Anaesthesia machine

Anaesthesia machine

1. DRTULSIRAMSHRESTHA, KMCTH

2. CONTENTS
▪History
▪Introduction
▪Essential safety features
▪Pneumatic system
▪High pressure system
▪Intermediate pressure system
▪Low pressure system
▪Anaesthesia machine checkup

3. HISTORY
▪1846:Publicdemonstrationofether
anaesthesia,WTGMorton
▪1917:Boyle’smachine,HenryEdmund
GaskinBoyle
▪1921:Waterstoandfroabsorption
apparatus
▪1927:FlowmeterforCO
2

4. ▪1930:Plungerofvaporizer;circle
absorptionsystem,BrianSword
▪1933:Drybobbinflowmeters
▪1952:PISSbyWoodbridge

5. THEANAESTHESIAMACHINE
▪Receivesmedicalgasesfromagassupply
▪Controlstheflowandreducesthepressure
ofgasestoasafelevel
▪Vaporizesvolatileanestheticsintofinalgas
mixture
▪Deliversgasestoabreathingcircuit
connectedtothepatient’sairway

6. 1.Gas-specificconnectionstopipelineinlets(DISS)
withpressuregauges,filter,andcheckvalve
2.PISSforcylinderswithpressuregauges,andat
leastoneoxygencylinder
3.Lowoxygenpressurealarm
4.MinimumO
2:N
2Oratiocontrollerdevice
5.Oxygenfailuresafetydevice
ESSENTIALSAFETYFEATURES

7. 6.O
2enterscommonmanifolddownstreamtoother
gases
7.O
2concentrationmonitorandalarm
8.Automaticallyenabledessentialalarmsand
monitors(eg,oxygenconcentration)
9.Vaporizerinterlockdevice
10.Capnographyandanestheticgasmeasurement
11.O
2flushmechanism

8. 12.Breathingcircuitpressuremonitorandalarm
13.Exhaledvolumemonitor
14.Pulseoximetry,BP,ECGmonitoring
15.Mechanicalventilator
16.Backupbattery
17.Scavengersystem

9. PNEUMATICSYSTEM

10. HIGHPRESSURESYSTEM
▪ReceivesgasesfromhighpressureE
cylinders
▪2000psigforO
2andair,745psigforN
2O
▪Handyincaseoffailureofhospitalpipeline
supplysource

11. Hanger Yoke
▪Orientsandsupportsthecylinder
▪Providesgastightseal
▪Ensuresunidirectionalgasflow
▪Parts
▪Body
▪Retainingscrew
▪PISSpins
▪Washer
▪Filter

12. Pressure regulator
▪Reduceshigh/variablepressurefrom
cylinder
▪Tolower/constantpressureforusein
anesthesiamachine(40-45psig)
▪Pressureatregulatoroutlet:setlowerthan
pipelinepressure

13. Check valve
▪Allowsgasfromcylindertoentermachine
▪Minimizestransferofgasfromacylinderathigh
pressuretoonewithlowerpressure
▪Helpsexchangeofemptycylinderwithafullone
▪Minimizesleakagefromanopencylindertothe
atmosphereifonecylinderisabsent

14. INTERMEDIATEPRESSURESYSTEM
▪Receivesgasesfrompressureregulatoror
pipelineinlet
▪Pressureof40-55psig

15. Pipeline inlet connections
▪Forair,O
2,N
2O
▪Fittedwiththreadednoninterchangeable
DISSconnectors
▪Containsfilter,unidirectionalcheckvalve

16. Pipeline pressure gauges
▪Tomonitorpipelinepressure
▪Colorcoded
▪50-55psig

17. Pneumatic safety systems
O
2failure protection device
▪When O
2pressure is normal->push the
diaphragm and stem downward
→opening valve
▪When O
2pressure falls→Fail-safevalves
shut off or proportionally decrease the
flow of the other breathing gases
▪If a gas other than O
2adequately
pressurizes the O
2circuit as a result of
hospital pipeline contamination, fail-safe
valves will remain open. In such a case,
only the inspired oxygen concentration
monitor will help

18. O
2supply failure alarm
▪Sensorwithanaudibleandvisualwarningif
O
2pressuredropsbelowaminimum
▪Cannotbesilenceduntilthepressureis
restoredtotheminimumvalue
▪DrägerFabiusseriesmachinesaresetto
alarmat20psig

19. Oxygen flush valve
▪Providesmanualdeliveryofahighflowrateof
100%O
2
▪High(35to75L/m)flowdirectlytoCGO
▪Flow bypasses the anesthetic vaporizers
▪Available even when machine is not turned on
▪Pressure: 50 psig

20. Auxiliary O
2flowmeter
▪AdministerO
2incaseofelectricfailure
▪Allowstheuseoflow-flowoxygenfordevices
independentofthepatient’sbreathingcircuit
▪Accessibleevenwhenthemachineisnot
turnedon

21. Second stage pressure regulator
▪Locateddownstreamfromthegassupply
sources
▪Constantpressuretotheflowcontrolvalves
regardlessofpotentialfluctuationsinhospital
pipelinepressures
▪Lowerlevelsthanthepipelinesupply,usually
between14and35psig

22. LOWPRESSURESYSTEM
▪Beginsatflowcontrolvalvesandendsat
machineoutlet
▪Flowcontrolvalves,flowmetersorflow
sensors,vaporizermanifold,andanesthetic
vaporizers
▪Mostvulnerablesectiontoleakswithinthegas
supplysystem

23. Flow adjustment control
▪Regulatesflowofgasestoflowmeter
▪Clockwise:decreasegasflow
▪Anticlockwise:increasegasflow
▪Inletpressureisdeterminedbypressure
characteristicsofintermediate-pressuresegment
▪Flowcontrolknob
▪Differenttexture,diameter,colorcoded,nameofgas
engraved
▪O
2:fluted,larger

24. Flowmeter
▪Variableorificeverticalglasstubewith
indicator(Thorpe’stube)
▪Upwardforceresultingfromgasflowequals
thedownwardforceonthefloatresulting
fromgravityatagivenflowrate
▪Heightofindicator:measureofgasflow
▪Widestdiameter:flowtoberead

26. ▪Flowratedependon
▪Pressuredropacrosstheconstriction
▪Sizeofannularopening
▪Physicalpropertiesofgas
▪Calibratedat atmospheric
pressure,roomtemperature

27. Flow indicator sequence
▪Where O
2
and other gases are delivered
by their respective flow indicators into a
common manifold, the O
2
should be
delivered downstream of all other gases.
▪In the event of a flowmeter leak, a
potentially dangerous arrangement exists
when N
2
O located in downstream
position (A and B).
▪A safer configuration exists when O
2
located in downstream position (C & D).
▪Hypoxic mixture less likely because all O
2
flow is advanced by N
2
O (the principle
known as the Eger flow sequence)

28. Proportioning system
▪NomatterhowhighN
2Oisturnedup,orhowlow
theO
2flowismadewhenN
2Oisrunning
▪Themachinewillautomaticallylimittheamountof
N
2Oflow→hypoxemicgaswillnotbedelivered
▪Protectsagainstdeliveryofamixturewithanoxygen
concentrationbelow21%oxygen(v/v%)

29. Outlet check valve
▪Onewaycheckvalvelocatedbetween
vaporizerandCGO
▪Preventbackflowintothevaporizerduring
positive-pressureventilation

30. Common Gas Outlet
▪Receivesgasmixturefrommachineand
deliverstobreathingcircuit
▪Fresh gas outlet, critical role in adding new
gas of fixed and known composition to the
circle system

31. Oxygen (inspired) analyzers
▪Polarographic(Clarkelectrode)
▪Galvanic(fuelcell)
▪Paramagnetic

32. Waste gas scavengers
▪Disposegasesthathavebeenventedfrom
breathingcircuitbyAPLvalve
▪Safelevel
▪RoomconcentrationofN
2O:25ppm
▪Halogenatedagents:2ppm

34. Anesthesia machine checkout

35. High pressure system
▪CheckO
2cylindersupply
▪Opencylinder,verifyatleasthalffull(1000psig)
▪Closecylinder
▪Checkcentralpipelinesupplies
▪Checkhosesareconnected
▪Pipelinegauge:50psig

36. Low pressure system
▪Closeflowcontrolvalves,turnoffvaporizers
▪Checkfilllevel,tightenfillercaps
▪Performleakcheck
▪Testflowmeters

37. Breathing system
▪CalibrateO
2monitor
▪Checkinitialstatusbreathingsystem
▪Leakcheck
▪Setallgasflowstozero
▪CloseAPLvalve,occludeYpiece
▪Pressurizetoabout30cmofH2O
▪Ensurepressureremainsfixed(atleast10second)
▪OpenAPLvalve:pressuredecrease

38. ▪Miller's Anaesthesia, 8th edn
▪Morgan and Mikhail’s
Clinical Anesthesiology, 5th
edn
References