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Welcome. Nitrox Diver. Utility Slides. Unit 1: Introduction. What is Nitrox A Bit of History Why Dive with Enriched Air Nitrox Common Misconceptions About Nitrox Terminology. Student Performance: By the end of the lesson you will be able to:. Describe what nitrox is.

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Welcome

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  1. Welcome Nitrox Diver Utility Slides

  2. Unit 1: Introduction • What is Nitrox • A Bit of History • Why Dive with Enriched Air Nitrox • Common Misconceptions About Nitrox • Terminology

  3. Student Performance:By the end of the lesson you will be able to: • Describe what nitrox is. • List other names for nitrox. • State the early history of diving with gases other than air. • State when NAUI sanctioned nitrox diving. • Describe what nitrox is not.

  4. What is Nitrox? • Nitrox is air in which fraction of nitrogen is reduced • Nitrox is also called: • Oxygen-enriched air • Enriched air nitrox • EANx • Reducing Nitrogen • Increasing Oxygen

  5. EANx36 EAN36 This represents an enriched air mixture with 36% oxygen

  6. A Bit of History • Development of nitrox use • Early research and use • Controversy • NAUI endorsement of EANX • NAUI Standards for EANX training

  7. Early Development: • 1878 Paul Bert shows nitrogen to be cause of DCS. • 1908 J. S. Haldane publishes first diving decompression tables. • 1935 Behnke et al. attribute narcosis to nitrogen. • 1959 U.S. Navy Diving Manual introduces oxygen-enriched air. • 1979 NOAA Diving Manual publishes NOAA Nitrox I as standard mix. • 1985 IAND formed–Rutkowski expands nitrox to recreational diving.

  8. Controversy: • 1991 Nitrox training agencies almost barred from DEMA Show. • 1992 aquaCorps/SDRG pre-DEMA Workshop. • 1992 NAUI sanctions teaching enriched air nitrox. • 1994 Rodale’s Scuba Diving supports nitrox training. • 1995 Other recreational training agencies accept nitrox.

  9. Why Dive With Enriched Air Nitrox • Extended Dive Time

  10. Why Dive With Enriched Air Nitrox continued • Repetitive dive times and surface intervals • Safety margins and post dive fatigue

  11. Common Misconceptions About Nitrox • Myth 1: “Nitrox is for technical diving.” • Myth 2: “Nitrox is for deep diving.” • Myth 3: “If you dive with nitrox you won’t get bent.” • Myth 4: “Nitrox is safer than air.” • Myth 5: “If you dive with nitrox you won’t get narcosis.” • Myth 6: “It is hard to dive with nitrox.”

  12. End of Unit 1Introduction • What is Nitrox • A Bit of History • Why Dive with Enriched Air Nitrox • Common Misconceptions About Nitrox • Terminology

  13. Unit 2: Gases & Gas Mixtures • Gas Basics • What’s in Air • Some Facts About Individual Gases • How Gases Behave • Converting Between Depth and Pressure • Calculating Partial Pressures

  14. Student Performance:By the end of the lesson you will be able to: • State the composition of air. • Describe how gases behave. • Explain the relationship between pressure and gas volume. • Describe the solubility of gases. • Explain what partial pressure is and determine various partial pressures. • Determine absolute pressure at depth. • Determine the partial pressure of a gas in a mixture at depth.

  15. What’s in Air? • Composition of air • Oxygen (O2) 0.2095 • Nitrogen (N2) 0.7808 • Argon (Ar) 0.00934 • Carbon dioxide (CO2) ~0.00035 (average) • Others 0.00004 • Simplifying the numbers: • 21% oxygen / 79% nitrogen

  16. How Gases Behave Boyle’s Law: Pressure, Volume, and Density

  17. How Gases Behave continued Henry’s Law: The Solubility of Gases

  18. How Gases Behavecontinued Dalton’s Law:Partial Pressure in Gas Mixtures

  19. Converting Between Depth and Pressure • Absolute vs. gauge pressure

  20. Converting Between Depth and Pressure continued • Converting by formula • To find absolute pressure: P ata = (D fsw / 33 fsw/atm) + 1 atm = (D fsw + 33 fsw) / 33 fsw/atm • To find depth: D fsw = (P ata – 1 atm) x 33 fsw/atm

  21. Converting Between Depth and Pressure Pressure = Depth + 1ATM 33

  22. Converting Between Depth and Pressure continued • Converting by table

  23. Calculating Partial Pressures • If you know the absolute pressure: • The basic formula: Pg = Fg x Ptotal • Using agraphical figure

  24. Using Dalton’s Key Partial Pressure of the GAS Pg Total Pressure ATA Fraction of the GAS Fg

  25. Calculating Partial Pressures continued • Moving between partial pressure and depth using formulas: • Depth to partial pressure • First find the absolute pressure at depth. • Then find the partial pressure of the component gas at that absolute pressure. • Partial pressure to depth • First find the absolute pressure of the gas mixture from the partial pressure and fraction of the component gas. • Then find the depth for that absolute pressure.

  26. Using Dalton’s Key What is the partial pressure of oxygen at 99fsw? STEP 1: What is the fraction of O2 in air? Pg Fg ATA

  27. Using Dalton’s Key • That’s right, 21% • Step 2 • Convert the depth to ATA: • + 1 • 33 Pg .21 ATA

  28. Using Dalton’s Key Good job! 4 ATA Now multiply the two known variables: That’s Right, the answer is .84 So, the partial pressure of O2 at 99fsw is .84 Pg .21 4

  29. Using Dalton’s Key The same principle applies when using EANx. NOW, do the same problem, using EAN32 Pg Fg ATA

  30. Calculating Partial Pressurescontinued Using a table

  31. End of Unit 2Gases & Gas Mixtures • Gas Basics • What’s in Air • How Gases Behave • Converting Between Depth and Pressure • Calculating Partial Pressures

  32. Unit 3: The Physiology of Diving and Nitrox • Narcosis • Decompression Sickness • Physiological Effects of High Oxygen Levels • Physiological Effects of High Oxygen Levels

  33. Student Performance:By the end of the lesson you will be able to: • List the physiological effects of nitrogen in diving. • State physiological effects of low oxygen levels. • List the physiological effects of high oxygen levels. • Recite signs and symptoms of oxygen toxicity. • State limits of hyperbaric oxygen exposure.

  34. Nitrogen Narcosis • The mechanisms of nitrogen narcosis are similar to that of gases used in general anesthesia. • Divers may not be aware that they are impaired. • There is no appreciable benefit to breathing nitrox. • Ascent to a shallower depth is all that is required.

  35. Nitrogen Narcosis • drunken state • impaired judgment • loss or orientation • reduction in problem solving capabilities

  36. Factors that Contribute to Nitrogen Narcosis • Anxiety • Stress • Fatigue • Cold • hard work • high CO2 • alcohol

  37. Decompression Sickness • What causes it • DCS signs and symptoms

  38. Decompression Sickness • Also known as DCS or the Bends • Can occur as the result of a rapid ascent • Ongassing (Ingassing) and Offgassing • Type I • Type II • Administer O2 and get medical assistance

  39. Decompression Sickness continued

  40. Oxygen: The Good and the Bad • Is necessary to sustain life • Too high an oxygen level can be just as harmful as too low

  41. Physiological Effects of Low Oxygen Levels (Hypoxia) • Hypoxia means “low oxygen” symptoms begin to appear if the partial pressure of inspired oxygen falls below about 0.16 atmosphere • Onset of symptoms at a PO2 of about 0.16 ata • Signs and symptoms include impaired mental performance and defective memory, blueness of the lips (cyanosis), fatigue, visual disturbances, and dizziness

  42. Physiological Effects of Low Oxygen Levels (Hypoxia) continued • If the PO2 falls below about 0.10 ata more severe symptoms leading to unconsciousness will occur. • Hypoxia must be monitored in some rebreather situations or deep diving applications.

  43. Physiology of Oxygen • 1.6 Used only for contingency planning • 1.4 NAUI recommended maximum PPO2 for recreational diving • .21 Normal O2 level in atmosphere • .14- .16 Initial stages of hypoxia • .09 - .10 Serious hypoxia /Unconsciousness • Below .08 Coma and death

  44. Oxygen Partial Pressure Limits • 1.4 ata PO2 is more than adequate for 99.9% of the dives you may want to accomplish

  45. Physical Effects of High Oxygen Levels • Central Nervous System Toxicity • has a wide range of signs and symptoms, the most dramatic being epilepsy-like convulsions • CNS toxicity can result from relatively short exposures to high partial pressures of oxygen • Pulmonary Toxicity or Whole Body Toxicity • results from prolonged exposure to elevated partial pressures of oxygen (above about 0.5 atmosphere) • not a concern for recreational nitrox diver

  46. Hyperoxic (above 21% O2) • EANx is actually a hyperoxic mix • 1.4 PPO2 is the recommended limit • Too much O2 can lead to oxygen toxicity

  47. Central Nervous System Toxicity • Factors that can increase your susceptibility to CNS oxygen toxicity • heavy exercise, increased carbon dioxide build-up, chilling or hypothermia, and water immersion • One cannot predict oxygen toxicity

  48. Central Nervous SystemToxicitycontinued • Central Nervous System Toxicity • The mnemonic acronym “ConVENTID” is useful for remembering the most obvious of them: • Convulsions • Visual disturbances • Ears • Nausea • Twitching or Tingling • Irritability • Dizziness or Dyspnea

  49. Managing Oxygen Exposure • The best way to avoid oxygen toxicity problems is to stay within correct oxygen exposure limits.

  50. Managing Oxygen Exposure continued • NOAA Oxygen Exposure Limits • In addition to a general PO2 limit, NOAA has oxygen exposure time limits for a range of oxygen partial pressures from 0.6 ata to 1.6 ata

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