Inhaled anesthetic Delivery Inhaled anesthetic Delivery Systems Systems Sahmeddini MD Department of Anesthesia Shiraz medical university
Jan 13, 2016
Inhaled anesthetic Delivery Inhaled anesthetic Delivery SystemsSystems
Sahmeddini MDDepartment of Anesthesia Shiraz medical university
Inhaled anesthetic Delivery Inhaled anesthetic Delivery SystemsSystems
Safety StandardsSafety Standards
ANSI - (American National Standards ANSI - (American National Standards Institute)Institute)
19791979 -- -- Standards set for all machines sold in Standards set for all machines sold in the U.Sthe U.S..
ASTM -- (American Society for Testing and ASTM -- (American Society for Testing and Materials 1988Materials 1988
19941994 : :ASTM F1161-94ASTM F1161-9420002000 : :ASTM F1850-00ASTM F1850-00
To comply with the 2000 ASTM F1850-00 standardTo comply with the 2000 ASTM F1850-00 standard
Continuous breathing system pressureContinuous breathing system pressureExhaled tidal volumeExhaled tidal volumeVentilatory carbon dioxide concentrationVentilatory carbon dioxide concentrationAnesthetic vapor concentrationAnesthetic vapor concentrationInspired oxygen concentrationInspired oxygen concentration Oxygen supply pressureOxygen supply pressure Arterial oxygen saturation of hemoglobinArterial oxygen saturation of hemoglobinArterial blood pressureArterial blood pressure Continuous electrocardiogramContinuous electrocardiogram . .
Functions of anesthesia machineFunctions of anesthesia machine
Convert supply gases from high pressure to Convert supply gases from high pressure to low pressurelow pressure
Convert liquid agent to gasConvert liquid agent to gasDeliver in a controlled mannerDeliver in a controlled manner Provide positive pressure for ventilationProvide positive pressure for ventilationAlert the provider to malfunctionAlert the provider to malfunction Prevent delivery of a hypoxic mixturePrevent delivery of a hypoxic mixture
Testing Specific Components of the Testing Specific Components of the Anesthesia Delivery SystemAnesthesia Delivery System
11))Calibration of the oxygen analyzerCalibration of the oxygen analyzer
22 ) )The low-pressure circuit leak testThe low-pressure circuit leak test
33 ) )The circle system testsThe circle system tests..
High Pressure SystemHigh Pressure System
Receives gasses from the high pressure E Receives gasses from the high pressure E cylinders attached to the back of the cylinders attached to the back of the
anesthesia machineanesthesia machine . .((22002200 psig for O2, 745psig for N2Opsig for O2, 745psig for N2O)
High Pressure System
Receives gasses from the high Receives gasses from the high pressure E cylinders attached pressure E cylinders attached to the back of the anesthesia to the back of the anesthesia
machinemachine 22002200 psig for O2psig for O2 745745 psig for N2Opsig for N2OUsually not used, unless Usually not used, unless
pipeline gas supply is offpipeline gas supply is off
High Pressure SystemHigh Pressure System
Hanger YokeHanger YokeHanger Yoke: orients Hanger Yoke: orients
and supports the and supports the cylindercylinder
Providing a gas-tight Providing a gas-tight sealseal
Ensuring a Ensuring a unidirectional gas flow unidirectional gas flow
into the machineinto the machine
Pin Index Safety System(PISS)
Prevents tank swapsPin positionsAir 1-5Oxygen 2-5Nitrous oxide 3-5
Pin Index Safety System(PISS)Pin Index Safety System(PISS)
•Pipeline 50 psig•Tanks•»Oxygen: 2200 psig• »Nitrous oxide: 745 psig• »Both reduced to 45 psig upon entering the
machine
Two sources of gas:
Tank
H TankH Tank
E TankE Tank
E Size Compressed Gas CylindersE Size Compressed Gas CylindersCylinder Characteristics Oxygen Nitrous Oxide Air
ColourColour WhiteWhite BlueBlue BlackBlack
StateState GasGas Liquid and gasLiquid and gas GasGas
Contents (L)Contents (L) 625625 15901590 625625
Empty WeightEmpty Weight((kgkg))
5.905.90 5.905.90 5.905.90
Full Weight (kg)Full Weight (kg) 6.766.76 8.808.80 6.506.50
Pressure FullPressure Full((psigpsig))
20002000 750750 18001800
Oxygen cylinder pressure(psig)Oxygen cylinder pressure(psig) 200200. . oxygen flow rate(L/minoxygen flow rate(L/min)
Approximate remaining time#Approximate remaining time#
Intermediate Pressure System
Intermediate Pressure SystemIntermediate Pressure System
Receives gassesReceives gasses from the regulatorfrom the regulator
or the hospitalor the hospitalpipeline at pressures of pipeline at pressures of
40-55 psig40-55 psig
Pipeline Inlet ConnectionsPipeline Inlet Connections
•Mandatory N2O and O2,usually have air and suction too
•Inlets are non interchangeable due to specific threading as per the Diameter Index
Safety System (DISS)
Diameter Index Safety System (DISS)Diameter Index Safety System (DISS)
Oxygen Pressure Failure Devices
Machine standard requires that an Machine standard requires that an anesthesia machine be designed so that anesthesia machine be designed so that whenever the oxygen supply pressure is whenever the oxygen supply pressure is
reduced below normal, the oxygen reduced below normal, the oxygen concentration at the common gas outlet does concentration at the common gas outlet does
not fall below 19%not fall below 19%
Oxygen Pressure Failure Devices
A Fail-Safe valve is present in the gas line supplying each of the flow meters except O2 .
This valve is controlled by the O2 supply pressure and This valve is controlled by the O2 supply pressure and shuts off or proportionately shuts off or proportionately decreases the supply decreases the supply
pressure of all other gasses as the O2 supply pressure of all other gasses as the O2 supply pressure decreasespressure decreases
Oxygen Pressure Failure Devices
Historically there are 2 kinds of fail-safe valvesHistorically there are 2 kinds of fail-safe valves
Pressure sensor shut-off valve (Ohmeda)Pressure sensor shut-off valve (Ohmeda)
Oxygen failure protection device (DragerOxygen failure protection device (Drager)
Pressure Sensor Shut-Off ValvePressure Sensor Shut-Off Valve
Oxygen supply pressure opens the valve as long as Oxygen supply pressure opens the valve as long as it is above a pre-set minimum value (e.g.20 psig)it is above a pre-set minimum value (e.g.20 psig)..
If the oxygen supply pressure falls belowIf the oxygen supply pressure falls below the threshold value the valve closes and thethe threshold value the valve closes and the gas in that limb (e.g..N2O), does not advance to its gas in that limb (e.g..N2O), does not advance to its
flow controlflow control
Pressure sensor shut-off valvePressure sensor shut-off valve
Oxygen Failure Protection Device Oxygen Failure Protection Device (OFPD(OFPD)
•Based on a proportioning principle rather than a shut-off principle.
• The pressure of all gases controlled by the OFPD will decrease proportionately with the
Oxygen failure protection deviceOxygen failure protection device
Oxygen Supply Failure AlarmOxygen Supply Failure Alarm
The machine standard specifies that whenever The machine standard specifies that whenever the oxygen supply pressure falls below a the oxygen supply pressure falls below a
manufacturer specified threshold manufacturer specified threshold (usually 30 (usually 30 psig) psig) alarm shall blow within 5 secondsalarm shall blow within 5 seconds.
Limitations of Fail-Safe Devices/AlarmsLimitations of Fail-Safe Devices/Alarms
Fail-safe valves do not prevent administration Fail-safe valves do not prevent administration of a hypoxic mixture because they depend on of a hypoxic mixture because they depend on
pressure and not flowpressure and not flow..
Do not prevent hypoxia from accidents such as Do not prevent hypoxia from accidents such as pipeline crossovers or a cylinder containing the pipeline crossovers or a cylinder containing the
wrong gaswrong gas..
OXYGEN FLUSH VALVEOXYGEN FLUSH VALVEBy passes vaporizerBy passes vaporizerDelivers large volumes Delivers large volumes
of oxygen to breathing of oxygen to breathing circuitcircuit
Is under high(er) Is under high(er) pressure cautionpressure caution!!!!!!
OXYGEN FLUSH VALVEOXYGEN FLUSH VALVEReceives O2 from pipeline inlet or cylinder
reducing device and directs high, unmetered flow directly to the common gas outlet (downstream
of the vaporizer)
Machine standard requires that the flow be between
35 and 75 L/minThe ability to provide jet ventilation Hazards:May cause barotraumasDilution of inhaled anesthetic
Second-Stage ReducingDevice
Located just upstream of the flow control valves
Receives gas from the pipeline inlet or the cylinder reducing device and reduces it further
to26 psig for N2O and14 psig for O2 Purpose is to eliminate fluctuations in
pressure supplied to the flow indicators caused by fluctuations in pipeline pressure
Low Pressure System
Extends from the flow control valves tothe common gas outlet Consists of: Flow metersFlow metersVaporizer mounting deviceVaporizer mounting deviceCheck valveCheck valveCommon gas outletCommon gas outlet
Flow Meter AssemblyFlow Meter Assembly
•When the flow control valve is opened the gas enters at the bottom and flows up the tube
elevating the indicator
• The indicator floats freely at a point where the downward force on it (gravity) equals the upward force caused by gas molecules hitting
Flow Meter Flow Meter
Flow Meter StandardsFlow Meter Standards
Oxygen flow control knob Physically differentOxygen flow control knob Physically differentLarger and projects furtherLarger and projects furtherDifferent shapeDifferent shape All knobs are colour codedAll knobs are colour coded Knobs are protectedKnobs are protected
•Some newer anaesthesia workstations have now replaced the conventional glass flow tubes with
electronic flow sensors that measure the flow of the individual gases .
•These flow rate data are then presented to the anaesthesia care provider in either numerical format,
graphic format, or a combination of the two.
Electronic flow sensors
Cracked tubesCracked tubes
In the presence of a flow meter leak (either
at the “O” ring or the glass of the flow tube)
a hypoxic mixture is less likely to occur if the O2
flow meter is downstream of all other
flow meters
Proportioning Systems
•Mechanical integration of the
•N2O and O2 flow control valves
•Maintain a minimum 25% concentration of oxygen with a maximum N2O:O2 ratio of 3:1
Proportioning Systems
Proportioning Systems
Proportioning Systems
VaporizersVaporizers
•A vaporizer is an instrument designed to change a liquid anesthetic agent into its vapor
and add a controlled amount of this vapor to the fresh gas flow
VaporizersVaporizers
Classification of VaporizersClassification of Vaporizers
Methods of regulating output concentrationConcentration calibrated Method of vaporizationFlow-overBubble throughInjectionTemperature compensation:ThermocompensationSupplied heat
Applied PhysicsApplied Physics
•Vapor pressure•Based on characteristics of agent•Varies with temperature•Boiling point: Vapor pressure equals atmospheric
pressure•Latent heat of vaporization: Heat required to
change liquid into a vapor•Comes from liquid •environment
Ohmeda and Drager CharacteristicsOhmeda and Drager Characteristics
•Variable bypass• Flow over• Temperature compensated•Agent specific•Out of circuit
Basic Design
•Gas enters vaporizer•Flow is split•Majority is by passed•Some enters vaporizing chamber•Saturated gas leaves chamber•Diluted by bypass gas•Delivered to patient
Generic Bypass VaporizerGeneric Bypass Vaporizer
•Flow from the flow meters enters the inlet of the vaporizer
•The function of the concentration control valve is to regulate the amount of flow
through the bypass and vaporizing chambers•Splitting Ratio = flow though vaporizing
chamber/flow through bypass chamber
Factors that Effect OutputFactors that Effect Output
Flow rateFlow rateAccurate at most flowsAccurate at most flowsLower than dial setting at both extremes of Lower than dial setting at both extremes of
flowflowTemperatureTemperatureVapor pressure varies with tempVapor pressure varies with tempAccurate at 20 - 35 CAccurate at 20 - 35 C
Factors that Effect OutputFactors that Effect Output
•Intermittent back pressure•Retrograde flow•Higher than dial setting•especially at low flows and high•ventilator pressures•Carrier gas composition•N2O causes transient drop
Carbon Dioxide Absorbents
•Two formulations of carbon dioxide absorbents are Two formulations of carbon dioxide absorbents are commonly available todaycommonly available today::
•soda limesoda lime • calcium hydroxide limecalcium hydroxide lime•Baralyme, or barium hydroxide limeBaralyme, or barium hydroxide lime
CO2 Absorption (con’t)
•Soda lime•–94% calcium hydroxide•–5% sodium hydroxide•–1% potassium hydroxide•–silica to harden granules•–ethyl violet as an indicator
CO2 Absorption (con’t)
•Ethyl violet is the pH indicator added to both soda Ethyl violet is the pH indicator added to both soda limelime
•Ethyl violet changes from colorless to violet when the Ethyl violet changes from colorless to violet when the pH of the absorbent decreases as a result of carbon pH of the absorbent decreases as a result of carbon
dioxide absorptiondioxide absorption.
•Unfortunately, in some circumstances ethyl violet Unfortunately, in some circumstances ethyl violet may not always be a reliable indicator of the may not always be a reliable indicator of the
functional status of absorbentfunctional status of absorbent
Anesthesia Ventilators
•The ventilator on the modern anesthesia workstation The ventilator on the modern anesthesia workstation serves as a mechanized substitute for the hand of the serves as a mechanized substitute for the hand of the
anesthesia care provider in manipulating the anesthesia care provider in manipulating the reservoir bag of the circle system, or another reservoir bag of the circle system, or another
breathing systembreathing system..
Ventilators Classified by:•Power source
–pneumatic–electric –both•Drive mechanism
–double circuit–driven by oxygen
Ventilator Problems (con’t)
•Leak in bellows assembly
•Mechanical problems
•Electrical problems
Setting the Ventilator
Based on the principle that PaCO2 is directly proportional
to alveolar ventilation
AV X CO2 = AV X CO2
(what you have) (what you want)
AV = alveolar ventilationCO2 = carbon dioxide
If you know 3, you can solve for the 4th
The Circuit: Circle System•Arrangement is variable, but to Arrangement is variable, but to
prevent re-breathing of CO2, the prevent re-breathing of CO2, the following rules must be following rules must be
followedfollowed::–Unidirectional valves Unidirectional valves
between the patient and the between the patient and the reservoir bagreservoir bag
–Fresh-gas-flow cannot enter Fresh-gas-flow cannot enter the circuit between the the circuit between the
expiratory valve and the expiratory valve and the patientpatient
–Adjustable pressure-limiting Adjustable pressure-limiting valve (APL) valve (APL) cannot be cannot be
located between the patient located between the patient and the inspiratory valveand the inspiratory valve
Circle System•Advantages:
–Relative stability of inspired concentration–Conservation of respiratory moisture and heat–Prevention of operating room pollution–PaCO2 depends only on ventilation, not fresh gas
flow–Low fresh gas flows can be used•Disadvantages:
–Complex design = potential for malfunction–High resistance (multiple one-way valves) = higher
work of breathing
The Adjustable Pressure Limiting (APL) Valve
•User adjustable valve that releases gases to the scavenging system and is
intended to provide control of the pressure in the breathing system
•Bag-mask Ventilation: Valve is usually left partially open. During inspiration the bag is squeezed pushing gas into
the inspiratory limb until the pressure relief is reached, opening the APL valve .
•Mechanical Ventilation: The APL valve is excluded from the circuit when the
selector switch is changed from manual to automatic ventilation
The Adjustable Pressure Limiting (APL) Valve
Scavenging Systems
•Scavenging is the collection and removal of vented anesthetic gases from the OR
•Since the amount of anesthetic gas supplied usually far exceeds the amount necessary for
the patient, OR pollution is decreased by scavenging
Scavenging Systems
Workers should not be exposed to an eight hour Workers should not be exposed to an eight hour time-weighted average of > 2 ppm time-weighted average of > 2 ppm
halogenated agents (not > 0.5 ppm if nitrous halogenated agents (not > 0.5 ppm if nitrous oxide is in use) or > 25 ppm nitrous oxideoxide is in use) or > 25 ppm nitrous oxide.
Evidence of harm to anesthesia personnel from waste gases is
suggestive but unproved (strongest relationship is N2O and reproductive difficulties).
Type of Scavenging Systems
•Scavenging may be active (suction applied)
•passive (waste gases proceed passively down corrugated tubing through the room
ventilation exhaust grill of the OR) .
Hazards of scavenging
•Obstruction distal to interfaceObstruction distal to interface
•Occupational exposureOccupational exposure
•Barotrauma or inability to ventilateBarotrauma or inability to ventilate
High-Pressure System Checkout Check Oxygen Cylinder SupplyCheck Oxygen Cylinder Supply . . Open the OOpen the O22 cylinder and verify that it is at cylinder and verify that it is at
least half full (≈1000 psi)least half full (≈1000 psi) Close the cylinderClose the cylinder..Check Central Pipeline SuppliesCheck Central Pipeline Supplies . . Check that hoses are connected and pipeline Check that hoses are connected and pipeline
gauges read about 50 psigauges read about 50 psi..
System Checkout
Low-Pressure System
Check Initial Status of Low-Pressure SystemCheck Initial Status of Low-Pressure System . .a. Close the flow control valves and turn the a. Close the flow control valves and turn the
vaporizers offvaporizers off . .b. Check the fill level and tighten the b. Check the fill level and tighten the
vaporizers’ filler capsvaporizers’ filler caps..
Perform Leak Check of Machine Low-Pressure System.
Verify that the machine master switch and flow Verify that the machine master switch and flow control valves are OFFcontrol valves are OFF
Attach a “suction bulb” to the common (fresh) Attach a “suction bulb” to the common (fresh) gas outletgas outlet
Squeeze the bulb repeatedly until it is fully Squeeze the bulb repeatedly until it is fully collapsedcollapsed . .
Verify that the bulb stays fully collapsed for at Verify that the bulb stays fully collapsed for at least 10 secondsleast 10 seconds . .
Open one vaporizer at a time and repeat steps c Open one vaporizer at a time and repeat steps c and d as aboveand d as above . .
Remove the suction bulb and reconnect the fresh Remove the suction bulb and reconnect the fresh gas hosegas hose..
Turn on Machine Master Switch and All Other Turn on Machine Master Switch and All Other Necessary Electrical EquipmentNecessary Electrical Equipment.
Test Flow MetersTest Flow Meters.. a.a. Adjust the flow of all gases through their Adjust the flow of all gases through their
full range while checking for smooth operation full range while checking for smooth operation of the floats and undamaged flow tubesof the floats and undamaged flow tubes . .
b. b. Attempt to create a hypoxic O Attempt to create a hypoxic O22/N/N22O O mixture and verify correct changes in flow mixture and verify correct changes in flow
and/or alarmand/or alarm..
Calibrate O2 Monitor
a.a. Ensure that the monitor reads 21% in Ensure that the monitor reads 21% in room airroom air . .
b. b. Verify that the low-O Verify that the low-O22 alarm is enabled alarm is enabled and functioningand functioning . .
c. c. Reinstall the sensor in the circuit and flush Reinstall the sensor in the circuit and flush the breathing system with Othe breathing system with O22 . .
d. d. Verify that the monitor now reads greater Verify that the monitor now reads greater than 90%than 90%..
Check Initial Status of Breathing System.
a. a. Set the selector switch to “Bag” mode Set the selector switch to “Bag” mode . . b.b. Check that the breathing circuit is Check that the breathing circuit is
complete, undamaged, and unobstructedcomplete, undamaged, and unobstructed . .c. c. Verify that CO Verify that CO22 absorbent is adequate absorbent is adequate . .d. d. Install the breathing circuit accessory Install the breathing circuit accessory
equipment (e.g., humidifier, positive end-equipment (e.g., humidifier, positive end-expiratory pressure [PEEP] valve) to be used expiratory pressure [PEEP] valve) to be used
during the procedureduring the procedure..
Perform Leak Check of Breathing System.
Set all gas flows to zero (or minimum)Set all gas flows to zero (or minimum) . .Close the APL (pop-off) valve and occlude the Close the APL (pop-off) valve and occlude the
Y-pieceY-piece . .Pressurize the breathing system to about Pressurize the breathing system to about
30 cm H30 cm H22O with an OO with an O22 flush flush . .Ensure that the pressure remains fixed for at Ensure that the pressure remains fixed for at
least 10 secondsleast 10 seconds . .Open the APL (pop-off) valve and ensure that Open the APL (pop-off) valve and ensure that
the pressure decreasesthe pressure decreases