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Decompression Theories, Models & Tables

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  1. DecompressionTheories, Models & Tables Karl E. Huggins USC Catalina Hyperbaric Chamber Wrigley Marine Science Center Catalina Island, CA

  2. Missions of theUSC Catalina Hyperbaric Chamber • Treatment of Scuba Diving Casualties • Educational Programs focused on Promotion of Scuba Diving Safety, Accident Response, and Treatment • Reporting Information on Diving Accidents and Diving Practices • Hyperbaric / Diving Research • Equipment Testing

  3. Location of the Chamber • USC Wrigley Marine Science Center • Big Fisherman Cove • West End of Catalina Island • Near Two Harbors • Isolated Location • Rugged Terrain • Where the Divers Are

  4. Popular Dive Sites within Minutes of Catalina Hyperbaric Chamber Lion’sHead EmeraldCove Ship Rock Eagle Reef  Bird Rock IsthmusReef Blue Cavern 

  5. Farnsworth Banks

  6. USC Catalina Hyperbaric Chamber Where Do the Patients Come From?

  7. Decompression Models,Tables & Computers What do they do? What don’t they do?

  8. The Case of the ShrinkingNo-Stop Times(100 fsw No-Stop Limit - mid 1980s) 25 min. - U.S. Navy 20 min. – NAUI / PADI / HUGI / BSAC 18 min. - Suunto SME-ML 17 min. - German Tables 15 min. - DCIEM Tables (Canada) 12 min. - Dacor Microbrain 11 min. - Dacor Microbrain Pro Plus 9 min. - Tekna Computek 8 min. - 1% Maximum Likelihood Tables

  9. WHAT ARE THEYALL TRYING TO DO?

  10. PREVENTDecompression Sickness Symptoms resulting from the evolution and growth of gas bubbles in the body fluids and tissues, following a reduction in ambientpressure. DCS The BENDS Caissons Disease

  11. BUBBLE FORMATION BLOOD VESSEL OBSTRUCTION TISSUE DISTORTION & DISRUPTION DCS PATHOPHYSIOLOGY Platelet Aggregation Arterial Thrombosis Fibrinolysis Venous Clotting Slugging of Venous Blood Plasma Loss

  12. Decompression SicknessVicious Cycle Bubbles Form Decreased Elimination of Gas Decreased Blood Flow Edema Tissue Hypoxia

  13. Blow-Ups From Deep Dives A 44-year-old male scuba diver died shortly after a solo dive in great depth. He used a dry diving suit and breathed Trimix diving gas with a composition of 9.3% oxygen, 53.4% helium, and 33.9% nitrogen. According to witness state-ments, he literally spurted out of the water, making movements with his arms and rapidly losing conscious-ness. After being rescued by diving colleagues, he suffered a cardiopulmonary arrest. Resuscitation attempts were futile. Analysis of the diving computer showed a diving depth of 100 to 125 m and a diving duration of 25 min. Thomas Plattner, et. al., J Forensic Sci, November 2003

  14. Decompression TermsSATURATIONExists when:The nitrogen pressure in the tissueis equal to the nitrogen pressure in the breathing gas.

  15. Dive to 80 fsw Nitrogen in Breathing Gas 80 fsw + 33 fsw = 113 fsw absolute x 0.79 (N2 fraction) = 89.3 fswNitrogen Pressure in breathing gas Nitrogen in Body Tissues 0 fsw + 33 fsw = 33 fsw absolute x 0.79 (N2 fraction) = 26.1 fswNitrogen Pressure in body tissues Nitrogen Gradient

  16. Nitrogen Pressure over Tissue RangeBody Saturated at Surface (1 ata) Fast Slow Tissues

  17. Nitrogen Pressure over Tissue RangeBody at 33 fsw (2 ata) Fast Slow Tissues

  18. Nitrogen Pressure over Tissue RangeBody at 33 fsw (2 ata) Fast Slow Tissues

  19. Nitrogen Pressure over Tissue RangeBody at 33 fsw (2 ata) Fast Slow Tissues

  20. Nitrogen Pressure over Tissue RangeBody at 33 fsw (2 ata) Fast Slow Tissues

  21. Nitrogen Pressure over Tissue RangeBody Saturated at 33 fsw (2 ata) Fast Slow Tissues

  22. Nitrogen Pressure over Tissue RangeBody at Surface (1 ata) after33 fsw (2 ata) Saturation Fast Slow Tissues

  23. Nitrogen Pressure over Tissue RangeBody at Surface (1 ata) after33 fsw (2 ata) Saturation Fast Slow Tissues

  24. Nitrogen Pressure over Tissue RangeBody at Surface (1 ata) after33 fsw (2 ata) Saturation Fast Slow Tissues

  25. Nitrogen Pressure over Tissue RangeBody Re-Saturated at Surface (1 ata) after33 fsw (2 ata) Saturation Fast Slow Tissues

  26. Decompression TermsSUPERSATURATIONExists when:The nitrogen pressure in the tissueexceeds the total ambient pressureexerted on the body.PtN2 > Pamb

  27. N2 1.58 ATA PT > PN2 OFFGASSING PT > PA SUPER- SATURATION N2 N2 1.58 ATA .79 ATA PT < PN2 PT = PN2 SATURATED SATURATE AT 33 FSW ON-GASSING PT < PA PT < PA N2 SEA LEVEL .79 ATA PA = 1.0 ATA PT = PN2 SATURATED PN2 = 0.79 ATA PT < PA PT = TISSUE N2 PRESSURE 33 FSW PA = 2.0 ATA PN2 = 1.58 ATA

  28. Shallow SupersaturationStudy Depth (fsw) # Of Divers Percent of Divers with Corresponding VGE Score 0 1 2 3 4 12.0 25 80.0% 16.0% 4.0% 0.0% 0.0% 16.0 54 44.4% 22.2% 16.7% 14.8% 1.9% 20.5 32 28.1% 21.9% 15.6% 15.6% 18.8% Eckenhoff - 1990

  29. Early 1900sLinear Decompression100 fsw / 20 min. – 1 ata / 20 min.

  30. HALDANE CONCEPT- - - - NUCLEI ARE NOT PRESENT PRIOR TO DECOMPRESSION Bubbles spontaneously form

  31. Decompression TermsCRITICALSUPERSATURATIONThe maximum nitrogen tissuepressure tolerated at any giventotal ambient pressureExpressed as a ratio of PtN2 to PambCRITICAL RATIO = PtN2 / Pamb

  32. N2 Haldane’s Assumption PT/PA > S.S. RATIO Nitrogen bubbles form in the body PT/PA < S.S. RATIO Nitrogen eliminated though lungs

  33. Haldane’s Observations Supersaturation Ratio 1.58/1 Sea Level (1 ATA) N2 Pressure = 1.58 ATA 33 fsw (2 ATA) Saturation Time Goats – 3 hours Man – 5 hours

  34. Haldane’s Observations Sea Level (1 ATA) Supersaturation Ratio 3.95/2.5 or 1.58/1 49.5 fsw (2.5 ATA) N2 Pressure = 3.95 ATA 132 fsw (5 ATA) Saturation Time Goats – 3 hours Man – 5 hours

  35. J.S. HaldaneDecompression ModelCompartment Half-Time

  36. J.S. HaldaneDecompression ModelCompartment Half-Time

  37. J.S. HaldaneDecompression ModelCompartment Half-Time

  38. J.S. HaldaneDecompression ModelCompartment Half-Time

  39. J.S. HaldaneDecompression ModelCompartment Half-Time

  40. J.S. HaldaneDecompression ModelCompartment Half-Time

  41. J.S. HaldaneDecompression ModelCompartment Half-Time

  42. J.S. HaldaneDecompression ModelCompartment Half-Time

  43. J.S. HaldaneMathematical Model

  44. J.S. HaldaneDecompression Model Calculations100 fsw / 20 min. OK @ 40 fsw OK @ 30 fsw 5-min N2 pressure = 3.03 ATA 3.03 ATA / 1.58 = 1.92 ATA (1.92 ATA – 1 ATA) x 33 fsw/ATA = 30.3 fsw FIRST STOP AT 40 FSW

  45. J.S. HaldaneDecompression Model Calculations40 fsw / 1 min. OK @ 30 fsw 5-min N2 pressure = 2.87 ATA 2.87 ATA / 1.58 = 1.82 ATA (1.82 ATA – 1 ATA) x 33 fsw/ATA = 26.9 fsw OK TO ASCEND TO 30 FSW

  46. J.S. HaldaneDecompression Model Calculations30 fsw / 3 min. OK @ 20 fsw 5-min N2 pressure = 2.41 ATA 2.41 ATA / 1.58 = 1.53 ATA (1.53 ATA – 1 ATA) x 33 fsw/ATA = 17.3 fsw OK TO ASCEND TO 20 FSW

  47. J.S. HaldaneDecompression Model Calculations20 fsw / 5 min. 10-min pressure = 2.02 ATA 2.02 ATA / 1.58 = 1.28 ATA (1.28 ATA– 1 ATA) x 33 fsw/ATA = 9.2 fsw OK TO ASCEND TO 10 FSW OK @ 10 fsw

  48. J.S. HaldaneDecompression Model Calculations10 fsw / 11 min. 20-min N2 pressure = 1.57 ATA 1.57 ATA / 1.58 = 0.99 ATA (0.99 ATA – 1 ATA) x 33 fsw/ATA = -0.2 fsw OK TO ASCEND TO SURFACE OK @ Surface

  49. J.S. HaldaneDecompression Model Calculations100 fsw / 20 min.