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 Properties of 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 Characteristics Critical 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

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 RsCr 220

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 RsCr 220

Semipermeable Membrane Pulls air through membrane Oxygen passes through faster than nitrogen Can produce 40% mixture Good for long-term low flow oxygen RsCr 220

Physical Separators Will produce concentrations for nasal cannula but only at low flows Used in oxygen concentrators IN THE HOME RsCr 220

Air (yellow cylinder) Characteristics Colorless, odorless, tasteless Non-flammable Supports combustion

Therapeutic Gases in Respiratory 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 in Respiratory 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 in Respiratory 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 Characteristics Colorless, 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 Characteristics Second lightest of gases Odorless, tasteless Non-flammable Brown cylinder

Helium – He Characteristics Good conductor of heat, sound, and electricity Inert Cannot support life

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

H Cylinders 2200 psi A.S.S.S safety system Threaded connection Need to be safety chained and in a secured dolly for moving RsCr 220

E Cylinders Small and lightweight (15 pounds) PISS – Pin Index Yoke connection RsCr 220

Types and colors of cylinders Air - Yellow Oxygen - Green – Int’l (White) Helium - Brown CO2 - Grey Nitrogen - Black Nitrous Oxide-Blue Do NOT trust the color of the tank as sole indicator of it’s contents RsCr 220

Other Oxygen Tank Markings RsCr 220

Bulk Oxygen Systems Large capacity Small system (or back up) Liquid oxygen Small system (or back up) Nitrous Oxide Bank of H cylinders RsCr 220

Large Oxygen Supply System RsCr 220

Small Bank of Cylinders RsCr 220

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 liquid No accurate gauge on liquid tank content RsCr 220

Go figure RsCr 220

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 RsCr 220

Wall (low pressure) systems D.I.S.S. 50 P.S.I The MJC lab has these Quick connect A newer “better system” RsCr 220

DISS RsCr 220

DISS Wall Outlet RsCr 220

Flowmeters Thorpe Tube is most common Can use Bourdon Gauge RsCr 220

RsCr 220

Zone Valves RsCr 220

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. RsCr 220

Cylinder connections A.S.S.S. (American Standard) P.I.S.S. (Pin Index) H cylinders High pressure, large tanks P.I.S.S. (Pin Index) E cylinders High pressure, small tanks RsCr 220

Pin Index System RsCr 220

Pin Index System RsCr 220

Pin Index Numbering RsCr 220

Cylinder Duration Calculations You can memorize size of tank then calculate how long it will last Or use: Conversion factors 3.14 for H cylinders 0.28 for E cylinders RsCr 220

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 RsCr 220

Storage and Distribution of 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 factor Flow

Cylinder Storage Cylinder cap in place when not in use Segregate full and empty cylinders

Cylinders Factors for determination of duration Liquid 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 Shut-off valves, zone valves 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=9uQzTA XZ59c&feature=related

American Standard Safety System (ASSS) 26 connections total within the system Thread 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 regulators Single stage – Reduces cylinder pressure to working pressure in one stage

Regulators Two types of high pressure reducing regulators Multiple 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 Tube Compensated

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