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Oxygen Enriched Air (Eanx)

Oxygen Enriched Air (Eanx)

-Enriched Air Larry “Harris” Taylor, Ph.D. Coordinator, U of Michigan

© Larry P. Taylor, Ph.D. All Rights Reserved LPT Your Instructor U of MI Diving Safety Coordinator AAUS sanctioned Internationally rated 3 - star instructor (CMAS) National Master Scuba Instructor (President’s Council) > 100 Diving Certifications > 100 Diving Publications > 1,200,000 visitors to “Diving Myths & Realities” web site Library: one of the best resources in North America Scuba Diver since 1977 Scuba Instructor since 1980 DAN Instructor since 1991

EANx Instructor since 1992 Ph.D. Biochemistry

LPT Lecture is a Democracy! You control speed with your questions

LPT There are no “stupid questions” !

The only “Dumb Question” is the one that is unanswered ‘cause it was not asked The “Dumbest Question” is the unasked question that could’ve solved a problem

LPT Socratic Method:

Asking & Answering Questions

Still one of the best learning tools

LPT The Water-work is Dictatorship! Do as instructed or leave the water

LPT Knowledgeable, Physically Fit Divers GospelAccording to “Harris” Have More Fun!

LPT Terminology

LPT Terms Used to Describe Recreational Mixes The following generic terms are used to describe mixtures of and oxygen God’s Air (atmospheric air) Norm Air (atmospheric air) Normoxic Air (atmospheric air) Denitrogenated Air (DNA) Enriched Air (EAN)

EANx (where x is the percentage of oxygen in the mix) Nitrox Oxygen Enriched Air (OEA) Oxy-Air Safe Air

There are two standard mixes:

NOAA I: 32% Oxygen (EAN32) NOAA II: 36% Oxygen (EAN36) Nitrox term original use: NOAA habitat mix Less oxygen than air Air I II Emphasizes N2 major component Consistent with “heli-ox”

LPT EANx Myths

LPT Nitrox Is Safe or Nitrox is Safer Than Air Safe (according to Webster) means without risk Nothing in diving (life) is without risk

EANx has significant advantages But, has concerns:

O2 toxicity (shallower onset than air) Time / depth limits for both N2 and O2 Proper mix determination, mixing, and analysis Additional equipment requirements Additional expense

LPT Nitrox Is For Deeper Diving

EANx has very stringent depth limits (mandated by oxygen ) Most useful in 50 – 110 fsw range

(many deaths on EANx have been deeper than 60 fsw)

LPT Nitrox Eliminates DCS Risk Nothing eliminates DCS risk in diving

There are techniques to reduce risks, but risk never equals zero

Benefits Never Infinite Risks Never Zero Risk / Benefit is an individual decision

LPT Nitrox Makes DCS Treatment Impossible

Divers using Air or EANx have same treatment protocols Advanced divers track oxygen exposure (OTU’s)

Recreational EANx dives do not get close to standard OTU limits Even if OTU limit exceeded, medical treatment would be done

LPT Nitrox Eliminates Narcosis

Narcosis related to total on board Your body chemistry on the day you dive No documented study to validate this myth

LPT Using Nitrox is Difficult

There are procedures for tracking both N2 and O2 (similar to basic air diving tables)

Diving is basically: inhale, exhale, repeat

LPT EANx Advantages

LPT Longer No-Deco-Required Diving

Depth No-stop deco times (minutes)

USN Air NN32 NN36 (fsw) (msw) 21% 32% 36%

50 15 100 200 310

60 18 60 100 100

70 22 50 60 60

80 25 40 50 60

90 28 30 40 50

100 31 25 30 40

110 34 20 25 30

120 37 15 25

130 40 10 20

LPT Longer No-Deco-Required Diving

This is termed the “Decompression Advantage” of EANx LPT Longer Repetitive Dives Air Example Dive # 1: 90 fsw / 20 min: F One hour SIT: F > E Dive # 2: 80 fsw  17 min allowed

Same Dive Using 36% O2 Dive # 1: 90 fsw / 20 min: E One hour SIT: E > D Dive # 2: 80 fsw  36 min allowed

Using EANx provided 19 minutes more no-stop dive time

Bottom Line: EANx allows more bottom time

LPT Shorter Surface Interval Two different teams dive 30 min to 80 fsw

Team 1 breathed air; Team 2 breathed EAN36

Team 1 emerges with a letter group of H Team 2 emerges with a letter group of F

For a 2nd dive to 80 fsw for 30 minutes

Team 2 must wait 0:53 to enter as E Team 1 must wait 6:33 to enter as A

Bottom Line: EANx allows more bottom time More on-site time = more cost effective diving LPT “Safer” Table Use Use EANx on dive (within pO2 limits) Use Air table of choice will have less nitrogen on board Common Practice in the Recreational Community Lowered DCS Risk More Expensive Fills

This is termed the “Physiological Advantage” of EANx LPT Divers Feel Less Fatigued After Dive The “Feel Good” Gas Appears to be a supported claim As long as there is no workload Most likely will never be rigorously studied

Explained by lowered “decompression stress”

O2 moved into cell used for N2 accumulates in cell N2 moves out on ascent Less N2  Less mechanical “abrasion” from gas movement

LPT Air Diving is all about Nitrogen Management

Oxygen Enriched Air Adds Oxygen Concerns When properly managed: Oxygen Enriched Air offers potential for extended bottom times

When first introduced to : Number of deaths in the 60 – 100 fsw range So many that diving oxygen enriched air was termed “death seeking behavior” Academics hoped recreational scuba would upgrade classes (we were wrong) This is a class in simultaneously managing nitrogen and oxygen while diving

LPT Medical Matters

LPT Gases in Air

Oxygen: necessary for life

We “burn fuel” C6H12O6 + 6 O2  6 CO2 + 6 H2O Too little oxygen (hypoxic) no life Too much oxygen (hyperoxic)  toxic reactions

Nitrogen: considered physiologically inert Involved in & DCS (DCI) Dilutes oxygen in air; limits combustion Others Most not considered in this class … assumed part of nitrogen component

LPT Air as a Mix

Air: Relatively inexpensive Commonly available Most common underwater breathing mix

But, N2 causes problems at deeper depths: Nitrogen Narcosis

LPT Nitrogen Narcosis Narcosis: Pronounced “anesthetic effect”

Observed when breathing N2 containing mixes at depth Deeper the depth, more intense the effect

So-called Martini’s Law: (Not considered valid) Every ~50 fsw of depth = 1 dry martini on an empty stomach

LPT Many Gases Have a Narcotic Potency

Meyer-Overton Theory of Anesthesia Gases dissolve in nerve tissue myelin ( layer) Altered electrical conduction of nerves

Oxygen metabolized, does not build up Diminishes at-depth narcotic potency

Lipids NOT total picture

GABA receptors involved

Complex Problem Not all understood

LPT Nitrogen Narcosis Signs & Symptoms Warm, clear water: euphoria (“Laughing Gas” as model) Tendency to giggle Tunnel vision (syncope) Idea fixation (repetitive behaviors) Shortened attention span Declining neuro-muscular coordination Numb lips Inability to concentrate Cold, limited visibility water: dread Sense of being stalked (“It” is out there … somewhere) Loss of confidence (sense of helplessness) Intense anxiety

LPT Nitrogen Narcosis Symptoms exacerbated by: cold

work load (CO2) anxiety fatigue drugs alcohol menses (?) Symptoms: Typically noticeable ~ 100 fsw, but onset as shallow as ~ 60 fsw Sense of well-being: masks CNS impairment May be not be noticed by affected diver Individually variable CNS impairment increases with time / depth Ascent relieves problems; typically, no residuals LPT Underwater “Narcosis Test”

“OK” signal is “automatic reflex” Narcosis Test Often NOT reliable indicator (for cognitive processing) Show 1 to 4 fingers to diver Diver adds 1 to # fingers Shows added count

LPT Nitrogen Narcosis: Classic Myth Narcosis is reason for 130 fsw depth limit

Turns out, 130 fsw is US Navy limit to use vintage scuba on a salvage dive ‘cause At the time diving rules were established, Double hose regulators would not support hard working below 130 fsw

LPT (CO2) Carbon Dioxide Metabolic waste product Potent vasodilator Helps maintains blood pH Breathing “Trigger” Excess levels in blood most undesirable

CO2 produced faster than eliminated

CO2 Production: Resting: 300 mL/min Working: 2000 mL/min (unfit person has >> production)

LPT Carbon Dioxide (CO2): Major Problem in Diving Sources of Carbon Dioxide: Contaminated Gas (very rare) Work load exceeding ventilation “Skip Breathing” Poor ventilation (equipment ) poor regulator full face mask

LPT Cardinal Rule of Diving “Never Hold You Breath”

But, you hold your breath every time you breathe with a regulator Breathing On Surface: Inhale … exhale … hold

Breathing With Regulator: Inhale … hold … slow exhale … hold

During the hold, you are: holding breath (embolism risk)

building up CO2 Don’t consciously extend the “hold phase” (called “skip breathing”)

LPT (High CO2)

A CO2 “Hit” Slight CO2 build-up Increased (attempt to vent) Poor ventilation

CO2 continues to increase

High CO2 perceived as “regulator not working” Suspicion: many “out of air” emergencies are CO2 hits

LPT CO2 Cascade Carbon dioxide exacerbates most dive maladies

Increased O2 in EANx raises density Greater density increases

Israeli military studies:

Breathing EANx increases CO2 retention

LPT Hypercapnia (High CO2)

Studies show oxygen-enriched air promotes CO2 retention Higher the O2 concentration, the greater the effect Greater density at depth requires more work to breathe Important to monitor breathing

Suspect CO2 build-up  Stop Breathe slowly (Imagine STOP sign) Until breathing returns to normal

LPT Hypercapnia (High CO2)

Main Diving Issues: Respiratory Starvation Headache Center of forehead

LPT Carbon Monoxide (CO)

CO binds to hemoglobin 250x > O2

Too much CO  No O2  lethal From incomplete combustion: Compressor oil Engine exhaust Cigarette smoke Kerosene heaters

Humans metabolism releases CO Minor amount: factor in closed environments (habitats, subs & space capsules)

1 cigarette: more CO than USN allows in their LPT Origin of “The Bends” Building of Brooklyn Bridge (1870’s) Caisson workers experienced pain on surfacing Assumed postures similar to women dancing “Grecian Bend” Wanted to return to work to lessen the pain Being “Bent” was an insult

Established: Caisson's disease and Sponge Diver’s disease Same malady

Haldane used goats to develop dive tables (1930’s) Goats forelimbs would bend on too rapid ascents So, they were “bent” Developed ascent tables that would not bend goats LPT Gases at Depth

On the surface: Gases diffuse across cell membranes Concentration reaches equilibrium Each gas acts independently On descent: Gases diffuse across cell membranes Movement based on gas Each gas acts independently At depth: Gases diffuse across cell membranes Concentration reaches equilibrium For all components in breathing gas

LPT Gases at Depth Gases eventually equilibrate tissue gas with environment Increased depth increases amount of dissolved gas Nitrogen: accumulates … not used by metabolism

Different tissues ( compartments) build up gas at different rates Compartment nitrogen level is mathematically approximated Basis of decompression tables

No correlation between a biological tissue and a mathematical compartment

Different models will use Different number of tissue compartments Different mathematical expressions to approximate gas concentration

Nitrogen Partial Pressures:

Surface: 0.79 x 1 ata = 0.79 ata

99 fsw: 0.79 x 4 ata = 3.16 ata

LPT Decompression Sickness On ascent, gas pressure in tissues greater than ambient Gas bubbles out of tissues Bubbles may form on dive (diver / profile dependent) Some dives /divers may not show significant bubbles) Too many bubbles: Decompression Sickness (DCS) Symptoms observed depend on where bubbles form

Bubbles in Tissue Bubbles in Veins

LPT Bubble Trouble Most bubbles safely eliminated via venous circulation and lungs Too many bubbles overwhelm physiology Proteins of coagulation cascade react to gas bubbles in tissues coat bubble and initiate clotting at site of bubble

Electron micrograph of protein coated bubble Arrow points to platelet adhering to coagulation protein coat

LPT Bubble Trouble

Bubbles in capillaries block flow Pressure builds up Vessel walls split Fluid leakage Activation of inflammatory response

Very complex biochemical complications Much still not understood

LPT Symptoms Depend on # Bubbles and their Location Frequency and Onset of Symptoms

LPT Bubble Trouble Bubble trouble assumed to be primarily a “too much N2” malady N2 builds up abundance of N2 in breathing mix increased time / depth drives N2 into tissues N2 not used in metabolism Over abundant N2 escapes tissues on ascent Basis of oxygen-enriched air

Obvious remedy: decrease amount of N2 in breathing mix Use gas involved in metabolism (oxygen)

LPT Oxygen Enriched Air Reduces Nitrogen Tissue Loads

Breathing Air Breathing EAN32

Primary advantage of oxygen enriched air

Decompression obligation depends on N2 tissue load Decompression obligation reduced by replacing N2 with O2

LPT Too Many Bubbles: Decompression Sickness Type I (Pain Only) Musculoskeletal Insult limb or joint pain Itching Skin rash Localized swelling Type II (CNS Involved) Spinal Involvement numbness / tingling bi-lateral paralysis no bladder function loss of sexual response Inner ear (staggers) DAN: Lungs (chokes) > 60% of DCS involve depths > 80 fsw Cardiac arrest Type I on ascent LPT Skin Bends Signs & Symptoms: Skin discoloration Purplish and flat Compared to a rash: More reddish and “textured” Itching

Most often associated with:

Chamber dives Females Hot shower post-dive

~ 20% show neurological involvement

LPT Patent Foramen Ovale Opening in septum secundum Patent: open Foramen: aperture in tissue or bone Ovale: oval shaped

Present in: Unborn (mom functions as lungs) ~25 – 30 % of population ~ 5% of serious DCS cases

PFO: Some blood flow bypasses the lungs (bubble filter) Bubbles in circulation: can pass into arterial circulation (Best to assume we bubble on every dive ascent) Sometimes present in severe DCS incidents Possible source of CNS lesions seen in brain and spinal cord)

LPT PFO: Allows Direct Path to Arterial Circulation

Equalizing Middle Ear Pressure

Vigorous Valsalva Dangerous technique Possible Round Window Rupture Can drive bubbles (if present) thru PFO

Frenzel Safest, most effective

LPT DCS Risk Factors The following conditions are considered to increase DCS risk: dive (deeper depth/longer time) profile older age obesity (poor physical condition) dehydration poor circulation (tight clothing) illness scar tissue alcohol (12 hours pre or post dive) fatigue strenuous exercise during dive cold repetitive dives multiple ascents / descents on same dive multi day diving history of DCS being female (?) misuse of dive tables / dive computers LPT Serious DCS Cases Involve Spinal Cord Bi-lateral dysfunction/numbness May increase with time May result in permanent dysfunction Affects Ability to: walk excrete have sex Every dive is gambling with spinal cord function: Your body chemistry on the day you dive Best tactic: Love your spinal cord: dive conservatively

LPT Lowering Bubble Formation Ascent Rate: A Compromise Minimize risk by:

Not “pushing” tables Slow ascents Especially shallow Safety Stops Staying hydrated US Navy Combat Swimmers: 120 fsw / min Agonizingly slow: US Navy Salvage Divers: 25 fsw/min

Monitor with gauges The compromise: 60 fsw / min

No correlation to physiology

LPT Swimmer’s Ear (Otitis Externa)

Most freshwater contains microbes and fungi They survive well in warm, dark places They do not survive well in acidic environments

Prevention: Rinse ears with vinegar after every diving day Avoid alcohol in ear: dissolves protective ear wax

LPT Physics

LPT Pressure = per Unit Area

UNITS: Related to of atmosphere mm Hg torr inches Hg

cm H2O inches H2O atm ata (absolute atmospheres) Related to force psi (pounds / in2 ) Pa ( Pascals: Newtons / m2) bar (100 kPa) Related to in-water depth ffw (feet fresh water) fsw (feet sea water)

Otto von Guericke 1654 LPT One atmosphere (atm) of Pressure 1 atm equals: 760 millimeters of mercury 760 torr 29.92 inches of mercury 101.3 kilopascals (kPa) 1.01325 bars 14.7 lbs/in2 (psi) 33 feet of sea water (fsw) 34 feet of fresh water (ffw)

LPT Absolute Pressure Total pressure on system: gauge pressure +

Pt = Pg + Pa For absolute pressure: Need to add 1 atm

0 fsw SPG Pressure

Use Appropriate Units

33 fsw

Pa Pg

66 fsw Gauges calibrated: fsw or msw

LPT The partial pressure:

Portion of the total pressure exerted by single component of a mix

Fraction of the component gas multiplied by the total pressure

Total pressure: sum of all the partial pressures of the component

Air at 1 atm

% Pa 79 % N2 = 0.79 atm 21 % O2 = 0.21 atm 100 % = 1.00 atm

LPT Converting Pressure Measurements

Converting depth sea water (fsw) to absolute pressure in atmospheres: 33 fsw of depth represents 1 atm of pressure (33 fsw / 1 atm)

(D fsw + 33 fsw) = P ata 33 fsw / atm

For a depth of 33 fsw

(33fsw + 33 fsw) = 2.0 ata 33 fsw / atm

LPT Converting Pressure Measurements Americans commonly use psig for cylinder pressures Others use units of bar (100 kiloPascals)

From psig to bar

1500 psi x 1 atm x 1.01325 bar = 103 bar 14.7 psi 1 atm

From bar to psig

100 bar x 1 atm x 14.7 psig = 1451 psig 1.01325 bar 1 atm

Let the units drive the

LPT Converting Pressure Measurements Converting absolute pressure in atmospheres to depth of sea water (fsw) 33 fsw of depth represents 1 atm of pressure (33 fsw / 1 atm) (ata x 33 fsw/atm) - 33 fsw = D fsw

For a pressure of 3 ata (3 ata x 33 fsw/atm) – 33 fsw = 66 fsw

LPT John Dalton

School teacher with contributions to: Atomic Theory Understanding Color Blindness Studies on Gas Behavior

Dalton’s Law of Partial Pressure (1803)

Ptotal = P1 + P2 + P3 + … Pn

For a mixture of ideal gases, total pressure = sum of the partial pressures of gases present

LPT Dalton’s Law: Partial Pressures Dalton’s law: In a mixture of gases, the total pressure is the sum of the partial pressures of the individual components

P = P1 + P2 + P3 + … + Pn

The partial pressure of a gas is the product of the fraction of that gas times the total pressure

Pg = Fg x P total

Where

Pg = partial pressure of the component gas Fg = fraction of the component gas in the mixture Ptotal = the total pressure of the gas mixture

LPT Dalton’s Law: Partial Pressures

Total pressure is always the sum of component gas pressures

LPT Dalton’s Law: Partial Pressures Pressure in alveolar spaces immediately equilibrates with blood

LPT

Irish Alchemist Father of modern chemistry Founder of Royal Society

Pressure - Volume relationship (1660) New Experiments: Phsico-Mechanical Touching the spring of air and their effects (1660)

The Sceptical Chymst (Air, Earth, Fire, & Water not elements) (1661)

In an evacuated chamber Observed bubble in snake’s eye Reduced Pressure Changes Physiology Bell produced no sound Air needed to carry sound

LPT Boyles’s Law At constant , the volume of a flexible container

depends upon the surrounding pressure

At constant temperature, in a FLEXIBLE container volume is indirectly proportional to the absolute pressure

P1 V1 = P2 V2

LPT Boyles’s Law

Hyperbolic Curve: Pressure & Volume Inversely Proportional Greatest volume change: pressure near zero

Means greatest risk to tissue: shallow water

Explains: Ear Discomfort while ascending / descending Grandpa’s knee forecasting weather Changes in all gas volumes with altitude / depth Changes in pressure with altitude / depth

LPT Boyles’s Law

LPT Jacques Charles French chemist

Scientific Advisor to Montgolfier brothers

Volume - Temperature Relationship (1787)

1783 – First hot air balloon Sack cloth and paper with 1800 buttons Redesigned the way hot-air balloons were built: Silk instead of paper construction Hydrogen instead of hot air line Wicker basket passenger compartment

LPT Charles’ Law

Heat energy increases molecular motion.

Volume of flexible container increases

At constant pressure, in a FLEXIBLE container volume is directly proportional to the absolute temperature

V = V 1 2 T1 T2

If T = negative, volume = negative (not realistic)

Need temperature to be positive So, temperature must be in absolute degrees (K) LPT Charles’ Law

Absolute Zero (-273.16 oC)

LPT Charles’ Law As your ambient temperature changes Gas volume in bcd / changes Must add air / vent to compensate

This is particularly noticeable at a

LPT Joseph Louis Guy-Lussac

French chemist Student of Jacques Charles Studied Gases In Chemical Reactions

Pressure - Temperature relationship (1809) Maybe called Charles’s Law or Charles’s Law #2 Sometimes called Amonton’s Law (Proposed relationship, but lacked technology to prove) But, Guy-Lussac was first to experimentally document P-T relation

LPT Guy-Lussac’s Law Heat energy increases molecular motion.

Volume of cylinder cannot increase, the pressure increases

At constant volume, in a RIGID container: pressure is directly proportional to the absolute temperature

P1 = P2

T1 T2

LPT Guy-Lussac’s Law

Plot is Linear: Pressure & Temperature Directly Proportional

Ambient temperature change: Affects cylinder pressure

Absolute Zero (-273.16 oC)

LPT General Gas Law

p1 v1 = p2 v2 t1 t2

If P constant: If V constant: If T constant:

v1 = v2 p1 = p2 p1v1 = p2v2

t1 t2 t1 t2

Charles Guy-Lussac Boyle

LPT William Henry

British chemist Solubility of gases

Composition of HCl and NH3 Disinfecting powers of heat

Gas in liquid solubility: Henry’s Law (1803) Determined solubility of gases in liquids a function of: Partial pressure of the gas Temperature of the system Characteristics of the liquid

LPT Henry’s Law The amount of any given gas that will dissolve in a liquid at a given temperature is a function of the partial pressure of the gas that is in contact with the liquid and the solubility coefficient of the gas in the particular liquid

Sg = KH x Pg

Sg solubility of the gas Kh liquid solubility constant Pg Partial pressure of the gas

LPT Henry’s Law Solubility of a gas in a liquid is directly related to the pressure of the gas on the liquid

Increase in pressure  increase in solubility Decrease in pressure  decrease in solubility

Reason for decompression sickness, nitrogen narcosis, and

LPT Henry’s Law – Additional Gas solubility changes with temperature

Colder water (Great Lakes): Divers carry additional gas loads Reason for adding dive table rep group in cold water

LPT Recreational Dive Tables

LPT Dive Tables Mathematical model of each compartment N2 Profile Ascent “deco stops” based on keeping tissue pressure below a limit “Controlling tissue” is tissue with highest partial pressure

Ascent defined by:

# compartments t1/2 of each Type of curve Allowed D p

Curves NOT correlated To any tissue

LPT Historically, Everyone used US Navy Tables Most used, most documented dive tables on the planet

In public domain, cannot be commercialized Until early ’80’s, all US training agencies used the US Navy tables LPT NuWay Table

First to do: RNT Arithmetic in table

US Navy Deco on back side

Circa 1972

LPT PADI Version US Navy Table

Credit Card Sized (larger version available) Extremely popular Exactly fit most log books Required flipping tables to use Circa early 1980’s

LPT 1980’s: Enter era of “Designer Tables” Every agency designed their own table So they could be copyrighted and sold for ~6x the $ US Navy tables

Recreational scuba marketing claim: US Navy Tables have a 5% failure rate Actual rate of DCS hits for US Navy diving: 0.0589 % Most had no testing or physiological basis … just changed some numbers

LPT DSAT Recreational Dive Planner (RDP)

Designed by Raymond Rogers, DDS

LPT Dive Table Comparison Summary of an Exercise from Karl Huggins’ Decompression Workshop

LPT Oxygen-Enriched Air History

LPT Antoine Lavoisier, ~ 1774 Demonstrated 1/5 of air volume supported life Called this “de-phlogistonized air” oxygen

Remaining 4/5 labeled azote (not animal) Now called nitrogen French lawyer with passion for chemistry As tax auditor, was skilled in tabulating data

Joseph Priestley, ~ 1774 Isolated Lavoisier’s oxygen Credited with discovery of oxygen as element English Minister Discovered 7 new “airs” (gases) 1772: Invented process of carbonation

Suggested breathing oxygen could be pastime for wealthy

LPT , 1870’s Father of 1874

Furnished balloonists with 40-70 % O2 Gas in pig bladders, sustained life during ascents

1878 Published results of 670 oxygen enriched air exposures Used breathing oxygen for treating Sponge Diver’s Disease

Proposed oxygen responsible for CNS seizures

LPT 1878 Revised first (1853) developed by Theodore Swann Master Diver for First documented oxygen (50 - 80%) enriched air in-water dive

LPT , Early 1900’s for Siebe Gorman 1910 Submarine escape apparatus using 50% oxygen rebreather

1912 With Leonard Hill: Commercial Hard Hat Used 50% oxygen mixes Competitive advantage: longer bottom time salvage operations

LPT Draegerwerk Underwater Sled, 1913 Underwater sled: allowed tourists to view underwater world Used 60 % oxygen rebreather (on sled and for salvage operations)

Scientific American reported: This might be a potential underwater recreation

LPT Siebe Gorman Commercial Salvage, 1930’s

Established diver problem if pO2 > 2 atm Controlled oxygen Varied concentration with depth

Developed commercial EANx dive tables Enormous competitive advantage

Coined phrase “Oxygen Pete” Monster that attacked divers at high oxygen concentrations

LPT WW II British Gibraltar Defenders Used 40 – 50 % oxygen Attacking Italian frogmen used 100% oxygen rebreathers

British grabbed attackers and took them deep Attackers had oxygen toxicity seizures and drowned

British Operational Orders: No rapid swimming unless provoked by enemy swimmers

(First hint of potential CO2 retention issues)

One of best kept secrets of WW II

Extensive oxygen research: basis of modern understanding

LPT Post WWII Developments EDU works on oxygen enriched air rebreathers British send data already done in the 40’s (1950’s) US Navy EDU publishes Oxygen Enriched Air tables (1950’s)

Robert Workman (Navy EDU) EANx and He- air decompression tables (1950’s)

International Union of Contractors use EANx in salvage operations (1960’s) 1970’s - DCIEM develops cold water tables

Designs rebreathers to deliver constant pO2

1978 – NOAA established formal procedures Standardizes on 32 (NOAA I) and 36 % (NOAA II) oxygen

LPT EANx For Scuba Operations 1979: Dr. Morgan Wells introduces scuba protocols to NOAA manual

Considered responsible for introducing EANx to scuba 1985: introduces EANx to recreational community (IAND) 1988: American Nitrox Divers International (ANDI) “safe air” formed

1988: NOAA Workshop … settled on EANx as descriptive term 1992: IAND becomes IANTD

LPT The Devil's Gas 1991: DEMA (Houston, Texas) banned nitrox training providers

1992: BSAC banned its members from using nitrox during BSAC activities

1993: Skin Diver published that nitrox was unsafe for sport divers

Early 90’s: Peter Bennett (of DAN): Nitrox divers cannot be treated for DCS

LPT “EANx” Arrives 1992: NAUI begins Nitrox training 1993: Technical Divers International (TDI) formed 1993: Dive Rite produces first Nitrox 1994: NASA standardizes Oxygen Enriched Air for astronaut training 1996: PADI offers Nitrox

LPT Oxygen Toxicity

LPT Oxygen Necessary For Life Metabolism: narrow oxygen partial pressure window Too little oxygen (hypoxic)  no life

C6H12O6 + 6 O2  6 CO2 + 6 H2O

Too much oxygen (hyperoxic)  toxic reaction

Cellular components + O2  “Bad stuff” (ROS)

Hypoxia

pO2 < 0.16 ata pO2 > 1.6 ata

LPT Symptoms

Ultimately: No oxygen  no life LPT Hyperoxia Reactive Oxygen Species (ROS) Constantly Produced Direct result of oxygen molecule’s chemical reactivity

ROS are biologically very destructive Numerous biological defenses against ROS SOD Superoxide Dismutase GTP Glutathione Peroxidase Lots of anti-oxidant molecules LPT Hyperoxia Effects

Higher pO2 increases ROS concentrations Le Châtelier’s Principle Increase partial pressure: drive reaction to the right

Cellular components + O2  “Bad stuff” (ROS)

LPT Hyperoxia Effects

Symptoms depend on pO2 and exposure time LPT VENTID – C Hyperoxia Effects on CNS

V Vision Not a progression … maybe no warning E Ears May start with convulsions N Nausea Twitching usually starts at lower lip T Twitching I Irritability Common causes: D Dizziness Exceeding the oxygen exposure limits C Convulsions Using an incorrect mix for the depth Using wrong deco gas at depth ConVENTID Recognition of ANY Symptom  immediately ascend

(reduce pO2)

LPT Hyperoxia Effects on CNS Oxygen toxicity effects may be enhanced by: Heavy exercise Breathing dense gas Breathing against resistance Increased CO2 buildup Chilling or Water immersion (as opposed to “chamber diving”) Individual tolerance to oxygen toxicity varies over time Tolerance varies from individual to individual

Oxygen tolerance tests no longer considered valid

LPT Hyperoxia Effects on CNS Seizure in sport is usually fatal Spit out regulator (reflex inhale) and breathe water and “escape to surface” (embolize)

Diving EANx requires monitoring oxygen exposure

Surviving convulsions: reason to use full face mask

LPT Hyperoxia Effects on CNS Anecdotal suggestion that Sudafed increases seizure risk (seizures are a side effect in children) Other concerns: anti-motion drugs (especially transderm (scopolamine)) aspirin, caffeine, viagra, nitro heart medication Never rigorously studied Best to avoid diving with any drugs

LPT Biological Defenses Occasionally Sold to Divers No evidence that ingestion of unprotected SOD has any physiological effects

Ingested SOD is broken down into amino acids before being absorbed

SOD bound to wheat proteins MIGHT improve its ROS protection

Nitrox Therapy is a power workout Nitric Oxide promoter An absolute contraindication for diving (Nitric oxide implicated in oxygen toxicity convulsions) Recent Findings suggest eating dark chocolate bar ~ 30 minutes pre-dive offers some protection from oxidative cell damage

LPT Whole Body Oxygen Toxicity Formerly Pulmonary Toxicity (Lorrain Smith Effect) Contrasted to CNS Toxicity (Paul Bert Effect)

CNS: Rapid Onset

Whole Body Slow Onset

LPT Whole Body Oxygen Toxicity

No-deco stop diving concerned primarily with CNS toxicity

Whole Body a concern for: Extended range Deco diving Intensive, multiple dive operations

Mixes with high O2 concentration

Onset: breathing high pO2 (> 0.5 ata) for hours Relief: breathing pO2 < 0.5 ata Primarily effects the lungs Typically, not a concern in standard range diving

LPT Whole Body Oxygen Toxicity Symptoms Pulmonary Body optimized for 21% O Chest pain or discomfort 2 High pO2 alters tissue structure Coughing Lung tissue Chest tightness Thickens Fluid in the lungs Becomes less pliable Reduction in vital capacity Reduces vital capacity

Non-pulmonary Skin numbness and itching Headache Dizziness Nausea Visual disturbances Diminished aerobic capacity

LPT Oxygen Toxicity Units (OTU)

Based on decreased lung vital capacity while breathing 100 % O2

1 OTU = Breathing 100% O2 for 1 minute

At constant depth:

-0.83 OTU = t [ (pO2 – 0.5) / 0.5 ]

Ascending and descending:

1.83 1.83 OTU = 0.27 t [ {(pO2 f – 0.5) / 0.5 )} - {(pO2 i – 0.5) / 0.5 } ] pO2 f – pO2 i

time (t) in minutes

pO2 at constant depth in absolute atmospheres pO2 f at final condition in absolute atmospheres pO2 I at initial condition in absolute atmospheres Solving involves integration of pressure over time  best done by computer

LPT Oxygen Toxicity Units (OTU)

EANx diving below OTU threshold, so typically not tracked OTU Daily (24 hours) Limits Divers Track OTU’s By Allowed Daily Exposure: 1440 Computer Planning Software Typical DCS Treatments: In-water Dive Computers Table 5: 297 OTU Tables Table 6: 607 OTU Spreadsheets Table 6A: 820

EANX Diving: ~ 40 - 300 Extended Range Diving: ~850 Typical Technical: ~300 - 400

LPT EANx

LPT Selecting the Appropriate EANx Mix

Objective: Optimize both O2 and N2 concentrations Minimize N2 levels to limit deco obligation Keep pO2 below CNS toxicity levels Wrong mix or tables can lead to catastrophe

LPT Oxygen Partial Pressure Limits : 1.6 ata is the standard NOAA Diving: 1.4 ata is standard (as of July, 2015) Recreational Diving: 1.4 ata is used by most agencies

Always have option to lower the pO2 you wish to dive The lower the pO2, the longer the allowed exposure

LPT NOAA Oxygen Exposure Limits

NOAA Oxygen Exposure Limits Used to determine dive time limits Maximum Single Maximum

PO2 Exposure per 24 hr (atm) (minutes) (minutes) Increased pO2  less in-water time 1.60 45 150 Decreased pO2  more in-water time 1.55 83 165 Increased % O2  shallower MOD 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

1.10 240 270

1.00 300 300

0.90 360 360

0.80 450 450

0.70 570 570

0.60 720 720 LPT NOAA Oxygen Exposure Limits

Example: Example:

EAN32 mix at 130 fsw EAN40 mix at 130 fsw

Determine pO2 at depth Determine pO2 at depth % O2 Depth to Pressure % O2 Depth to Pressure

pO2 = 0.32[(130 fsw /33 fsw/atm) +1 atm] pO2 = 0.40[(130 fsw /33 fsw/atm) +1 atm] pO2 = 1.58 ata pO2 = 1.98 ata

NOAA Oxygen Exposure Limits pO2 exceeds oxygen exposure limits

Maximum Single Maximum pO2 too high for 130 fsw PO2 Exposure per 24 hr Unacceptable oxygen toxicity risk (atm) (minutes) (minutes) 1.60 45 150 1.55 83 165

Single Dive limit of 45 minutes LPT NOAA Oxygen Exposure Limits Example:

Using EAN32

Reduce allowed pO2 to 1.40 ata

1.45 135 180 Decreased allowed pO2 Lowers maximum depth (MOD) 1.40 150 180

1.35 165 195 MOD = [ (1.4 ata) - 1 atm] 33 fsw 0.32 atm Single Dive limit of 150 minutes MOD = 111 fsw

Need to determine time and max depth for all EANx dives

LPT Percent CNS Oxygen Exposure

% Daily O2 Allowance = [Dive Time / 24 hour Allowed] x 100

NOAA Summary for Common Dives For repetitive Dives:

Treat Residual O2 Like Residual N2

Use Surface Credit Table (Next Slide)

LPT LPT Cumulative % CNS Oxygen Exposure Example:

First Dive: 40 minutes at pO2 of 1.60 ata % CNS Oxygen Exposure: ( 40 min / 45 min x 100) = 89%

Surface Interval: 120 minutes New (Residual) % CNS Oxygen Exposure: 37 %

Second Dive: 30 minutes at pO2 of 1.2 ata Dive % CNS Oxygen Exposure: (30 min / 210 min) x 100 = 14 %

Total CNS Exposure = (14 + 37) % = 51 %

LPT Per Minute % CNS Oxygen Exposure

LPT (MOD)

MOD – the maximum depth that should be dived with a given EANx mixture

 PO2 limit, ata  MOD    1 atm 33 fsw / atm  FO2 mix  

Example: Determine MOD for a 36% mix with a pO2 1.60 ata:

 1.60 ata  MOD    1 atm 33 fsw / atm  114 fsw  0.36 

LPT Maximum Operating Depth (MOD)

For NOAA I (32% O2)

 1.60 ata  pO 1.60 MOD    1 atm 33 fsw/atm  132 fsw 2  0.32   1.60  MOD    1 atm 33 fsw  132 fsw  1.500.32 ata  pO2 1.50 MOD    1 atm 33 fsw/atm  122 fsw  0.32 

 1.40 ata  MOD    1 atm 33 fsw/atm  111 fsw pO2 1.40    0.32 

LPT Maximum Operating Depth (MOD)

For NOAA II (36% O2)

 1.60 ata  pO 1.60 MOD    1 atm 33 fsw/atm  114 fsw 2  0.36 

 1.50 ata  MOD    1 atm 33 fsw/atm  105 fsw pO2 1.50    0.36 

 1.40 ata  pO 1.40 MOD    1 atm 33 fsw/atm  95 fsw 2  0.36 

LPT EANx has shallower onset of CNS toxicity than air (Has more O2) For 1.4 ata limit Air 187 fsw NOAA I 111 fsw NOAA II 95 fsw

For 1.6 ata limit Air 218 fsw NOAA I 132 fsw NOAA II 114 fsw

Higher the pO2 Shallower the MOD

LPT Using Dalton’s Law (Determine Partial Pressures) Dalton’s law (based on fraction of component gas)

Pg = Fg x Pt

Pg = partial pressure of the component gas Fg = fraction of the component gas Pt = total pressure of gas mixture (determined from depth)

For air (21 % O2) being breathed at 90 fsw:

Pg = Fg x P where P = [( D fsw /33 fsw/atm) +1 atm]

pO2 = 0.21 [ (90 fsw / 33 fsw/atm ) + 1 atm)

pO2 = 0.78 ata

LPT Classic Recreational Diving Dalton’s “Pie” Hide wanted segment: Result Solves for hidden segment

Also called: “T” Pg Diamond Gas Partial Pressure

Pg = Fg x Pt Fraction Total Of a Gas Pressure Fg Pt Fg = Pg Pt = Pg Pt Fg

LPT NOAA pO2 for Depth vs. Fraction of Oxygen in the Breathing Mix

LPT Using the NOAA pO2 Chart Determine pO2 of a 32% mix being breathed at 110 fsw

pO2 1.39 ata

LPT Calculating “Best” Mix Most diving can be addressed with NOAA I or NOAA II mixes For special situations (need to extend to the max), use “best mix”

FO = pO ata 2 FO2 2 D ata

Calculate best mix for 120 fsw using a pO2 of 1.4 ata:

LPT PO2 NOAA Best Mix Table fsw msw atm 1.3 1.4 1.5 1.6 40 12 2.21 58% 63% 67% 72% For: 45 14 2.36 55% 59% 63% 67% 65 fsw 50 15 2.52 51% 55% 59% 63%

55 17 2.67 48% 52% 56% 59% pO2 of 1.5 ata

60 18 2.82 46% 49% 53% 56% 65 20 2.97 43% 47% 50% 53% Best Mix = EAN50 70 22 3.12 41% 44% 48% 51%

75 23 3.27 39% 42% 45% 48%

80 25 3.42 38% 40% 43% 46%

85 26 3.58 36% 39% 41% 44%

90 28 3.73 34% 37% 40% 42%

95 29 3.88 33% 36% 38% 41%

100 31 4.03 32% 34% 37% 39%

105 32 4.18 31% 33% 35% 38%

110 34 4.33 30% 32% 34% 36%

115 35 4.48 29% 31% 33% 35%

120 37 4.64 28% 30% 32% 34%

125 38 4.79 27% 29% 31% 33% 130 40 4.94 26% 28% 30% 32% LPT EANx Dive Planning Tools

LPT NOAA EANx Tables In use since 1979 Based on US Navy Dive tables Have consistent rep groups Allows moving between tables Latest Revision (July, 2015)

Max allowed pO2 of 1.4 ata Shows values to 1.6 ata

Tables for 28 – 40 % in 1 % O2 increments

LPT NOAA No-Deco Air Table Based on US Navy Tables Standard “3-table” format 1: Dive Time/Depth 2: Surface Interval 3: Residual Bottom Time

1 Multiple Dives within 12 hours Basis for the EANx Tables Calculated using EAD Concept EAD:

Mix having same pN2 as air Shows pO2 in ata

Two formats Abbreviated: No Deco Full: For Deco Diving

3 2 Full size EANx Tables follow

LPT

Decompression Dive Planning With NOAA Tables

Decompression Tables for EAN32 and EAN36 Found in NOAA Dive Manual Appendix

LPT Decompression Dive Planning With NOAA Tables

Decompression Tables for EAN32 For EAN32 dive: 70 min @ 80 fsw: Deco stop 14 min @ 10 fsw End as L diver

pO2 @1.1 ata CNS Allows: 240 min

Demo Only U of MI Does NOT Authorize Deco Diving

LPT Decompression Dive Planning With NOAA Tables

Decompression Tables for EAN36 For EAN36 dive: 70 min @ 80 fsw: Deco stop 2 min @ 10 fsw End as K diver

pO2 @1.25 ata CNS Allows: 195 min

Demo Only U of MI Does NOT Authorize Deco Diving

Higher O2: less N2  Less Deco Obligation LPT Equivalent Air Depth (EAD)

Uses US Navy tables as a reference

Equilibrates time and depth for different N2 and O2 mixes

Uses pN2 of breathing mix for table entry point Not the physical depth of the dive

Less N2 in mix, equilibrates to shallower air dive

Diver Physically at a greater depth than equivalent air dive This is the “physiological advantage”

Once pN2 equivalent depth is determined, can use air table

LPT Equivalent Air Depth (EAD) Use Equation:

 D fsw  33 fsw1 FO2 EAD fsw     33 fsw  0.79  Use Standard Table:

Determine EAD

Use Air Table

NOAA US Navy

LPT Equivalent Air Depth (EAD): Extended Table

Equivalent Air Depth Conversion Table (Fraction of Oxygen and Actual Depths)

EAD (fsw) 28% 29% 30% 31% 32% 33% 34% 35% 36% 37% 38% 39% 40% 30 36 37 38 39 40 41 42 43 44 46 47 49 50 40 47 48 49 50 51 53 54 55 57 58 60 62 63 50 58 59 61 62 63 64 66 67 69 71 72 74 76 60 69 70 72 73 75 76 78 80 81 83 85 87 89 70 80 81 83 84 86 88 90 92 94 96 98 100 102 80 90 92 95 96 98 100 102 104 106 108 110 113

90 101 103 106 107 109 112 114 116 118 121

100 112 114 117 119 121 123 126 128

110 123 126 128 130 133 135

120 134 137 139 142

130 145 148 150

140 156 159

150 167 Numbers in grey boxes = exceptional exposure depth for mix LPT Using EAD Table Find EAD for diving 34 % O2 at a depth 82 fsw Use next greatest depth Diving EAN34 at 82 fsw same as air at 70 fsw

EAD (fsw) 28% 29% 30% 31% 32% 33% 34% 35% 36%

30 36 37 38 39 40 41 42 43 44

40 47 48 49 50 51 53 54 55 57

50 58 59 61 62 63 64 66 67 69

60 69 70 72 73 75 76 78 80 81

70 80 81 83 84 86 88 90 92 94

80 90 92 95 96 98 100 102 104 106

90 101 103 106 107 109 112 114 116 118

LPT Using EAD Formula

Find EAD for dive to 81 fsw using EAN37

 D fsw  33 fsw1 FO2 EAD fsw     33 fsw  0.79   81 33fsw1 0.37 EAD fsw    33 fsw  58 fsw  0.79  Enter air table at 60 fsw Diver physically at 81 fsw Diver on-gases as if diving air at 58 fsw

LPT Time To Wait Before Ascending To Altitude Post-dive changes in pressure can trigger DCS hits Lower pressure environments Driving over mountain pass Flying Passing thunderstorm (weather low)

LPT Time To Wait Before Ascending To Altitude

LPT Time To Wait Before Ascending To Altitude

J Diver: waits 8:39 before ascending to 6000’ J Diver waits 14:13 before flying (cabins often pressurized to ~ 8,000’ ) Best to wait 24 hours before flying LPT Using Dive Computers

Two options for using dive computers with EANx Use a computer designed for use with EANx Breathe EANx while diving an air based computer Cannot totally rely on computers ‘cause They flood Batteries die Most divers never read instructions So, computer users still need to know how to use tables

LPT Dive Computer Features Allow for a variety of nitrox mixes

Compute the deco profile based on user entered % O2

Provide MOD limits based on the mix and pO2

Track O2 and N2

Allow extended dive time by adjusting pO2 on ascent

Multi-leveled dives best done with computers

LPT Using Air Computers While Diving EANx Uses physiological advantage: Diver on-gassing at rate less than physical depth

Computer “thinks” is breathing air Will not alert the diver if MOD exceeded

Divers using air computers to dive EANx must Know MOD of mix Know maximum O2 exposure time Computer is only a tool Diver must furnish thinking Diver must use properly

Gi  Go

LPT Dive Planning Software

Programs available for Desktops Laptops Mobile Devices Issues: Legal Agreements Developer Paranoia OS Updates Correct usage Essential for “”

LPT Using EANx Dive Tables

LPT NOAA EANx Tables Require a tolerance of +/- 1 % of O in cylinder 2 When using EAD, use exact mix in cylinder (analyzed on-site)

Table 1 has pO2 information Always use: Next greatest time Next greatest depth

LPT NOAA EANx Tables Calculate 2 EAN32 dives: First:100 fsw for 23 min, followed by a 1 hr SIT

Second: 60 fsw for 30 min. What is your max pO2 during dive 1? Start with Table 1; enter table at 100 fsw … slide to 24 minutes

End of Dive 1: G Diver pO2 = 1.29 ata

Move to Table 2 for Surface Interval (SIT) LPT NOAA EANx Tables Enter Table 2 as a G Diver … slide down to 0:53 – 1:44 Move to Table 3 … Enter as an F Diver

LPT NOAA EANx Tables Enter Table 3 as an F Diver … slide across to 60 fsw Move to Table 1 … Enter as an F Diver ESDT: Equivalent Single Dive Time As an F Diver at 60 fsw: 42 min RNT 50 min allowed no deco time

For 30 additional min 30 (Dive) + 42 (RNT)  72 min

LPT NOAA EANx Tables Follow 60 fsw arrows to 60 fsw in Table 1 Slide across to 80 min Finish as a K Diver

LPT EAD for Non-Standard Mix

Calculate a 30 minute dive to 100 fsw using EAN30 Useful for mix (or analysis) that is not NOAA I or II Calculate EAD for 100 fsw with 30 % oxygen  100 fsw 33 fsw1 0.30 EAD fsw     33 fsw  0.79   93.1 EAD    fsw 33 fsw  118 fsw  33fsw  0.79 EAD  85fsw

LPT EAD for Non-Standard Mix With EAD of 85 fsw, can enter any US Navy or NOAA Air Chart

End as H diver

US Navy Table 1

When using EAD, rep groups only valid for US Navy or NOAA Tables Do NOT use rep groups in any table not based on NOAA or US Navy

LPT Repetitive Dive Planning With NOAA Tables Repetitive diving same mix: no different from the air diving

Repetitive dives different mixes: same as air, but RNT must be obtained from the RNT table for the gas mix to be used on the repetitive dive, not the table from the previous dive A diver dives NOAA I to 118 fsw for 25 minutes and has a SIT of 2:48

Enter Table 1 at 120 fsw Slide to 25 minutes Slide down to Rep Group H

SIT of 2:48  Rep Group E

Enter any NOAA Table 3 As E Diver

LPT Repetitive Dive Planning With NOAA Tables

For a Second Dive to 64 fsw: Enter Table 3 of Mix as E Diver

For Bottom Time Air @ 70 fsw  23 minutes

EAN28 @ 70 fsw  23 minutes EAN30 @ 70 fsw  31 minutes EAN32 @ 70 fsw  31 minutes EAN34 @ 70 fsw  42 minutes EAN36 @ 70 fsw  57 minutes EAN38 @ 70 fsw  57minutes EAN40 @ 70 fsw  85 minutes

LPT Repetitive Dive Planning As E Diver: As E Diver: 23 min @ 73 fsw (Read 80 fsw) DCIEM: 25 min@73 fsw DSAT RDP: 15 min@73 fsw HUGI: 18 min@73 fsw Jeppessen: 20 min@73 fsw NASDS: 17 min@73 fsw NAUI: 17 min@73 fsw SSI: 7 min@73 fsw Swiss: 4 min@27 m YMCA: 7 min@73 fsw

LPT NOAA Planning Worksheet

Useful multiple dives planning aid

LPT NOAA Planning Worksheet

H 2 48 E J

32 120 Air 70

64 118

1.48 25 0.62 20 21 20 25 45

LPT Repetitive Dive Planning With NOAA Tables Use lowest concentration of oxygen first (analogous to air diving: deepest dive first)

For three consecutive 60 fsw for 30 min; 1:00 SIT:

Air: 30@60: F  E

EAN32: 65@60: J  I EAN36: 103@60: M

EAN36: 30@60: D C EAN32: 53@60: H G Air: 70@60: only 20 min allowed As G diver, need to wait 1:45 (E Diver) to make

LPT Diving Table Procedures

Descent rate: 75 fpm (25 mpm) Flying after diving Ascent rate: 30 fpm ( 9 mpm) use the table Safety-Stop 3-5 minutes at 10-20 fsw (3-6 msw) Tables good to 1,000 ft (328 m) Cold or Strenuous dive Omitted decompression use the next greater bottom time stay on surface Repetitive dives breathe 100% oxygen less than 12 hours monitor for DCS plan to evacuate to chamber

LPT Other Rules

10 minute minimum between dives Bottom Time: time you enter the water until you leave the bottom for a direct assent (exception if delayed) Required Decompression stops are taken at specified depth and measured at diver’s mouth Whenever possible, make dives progressively shallower

LPT Out of Gas Emergencies

LPT Out of Gas Emergencies Dives Within No-Decompression Limits:

EANx diver who has not exceeded the dive’s no-stop time Breath air or any EANx mix for immediate ascent

Air diver can breath an O2 rich mix

Shifting to Air During a Decompression Dive:

EANx diver required to switch to air during a deco stop Complete the deco schedule without adjustment

NOAA EANx Table deco stops are based on USN Air Deco Tables: Assumes the diver is breathing air

LPT Gas Preparation & Handling

LPT Handling Oxygen Oxygen Supports life Does not burn Enhances combustion Fire is a rapid chemical reaction Virtually everything will burn in oxygen Fire triangle: Oxygen Fuel Heat Source

LPT Oxygen Explosions Are Not Trivial

Never use ball for O2

LPT Sources of Oxygen Ignition

Adiabatic Compression Gas at high pressure moves at hypersonic speeds Encounters closed valve Temperature can increase > 800 oC / 1500 oF

Particle Impingement Loose metal/plastic particles carried by gas stream Impact on interior parts

Flow Friction Heat generated by movement of high velocity gas

Static Spark Nearby improperly grounded equipment

LPT Ignition From Adiabatic Compression

Always open O2 valves slowly Point regulator away from all individuals

LPT Grades of Oxygen Aviator’s Oxygen: Preferred for blending Nitrox Analysis: 99.9 % oxygen Dew Point -85 oF (minimizes possible freeze-up) Most expensive grade commonly available

Medical Grade Oxygen: Used in medical procedures Analysis: 99 % oxygen No dew point specification Higher moisture  cylinder corrosion

(not recommended for EANx cylinders)

Industrial Grade Oxygen (welding) Analysis: 99 % oxygen

Difference in grades is method of filling cylinder (all use same lox source)

Industrial: smell for acetylene (any odor); top cylinder with USP O2 Medical: evacuate cylinder; fill with USP O2 Aviation: evacuate cylinder; fill with USP O2 using extra moisture filters

LPT CGA Grades of Compressed Air Scuba Air (to 130 fsw)

Grade E or Better Dew Point: Not to exceed -50 oF - 10 oF < water temp Primary Concerns; Water Regulator Freeze Hydrocarbons Explosions condensable oil: < 0.1 mg / m3

LPT Breathing Gas Dew Point is Important Joule-Thomson Effect Gas moving from high to low pressure expands Expansion results in significant temperature drop Dew point: Temperature at which condensation MUST occur Moisture in cylinder air: Must condense if temp falls below Dew Point Can freeze and mechanically jam regulator parts Result: No air or total free flow External Ice Formation Can freeze water surrounding regulator Result: Ice hinders mechanical movement (both stages) Breathing “Free Ice” can injure lungs

LPT Oxygen Compatible Compressed Air (OCA) NOAA wanted Grade J Air Grade J Air is expensive

Industry uses “Modified Grade E”

Modified Grade E Standards Grade J Item Specification % Oxygen 20-22 19.5-22.5 Oil 0.1mg / m3 - CO 2 ppm 1 ppm

CO2 500 ppm 0.5 ppm Odor No objectionable No objectionable Hydrocarbons 25 ppm 0.5 ppm

LPT Blending EANx Partial Pressure Mixing

Adds pure O2 directly into an empty and O2 clean SCUBA tank Topped off with Oxygen Compatible Air (OCA)

Advantages: Low initial cost Mix to any concentration

Disadvantages: Tedious

Must be O2 clean Explosive if oil in system

Need O2 booster for O2 source Accuracy depends on technician

LPT Blending EANx Nitrogen Separating Membrane

Heated OCA forced through a membrane

N2 concentration lowered Advantages: Uses no oxygen cylinders

Can use non-O2 clean cylinders Can supply up to ~40% Useful for portable LP systems

Disadvantages: Expensive to set up Slow to initialize Need a second compressor Expensive to replace membrane Needs constant monitoring

Most expensive source of EANx LPT Blending EANx Continuous Blending with a Nitrox Stik

Advantages: Moderate Cost

Can use non-O2 clean cylinders Can supply up to ~40% Nitrox Controller saves labor Lowest cost per fill

Disadvantages: Without controller, needs monitoring

Need constant O2 supply

LPT Blending EANx Continuous Blending with Mixing Panel Advantages: Moderate Cost

Can use non-O2 clean cylinders Can supply any mix Automated controller saves labor

Disadvantages:

Need constant O2 supply Portions see 100% O2 High liability Requires knowledgeable operator

LPT Blending EANx Pressure Swing Adsorption (PSA) Uses “molecular sieves”

Removes N2 from air (makes denitrogenated air (DNA)

Advantages: Low initial cost

Mix to any concentration up to 95 % O2 Typically feed into continuous system

Disadvantages: Tedious

Requires O2 cleaning for > 40 % O2 Expensive membrane replacement

LPT Blending EANx Mixing by mass ()

Advantages Very precise mixing Used on industrial scale

Disadvantages Requires real gas equations Expensive scales

Industrial scale mixing

LPT Purchase Custom Mix

Advantages: Minimum blending cost

Can use non-O2 clean cylinders Reliable concentrations

Disadvantages: Demurrage (cylinder rental) Possible delivery (time) issues Requires

LPT Filling Cylinders with Oxygen

Scuba Valves: Medical Cylinders: Fill at dive shop Fill at FDA Licensed Facility Felony Otherwise

LPT Cylinder Valves

DIN Yoke

DIN Insert

Allows Yoke Regulator use on DIN Valve

Encapsulated O-ring

Higher Pressure LPT Color of Gas Cylinders

Gas USA International

LPT Identifying EANx Cylinders

4 “ green band on yellow cylinder NITROX or Enriched Air stenciled in 2” high letters Non-yellow cylinders: Additional 1” yellow band above and below the green Additional Labels Contents (filled out by blender) Validated by user

LPT Software Calculations can be cumbersome Best to use software

LPT Station Log

Log kept at the blending station

Minimum Contents:

Cylinder ID number Analysis by the person mixing the gas (O2% & initials) Analysis by the diver diving the gas (O2%) Cylinder pressure MOD Date of analysis Signature of diver performing the analysis

LPT Oxygen Cleaning

LPT The NOAA 40% Rule Gas mixtures < 40% can be handled as if the mix were air for < 40% no special equipment or procedures

NOAA has always used the “40% rule”

European Standards: > 23 % Oxygen Treated as pure O2

LPT The NOAA 40% Rule Any cylinder, valve, regulator, or hose for > 40% oxygen: Material must be oxygen compatible (oxygen compatible O-rings) Material must by oxygen-cleaned Lubrication must be oxygen compatible (no silicone)

LPT Oxygen Cleaning There are two levels of oxygen cleaning Formal Oxygen Cleaning Strict procedures or regulations Highly trained technicians Massive documentation Military, Space, or Research

Institutions: High risk environments

Informal Oxygen Cleaning

Same level of cleanliness Without documentation

Dive shops

LPT Informal Oxygen Cleaning Completely disassemble Inspect each part and remove visible debris and lubricants Scrubbing and/or ultrasonic cleaning with an acidic detergent in hot water Rinsing thoroughly in clean hot water Clean with basic cleaner, rinse, and dry Inspect and test for cleanliness pH (check for remaining caustic detergent) White light inspection (see contamination > 50 microns) UV light inspection (some inks, greases and fibers fluoresce) Water Break (residual silicone oils force water into beads) Shake test (presence of foam indicates detergent still present) Swipe test (Mclean cloth picks up materials) Re-clean, if needed Oxygen-compatible lubricants are then used where necessary

LPT Common Contaminants (Ignition Source)

Machining oils (including residual oil film) Hydrocarbon-based grease and lubricants (including compressor oil) Some soaps, detergents, solvents and cleaning (contain organic compounds) Skin lotions and emollients and cosmetics Sun-tanning oils and lotions Human skin oil and bodily fluids Insects and insect body parts Paint, wax, and marking crayons Carbon dust from filtration systems Metal fines, filings, scale and burrs Chrome chips (usually from valves and other chrome-plated parts) Rust particles and dust Metallic oxides in general Airborne soot and dust Pipe thread sealants Residue from soapy water and leak-detection fluids used to check for leaks Lint from cloths used in cleaning Any other material containing organic compounds and hydrocarbons

LPT Informal Oxygen Cleaning After cleaning, material inspected with both white and UV lights

Some greases, oils, inks, fibers are visible under UV light

LPT Equipment Cleaning List

Must be cleaned for EANx Recommended to be cleaned Cylinder valves Regulator first stage Scuba cylinders Regulator second stage (Means dedicated equipment) High pressure hoses Submersible pressure gauges Not necessary compensators Low pressure inflator Dry suit inflator

If used with >40% Everything used in gas supply / containment

LPT Using Oxygen Cleaned Equipment Once cleaned

Equipment should be dedicated for use only with EANx Equipment not used with air from an oil-lubricated compressor

If filled with air from oil lubricated compressor Re-clean Re-label

LPT Routine Care and Maintenance Wash gear in fresh water Protect from dirt and grease Periodic service by trained technician annual for normal use more often if heavy use Maintain warranties Don’t contaminate with ordinary scuba air

LPT Oxygen Compatible Materials

Good Compatibility Nickel 201 Monel Viton A Inconel (600 series) TFE Teflon (nonfilled) Copper Vespel SP21 Yellow & Red Brass Fluorel

Suitable Aluminum Silicon Bronze Inconel (800 series) Stainless (300 series) Brass

Unsuitable Silicone Rubber Ethylene Propylene Rubber Neoprene Buna N Carbon Steel Aluminum

LPT O-Rings O-rings and lubricants must be oxygen compatible No silicone grease Cannot rely on 0-ring color as compatibility indicator

LPT Gas Analysis

LPT The Triple Analysis “Ritual”

All EANx cylinders are analyzed for O2 content 3 times:

When Mixed When Obtained Just Before Dive

LPT Oxygen Analyzers: Electrochemical

Typical scuba O2 analyzers use chemical reactions with oxygen as a reactant The reaction generates a current

Amount of current: function of pO2 (correlates to percentage O2 ) in the gas

- - Pb Anode: 2 Pb + 4 OH → 2 PbO + 4 e + 2 H2O - - Air Cathode: O2 + 2 H2O + 4 e → 4 OH Every measurement degrades electrodes Standard: no more than 1 year use of any electrode (Can degrade in a few months of intense use) Meter sensitive to +/- 0.1 %

LPT Oxygen Analyzers: Polarographic Uses electrochemical analytical technique called polarography;

O2 flows through Teflon membrane into KCl bath Generates current flow proportional to pO2 Display calibrated to % O2

Ag Anode: 4 Ag+ + 4 Cl-  4 AgCl + 4 e- + - Pt Cathode: O2 + 4 H + 4 e  2 H2O

High end, stationary systems Quite expensive Clark Electrode Difficult to replace LPT Analysis Procedure Calibrate with air Slowly vent cylinder (~ 1 - 2 L / min) (Gas flow before attaching analyzer) Run gas for ~ 30 sec Ensure good seal with analyzer sensor Wait until display stabilizes

LPT Flow Restrictors Flow restrictors typically sold separate from analyzer Provide constant flow through restrictor at ~ 3 L / min Add Tygon Tubing to connect restrictor to analyzer Analyzer Barb Restrictor Tygon Tubing Restrictor (1/16” ID)

Connect restrictor to BCD Start gas flow Wait 30 sec Connect to analyzer Read meter

LPT Flow Meter Allows precise, consistent, and reliable analysis Tygon tubing (1/16” ID) connects flow meter to analyzer barb

Start gas flow Set flow at ~ 1 L / min Wait 30 sec Connect to analyzer Read meter

LPT “Tech” (Tri-Mix) Analyzers Use electrochemical sensor to determine oxygen concentration Use thermal conductivity sensor to measure concentration Nitrogen, if present, by subtraction

LPT Oxygen Analyzers: Drawbacks Humidity / Moisture Too high a flow rate (Should be ~ 1 - 2 L / min) Inflator hose restrictors typically ~ 3 L per min) Physical abuse Major temperature fluctuations Mechanical connection to analyzer Sensor degradation with time Low battery Expense Sensor Obsolescence

LPT On-Site Analysis Variability

Device 1: 36.0 % Oxygen Device 2: 39.0 % Oxygen

Depth limit based on highest pO2 NOAA 39 % O2 Table: pO2 1.40  80 fsw; pO2 1.60  100 fsw MOD calculation:

 1.40 ata  MOD    1 atm 33 fsw / atm  85 fsw  0.390 

Nitrogen Tracking (Dive Tables) based on highest N2 (lowest O2) NOAA 36 % O2 Table or EAD Calculation

LPT Storing Analyzer

Ensure device is turned off Store in protective case (O-ring seal preferred) Cap electrode (if possible) Avoid contact with water Store in cool, dry place

LPT Dive long and Prosper

LPT Open Water

LPT Open Water Experience

EANx diving is simply a matter of: Inhale, Exhale, Repeat (The diving is no different than swimming with compressed air cylinders) Purpose of the day is to reinforce the “ritual” of triplicate analyses When Mixed When Obtained Just Before Dive

2 Repetitive Dives: one each on NOAA I and NOAA II Assume a first dive of the day on air Dive times / depths determined by NOAA tables And Do some on-site calculations simulating analysis different from label

LPT Woo Hoo! All done!

End of Class This Is Dive long and prosper LPT

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