Technology in anesthesia: anesthesia delivery systems Medical gas delivery

1
Technology in anesthesia anesthesia delivery
systemsMedical gas delivery

• Vicente Gonzalez DNP, CRNA. With contribution by
  Gil Soto, CRNA

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Introduction

• Regulations are legal mandates
• Standards are accepted methods of practice, they
  are voluntary standards may become basis for or
  part of regulations leading to laws

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Medical Gas Cylinders

• Regulatory Agencies
• FDA-Food drug Administration- regulates medical
  devices enacted the safe medical device act
  1990
• Report of serious injury or death to FDA. Gave
  FDA subpoena power
• Gave authority to levy civil penalties
• Tracking mechanism for notification
• FDA can recall without public hearings, issue
  stop shipment orders

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Regulations

• Regulatory Agencies
• DOT-Department of Transportation Regulates
  design, performance, labeling, testing,
  transportation, filling and storage, construction
  of medical gas cylinders The United States
  Department of Transportation (DOT) is a federal
  Cabinet department of the United States
  government concerned with transportation. It was
  established by an act of Congress on October 15,
  1966 and began operation on April 1, 1967. It is
  administered by the United States Secretary of
  Transportation.
• Its mission is to "Serve the United States
  by ensuring a fast, safe, efficient, accessible
  and convenient transportation system that meets
  our vital national interests.

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• Voluntary Standards
• NFPA-National Fire Protection Agency
• Writes standards for prevention, detection and
  suppression of fires
• NFPA 99- Standard for health care facilities
• Updated every 3 years
• Governs anesthetizing locations, emergency power
  supplies, electrical, medical gas pipeline
  systems and hyperbaric oxygen systems

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Regulations

• Voluntary Standards
• American National Standards Institute (ANSI)-
  ANSI committee Z-79 for Anesthesia and
  Respiratory Therapy. Writes standards for
  humidifiers, reservoir bags, ventilators, ETTs
  and anesthesia machines.

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• Z-79.9 standards Anesthesia machines
• Legible visible dials and gauges wall and
  cylinder, fail safe mechanisms, vaporizer lock
  out exclusion, PISS DISS, oxygen pressure
  regulators, O2 oxygen flush vales, single flow
  meter knob for each gas, 15/22mm connections to
  machines

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• Voluntary Standard
• American Society for Testing and Materials (ASTM)
• Handles most standards affecting anesthesia
• ASTM F1161-88 Specs for minimum performance
  safety requirements for components and systems of
  anesthesia machines
• Components of standards Pre-use checklist,
  Concentration calibrated vaporizers, O2 analyzer,
  alarms enabled by the master switch, breathing
  system pressure monitoring, volume monitoring ,
  capnometry, alarm hierarchy ( prioritized by
  severity of condition)

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• Other standard agencies
• JCAHO- Joint accreditation of Health Care
  Organizations
• AANA- American Association of Nurse Anesthetist-
  Writes guidelines for the practice of Nurse
  Anesthesia
• Centers for disease control (CDC) Recommendations
  for the prevention of infectious diseases.

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Cylinder sizes
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• E cylinder- Oxygen Color Green, PSI- 1900-2200,
  Volume 660 liters, Physical state GAS, PISS- 2-5
• E cylinder- N2O, PSI 745, Volume liters 1590,
  Physical State Liquid, PISS 3-5

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• Gases that exist as a gas at room temp, oxygen
  drop in cylinder volume is proportionate to a
  drop in cylinder pressure
• Gases that exist as a liquid at room temp, N20,
  Cylinder pressure remains constant until all
  agent in liquid phase enters the gas phase,
  pressure in N20 cylinder will remain constant
  until 75 of cylinder is exhausted or 400Liters
  remain.

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Medical Gas Cylinders

• Medical Gas Cylinders
• Cylinder
• Valve
• Pressure Relief Device
• Conical depression

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• Large cylinders E-Cylinders

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Physics of Cylinders

• Adiabatic compression- Fire hazard- Recompression
  of high pressure gas in the cylinder yoke, when
  cracking open, heats up to 1000f can ignite dust,
  grease , oil
• Adiabatic expansion ( Joule-Thompson effect-
  Icing over cylinder, due to expansion of high
  pressure gas to low pressure atmosphere through
  leaks from improper seals of cylinder to yoke or
  leaks around the valve stem

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Physics

• There are a variety of tests that may be
  performed on various cylinders. Some of the most
  common types of tests are hydrostatic test, burst
  test, tensile strength, Charpy impact test and
  pressure cycling.
• Cylinders are tested every five years. Over
  pressuring of cylinder _at_ 1.66 Xs normal. Ex O2 E
  cylinder 2200psi x 1.66 3154psi

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Cylinders

• Cylinders (tanks) made out of steel (various
  alloys added for strength)
• Aluminum (recent years) useful in MRI
• If cylinder is unsecured, place it on its side
  (never stand upright w/o support)
• Explosion/fires with Aluminum O2 regulators
  (Brass O2 regulators OK) Adiabatic Compression

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Valves

• Tanks are filled discharged via valve (spindle
  valve) attached to neck
• Valve most fragile part (bronze or brass)
  protect during transport
• Valve consists of
• body
• port (where the gas exits)
• stem (shaft) closes valve by sealing against the
  seat
• handle or hand wheel (to open the valve)
• safety relief device
• conical depression (opposite the port, it accepts
  the tip of the screw which secures the cylinder
  in the yoke)
• PISS pins (Pin Index Safety System)

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Pressure Relief Device

• (Also known as safety release device) vents the
  contents of the cylinder to atmosphere if
  pressure increases too much
• Types
• Rupture Disc when predetermined pressure is
  reached from improper filling, the disc ruptures
  contents dcd (air, CO2, He, N2O, O2)
• Fusible Plug thermally operated .Metal alloy,
  has low melting point, high pressures caused by
  high temps 212F- will cause venting When pressure
  increases from high temp, fusible material turns
  soft extrudes from holder
• (N2, air)

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Pressure Relief Device

• Combination Ruptured Disc/Fusible plug Found on
  O2, Air, N20, Nitrogen, Helium, and mixture
  agents Helium-Oxygen. High temps of 165F,
  responds to high temp and high pressure.

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Pressure Relief Valve

• Spring loaded device designed to re close
  prevent discharge of cylinder contents after
  normal pressures are restored
• Set pressure is marked on valve
• (Air, He, O2, N2, CO2)
• More prone to leakage than rupture discs or
  fusible plugs

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Conical Depression

• Placed above the safety relief device on E
  tanks
• Receives the retaining screw of the yoke
• DO NOT CONFUSE WITH SAFETY RELIEF DEVICE!!!!
• If retaining screw is tightened into safety
  relief device, the device will be damaged the
  contents will escape

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More Pictures
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Medical Gas Cylinders

• Medical Gas Cylinders
• Noninterchangeable Safety Systems
• Pin Index Safety System
• Diameter Index Safety System
• Cylinder Sizes and Contents
• Physics of medical gas cylinders

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PISS

• Each type of gas cylinder has a specific
  arrangement of protruding pins on the yoke hanger
  that must seat in the matching depressions on the
  cylinder head
• O2 (piss 2-5)
• N2O (piss 3-5)
• Air (piss 1-5)

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DISS

• series of increasing and decreasing diameters in
  the components of the connections
• specific diameters act in a key-like fashion, so
  the fittings within the gas service "family"
  (suction evacuation included) will connect only
  with their own "family members"

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DISS
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Cylinder Sizes

• Gas Color Pressure Capacity (E) Capacity (G)
  State
• O2 green 2,000 660 L
  5,300 L gas
• N2O blue 745 1,590 L
  13,800 L gasliquid (below 98F)
• Air yellow 2,000 625 L
  5,050 L gas
• CO2 gray 838 1,590 L
  12,300 L gasliquid (below 88F)
• He brown 1,600 500 L
  4,000 L gas

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Contents Pressure Physics

• Non-liquefied gas
• As content is released, pressure decreases
  proportionally (air, O2)
• Liquefied gas
• Pressure depends on vapor pressure of liquid
• Pressure is not an indicator of amount of gas
  remaining as long contents are partly in liquid
  phase
• Pressure remains constant until liquid is
  evaporated (N2O)

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N2O vs. O2

• O2 cylinders are filled to a gauge pressure of
  2000 pounds per square inch (psig)
• N2O cylinders are filled to a gauge pressure of
  750 psig.
• A full "E" cylinder contains 660 L of O2
• A full "G" cylinder contains 5,300 L of O2
• The gauge pressure on an O2 cylinder will
  decrease in a manner proportional to the amount
  of gas in the cylinder.
• Example a gauge pressure of 1000 psi on a "G"
  cylinder of O2 indicates that it contains about
  2,650 L
• (5,300 L divided by 2 2,650 L)

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Medical Gas Cylinders

• Testing and Inspection
• Filling
• Color coding
• Markings
• Labeling
• Tags

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Testing Cylinders

• Must be inspected Q 5yr (10yr with permit)
• Month Yr permanently stamped on tank
• External/internal visual check for corrosion and
  evidence of impact or distortion
• Leak-tested by increasing their service pressure
  by 1.66 times
• Service pressure max press to which the cylinder
  may be filled at 70 F (21 C)

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Filling Tanks

• The pressure in a filled cylinder at 70F (21C)
  may not exceed the service pressure marked
• Exception non-liquefied, nonflammable gases (O2,
  He, CO2/O2 mixtures, He-O2 mixtures) are allowed
  an extra 10 beyond service pressure
• For gases other than N2O CO2, the pressure at
  130F (55C) may not exceed 1.25 times service
  pressure

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Color Coding

• US and International colors
• Color at least on top shoulder of tank
• Color should not be used as the primary means for
  ID d/t tone variations, changes in paint
  pigments, lighting effects, different color
  perception by personnel

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Markings

• DOT and TC( Transport Canada) require specific
  markings permanently stamped on shoulder of tank
• First number type of material tank is made of
• Next service pressure in PSI
• Then serial number symbol of purchaser, user
  or manufacturer
• Initial qualifying test date and retest date
• If plus () sign, can add 10 service press.

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Labeling (most accurate ID)

• Label on side or shoulder (do not cover permanent
  markings)
• Diamond-shaped figure denotes hazard class
• Oxidizer (yellow)
• Non-flammable (green)
• Flammable (red)

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Labeling

• Signal word (what if gas is released)
• Danger immediate hazard
• Warning less than immediate hazard
• Caution no immediate hazard

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Tags

• Primarily a means of denoting the AMOUNT of
  cylinder contents and NOT an ID device
• Full
• In Use
• Empty

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Medical Gas Cylinders

• General Safety Considerations
• Safety when using Medical Gas Cylinders
• Dangers and Hazards of Gas Cylinders
• Transfilling Medical Gas Cylinders
• Medical Gas Cylinder Hazards

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General Safety Considerations

• Handle only by trained personnel
• Valves, regulators, gauges fittings should not
  come in contact with oil, greases, lubricants,
  rubber or combustible substance
• Never exceed Temp of 125F (52C)
• Avoid extremes of cold
• Keep connections tight

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General Safety Considerations

• Discharge port of press relief valve must not be
  obstructed
• Do not use adapters to change outlet size
• Valve should be kept closed except when tank is
  in use
• Do not alter markings, labels, tags
• Keep away from electricity

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Safety

• Protective cover should be removed before fitting
  tank to yoke
• A sealing washer (gasket) should be used with a
  small cylinder valve to fit over the port
• If more than washer (gasket) is used, the pins in
  the yoke may not extrude far enough to engage the
  mating holes and the PISS wont work properly
  (leak)

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Safety

• A cylinder valve should ALWAYS be opened SLOWLY
• If gas passes quickly into the space between the
  valve the yoke, the rapid recompression will
  generate large amount of heat. This is an
  ADIABATIC PROCESS (heat is neither lost nor
  gained from environment). Particles of dust,
  grease present in this space may be ignited by
  heat, causing a flash fire or explosion

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Transfilling (transfer of gas from one cylinder
to another)

• Best done by gas manufacturer/distributor
• May adversely affect purity
• Going from large to small tank, recompression of
  gas in small tank may cause increase temp to
  ignite combustible material
• Wrong gas can be added to cylinder

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Cylinder Hazards

• Incorrect tank (despite PISS)
• Incorrect Contents
• Incorrect Valves
• Wrong color
• Wrong label
• Inoperable/damaged valves
• Suffocation

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Cylinder Hazards

• Fires
• Explosions (rapid escape of contents or rocketing
  of tank)
• Contamination
• Theft of N2O (substance abuse)
• Overfilled
• Thermal injury (frostbite reported with
  recreational use of N2O)

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Medical Gas Pipelines

• Standards
• Pipeline Components
• Gas Supply
• Piping systems
• Valves
• Alarms
• Gauges
• Hoses and Connections

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Pipeline Standards

• The National Fire Protection Association (NFPA)
• The Compressed Gas Association (CGA)
• The Canadian Standard Association (CSA)
• The International Standard Assoc (ISO)
• JCAHO monitors compliance w/ standards
• Failure to adhere to regulations is widespread

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Pipeline Components

• Central Supply
• Piping extending to anesthetizing locations
• Terminal units (point where user makes
  connections and disconnections)
• Hoses from terminal units to anesthesia machine

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Gas Supply

• O2 stored as
• Liquid at low pressure (large Hospitals)
• Compressed gas in G or H cylinders (manifolded)
• N2O usually stored as
• Manifolded cylinders (most common)
• Liquid at low pressure

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Gas Supply

• Medical Air
• Air for breathing (different from gas-powered
  devices) supplied from
• manifolded cylinders (a proportioning device that
  mixes gas from O2 and N2 cylinders
• Motor-driven compressors (less clean and dry but
  less expensive when large volume needed)
• Majority of piped air systems employs 2 or more
  compressors that operate alternatively or
  simultaneously, depending on demand

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Gas Supply

• Central Nitrogen (N2) consists of
• manifolded high-pressure cylinders or
• cryogenic liquid N2 containers
• CO2 (laparoscopy) piped in high-pressure cylinder

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Piping Systems

• Main lines pipes connecting the source to risers
  or branch lines or both
• Risers (vertical) pipes connecting the main line
  with branch lines on various levels of the
  facility
• Branch (lateral) pipes that service a room or
  group of rooms on same level of facility

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Pressure Relief Valves

• Each central supply system has a press relief
  valve set 50 above normal press
• Downstream of the line regulator(s) and
• Upstream of shutoff valve
• Prevents buildup of pressure if a shutoff valve
  is closed
• The press relief valve closes automatically when
  excess pressure is relieved

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Shutoff Valves

• Permit isolation of specific areas in case of
  problem or if maintenance, repair, testing is
  needed
• No need to switch off entire Central supply
• Two types
• Manual must be visible accessible
• Service authorized personnel

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Manual Shutoff Valves(pull a quarter turn)
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ALARMS

• Master Alarm System monitors central supply and
  pressure in the main line for all medical gases
• Area Alarm System provides audible and visual
  signals to specific locations
• OR, PACU, ICU have individual area alarms to
  indicate if increases or decreases of pressure of
  20 of normal operating pressure take place

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Gauges

• A pressure gauge must be installed in the main
  line adjacent to the actuating switch for the
  main supply line pressure alarm
• A pressure gauge must be present in each line
  being monitored at each area alarm panel

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Medical Gas Pipelines

• New systems, testing and verification
• Pipeline system problems
• Pressure
• Leaks
• Alarms
• Contamination
• Fire
• Reserve
• Abuse

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New systems, testing and verification

• Blow Down before installation of terminal units,
  the lines must be blown clear using oil-free dry
  nitrogen
• Initial Press Test after terminal unit
  installation, each section of piping system must
  be subjected to a test pressure of 1.5 times
  working pressure to check leaks
• Standing Press Test entire system undergoes 24hr
  test at pressure 20 higher than standard
• Piping Purge purging on each outlet until no
  discoloration of white cloth held over outlet
• Cross Connection Test one gas system at a time

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Pipeline Problems

• Inadequate pressure (most common reported)
• Sources
• Damage during construction projects
• FIRES
• Car accidents
• Theft of N2O tanks
• Environmental (earthquakes, lightning)
• Depletion of central supply
• Human error (accidental closure of shutoff valve)
• Obstruction (debris following installation)
• Kinking, leak, obstruction of a hose

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Contamination

• Particulate Foreign material
• Gaseous Inlet of air compressor location
• Water can damage equipment, be a source for
  bacteria, can freeze and occlude pipes
• Bacterial Piped medical gases are not sterile.