Elevation dive and then backpacking?

[FishLovingStudent]

I am planning a trip to Pavilion Lake (elevation 820m), planning to do 2 dives around 30-80ft/40minutes each. Afterwards, with a 3+
hour surface interval, do a back packing trip to 1500m (400m in 3.5k trail).

Risking the bends?

 

[g2]

Looks beautiful!

The depth range of your dive plan is pretty vague...

Do this: plan the dives as if you were already at 1500m (this will require an altitude table or software, of course, not just an altitude-compensating computer).

Dive conservatively, stay well within your NDLs, and you should be good to go.

 

[John C. Ratliff]

FishLovingStudent,

Take a look at this website, which explains the physics and physiology of altitude diving.

8th Element Diving - Scuba Math - Altitude Diving: Understanding the Tables

Then take these dive tables, print them off, laminate them, and use them in the water to determine your Theoretical Depth at Altitude.

8th Element Diving - Scuba Math - Theoretical Depth at Altitude - Metric (Updated Version)

8th Element Diving - Scuba Math - Theoretical Depth at Altitude - Imperial (Updated Version)

Make your deeper dive first, and don't confuse metric and imperial units. Use the altitude of your hike rather than the altitude of the lake, as stated above too.

Now, you'll need to do a few things to know what your depth is at altitude. If you have a dive computer, set it to fresh water, and the altitude of the lake to get the correct depth. But unless the computer has these tables built into it, use the theoretical depth at altitude tables with regular decompression tables.

If you have an old-style Bourden tube depth gauge, then you'll need to make corrections to the depth shown on the dial. Many years ago, I wrote this information on the back of my circular slide rule (yes, it was that long ago) from information developed by Dr. Richard Bell, who was at that time writing about his altitude diving tables (he's where the above tables originated). Since these depth gauges are made for salt water, you also need to add a 3% correction to the depth shown with the altitude factor added.


Units for the Bourden tube depth gauge are in feet.

SeaRat

 

[guyharrisonphoto]

Be extra conservative as stated above. There are some studies suggesting that vigorous exercise after a dive can contribute to or aggravate DCS and DAN cautions against this. So, it's not just the altitude, but the post-dive exercise as well.

 

[boulderjohn]

Some things to consider.

1. Here is the NOAA ascent to altitude table. If you are in pressure group J with the U.S. Navy tables after your dive, you are good to go after about 3+ hours. Pressure group J in the Navy tables does not correspond to Pressure Group J in the PADI tables. It is a much more serious level of residual nitrogen.

2. DAN does not consider an altitude change of 2,000 feet or less to be problematic at all. You can do that immediately. You will be ascending about 2,200 feet--barely a cause for concern for an immediate ascent by their standards.

3. According to a reply to a question I sent to DAN, the danger of ascending to altitude varies according to your starting altitude. Ascending 2,000 feet from sea level is a bigger issue than ascending 2,000 feet from 3,000 feet.

4. A gradual ascent to altitude such as you will be doing has not been studied enough for anyone to draw conclusions, but it is obviously very different from the rapid ascent of a plane taking off. You will continue to off-gas as you ascent gradually.

It's your decision, but putting those 4 points together would lead me to believe I could do the hike safely.