This is what I was asking. Chamber tests, and not in the Manual. Thanks.
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Elevation after diving
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Your snark is ignored.
We drive to an elevation of ~850m after diving- every other weekend. Have two instances of high elevation, the first about half an hour from diving sites, the second after two hours, like in the chart attached.
Been doing this trip for about 35 years: sometimes after decompression dives although in the last years we seldom do deco dives.
I was once concerned about it, was driving alone after a long series of dives. In order not to get sleepy in the long ride, I opened the window and had the hot desert wind on my face. At some point began to feel my skin itching like crawling with ants, I thought that I finally got a chance to know the chamber from the inside, but after closing the window it went away
So, I tried to read about driving to high altitude after diving and couldn't find much at the time. I did find some medical paper published from Jordan which reviewed several cases of DCS: local divers who drove after diving from Aqaba to Aman. The road climbs up to 1800 meters, and several decompression sickness cases were reported over the years. but I suspect this is quite rare though.
Been doing this trip for about 35 years: sometimes after decompression dives although in the last years we seldom do deco dives.
I was once concerned about it, was driving alone after a long series of dives. In order not to get sleepy in the long ride, I opened the window and had the hot desert wind on my face. At some point began to feel my skin itching like crawling with ants, I thought that I finally got a chance to know the chamber from the inside, but after closing the window it went away
So, I tried to read about driving to high altitude after diving and couldn't find much at the time. I did find some medical paper published from Jordan which reviewed several cases of DCS: local divers who drove after diving from Aqaba to Aman. The road climbs up to 1800 meters, and several decompression sickness cases were reported over the years. but I suspect this is quite rare though.
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That is correct. Last dive 5pm the day prior. The next day we will be starting at sea level, driving north in the morning leaving at 8am then staying at that altitude (~2200 ft or 700 meters) for most of the day.
I imagine it could take us one to one and a half hours to reach our destination which is something I didn’t give a lot of thought about until someone here mentioned it. With traffic being a little slow it could take some time to get there and that ascent won’t be too fast.
I’m reading now how these standards were made and when I compare to the navy tables they are pretty far apart. With Navy’s worst case nitrogen loading requiring only 9ish hours of off gassing to ascend to 2000 feet if I read that correctly.
Kendall Raine
Contributor
In the 7A version (April 2018) a Z group repet requires 7:29 hours before going to 2000 feet. Assumes no Exceptional Exposure. Repet group designation applies to highest repet group in last 24 hours. Other Notes apply.
MonkeyBubbles
Registered
There’s been some really informative comments in this thread, hopefully someone can help me figure out a scenario:
Scenario: I have accommodations at approx 1800 ft elevation, which is about a 15 minute drive away from the dive boats at sea level (Kona). I am planning a series of dives over a few days, probably 3-6 dives, 32%EAN. Looking through the Navy Dive Tables, I think this should be feasible for the morning dives, easy enough to do 2+ hours afternoon surface interval, which meets the recs for up to Group K . The dives that concern me a bit are the night dives, after which it would be great to just go straight home. The night dives will be pretty passive, though. Very low work, just passively hanging out around 50fsw breathing 32%EAN.
Most of the literature I’ve found addresses diving AT elevation, meaning that you surface at elevation and thus use adjusted dive depths, OR it discusses only ascending to elevation AFTER diving. I haven’t been able to find anything that addresses DESCENDING from elevation to then dive, and the RE-ASCENDING after, where I assume some acclimitization and more rapid off-gassing will occur.
How should I handle this scenario?
Scenario: I have accommodations at approx 1800 ft elevation, which is about a 15 minute drive away from the dive boats at sea level (Kona). I am planning a series of dives over a few days, probably 3-6 dives, 32%EAN. Looking through the Navy Dive Tables, I think this should be feasible for the morning dives, easy enough to do 2+ hours afternoon surface interval, which meets the recs for up to Group K . The dives that concern me a bit are the night dives, after which it would be great to just go straight home. The night dives will be pretty passive, though. Very low work, just passively hanging out around 50fsw breathing 32%EAN.
Most of the literature I’ve found addresses diving AT elevation, meaning that you surface at elevation and thus use adjusted dive depths, OR it discusses only ascending to elevation AFTER diving. I haven’t been able to find anything that addresses DESCENDING from elevation to then dive, and the RE-ASCENDING after, where I assume some acclimitization and more rapid off-gassing will occur.
How should I handle this scenario?
The conservative approach is to ignore the fact you first descended from altitude. After being at sea level all day, any slight advantage you would have had coming from altitude is gone from the tissue compartments that will control a recreational dive.
I suspect that will be doable. With an equivalent depth of 38 fsw on the night dive, there's a fair bit of room before exceeding Group K.
There is no problem ascending to 1800 ft after diving, as contrary to flying a commercial airliner that pressure the cabin to ~8000 ft. Enjoy your dives.
MonkeyBubbles
Registered
Ignoring the minor potential benefit of the descent makes sense. From a conservative perspective, ignoring any benefit in decreased nitrogen loading due to sleeping at altitude for the next day’s dives also makes sense.
I got some feedback from local divers who live above 1000 ft and dive regularly. Sounds like the consensus is stay below 2000 ft and don’t worry about it.
I also did some math looking at the comparative rate of ascent/pressure change of ascending from two context-relevant ascent scenarios:
A) Ascent from a 15 ft safety stop (delta=~46 kPa; >60 ft/min= >184kPa/min), compared to:
B) 15 minute car ride to 2000 ft (delta= ~7 kPa, 133 ft/min= 0.47kPa/min). And this is ignoring the built in minimum 45 min surface interval getting back to the docks and unloading, etc.
All of this makes me question what the additional variables are that factored into the creation of these Navy table values?
I got some feedback from local divers who live above 1000 ft and dive regularly. Sounds like the consensus is stay below 2000 ft and don’t worry about it.
I also did some math looking at the comparative rate of ascent/pressure change of ascending from two context-relevant ascent scenarios:
A) Ascent from a 15 ft safety stop (delta=~46 kPa; >60 ft/min= >184kPa/min), compared to:
B) 15 minute car ride to 2000 ft (delta= ~7 kPa, 133 ft/min= 0.47kPa/min). And this is ignoring the built in minimum 45 min surface interval getting back to the docks and unloading, etc.
All of this makes me question what the additional variables are that factored into the creation of these Navy table values?
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