Altitude Diving

**Dave1w** · 28th June 2007, 01:35

I am planning to be diving in a Lake in Mongolia in August at an altitude of approximately1650 metres.

Here are some thoughts I have on planning for this, and I would appreciate any further points you think I need to consider.

I will be in country for about a week before commencing the diving - Others in the party should be there at least a couple of days. I think this would be sufficient acclimatisation.

For my PO2 sensors, I feel I have 2 choices. 1) calibrate at sea level, and accept that it would be accurate at altitude, or 2) Calibrate at altitude using a pressure chart (barometer woudl be best) to give me the actual pressure and apply 21 odd% as applicable.

Dive Table / Computer - Due to remoteness, would probably dive as if on air (with suitable adjustment factors for altitude). BSAC produce easy to use tables up to 4000 m altitude, with repeat dives being a strong feature. As everyone else, I would also be adding some little conservatism points to the BSAC tables (ascent rates, safety stops), and then always go worst case betwen the tables and computer. (SUUNTO)

Limit on repetitive dives per day (?)

Depth Limit (?)

I would also intend to take along a tape measure and do some real figuring out so that I have a true understanding of what my gauges are "trying" to tell me.

Any thoughts?

Dave

Gene_Hobbs · 28th June 2007, 02:44

There is actually some nice history on the development of altitude diving procedures in the last two chapters of Decompression in Depth. Proceedings of a Seminar. Diving Science & Technology Corp. 1979. RRR ID: 4230

Beyond that, there seems to be quite a bit of theoretical work done. We have many of those reports in the Repository that can be found by searching for altitude diving. Some of these go into gauge behavior. Others are just case reports but there are some good reviews in there as well:

Decompression Procedures for Flying After Diving, and Diving at Altitudes above Sea Level.
Bassett, 1982 USAF-SAM Report 82-47
RRR ID: 4531

Diving at altitude: a review of decompression strategies.
Egi and Brubakk, Undersea Hyperb Med. 1995 Sep;22(3):281-300.
RRR ID: 2194

Computation of decompression tables using continuous compartment half-lives.
Egi and Gurmen. Undersea Hyperb Med. 2000 Fall;27(3):143-53.
RRR ID: 2341

ASEM also has some great work:
Field trials of no-decompression stop limits for diving at 3500 m.
Egi et. al. Aviat Space Environ Med. 2003 Mar;74(3):228-35.

Good luck with your plan!

boomx5 · 28th June 2007, 03:00

Great stuff Gene!

If we can get our funding for next year, I'm going to do everything I can to twist your arm to come work with us for a few days on the project I told you about.

Gene_Hobbs · 28th June 2007, 03:19

Quote: (Originally Posted by boomx5)

Great stuff Gene!

If we can get our funding for next year, I'm going to do everything I can to twist your arm to come work with us for a few days on the project I told you about.

Have Doppler, will travel!

DOPPLER MONITORING FOR PREDICTING DECOMPRESSION ILLNESS AT ALTITUDE AFTER DIVING.
Johanson and Chimiak, 1998 UHMS abstract
RRR ID: 670

GuyW · 28th June 2007, 12:12

An important point is to understand the relationship between linear depth (as measured with a tape measure), depth as measured by a surface calibrated depth gauge (like a VR3), and a non-calibrated depth guage (that just uses pressure).

So if the ambient pressure is 0.8Bar, at 2m underwater your standard depth gauge reads 0m.

If you are looking at a set of deco tables, what does "depth" mean ?

Similarly if you add a Rebreather into the mix, how is that calibrated ? With my YBOD I can enter 800mb when I calibrate so it is reading correct. On the surface it would read 0.17 ! On pure oxygen at 3m (linear) underwater the ppO2 is 1.1

You should be very clear on how all this effects your equipment and deco tables before attempting any significant dive at a significant altitude.

Guy

Gene_Hobbs · 29th June 2007, 14:23

There is also a review available online from:
Hamilton RW, Thalmann ED. Decompression practice. In: Bennett and Elliott's Physiology and Medicine of Diving (5th ed.), edited by Brubakk AO and Neuman TS. Philadelphia: Saunders, 2003.

http://intl.elsevierhealth.com/e-books/pdf/317.pdf

Altitude starts on page 481

28th June 2007, 01:35	#11 (permalink)
Dave1w Born Again Diver! Current Rebreather/s: Sport Kiss Dolphin Ray Home Build Other Rebreather/s: Classic Kiss Dolphin Ray Home Build Join Date: Jan 2005 Location: Singapore / UK Posts: 347	Re: Altitude Diving I am planning to be diving in a Lake in Mongolia in August at an altitude of approximately1650 metres. Here are some thoughts I have on planning for this, and I would appreciate any further points you think I need to consider. I will be in country for about a week before commencing the diving - Others in the party should be there at least a couple of days. I think this would be sufficient acclimatisation. For my PO2 sensors, I feel I have 2 choices. 1) calibrate at sea level, and accept that it would be accurate at altitude, or 2) Calibrate at altitude using a pressure chart (barometer woudl be best) to give me the actual pressure and apply 21 odd% as applicable. Dive Table / Computer - Due to remoteness, would probably dive as if on air (with suitable adjustment factors for altitude). BSAC produce easy to use tables up to 4000 m altitude, with repeat dives being a strong feature. As everyone else, I would also be adding some little conservatism points to the BSAC tables (ascent rates, safety stops), and then always go worst case betwen the tables and computer. (SUUNTO) Limit on repetitive dives per day (?) Depth Limit (?) I would also intend to take along a tape measure and do some real figuring out so that I have a true understanding of what my gauges are "trying" to tell me. Any thoughts? Dave
(Offline)

28th June 2007, 02:44	#12 (permalink)
Gene_Hobbs Resident bibliophile Current Rebreather/s: Not Bought Yet Other Rebreather/s: Not Bought Yet Join Date: Sep 2006 Location: Durham, NC, USA Posts: 122	RRR: Altitude Diving There is actually some nice history on the development of altitude diving procedures in the last two chapters of Decompression in Depth. Proceedings of a Seminar. Diving Science & Technology Corp. 1979. RRR ID: 4230 Beyond that, there seems to be quite a bit of theoretical work done. We have many of those reports in the Repository that can be found by searching for altitude diving. Some of these go into gauge behavior. Others are just case reports but there are some good reviews in there as well: Decompression Procedures for Flying After Diving, and Diving at Altitudes above Sea Level. Bassett, 1982 USAF-SAM Report 82-47 RRR ID: 4531 Diving at altitude: a review of decompression strategies. Egi and Brubakk, Undersea Hyperb Med. 1995 Sep;22(3):281-300. RRR ID: 2194 Computation of decompression tables using continuous compartment half-lives. Egi and Gurmen. Undersea Hyperb Med. 2000 Fall;27(3):143-53. RRR ID: 2341 ASEM also has some great work: Field trials of no-decompression stop limits for diving at 3500 m. Egi et. al. Aviat Space Environ Med. 2003 Mar;74(3):228-35. Good luck with your plan! __________________ http://rubicon-foundation.org/ Home of the Rubicon Research Repository. For help getting started with the Repository, please visit our FAQ page. PLEASE support our work. "Oxygen is addictive and deadly. Everyone who uses it will eventually die" --RW Hamilton, PhD 1991 Last edited by Gene_Hobbs : 28th June 2007 at 02:54.
(Online)

28th June 2007, 03:00	#13 (permalink)
boomx5 New Member Current Rebreather/s: Not Bought Yet Other Rebreather/s: Not Bought Yet Join Date: Apr 2005 Location: California Posts: 12	Re: Altitude Diving Great stuff Gene! If we can get our funding for next year, I'm going to do everything I can to twist your arm to come work with us for a few days on the project I told you about.
(Offline)

28th June 2007, 03:19	#14 (permalink)
Gene_Hobbs Resident bibliophile Current Rebreather/s: Not Bought Yet Other Rebreather/s: Not Bought Yet Join Date: Sep 2006 Location: Durham, NC, USA Posts: 122	RRR: Altitude Diving Quote: (Originally Posted by boomx5) Great stuff Gene! If we can get our funding for next year, I'm going to do everything I can to twist your arm to come work with us for a few days on the project I told you about. Have Doppler, will travel! DOPPLER MONITORING FOR PREDICTING DECOMPRESSION ILLNESS AT ALTITUDE AFTER DIVING. Johanson and Chimiak, 1998 UHMS abstract RRR ID: 670 __________________ http://rubicon-foundation.org/ Home of the Rubicon Research Repository. For help getting started with the Repository, please visit our FAQ page. PLEASE support our work. "Oxygen is addictive and deadly. Everyone who uses it will eventually die" --RW Hamilton, PhD 1991
(Online)

28th June 2007, 12:12	#15 (permalink)
GuyW Old Member Current Rebreather/s: Inspiration Classic Other Rebreather/s: Join Date: Apr 2006 Location: Sydney, Australia Posts: 61	Re: Altitude Diving An important point is to understand the relationship between linear depth (as measured with a tape measure), depth as measured by a surface calibrated depth gauge (like a VR3), and a non-calibrated depth guage (that just uses pressure). So if the ambient pressure is 0.8Bar, at 2m underwater your standard depth gauge reads 0m. If you are looking at a set of deco tables, what does "depth" mean ? Similarly if you add a Rebreather into the mix, how is that calibrated ? With my YBOD I can enter 800mb when I calibrate so it is reading correct. On the surface it would read 0.17 ! On pure oxygen at 3m (linear) underwater the ppO2 is 1.1 You should be very clear on how all this effects your equipment and deco tables before attempting any significant dive at a significant altitude. Guy
(Offline)

29th June 2007, 14:23	#16 (permalink)
Gene_Hobbs Resident bibliophile Current Rebreather/s: Not Bought Yet Other Rebreather/s: Not Bought Yet Join Date: Sep 2006 Location: Durham, NC, USA Posts: 122	Hamilton RW, Thalmann ED. Decompression practice. There is also a review available online from: Hamilton RW, Thalmann ED. Decompression practice. In: Bennett and Elliott's Physiology and Medicine of Diving (5th ed.), edited by Brubakk AO and Neuman TS. Philadelphia: Saunders, 2003. http://intl.elsevierhealth.com/e-books/pdf/317.pdf Altitude starts on page 481 __________________ http://rubicon-foundation.org/ Home of the Rubicon Research Repository. For help getting started with the Repository, please visit our FAQ page. PLEASE support our work. "Oxygen is addictive and deadly. Everyone who uses it will eventually die" --RW Hamilton, PhD 1991
(Online)

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