, it won't be "undeserved" according to our tables. Which, incidentally, are developed for both no-stop and staged stop diving and are the prescribed tables for commercial diving up here.

I'm not giving any recommendations here, just showing what the numbers are.