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Safety of accepted decompression table

Safety of accepted decompression table. Brubakk AO et al Trondheim / Split /UWATEC AG Bergen Nov. 2007. Effect of Nitroglycerin on bubble formation in man Valade et al 2006 . Bubbles/cm2. *. *. Dry / In-water dives 54msw/20min 24msw/70min. Bub/cm2 – P(DCS)%.

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Safety of accepted decompression table

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  1. Safety of accepted decompression table Brubakk AO et al Trondheim / Split /UWATEC AG Bergen Nov. 2007

  2. Effect of Nitroglycerin on bubble formation in manValade et al 2006. Bubbles/cm2 * *

  3. Dry / In-water dives54msw/20min 24msw/70min Bub/cm2– P(DCS)%

  4. Total decompression timeAir dives Minutes

  5. HSE 1997 • The outcome of a particular dive is determined by many different physical and physiological factors normally not accounted for in present decompression tables. • All present tables seem to be unsatisfactory for very high gas loads. A.O.B., November 1997

  6. Health & Safety Executive 1997 • The amount of separated gas in the pulmonary artery can be used as an indicator of decompression risk. • Present procedures probably produce an unacceptable large amount of separated gas in the pulmonary artery in a significant number of divers. A.O.B., November 1997

  7. The effect of prT on DCS incidence (HSE 1996)

  8. Dive Computer Tests60 fsw Multi-Level Dive #1(24 min. @ 40 fsw) Required Decompression Time No-Decompression Time Neuman T., Pers. Comm.

  9. Behnke 1951/1969 • From the point of view of decompression procedures the problem is straightforward • regulate decompression so as to prevent bubble evolution • if bubbles form, control their number and size so that symptoms do not supervene. • Bubbles form as soon as a state of supersaturation is initiated and …… tolerance to decompression is in reality an index of the degree of gas embolism tolerated • There is a sharp demarcation limit of perhaps 5 feet in diving depth separating injury from a state of well-beeing

  10. Air dives SurDO2 SNSC 1992 DCS incidence 17% DCS incidence 0%

  11. Risk of DCS • 60 feet / 80 minutes • Decompression: • 8 min - pDCS 2.8% • 80 min - pDCS 2% • Wheathersby et al 1984

  12. 318 msw. 9 different gas mixes, 11 hours decompression

  13. Copernicus

  14. Copernicus • Copernicus consists of: • The model itself. A descriptive model of the mechanisms behind the occurence of serious (CNS) DCS (evolution of vascular bubbles) • A control algorithm. It calculates a procedure that control the model according to our request (Dynamic optimization algorithm) • Validation strategy through bubble measurement rather than DCS/NO-DCS endpoint • The model will have two distinct applications: • Use the model as a simulator to compare and evaluate procedures and logged dives • Use accepted risk/bubble scores as threshold for calculating optimal decompression schedules

  15. Physiological model • Individually adaptive • Input: • Weight • Height • Fitness (fat percentage) • Gender • Cardio-pulmonary performance • Workload

  16. Total decompression timeAir dives Minutes

  17. Air-dive 24msw/70min Min Total deco 72 min Total deco 69 min.

  18. Buhlman / Copernicus24msw/70 min

  19. Possible, tentative and surprising conclusion • Dives with long, < 30 minutes, bottom time maybenefit from deep stops • Dives with short. > 30 minutes, bottom time will not benefit from deep stops.

  20. “People who think they know it all really annoys those of us who really do…….”

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