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Student Performance: By the end of the lesson you will be able to:

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. Unit 1: Introduction. What is Nitrox

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Student Performance: By the end of the lesson you will be able to:

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  1. 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.

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

  3. 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

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

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

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

  7. 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

  8. 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.

  9. Gas Basics • Matter • Composition of a gas • Gas mixtures • Gas pressure • Dissolved gases

  10. 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

  11. How Gases Behave Dalton’s Law:Partial Pressure in Gas Mixtures Henry’s Law: Solubility Boyle’s Lay: Pressure and volume

  12. Converting Between Depth and Pressure Gauge • Absolute vs. gauge pressure

  13. 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

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

  15. What is the PO2 of EAN38 at 34 msw (112 fsw)? Pg = Fg x Ptotal 0.38 * 4.4 atm = 1.67 ata

  16. 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.

  17. Calculating Partial Pressurescontinued Using a table

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

  19. 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.

  20. 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.

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

  22. Decompression Sickness continued • How to avoid DCS • Treatment for DCS NITROX REDUCES THE RISK OF DCS . IT DOES NOT ELIMINATE IT!!!!!!!!

  23. Oxygen: The Good and the Bad • Is necessary to sustain life • Too high an oxygen level can be just as harmful as too low • Oxygen is our life-support gas • Theprimary waste product is carbon dioxide Oxygen and Metabolism

  24. 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

  25. To avoid Oxygen Toxicity we have Partial Pressure Limits • The generally accepted limit for nitrox diving is: • 1.4 ata PO2 • 1.6 ata PO2 as a contingency • 1.4 ata PO2 is more than adequate for 99.9% of the dives you may want to accomplish and is the standard at MLML

  26. 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

  27. 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

  28. 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

  29. Central Nervous SystemToxicitycontinued • Central Nervous System Toxicity • Convulsions are the most obvious and most serious signs. • Possible precursors to convulsions are: • Visual disturbances, tunnel vision, dazzle or seeing “fireflies.” • Ear ringing, tinnitus, or sounds like an approaching train in a tunnel. • Nausea, including vomiting. • Twitching, especially of the lips and small facial muscles or the hands, or tingling (paresthesia) especially in the fingers. • Irritability, restlessness, euphoria, dysphoria (uneasiness or feelings of impending doom), anxiety, or general confusion. • Dizziness and vertigo or dyspnea (difficult or labored breathing).

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

  31. 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 • PO2=1.4 ata 111’ on EAN32

  32. Avoiding CNS Toxicity • CNS toxicity is avoided by abiding by easily managed limits. • Remember that the recommended maximum PO2 for recreational nitrox diving is 1.4 atmospheres, with a PO2 of 1.6 atmospheres as a contingency amount. • Plan your dives and choose a nitrox mix that is appropriate to the dive.

  33. Unit 4:Choosing the Best Nitrox Mix • Enriched Air Nitrox Mixtures • Calculating MOD • Choosing your “Best Mix”

  34. Student Performance:By the end of the lesson you will be able to: • Define Maximum Operating Depth and determine it for any nitrox mixture. • Describe what “Best Mix” means and how to calculate it.

  35. Enriched Air Nitrox Mixtures • Two Standard Nitrox Mixes • EANx 32 or NOAA Nitrox I • EANx 36 or NOAA Nitrox II • Partial Pressure of Oxygen is the Limiting Factor • Limit P02 to 1.4 ATA • 1.6 ATA as a contingency

  36. Maximum Operating Depth • The maximum operating depth (MOD) is the maximum depth that should be dived with a given nitrox mixture. • MOD should be derived from the recommended maximum oxygen partial pressure of 1.4 atmospheres • MOD should be written prominently on the cylinder’s contents label

  37. Find the MOD for EAN36 (use 1.4 ata as O2 partial pressure limit)? Maximum Operating Depthcontinued • Calculating MOD • Begin by finding the total pressure that it takes to produce the maximum acceptable oxygen partial pressure Pg = Fg x Ptotal • Then convert to a depth D fsw = (P ata – 1 atm) x 33 fsw/atm

  38. Maximum Operating Depthcontinued • MOD by Table (imperial)

  39. Best Mix • “Best mix” is the nitrox mixture with highest fraction or percentage of oxygen that can be used at the target depth.

  40. Choosing Best Mix continued • Calculating best mix is similar to the calculation for maximum operating depth in reverse. • Step 1: Determine the absolute pressure at the target depth or

  41. Choosing Best Mix continued • Step 2: Determine what fraction will produce the target partial pressure at that absolute pressure Fg = Pg/ P total or FO2=PO2 / P total

  42. Choosing Best Mix continued For my thesis work dive surveys my maximum depth will be 120’ as a contingency I am planning my maximum depth as 125’. I want to find the EAN mix with the highest percentage of O2 that I can use for my survey dives. What is the EAN mix I should take with me??????????? My oxygen partial pressure limit is the MLML/AAUS standard. Pg = Fg x Ptotal

  43. Choosing Best Mixcontinued • The Best Mix Table

  44. Unit 5:Dive Tables and Dive Computers • Dive Tables • Equivalent Air Depth and Standard Air Tables • Using NAUI’s RGBM Tables • The Rule of Halves • Dive Computers

  45. Student Performance:By the end of the lesson you will be able to: • Demonstrate the use of NAUI EANX Dive Tables. • Define Equivalent Air Depth and how it is used with Air Dive Tables. • Demonstrate how to determine and calculate Equivalent Air Depth. • Demonstrate the use of the NAUI RGBM Nitrox Dive Tables. • State the “Rule of Halves” and how to use it in all of your diving. • Describe the procedures for using dive computers for EANX diving.

  46. Dive Tables • There are many different dive tables in use today • NAUI Dive Tables • NAUI RGBM Tables • U.S. Navy Tables • DCIEM Tables • Buhlmann based tables • Other Tables

  47. Air Dive Tables • So-called “standard dive tables” are designed for diving while breathing air.

  48. No-required Stop Times • EANx Dive Tables give increased maximum dive times for standard mixes.

  49. Enriched Air Nitrox Dive Tables • Enriched Air Nitrox Tables

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