MEDICAL GAS SYSTEMS

210a

MEDICAL GASES Oxygen – O2

Air

Carbon dioxide – CO2

MEDICAL GASES Helium – He

Nitrous oxide – N2O

Nitric oxide - NO

CHEMICAL AND PHYSICAL PROPERTIESOF THERAPEUTIC GASES Oxygen and air are life supportive

because these gases supports the metabolic production of energy in the carbon-based organisms found on earth.

Atmospheric concentrations are given in percentage values (%), which represent the relative quantities of gases as they are present in the earth’s atmosphere.

OXYGEN – O2 (GREEN TANK)

Characteristics Colorless, odorless, tasteless

Non-flammable

Supports combustion

OXYGEN – O2

CharacteristicsCritical temperature

-118.6 °C (-181 °F)

Makes up approximately 21% of air

OXYGEN – O2

Commercially produced through fractional distillation

Physical separation Used in oxygen concentrators

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FRACTIONAL DISTILLATION Atmospheric air is filtered of pollutants,

carbon dioxide and water Air is compressed and cooled to a liquid Then it is slowly heated and the

nitrogen boils off. Liquid oxygen remains

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MOLECULAR SIEVE Composed of inorganic sodium

aluminum silicate pellets These pellets absorb the nitrogen and

water vapor from the air Produces up to 90% mixture

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SEMIPERMEABLE MEMBRANE Pulls air through membrane Oxygen passes through faster than

nitrogen Can produce 40% mixture Good for long-term low flow oxygen

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PHYSICAL SEPARATORS Will produce concentrations for nasal

cannula but only at low flows Used in oxygen concentrators IN THE

HOME

AIR (YELLOW CYLINDER) Characteristics

Colorless, odorless, tasteless

Non-flammable

Supports combustion

THERAPEUTIC GASES INRESPIRATORY CARE At normal atmospheric conditions, air is

an odorless, colorless, transparent, tasteless mixture of gases and water vapor that is nonflammable and supports combustion.

Air is composed of about 78% nitrogen and 21% oxygen by volume.

Compressed air may be referred to in medical settings as room air or ambient air.

THERAPEUTIC GASES INRESPIRATORY CARE Compressed air is supplied in cylinders

that are color coded yellow. Piped compressed air is commonly

provided in hospital medical gas systems for use in areas such as the operating room and intensive care units.

Smaller, portable air compressors are available for hospital or home use.

AIR Produced by filtering and

compressing atmospheric air

Must be dry

Must be free of oil

THERAPEUTIC GASES INRESPIRATORY CARE Carbon dioxide (CO2) is a colorless,

transparent, odorless to pungent, and tasteless or slightly acid-tasting gas with a specific gravity of 1.522, making it heavier than air.

CO2 is nonflammable and does not support combustion or animal life.

CO2 is a by-product of animal metabolism and the burning of carbonaceous fuels.

CARBON DIOXIDE – CO2

CharacteristicsColorless, odorless

Does not support combustion

Cannot support life

Grey cylinder

CARBON DIOXIDE – CO2

Produced by heating limestone in contact with water

Critical temperature above room temperature; stored as liquid in cylinder

CARBON DIOXIDE – CO2

Used in the past in mixtures with oxygen (90% O2 with 10% CO2, 95% O2 with 5% CO2); current use is limited

CARBON DIOXIDE – CO2

Current CO2 mixtures used primarily in membrane oxygenators and for calibration of analyzers

HELIUM – HE

CharacteristicsSecond lightest of gases

Odorless, tasteless

Non-flammable

Brown cylinder

HELIUM – HE

CharacteristicsGood conductor of heat, sound, and

electricity

Inert

Cannot support life

HELIUM – HE

Produced through liquefaction

When used therapeutically, must be mixed with at least 20% O2 (Heliox)

http://www.youtube.com/watch?v=nripiMQt0ls

HELIUM – HE

Used to manage severe airway obstruction to decrease work of breathing

THERAPEUTIC GASES INRESPIRATORY CARE Nitric oxide (NO) is a colorless,

tasteless gas with a slight metallic odor. This nonflammable and non-life-supporting gas supports combustion and is toxic.

Nitrogen (N2) is the major component of the atmosphere, 78% by volume.

Nitrogen gas is responsible for the blue color of the sky on earth.

NITROUS OXIDE – N2O Characteristics

Colorless

Slightly sweet odor and taste

Supports combustion

Cannot support life

NITROUS OXIDE – N2O Produced by thermal

decomposition of ammonium nitrate

NITROUS OXIDE – N2O Critical temperature above room

temperature; stored as liquid in cylinder

Used as an anesthetic agent

NITRIC OXIDE - NO Characteristics

Colorless

Non-flammable

Supports combustion

NITRIC OXIDE - NO Produced by oxidation of

ammonia at high temperature in the presence of a catalyst

NITRIC OXIDE - NO Respiratory irritant capable of

causing chemical pneumonia and pulmonary edema

NITRIC OXIDE - NO High concentrations can cause

methemoglobin to form

Used in term and near-term infants for the treatment of persistent pulmonary hypertension

CYLINDERS Markings Sizes/oxygen contents

D – 12.6 cu.ft./356 L

E – 22 cu.ft./636 L

G – 186 cu.ft./5260 L

H/K – 244 cu.ft./6900 L

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H CYLINDERS 2200 psi A.S.S.S safety system Threaded connection Need to be safety chained and in a

secured dolly for moving

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E CYLINDERS Small and lightweight (15 pounds) PISS – Pin Index Yoke connection

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TYPES AND COLORS OF CYLINDERS Air - Yellow Oxygen - Green – Int’l (White) Helium - Brown CO2 - Grey Nitrogen - Black Nitrous Oxide-BlueDo NOT trust the color of the tank as sole

indicator of it’s contents

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OTHER OXYGEN TANK MARKINGS

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BULK OXYGEN SYSTEMS Large capacity

Liquid oxygen

Small system (or back up)Nitrous OxideBank of H cylinders

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LARGE OXYGEN SUPPLY SYSTEM

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SMALL BANK OF CYLINDERS

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LIQUID VS GAS Insulated – Liquid Solid metal - Gas Large continuous demand – Liquid Small portable – Liquid or tank

Tanks act differently if they contain gas or liquidNo accurate gauge on liquid tank content

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GO FIGURE

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LIQUID OXYGEN Constantly losing oxygen despite

insulation Needs pressure and insulation for cold

temperature (-118oC) Low pressure (200 psi) Large system has vaporizers fins to

help with heat transfer when liquid turns to gas (frozen year round)

Small system is great for mall shopping

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WALL (LOW PRESSURE) SYSTEMS D.I.S.S.

50 P.S.IThe MJC lab has these

Quick connectA newer “better system”

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DISS

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DISS WALL OUTLET

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FLOWMETERS Thorpe Tube is most common Can use Bourdon Gauge

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ZONE VALVES

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REGULATORS They decrease internal tank pressure

down to a working pressure (50psi) They read and display the internal

tank pressure They meter out the precise flow for

patient use.

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CYLINDER CONNECTIONS A.S.S.S. (American Standard)

H cylindersHigh pressure, large tanks

P.I.S.S. (Pin Index)E cylindersHigh pressure, small tanks

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PIN INDEX SYSTEM

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PIN INDEX SYSTEM

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PIN INDEX NUMBERING

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CYLINDER DURATION CALCULATIONS You can memorize size of tank then

calculate how long it will last

Or use: Conversion factors

3.14 for H cylinders0.28 for E cylinders

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LIQUID OXYGEN DURATION Convert pounds to liters Multiply by 860 to get volume of

gaseous oxygen (Liters) Divide by the liter flow (L/min) Convert minutes to hours and minutes

STORAGE AND DISTRIBUTIONOF MEDICAL GASES Steel cylinders are used to store

compressed oxygen and other gases. Medical gases can be stored and

transported in the gaseous state or as liquefied gas in various-sized cylinders and cryogenic bulk containers.

CYLINDERS Filling cylinders

Compressed gas cylinders filled to service pressure plus 10%

CYLINDERS Measuring contents

Compressed gas cylinders Contents directly proportional to pressure

Liquid gas cylinders Contents determined by weight of

cylinder

CYLINDERS Duration of flow

Duration of flow = Contents Flow

CYLINDERS Factors for determination of

duration“E” cylinder = 0.28

“H/K” cylinder = 3.14 Duration of flow = Pressure x Cylinder

factorFlow

CYLINDER STORAGE Cylinder cap in place when not

in use

Segregate full and empty cylinders

CYLINDERS Factors for determination of

durationLiquid system = 860

Amount of gas in liquid = Weight of liquid x

860 2.5

CYLINDER STORAGE Must be in racks or chained to

wall

No combustible material in the vicinity

CYLINDER STORAGE Flammable gases stored

separately from gases that support combustion

CYLINDER STORAGE Always use “No Smoking” signs

when oxidizing gas is present

Liquid oxygen containers must be in a cool, well-vented area

CYLINDER TRANSPORT Use approved carts for

transporting cylinders

Keep protective cap in place during transport

CYLINDER USE Cylinders must always be

secured either with a chain to the wall, or an approved cart or stand

CYLINDER USE Cylinders must be uncovered

“Crack” a cylinder valve before use

Storing cylinders:

http://www.youtube.com/watch?v=AtyUn0aBYiw&feature=related

CYLINDER USE Do not position cylinders near

sources of heat

Do not alter the safety system for the cylinder

BULK SYSTEMS Defined as containing at least

20,000 cubic feet of gas

May be in either gaseous or liquid form

BULK SYSTEMS - ADVANTAGES More economical over the long

term

More dependable; less prone to interruption

BULK SYSTEMS - ADVANTAGES Eliminates need to transport

large numbers of cylinders

Delivery pressure uniform

Operating pressure is lower (50 psig)

BULK SYSTEMS - DISADVANTAGES Expensive to construct

Failure may affect large numbers of patients

BULK SYSTEMS Supply systems

Cylinder manifold system

Cylinder supply system with reserve supply

BULK SYSTEMS Supply systems

Bulk gas system with reserve

Shut-off valves, zone valves

REGULATION OF MEDICAL GASES Food And Drug Administration

(FDA) Oversees purity of gases produced

REGULATION OF MEDICAL GASES Department of Transportation

(DOT) Oversees construction of cylinders

and transportation of medical gases

REGULATION OF MEDICAL GASES National Fire Prevention

Association (NFPA) Oversees construction of bulk

systems and sets standards for storage of medical gases

REGULATION OF MEDICAL GASES Compressed Gas Association

(CGA) Regulates handling, storage,

fittings, and markings

SAFETY INDEXED SYSTEMS American Standard Safety

System (ASSS)Standardizes threaded high-

pressure connections for cylinder sizes “F” to “H/K”

http://www.youtube.com/watch?v=9uQzTAXZ59c&feature=related

AMERICAN STANDARD SAFETY SYSTEM (ASSS) 26 connections total within the

systemThread diameter

Threads per inch

AMERICAN STANDARD SAFETY SYSTEM 26 connections total within the

system

Right-handed vs. left-handed

External vs. internal

PIN-INDEX SAFETY SYSTEM (PISS) Sub-system of ASSS

Applies only to cylinders up to size “E”

PIN-INDEX SAFETY SYSTEM (PISS) System of two pins aligning with

holes in cylinder valve face; six possible positions

PIN-INDEX SAFETY SYSTEM (PISS) Pin Positions

Oxygen – 2-5

Oxygen/Carbon dioxide – 2-6

Helium/Oxygen – 2-4

Nitrous oxide – 3-5

Air – 1-5

PIN-INDEX SAFETY SYSTEM (PISS)

DIAMETER-INDEX SAFETY SYSTEM (DISS) Used For low pressure (<200

psig) medical gas connectors

Consists of an externally threaded body and mated nipple with a nut

Twelve standardized connections

QUICK-CONNECT SYSTEMS Made by various manufacturers

Each connector has distinct shape so it cannot be used with a different gas

REGULATORS Two types of high pressure

reducing regulatorsSingle stage – Reduces cylinder

pressure to working pressure in one stage

REGULATORS Two types of high pressure

reducing regulatorsMultiple stage – reduces cylinder

pressure to working pressure in two or more stages

REGULATORS Pre-Set pressure

reducing regulator Delivers fixed,

pre-set outlet pressure

Adjustable reducing regulator Delivers outlet

pressure adjusted to specific need

FLOWMETERS Used to set and control the flow of

gas to the patient from a 50 psig source

FLOWMETERS Three types

Bourdon gauge

Thorpe tube

Flow restrictor

BOURDON GAUGE Measures pressure within the

flowmeter; calibrated to read as flow

Unaffected by gravity; can be used in any position

BOURDON GAUGE Inaccurate when pressure distal

to the orifice increases, causing back pressure to increase; causes flowmeter to read high

BOURDON GAUGE

Figure 15-15: DISS safety systems: flow meter and 50-psig outlet.Courtesy of Western/Scott Fetzer Company

THORPE TUBE Measures true flow

Must be used in the upright position

http://www.youtube.com/watch?v=6UwXKXS9Xao

Figure 15-11A: ASSS, PISS, and DISS connections. Courtesy of Western/Scott Fetzer Company

THORPE TUBE Pressure compensated

Flow control valve distal to the meter; Prevents changes in downstream resistance from affecting accuracy of reading

THORPE TUBE Uncompensated

Flow control valve proximal to the meter; records less than actual flow

THORPE TUBECompensated

FLOW RESTRICTOR Has a fixed orifice capable of

delivering one specific flow

Need variety of restrictors in the event of patient needs changing

FLOW RESTRICTOR Cannot be used during

resuscitation Unable to increase flow for CPR