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 • A Bit of History • Why Dive with Enriched Air Nitrox • Common Misconceptions About Nitrox • Terminology
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
A Bit of History • Development of nitrox use • Early research and use • Controversy • NAUI endorsement of EANX • NAUI Standards for EANX training
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.”
Why Dive With Enriched Air Nitrox • Extended Dive Time
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
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.
Gas Basics • Matter • Composition of a gas • Gas mixtures • Gas pressure • Dissolved gases
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
How Gases Behave Dalton’s Law:Partial Pressure in Gas Mixtures Henry’s Law: Solubility Boyle’s Lay: Pressure and volume
Converting Between Depth and Pressure Gauge • Absolute vs. gauge pressure
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
Calculating Partial Pressures • If you know the absolute pressure: • The basic formula: Pg = Fg x Ptotal • Using agraphical figure
What is the PO2 of EAN38 at 34 msw (112 fsw)? Pg = Fg x Ptotal 0.38 * 4.4 atm = 1.67 ata
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.
Calculating Partial Pressurescontinued Using a table
Unit 3: The Physiology of Diving and Nitrox • Narcosis • Decompression Sickness • Physiological Effects of High Oxygen Levels • Physiological Effects of High Oxygen Levels
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.
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.
Decompression Sickness • What causes it • DCS signs and symptoms
Decompression Sickness continued • How to avoid DCS • Treatment for DCS NITROX REDUCES THE RISK OF DCS . IT DOES NOT ELIMINATE IT!!!!!!!!
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
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
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
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
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
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
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).
Managing Oxygen Exposure • The best way to avoid oxygen toxicity problems is to stay within correct oxygen exposure limits.
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
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.
Unit 4:Choosing the Best Nitrox Mix • Enriched Air Nitrox Mixtures • Calculating MOD • Choosing your “Best Mix”
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.
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
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
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
Maximum Operating Depthcontinued • MOD by Table (imperial)
Best Mix • “Best mix” is the nitrox mixture with highest fraction or percentage of oxygen that can be used at the target depth.
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
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
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
Choosing Best Mixcontinued • The Best Mix Table
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
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.
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
Air Dive Tables • So-called “standard dive tables” are designed for diving while breathing air.
No-required Stop Times • EANx Dive Tables give increased maximum dive times for standard mixes.
Enriched Air Nitrox Dive Tables • Enriched Air Nitrox Tables