Altitude diving

Altitude diving is scuba diving where the surface is 300 meters (1,000 feet) or more above sea level (for example, a mountain lake).[1][2] The U.S. Navy tables recommend that no alteration be made for dives at altitudes lower than 91 meters (300 feet) and dives between 91 meters and 300 meters correction is required for dives over 44 meters sea water (145 feet sea water) (actual depth).[3] Altitude diving is significant in recreational diving because the depths and durations used for dives at altitude are different from those used for the same dive profile at sea level.[4]

Contents

Measurement of depth at altitude

Special consideration must be given to measurement of depth given the effect of pressure on gauges. The use of bourdon tube, diaphragm, and digital depth gauges may require adjustment for use at altitude.[2] Capillary gauges have been shown to be a conservative method for measurement of compensated depth at altitude.[5] Modern dive computers detect changes in altitude and automatically adjust their calculation of a safe decompression regime for a dive at that altitude. If an altitude-aware computer is not used, altitude decompression tables must be used.

Decompression when diving at altitude

At altitude, atmospheric pressure is lower than at sea level, so surfacing at the end of an altitude dive leads to a greater reduction in pressure and an increased risk of decompression sickness.[6] The dives are also typically carried out in freshwater at altitude so it has a lower density than seawater used for calculation of decompression tables.[6] The amount of time the diver has spent at altitude is also of concern as divers with gas loadings near those of sea level may also be at an increased risk.[6] The US Navy recommends waiting 12 hours following arrival at altitude before performing the first dive.[3]

Decompression tables

The most common of the modifications to decompression tables at altitude are the "Cross Corrections" which use a ratio of atmospheric pressure and sea level to that of the altitude to provide a conservative equivalent sea level depth.[7][8] The Cross Corrections were later looked at by Bassett and by Bell and Borgwardt.[9][10][11][12]

Hennessy formulated that is was possible to convert standard air decompression tables for no-stop diving at altitude or from a habitat based on phase equilibration theory.[13]

Albert A. Bühlmann recognized the problem[14][15][16] and proposed a method which calculated maximum nitrogen loading in the tissues at a particular ambient pressure.[17][18]

Wienke proposed guidelines for decompression diving at altitude in 1993.[19]

Egi and Brubakk reviewed various models for preparing tables for diving at altitude.[20]

Paulev and Zubieta have created a new conversion factor in order to make any sea level dive table usable during high altitude diving in 2007.[21]

Repetitive diving

Repetitive dives should be conducted in the same manner as other dives including "Cross Corrections" for altitude. The US Navy does not allow repetitive diving for surface-supplied helium-oxygen diving and a 12 hour surface interval is required. An 18 hour surface interval is required if the dive requires decompression.[3]

Pre and Post Dive Ascents

In addition to making depth adjustments using the Cross Conversions, dives at altitude often require pre and post dive altitude ascents which must be taken into consideration. Several methods for performing post dive ascents are used. One is to adjust the dive times needed for an altitude ascent.[9][22] Another is to use surface intervals to allow for an ascent.[3]

Extreme altitude diving

Although no official records are recognized, the highest recorded altitude at which a scuba dive has been conducted was 19,300 feet (5,900 m), by a team led by Dr Charles Brush and Dr. Johan Reinhard in 1982 in Lago Licancabur.[23]

The deepest known staged decompression altitude dive was conducted by Nuno Gomes at Boesmansgat (Bushman's hole) in South Africa. Conducted at an altitude of approximately 5,000 feet (1,500 m), Gomes dived to a depth of 927 feet (283 m).[24] Gomes's decompression schedule was calculated as being equivalent for a dive to 1,112 feet (339 m) if it had been conducted at sea level.

References

  1. ^ Brylske, A. (2006). Encyclopedia of Recreational Diving, 3rd edition. United States: PADI. ISBN 1-878663-01-1. 
  2. ^ a b Murphey, M. (1991). "Altitude Diving". Advanced Diving: Technology and Techniques. Montclair, CA: NAUI. pp. 150–56. 
  3. ^ a b c d US Navy Diving Manual, 6th revision. United States: US Naval Sea Systems Command. 2006. http://www.supsalv.org/00c3_publications.asp?destPage=00c3&pageID=3.9. Retrieved 2008-04-24. 
  4. ^ Morris R, Berthold R, and Cabrol N (2007). "Diving at Extreme Altitude: Dive Planning and Execution During the 2006 High Lakes Science Expedition". In: NW Pollock and JM Godfrey (Eds.) the Diving for Science…2007 (Dauphin Island, Ala.: American Academy of Underwater Sciences) Proceedings of the American Academy of Underwater Sciences (Twenty–sixth annual Scientific Diving Symposium). ISBN 0-9800423-1-3. http://archive.rubicon-foundation.org/7003. Retrieved 2008-06-14. 
  5. ^ Mackay RS (1976). "Automatic compensation by capillary gauge for altitude decompression". Undersea Biomed Res 3 (4): 399–402. ISSN 0093-5387. OCLC 2068005. PMID 10897866. http://archive.rubicon-foundation.org/2440. Retrieved 2008-04-24. 
  6. ^ a b c Brubakk, A. O.; T. S. Neuman (2003). Bennett and Elliott's physiology and medicine of diving, 5th Rev ed.. United States: Saunders Ltd.. pp. 800. ISBN 0-7020-2571-2. 
  7. ^ Cross, E. R. (1967). "Decompression for high-altitude diving". Skin Diver 16 (12): 60. 
  8. ^ Cross, E. R. (1970). "Technifacts: high altitude decompression". Skin Diver 19 (11): 17–18, 59. 
  9. ^ a b Bassett, B. E. (1979). "And yet another approach to the problems of Altitude Diving and Flying After Diving.". Decompression in Depth Symposia. Santa Ana, California: Diving Science & Technology Corp.. pp. 38–48. http://archive.rubicon-foundation.org/4230. Retrieved 2008-04-24. 
  10. ^ Bassett, B. E. (1982). "Decompression Procedures for Flying After Diving, and Diving at Altitudes above Sea Level". US Air Force Technical Report SAM-TR-82-47. http://archive.rubicon-foundation.org/4531. Retrieved 2008-04-24. 
  11. ^ Bell, R.; Thompson A.; Borowari R. (1979). "The theoretical structure and testing of high altitude diving tables". Decompression in Depth Symposia. Santa Ana, California: Diving Science & Technology Corp.. pp. 49–79. http://archive.rubicon-foundation.org/4230. Retrieved 2008-04-24. 
  12. ^ Bell RL, Borgwardt RE (1976). "The theory of high-altitide corrections to the U.S. Navy standard decompression tables. The cross corrections". Undersea Biomed Res 3 (1): 1–23. ISSN 0093-5387. OCLC 2068005. PMID 1273981. http://archive.rubicon-foundation.org/2748. Retrieved 2008-04-24. 
  13. ^ Hennessy T. R. (1977). "Converting standard air decompression tables for no-stop diving from altitude or habitat". Undersea Biomed Res 4 (1): 39–53. ISSN 0093-5387. OCLC 2068005. PMID 857357. http://archive.rubicon-foundation.org/2784. Retrieved 2008-04-24. 
  14. ^ Bühlmann AA (1989). "[Decompression problems in diving in mountain lakes]" (in French). Schweiz Z Sportmed 37 (2): 80–3; discussion 99–102. PMID 2799365. 
  15. ^ Bühlmann AA (1984). "[Decompression during lowered air pressure]" (in German). Schweiz Med Wochenschr 114 (26): 942–7. PMID 6087447. 
  16. ^ Bühlmann AA, Schibli R, Gehring H (March 1973). "[Experimental studies on decompression following diving in mountain lakes at reduced air pressure]" (in German). Schweiz Med Wochenschr 103 (10): 378–83. PMID 4144210. 
  17. ^ Böni M., Schibli R., Nussberger P., Bühlmann A. A. (1976). "Diving at diminished atmospheric pressure: air decompression tables for different altitudes". Undersea Biomed Res 3 (3): 189–204. ISSN 0093-5387. OCLC 2068005. PMID 969023. http://archive.rubicon-foundation.org/2750. Retrieved 2008-04-24. 
  18. ^ Bühlmann, A. A. (1984). Decompression-Decompression Sickness. Berlin New York: Springer-Verlag. ISBN 0-387-13308-9. 
  19. ^ Wienke, B. R. (1993). Diving above sea level. Flagstaff, AZ: Best Publishing. ISBN 0-941332-30-6. 
  20. ^ Egi S. M., Brubakk A. O. (1995). "Diving at altitude: a review of decompression strategies". Undersea Hyperb Med 22 (3): 281–300. ISSN 1066-2936. OCLC 26915585. PMID 7580768. http://archive.rubicon-foundation.org/2194. Retrieved 2008-04-24. 
  21. ^ Paulev, Poul-Erik; Zubieta-Calleja, Gustavo (2007). "High Altitude Diving Depths". Research in Sports Medicine (Taylor & Francis) 15 (3): 213–23. doi:10.1080/15438620701526795. PMID 17987509. 
  22. ^ Morris, B.R. (1984, 2010). Practical Altitude Diving Procedures. pp. 24–27, 50. http://www.scubalaketahoe.com/books.htm. 
  23. ^ "Brush Engineered Materials Mourns Loss of Dr. Charles F. Brush III, Director Emeritus". http://www.thefreelibrary.com/Brush+Engineered+Materials+Mourns+Loss+of+Dr.+Charles+F.+Brush+III,...-a0146898905. Retrieved 2010-03-26. 
  24. ^ Farr, Martyn (8 February 2007). "South Africa - Bushmansgat". http://www.nunogomes.co.za/record.htm. Retrieved 2010-04-30. 

External links

Types
Specialities
Equipment
Disciplines
Hazards
Related