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NAUI Nitrox: Diving With Oxygen Enriched Air

NAUI Nitrox: Diving With Oxygen Enriched Air. Open Water Requirements. Two dives with oxygen enriched air one of which is to be a repetitive dive Students analyze their own gases Plan and safely execute each dive. Academic Requirements. NAUI: 75 % on multiple choice test

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NAUI Nitrox: Diving With Oxygen Enriched Air

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  1. NAUI Nitrox:Diving With Oxygen Enriched Air

  2. Open Water Requirements • Two dives with oxygen enriched air • one of which is to be a repetitive dive • Students analyze their own gases • Plan and safely execute each dive Academic Requirements • NAUI: 75 % on multiple choice test • MLML: 100% on Final exam ?’s

  3. 1. Introduction 2. Gases and gas properties 3. Pressure and partial pressure 4. Oxygen physiology, toxicity, and tolerance 5. How to pick a nitrox mix 6. Decompression principles 7. Diving tables 8. Using NAUI diving tables with enriched air nitrox 9. Overview of gas mixing 10. Obtaining and analyzing enriched air nitrox 11. Diving equipment considerations 12. Having enough to breathe and staying warm 13. Contingencies: if things don’t go as planned 14. Technical diving overview

  4. Benefits of Enriched Air • Longer no-stop dive times • Shorter surface intervals • Longer repetitive dives • Less nitrogen absorbed • Lower risk of decompression illness

  5. Myths of Enriched Air Nitrox • Nitrox is safer than air • Nitrox is for deep diving • You can’t get decompression sickness • Narcosis is eliminated • Using enriched air nitrox is difficult

  6. Oxygen Enriched Air Enriched Air Nitrox NOAA Nitrox I NOAA Nitrox II Common Mixes 32% oxygen 36 % oxygen EAN32 EAN36 Oxygen Enriched Air: Terminology All the mixes have more oxygen and less nitrogen than in normal air.

  7. The lower nitrogen content in oxygen enriched air allows for longer no-stop dive times. Some are almost 100% longer. Justification for Enriched Air

  8. Air Example Dive # 1 90 fsw / 20 min no-stop One hour surface interval Group F > G Dive # 2 80 fsw / 12 min no-stop 36% O2 Example Dive # 1 90 fsw / 20 min no-stop One hour surface interval Group E > D Dive # 2 80 fsw / 36 minutes no-stop time Repetitive Dive (fsw) Enriched air provided 24 minutes more no-stop dive time.

  9. History of enriched air in recreational diving • USN had explored nitrogen-oxygen mixtures in 1950's • International Underwater Contractors (IUC) and others had used it in commercial diving since the 1960’s • Dr. Morgan Wells introduced enriched air to NOAA, published in 1979 • University of NC Wilmington had a strong NOAA program • Dick Rutkowski introduced “nitrox” to recreational divers in 1988 in Key Largo

  10. NOAA sponsored high-level workshop at Harbor Branch 1989 • 1992 Nitrox Workshop in Houston • Scuba Diving Resource Group • aquaCorps Journal • Industry agreed to a standard for air to be mixed with oxygen • NAUI approved enriched air training 1992 • Enriched air computers enter the market 1992 • Enriched air diving centers expand all over the world 1992 through the present.

  11. Gases:Basic Principles • Matter takes 3 forms: solid, liquid, and gas • Gases are compressible and fill the container • Gases are affected by temperature • Gas mixtures are made up of individual gases • Once mixed, gases stay mixed and are hard to separate • Gases dissolve in liquids in proportion to pressure

  12. Boyle’s Law • As pressure on a given mass of gas is increased, the volume decreases, or as volume is reduced the pressure increases. surface 33 fsw (10 msw) 66 fsw (20 msw) 99 fsw (30 msw) 1 1/2 1/3 1/4 Air Balloon P V = kt Or P1 V1 = P2 V2

  13. Composition of air • Oxygen 0.2095 • Nitrogen 0.7808 • Argon 0.00934 • Others • Total 1.0000

  14. Composition of air • Oxygen, O2 20.95% • essential component of all breathing mixes • Nitrogen, N2 78.08% • inert gas in air and nitrox mixtures • narcotic properties are main disadvantage • Argon, Ar 0.934 % • makes up about 1% of air and is considered with the nitrogen component. • Trace gases include • CO2, neon, helium, methane, nitrogen oxides

  15. Nitrogen and Narcosis • What is narcosis? • Numbing or state of stupor • Is sneaky because of its euphoric feeling. • Slows down information processing • Affects most people at 100-130 fsw (30-40 msw) • Dangers of narcosis at depth • Unable to deal with problems • Difficulty in managing multiple tasks

  16. Gas Laws • Pressure and temperature • On compression gases get hot • Heating increases pressure • Heating increases volume at constant P • Solubility • Gases dissolve in liquids • Amount dissolved proportional to pressure • Solubility is a function of gas and liquid • Most gases have higher solubility in fat • N2 is more soluble than He or Ne

  17. Partial Pressure • The effect of a single gas component in a gas mixture. • The fraction of the component gas multiplied by the total pressure. • When added, all of the partial pressures of the component gases become the total pressure. Air at 1 atm Percentage Partial Pressure 79% N2 = 0.79 atm 21% O2 = 0.21 atm 100% = 1.00 atm

  18. Partial Pressure of Gases in a Mix • In a mixture of gases, the total pressure is made up of the sum of the pressures of the individual components. • The partial pressure of a gas, is the product of the fraction of that gas times the total pressure. P = P1 + P2 + P3 +…+Pn Pg = Fg X P total Dalton’s Law

  19. Pg = P x Fg Pg = partial pressure P = absolute pressure Fg = fraction of the gas Calculating Partial Pressures

  20. Calculating Partial Pressures Pg Partial pressure Gas fraction P Total pressure Fg

  21. Maximum depth for EAN32 ? P = 1.4 atm / 0.32 P = 4.375 atm Dfsw = (4.375 atm - 1atm) x 33 fsw or Dmsw = (4.375atm - 1atm) x 10 msw D fsw = 111 D msw = 34 1.4 atm P 0.32 110 fsw is maximum operating depth 33 msw is maximum operating depth

  22. Maximum depth for EAN40 ? P = 1.4 atm / 0.40 P = 3.5 atm Dfsw = (3.5 atm - 1atm) x 33 fsw Dmsw = (3.5atm - 1atm) x 10 msw D fsw = 82.5 D msw = 25 1.4 atm 0.40 P 80 fsw is maximum operating depth 25 msw is maximum operating depth

  23. Oxygen • Metabolism: • Oxygen is essential for life and energy • The need for oxygen: • Hypoxia • Oxygen’s role in decompression • Oxygen as an inert gas: • Narcosis and decompression • Toxic effects of oxygen: • The need for management • Oxygen is a powerful oxidizing agent

  24. Effects of different levels of oxygen partial pressure (atm) • 3.0 50/50 enriched air nitrox recompression treatment gas for use in the chamber at 6 atm abs. • 2.8 100% O2 recompression treatment gas at 60 fsw (18 msw) • 2.4 40% O2-60% N2 enriched air nitrox recompression treatment gas at 6 atm abs. • 2.2 Commercial/military “Sur-D” chamber surface decompression, 100% O2 at 40 fsw (12 msw) pressure. • 1.6 Maximum exposure for working diver, NOAA limits. • 1.4 Recommended maximum exposure for recreational diver.

  25. Effects of different levels of oxygen partial pressure (atm) • 0.50 Threshold for whole-body effects; maximum saturation dive exposure. • 0.35-0.40 Normal saturation dive PO2 level. • 0.21 Normal environment oxygen (sea level air). • 0.14-0.16 Initial signs/symptoms of hypoxia. • 0.09-0.10 Serious signs/symptoms of hypoxia. • <0.08-0.10 Unconsciousness in most people. • <0.08 Coma leading to death.

  26. Oxygen Toxicity • CNS: Effects on the central nervous system • Variations in tolerance • Benefits of intermittent exposure

  27. CNS Oxygen ToxicitySigns and Symptoms • Convulsion • Visual disturbances, tunnel vision • Ear ringing • Nausea • Tingling, twitching (facial or muscle spasms) • Irritability, restlessness, euphoria, anxiety • Dizziness, dyspnea

  28. Managing oxygen exposure:CNS limits • A convulsion can be fatal • Methods exist for management • Uses limits; NOAA • Monitor percentage of limit • Limit fraction • Oxygen clock Single Dive Oxygen Exposure Limits PO2 atmMinutes 1.60 45 1.55 83 1.50 120 1.45 135 1.40 150 1.35 165 1.30 180 1.25 195 1.20 210

  29. Oxygen Exposure Chart

  30. Toxicity Prevention • Keep PO2 levels at 1.4 atm or less • 1.5 and 1.6 for contingency purposes only • If signs of toxicity appear • Ascend to a shallower depth • Diver should be taken to surface • Do not delay ascent

  31. The Nitrox Mixes

  32. How to pick the right mix?Concerns of the Mix Maximum and Contingency Operating Depths EAN32 EAN 36 PO21.39 1.34 Maximum 110 fsw 90 fsw 33 msw 27 msw PO2 1.58 1.56 Contingency 130 fsw 110 fsw 40 msw 33 msw • Maximum Operating Depth • Contingency Operating Depth • These are recommended and contingency limits

  33. Concerns of the mix • Consider upper limits of mix at depth • Pick a mix for planned dive time NOAA Oxygen Exposure Limits Maximum Maximum PO2 atm Single Limit 24-Hour Limit 1.60 45 150 1.55 83 165 1.50 120 180 1.45 135 180 1.40 150 180 1.35 165 195 1.30 180 210 1.25 195 225 1.20 210 240

  34. Calculating:Maximum Operation Depth (fsw) To calculate the MOD for 32% oxygen, which has an FO2 of 0.32, at a limit of 1.4 atm:

  35. Use the chart

  36. Choosing a “Best Mix” Percentage of Oxygen at Various PO2 Levels • Fraction of Oxygen for the Mix 1.4 3.73 atm 0.38 = 38% mix is best for 90 fsw (27 msw)

  37. Selecting the Appropriate Table • Prepared table • EAN 32% and EAN 36 % tables • EAD principle • convert and use air table • Oxygen Exposure • NOAA oxygen exposure limits • Breathing gas • Repetitive diving procedures • Mix in the tank

  38. EAD and NAUI Air Tables • Air table at theoretical shallower depth • Use EAD chart or OCEANx calculator • Use EAD formula • Write down dive plan on a slate

  39. EAD Formula (fsw) • This is a dive to 81 fsw using 37% oxygen EAN. • The EAD computes to 57.9 rounds to 58. • A 60 fsw air schedule would be used.

  40. EAD Conversion Chart Use the air schedule for no-stop times

  41. Descent rate 75 fpm (25 mpm) Ascent rate 30 fpm (9 mpm) Safety-Stop 3-5 minutes at 15 fsw (5 msw) Cold or strenuous dive use the next greater bottom time Repetitive dives less than 24 hours Flying after diving 12 hours for single dive 24 hours for all others Altitude diving tables good to 1,000 foot (328 meters) elevation only Omitted decompression stay on surface breathe 100% oxygen monitor for DCS plan to evacuate to recompression chamber Diving Table Procedure Review

  42. 36% oxygen 32% oxygen

  43. Table #1 Start No-stop time limits

  44. Table #2 Surface interval time table

  45. Table #3 Repetitive dive time table

  46. Repetitive Diving • With same gas • use same table • dives should be progressively shallower • shallower than 50 fsw (16 msw) use 50 fsw (16 msw) schedule • With different gas • must use EAD conversion and air table • Monitor oxygen exposure

  47. Dive Computers overview • Air • Enriched Air • Multi-level diving • Repetitive diving with computers • Return to dive from computer failures

  48. Using an air computer • OK to use • Show “air” limits • Monitor depth • Observe O2 limit • Watch MOD • Make a safety stop Write MOD on computer

  49. Using an enriched air computer • Mix specific • program oxygen % • Calculates • no-stop time • deco time • Monitors • oxygen exposure • Make a safety stop

  50. Other dive computer applications • Multi-level diving • makes it easy to do • calculates no-stop dive time in real time • monitors oxygen exposure • Repetitive diving • calculates surface intervals • updates no-stop dive time • monitors oxygen exposure

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