The document details the history and function of anesthetic vaporizers, explaining how they convert liquid anesthetics into vapor and control their release into the breathing system. It discusses various types of vaporizers, principles of gas laws, evaporation, and the influence of factors like temperature and gas flow on vaporizer output. Additionally, it highlights the importance of specific features in modern vaporizers to ensure accurate and safe administration of anesthetic agents.

1. ANESTHETIC VAPORIZERS
DR. CHIRANJEEVI REDDY DWARAMPUDI
JUNIOR RESIDENT IN ANAESTHESIOLOGY
KIMSDU, KARAD, MAHARASTRA

2. • A VAPORIZER (ANAESTHETIC AGENT OR VAPOR DELIVERY
DEVICE) CHANGES A LIQUID ANAESTHETIC AGENT INTO ITS
VAPOR AND ADDS A CONTROLLED AMOUNT OF THAT VAPOR
TO THE FRESH GAS FLOW OF THE BREATHING SYSTEM

3. HISTORY
• IN 1846, WILLIAM T. G. MORTON PERFORMED THE FIRST PUBLIC
DEMONSTRATION OF ETHER ANESTHESIA USING AN INGENIOUS, YET SIMPLE
INHALER.
• DRAWBACKS- MORTON’S ETHER INHALER HAD NO MEANS OF REGULATING
OUTPUT CONCENTRATION OR COMPENSATING FOR TEMPERATURE CHANGES
CAUSED BY VAPORIZATION OF THE LIQUID ANESTHETIC AND THE AMBIENT
ENVIRONMENT.

4. PHYSICS
• IDEAL GAS LAW:PRESSURE IS DIRECTLY PROPORTIONAL TO THE NUMBER OF
MOLECULES OR MOLES (N) OF GAS PRESENT WITHIN THE CONTAINER AND TO
THE TEMPERATURE (T) IN DEGREES KELVIN, AND INVERSELY PROPORTIONAL TO
THE VOLUME (V) THAT CONFINES THE GAS.
PV = N RT
R (THE UNIVERSAL GAS CONSTANT)= 8.314 L KPA/MOL *K OR 62.364 L MM
HG/MOL*K

5. • DALTON’S LAW OF PARTIAL PRESSURES :WHEN A MIXTURE OF IDEAL GASES
EXISTS IN A CONTAINER, EACH GAS CREATES ITS OWN PRESSURE, WHICH IS THE
SAME PRESSURE AS IF THE INDIVIDUAL GAS OCCUPIED THE CONTAINER ALONE
.THE TOTAL PRESSURE MAYBE CALCULATED BY SIMPLY ADDING TOGETHER THE
PRESSURES OF EACH GAS. THIS IS KNOWN AS DALTON’S LAW OF PARTIAL
PRESSURES
WHERE THE INDIVIDUAL PRESSURES (PI) EXERTED BY EACH OF THE CONSTITUENT
GASES ARE REFERRED TO AS PARTIAL PRESSURES
P TOTAL = P1 + P2 + P3 + …
PA = (NA/NTOTAL) PTOTAL = (V/V%) PTOTAL
THE PARTIAL PRESSURE OF GAS A CAN BE CALCULATED BY MULTIPLYING THE
TOTAL PRESSURE OF THE MIXTURE BY THE MOLE FRACTION (NA/NTOTAL), OR THE
VOLUME PERCENT (V/V%), OF GAS A.

7. EVAPORATION AND VAPOR PRESSURE
• WHEN A VOLATILE LIQUID IS EXPOSED TO AIR OR OTHER GASES, MOLECULES AT THE
LIQUID SURFACE WITH SUFFICIENT KINETIC ENERGY ESCAPE AND ENTER THE VAPOR
PHASE. THIS PROCESS IS KNOWN AS EVAPORATION, WHICH IS PURELY A SURFACE
PHENOMENON (IN CONTRAST TO BOILING, WHICH OCCURS THROUGHOUT THE
LIQUID).
• ANESTHETIC MOLECULES IN THE GAS PHASE CREATE A PARTIAL PRESSURE KNOWN AS
THE SATURATED VAPOR PRESSURE, OR SIMPLY VAPOR PRESSURE.
• VAPOR PRESSURE IS AN UNIQUE PHYSICAL PROPERTY OF A SUBSTANCE AT ANY GIVEN
TEMPERATURE AND IT IS NOT AFFECTED BY CHANGES IN ATMOSPHERIC PRESSURE.

8. • EVAPORATION IS DIMINISHED AT COLDER TEMPERATURES BECAUSE FEWER
MOLECULES POSSESS SUFFICIENT KINETIC ENERGY TO ESCAPE INTO THE VAPOR
PHASE. CONVERSELY, AT WARMER TEMPERATURES, EVAPORATION IS ENHANCED
AND VAPOR PRESSURE INCREASES.
• THE IMPACT OF EVAPORATIVE TEMPERATURE CHANGE ON VAPORIZER AND
ANESTHETIC INHALER OUTPUT HAS BEEN RECOGNIZED SINCE THE MID-1800S,
AND ADDRESSING THIS PHENOMENON HAS BEEN ONEOF THE PRINCIPAL
FACTORS INFLUENCING DESIGN OF ANESTHETIC VAPORIZERS.

9. EXPRESSING GAS CONCENTRATIONS AND MINIMUM ALVEOLAR
CONCENTRATION.
• VOLUME PERCENT (V /V %) =(PARTIAL PRESSURE OF GAS X /TOTAL PRESSURE) * 100%
• THE VOLUME THAT AN IDEAL GAS OCCUPIES AT A GIVEN TEMPERATURE AND PRESSURE IS
RELATED TO THE NUMBER OF MOLECULES OF GAS PRESENT, BUT NOT THE SIZE OR
IDENTITY OF THE MOLECULES. THIS STATEMENT IS KNOWN AS THE AVOGADRO
HYPOTHESIS
• BECAUSE PARTIAL PRESSURE IS DIRECTLY PROPORTIONAL TO THE NUMBER OF MOLECULES
OF A GAS PRESENT IN THE MIXTURE, WE CAN ALSO USE PARTIAL PRESSURES TO
CALCULATE THE VOLUME PERCENT OF ANY CONSTITUENT GAS
• 1 MOLE OF AN IDEAL GAS OCCUPIES A VOLUME OF ABOUT 24 L.
FOR EXAMPLE P ATM =760MM HG =(160 MM HG OXYGEN)+ (592 MM HG NITROGEN )+
(8 MM HG OTHER GASES)
• WE CAN THEN CALCULATE THE VOLUME PERCENT (V/V%) OF OXYGEN
• OXYGEN(V/V%)=P OXYGEN / P ATM = 160 MM HG / 760 MM HG =21%

11. • THE MINIMUM ALVEOLAR CONCENTRATION (MAC) IS DESCRIBED IN TERMS OF VOLUME
PERCENT.
• HOWEVER, IT IS ACTUALLY THE ANESTHETIC PARTIAL PRESSURE (MM HG) VALUE IN THE
BRAIN THAT IS RESPONSIBLE FOR ANESTHETIC DEPTH.
• THE CORRESPONDING PARTIAL PRESSURE FOR EACH MAC VALUE IS KNOWN AS THE
MINIMAL ALVEOLAR PARTIAL PRESSURE (MAPP),

12. LATENT HEAT OF VAPOURIZATION
• THE AMOUNT OF ENERGY ABSORBED BY A SPECIFIC LIQUID DURING EVAPORATION IS
REFERRED TO AS THE LATENT HEAT OF VAPORIZATION.
• WHEN A LIQUID SUCH AS A VOLATILE ANESTHETIC EVAPORATES INTO THE GAS PHASE,
ENERGY IS REQUIRED TO OVERCOME THE ATTRACTIVE INTERMOLECULAR FORCES BETWEEN
MOLECULES IN THE LIQUID PHASE (A PROPERTY KNOWN AS COHESION).
• THE NEEDED ENERGY IS ABSORBED FROM THE SURROUNDINGS IN THE FORM OF HEAT, AND
IS THE REASON WHY THE HUMAN BODY IS COOLED BY THE EVAPORATION OF SWEAT.
• IT IS MORE PRECISELY DEFINED AS THE AMOUNT OF ENERGY IN JOULES OR CALORIES (1
CALORIE = 4.184 JOULES) REQUIRED TO CHANGE 1 G OF LIQUID INTO VAPOR AT A
CONSTANT TEMPERATURE.

13. SPECIFIC HEAT
• THE SPECIFIC HEAT IS THE AMOUNT OF ENERGY REQUIRED TO INCREASE THE
TEMPERATURE OF 1 G OF A SUBSTANCE BY1°C.
• WATER, FOR EXAMPLE, HAS A SPECIFIC HEAT OF EXACTLY 1 CALORIE /G/ DEG.
• THE CONCEPT OF SPECIFIC HEAT IS IMPORTANT TO THE DESIGN, OPERATION, AND
CONSTRUCTION OF VAPORIZERS IN TWO WAYS.
• FIRST, THE SPECIFIC HEAT OF A LIQUID ANESTHETIC DETERMINES HOW MUCH HEAT
MUST BE SUPPLIED TO MAINTAIN A CONSTANT TEMPERATURE DUE TO THE LATENT
HEAT OF VAPORIZATION.
• SECOND, VAPORIZERS ARE BUILT FROM MATERIALS WITH A HIGH SPECIFIC HEAT IN
ORDER TO BETTER RESIST TEMPERATURE CHANGES ASSOCIATED WITH EVAPORATIVE
COOLING

14. THERMAL CONDUCTIVITY
• THERMAL CONDUCTIVITY IS A PROPERTY THAT DESCRIBES HOW WELL HEAT
FLOWS THROUGH A SUBSTANCE.
• THE HIGHER THE THERMAL CONDUCTIVITY, THE BETTER A SUBSTANCE
CONDUCTS HEAT.44 VAPORIZERS ARE CONSTRUCTED OF METALS WITH
RELATIVELY HIGH THERMAL CONDUCTIVITY, WHICH HELPS MAINTAIN A
UNIFORM INTERNAL TEMPERATURE DURING EVAPORATION BY ALLOWING
EFFICIENT HEAT ABSORPTION FROM THE ENVIRONMENT.
• BY CONTRAST, COFFEE MUGS SHOULD BE MADE OF MATERIALS WITH A LOW
THERMAL CONDUCTIVITY TO SLOW HEAT LOSS TO THE ENVIRONMENT.

15. DEPENDING ON METHOD OF VAPORIZATION
• 1. FLOW OVER
• 2. BUBBLE THROUGH
• 3. INJECTION

16. A)FLOW OVER:
• A STREAM OF CARRIER GAS PASSES OVER THE SURFACE OF THE LIQUID.
• MOST COMMONLY USED.
• EFFICIENCY OF VAPORIZATION ENHANCED BY INCREASING THE AREA OF CARRIER GAS-LIQUID
INTERFACE BY
- USING BAFFLES OR SPIRAL TRACKS TO LENGTHEN THE PATHWAY OF GAS OVER LIQUID.
- USING WICKS THAT HAVE THEIR BASES IN THE LIQUID.
THE LIQUID MOVES UP THE WICK BY CAPILLARYACTION.

17. B) BUBBLE THROUGH:
THE CARRIER GAS IS BUBBLED THROUGH THE VOLATILE LIQUID, FURTHER
INCREASING THE GAS-LIQUID INTERFACE.
C) INJECTION:
VAPOR CONCENTRATION CONTROLLED BY INJECTING A KNOWN AMOUNT OF LIQUID
ANESTHETIC AGENT (FROM A RESERVOIR IN THE VAPORIZER OR FROM THE BOTTLE
OF AGENT) INTO A KNOWN VOLUME OF GAS.

18. FLOW OVER INJECTION

19. DEPENDING ON THE LOCATION
Outside the breathing system (VOC) Inside the breathing system. (VIC)

20. DEPENDING ON TEMPERATURE COMPENSATION
• MECHANICAL THERMO COMPENSATION
• SUPPLIED HEAT
• COMPUTERIZED THERMO COMPENSATION
• DEPENDING ON THE SPECIFICITY
-AGENT SPECIFIC
-MULTIPLE AGENTS

21. • BOYLE’S BOTTLE
• MAINLY FOR ETHER AND TRICHLOROETHYLENE.
• FLOW OVER OR BUBBLE THROUGH TYPE.
• NO TEMPERATURE COMPENSATION OR CALIBRATION.
• MULTIPLE AGENT TYPE.
• AGITATION OF VAPORIZER AND SPLASHING MAY ALSO
INCREASE THE CONCENTRATION MOST PROBABLY DUE
TO A LITTLE WARMING OF THE LIQUID

24. GOLDMAN VAPORIZER
• VARIABLE BY PASS, FLOW OVER.
• NO TEMPERATURE COMPENSATION
• MULTIPLE AGENT
• 3 POSITIONS BETWEEN ON AND OFF IN MARK I AND MARK II MODELS
• MARK III HAS TWO SETTINGS ONLY
• SMALL GLASS BOWL-20CC
• BOWL IS ATTACHED TO THE HEAD.
• EASY TO OPERATE AND DOES NOT DELIVER HIGH CONCENTRATIONS.

26. EPSTEIN MACINTOSH OXFORD (EMO) VAPORIZER
• IT WAS INTRODUCED BY EPSTEIN, MACINTOSH AND OXFORD IN 1952
• VARIABLE BYPASS AND FLOW OVER (WITH WICK)
• TEMPERATURE COMPENSATED
• AGENT SPECIFIC-ETHER,CHOLORFORM, HALOTHANE
• THERE IS A THERMO COMPENSATOR SMALL METAL BELLOWS CONTAINING A
LIQUID AT THE VAPORISING CHAMBER OUTLET.
• CONCENTRATION CALIBRATED.

28. COPPER KETTLE
• IT IS CLASSIFIED AS A MEASURED-FLOW VAPORIZER (OR FLOWMETER-CONTROLLED
VAPORIZER)
• COPPER IS USED AS THE CONSTRUCTION METAL BECAUSE ITS RELATIVELY HIGH
SPECIFIC HEAT (THE QUANTITY OF HEAT REQUIRED TO RAISE THE TEMPERATURE OF
1 G OF SUBSTANCE BY 1°C) AND HIGH THERMAL CONDUCTIVITY (THE SPEED OF
HEAT CONDUCTANCE THROUGH A SUBSTANCE) ENHANCE THE VAPORIZER’S
ABILITY TO MAINTAIN A CONSTANT TEMPERATURE.
• BECAUSE THE VAPOR PRESSURE OF VOLATILE ANESTHETICS IS GREATER THAN THE
PARTIAL PRESSURE REQUIRED FOR ANESTHESIA,THE SATURATED GAS LEAVING A
COPPER KETTLE HAS TO BE DILUTED BEFORE IT REACHES THE PATIENT
• HOWEVER, IF TOTAL GAS FLOW DECREASES WITHOUT AN ADJUSTMENT IN COPPER
KETTLE FLOW (EG, EXHAUSTION OF A NITROUS OXIDE CYLINDER), THE DELIVERED
VOLATILE ANESTHETIC CONCENTRATION RISES RAPIDLY TO POTENTIALLY
DANGEROUS LEVELS.

31. TEC 2
• HALOTHANE AND METHOXYFLURANE.
• PLENUM VAPORIZER, FLOW OVER WITH WICKS.
• TEMPERATURE COMPENSATED
• BIMETALLIC STRIP FOR TEMPERATURE COMPENSATION.
• FILLING TAP AND LEVEL INDICATOR AT THE SIDE
• EXTERNAL CALIBRATED CONTROL BACK.
• NOT SUITABLE FOR BELOW 4L/MIN

32. • THE CONTROL KNOB IS CALIBRATED- 4% IN 0.5% INCREMENTS.
• A PRESSURING VALVE HAS BEEN DESIGNED TO PREVENT PUMPING EFFECT.
• FLOW OF 2L/MIN , OUTPUT IS LESS THAN 2%.
• SMALL LEAK IN OFF POSITION.

33. TEC 3
• VARIABLE BYPASS, FLOW OVER WITH WICK TYPE.
• TEMPERATURE AND FLOW COMPENSATED.
• BIMETALLIC STRIPS PROVIDE TEMPERATURE COMPENSATION.
• AGENT SPECIFIC.
• IT HAS A LARGER BYPASS. IT IS MORE RELIABLE AND ACCURATE.
• THE DIAL HAS 0.5% TO 5% GRADUATION WITH A LOCK.

34. • TUBES LEADING TO VAPORIZING CHAMBER ARE LONGER AND HAS AN
EXPANSION AREA.
• LOW VAPOURISING CHAMBER.
• ALL ACCURATE WITH LOW DIAL SETTINGS.
• HIGHER THAN EXPECTED CONCENTERATION AT LOW FLOW RATES AND LOWER
THAN EXPECTED CONC AT HIGHER FLOW RATES.
• TIPPING MORE THAN 90 CAUSES LEAK.

35. Tec 2 Tec 3
Vaporizing
chamber
Round in shape with
capacity of 150ml
Capacity is around 70ml
Bypass Only one Two
Effect of
back
pressure
Increased output Negligible
Accuracy Less More compared to tec 2
Calibration 4% 5%
Bimetallic
strip
Present in chamber Present in the bypass

36. TEC 4
• VARIABLE BYPASS, FLOW OVER WITH WICKS VARIETY.
• TEMPERATURE COMPENSATED AND AGENT SPECIFIC
• THIS HAS SIMILAR FEATURES OF FLOUTEC3.
• ADDED FEATURES ARE THAT IF IT IS ACCIDENTALLY INVERTED, THE LIQUID
AGENT WILL NOT SPILL INTO THE BYPASS.
• IT INCORPORATES AN INTERLOCKING FACILITY OF PUSH ROD MECHANISM, SO
THAT TWO VAPORIZER MOUNTED SIDE BY SIDE ARE NOT TURNED ON AT THE
SAME TIME

37. • ON TOP IS THE CONTROL DIAL.
• RELEASE BUTTON LOCATED TO THE LEFT OF CONCENTERATION DIAL.
• LOCKING LEVER CONNECTED WITH CONTROL DIAL.
• GREATER EFFECTS ARE SEEN WITH LOW FLOW RATES, LOW DIAL SETTINGS.
• LARGE AND FREQUENT PRESSURE FLUCTUATION.

38. 38

39. TEC 5
• THE WICK ASSEMBLY IS CONSTITUENT OF A HOLLOW CLOTH TUBE HELD OPEN
BY A STEEL WIRE SPIRAL, WHICH IS WOUND INTO A HELIX WITHIN THE
VAPORIZER.
• BIMETALLIC STRIP WHICH ACTS AS A THERMOSTAT.
• IT HAS A KEYED FILLING SYSTEM.
• GREATEST ACCURACY IS AT GAS FLOW OF 5L/MIN, 150 C AND 350C AND DIAL
SETTINGS LESS THAN 3%.
• AT HIGHER FLOW RATES AND AT HIGHER DIAL SETTINGS THERE IS A DECREASE
IN OUTPUT.

41. Tec 4 Tec 5
Vaporizing
chamber
Smaller capacity Larger capacity
Quantity 135ml when dry and
100ml when wicks are
wet
300ml when dry and
225ml when wicks are
wet
Thermostat Present in centre of
vaporizer
Present at the base
Concentration
control dial
Complicated Easier and simpler
Accuracy Less accurate More accurate
Service Annual Triannual

42. TEC 6
• CONCENTRATION CALIBRATED.
• THERMOCOMPENSATION
• AGENT SPECIFIC AND PLENUM VAPORIZER.
• THE CONCENTRATION DIAL IS AT THE TOP AND IS CALIBRATED FROM 1% TO
18%, IN GRADUATION OF 1% UPTO 10% AND 2% FROM 10% TO 18%.
• THE FILLER PORT IS IN FRONT AND IS DESIGNED THAT ONLY A DESFLURANE
SPECIFIC BOTTLE CAN BE INSERTED INTO IT.

43. TEC 6
• CONCENTRATION CALIBRATED.
• THERMOCOMPENSATION
• AGENT SPECIFIC AND PLENUM VAPORIZER.
• THE CONCENTRATION DIAL IS AT THE TOP AND IS CALIBRATED FROM 1% TO
18%, IN GRADUATION OF 1% UPTO 10% AND 2% FROM 10% TO 18%.
• THE FILLER PORT IS IN FRONT AND IS DESIGNED THAT ONLY A DESFLURANE
SPECIFIC BOTTLE CAN BE INSERTED INTO IT.

44. • VAPORISER HAS 2 INDEPENDENT CIRCUIT ARRANGED IN PARALLEL.
• FRESH GAS FLOWS THROUGH ONE CIRCUIT.
• DESFLURANE FLOWS THROUGH THE OTHER CIRCUIT.
• COLOUR CODED ALARMS:
a)AMBER- INITIAL WARM UP PERIOD
b)GREEN- CAN BE TURNED ON
c)RED- NO OUTPUT

46. TEC 7
• HALOTHANE, ENFLURANE, ISOFLURANE AND SEVOFLURANE
• EASY FILLER MECHANISM
• IMPROVED SLIGHT GLASS DESIGN
• ACCURACY-52L/MIN FOR 3%
• AT HIGHER FLOW, DECREASE IN OUTPUT
• BETWEEN 15-30 DEGREE
• GREATEST- LOW FLOW RATES AND LOW DIAL SETTINGS

47. 47

48. MODERN VAPORIZER TYPES
• VIRTUALLY ALL MODERN VAPORIZERS ARE OUT-OF-CIRCUIT, AND THEIR
CONTROLLED OUTPUT IS INTRODUCED INTO THE BREATHING CIRCUIT THROUGH A
FRESH GAS LINE.

49. VARIABLE BYPASS VAPORIZERS
• VARIABLE BYPASS REFERS TO THE METHOD OF DILUTING GAS FULLY SATURATED WITH
ANESTHETIC AGENT WITH A MORE VOLUMINOUS FLOW OF GAS.

53. • VIRTUALLY ALL VARIABLE BYPASS VAPORIZERS ARE EQUIPPED WITH A MECHANISM
THAT HELPS MAINTAIN CONSTANT VAPORIZER OUTPUT OVER A WIDE RANGE OF
OPERATING TEMPERATURES (HENCE THE DESIGNATION TEMPERATURE-
COMPENSATED)
• TEMPERATURE COMPENSATION IS ACCOMPLISHED BY AN EXPANSION-
CONTRACTION ELEMENT, OR A BIMETALLIC STRIP
• VARIABLE BYPASS VAPORIZERS ARE ALSO CONSTRUCTED FROM MATERIALS WITH
HIGH SPECIFIC HEAT, YIELDING TEMPERATURE STABILITY, AND HIGH THERMAL
CONDUCTIVITY, WHICH ALLOWS RAPID TRANSFER OF AMBIENT HEAT
• VARIABLE BYPASS VAPORIZERS CANNOT BE USED TO DELIVER DESFLURANE

55. FACTORS THAT INFLUENCE VARIABLE BYPASS
VAPORIZER OUTPUT
• IMPACT OF GAS FLOW RATE
• TEMPERATURE CHANGE
• INTERMITTENT BACK PRESSURE
• IMPACT OF CARRIER GAS COMPOSITION
• HYPERBARIC CONDITIONS
• ALTITUDE CHANGES

56. IMPACT OF GAS FLOW RATE:
• THIS FACTOR IS NOTABLE ONLY AT THE EXTREMES OF FLOW RATES AND AT HIGHER
CONCENTRATION CONTROL DIAL SETTINGS.
• AT LOW FLOW RATES (<250 ML/MIN), THE OUTPUT TENDS TO BE SLIGHTLY LESS
THAN THE DIAL SETTING DUE TO THE RELATIVELY HIGH DENSITY OF VOLATILE
ANESTHETIC AGENTS. INSUFFICIENT TURBULENCE IS GENERATED IN THE
VAPORIZING CHAMBER TO ADVANCE THE VAPOR MOLECULES UPWARD.
• AT HIGH FLOW RATES (SUCH AS 15 L/MIN), THE OUTPUT OF MOST VARIABLE BYPASS
VAPORIZERS IS SOMEWHAT LESS THAN THE DIAL SETTING. THIS DISCREPANCY IS
DUE TO: COOLING DURING RAPID EVAPORATION ,INCOMPLETE MIXING, AND
FAILURE TO SATURATE THE CARRIER GAS IN THE VAPORIZING CHAMBER

57. IMPACT OF TEMPERATURE CHANGE:
• MODERN VAPORIZERS MAINTAIN FAIRLY CONSTANT CONCENTRATION OUTPUT OVER A
WIDE RANGE OF COMMON WORKING TEMPERATURES
• A DANGEROUS BUT HIGHLY UNLIKELY CIRCUMSTANCE COULD OCCUR IF THE BOILING
POINT OF A VOLATILE AGENT WITHIN A VARIABLE BYPASS VAPORIZER WERE REACHED
• IN THIS SITUATION, THE VAPORIZER OUTPUT WOULD BE IMPOSSIBLE TO CONTROL BY ANY
COMPENSATORY MECHANISM.

58. • IMPACT OF INTERMITTENT BACK PRESSURE:
• IT RESULTS FROM EITHER POSITIVE-PRESSURE VENTILATION OR USE OF THE OXYGEN FLUSH
VALVE MAY LEAD TO HIGHER THAN EXPECTED VAPORIZER OUTPUT ,THIS PHENOMENON IS
KNOWN AS PUMPING EFFECT,
• THE PUMPING EFFECT IS CAUSED BY RETROGRADE TRANSMISSION OF PRESSURE FROM THE
PATIENT CIRCUIT TO THE VAPORIZER DURING THE INSPIRATORY PHASE OF POSITIVE-
PRESSURE VENTILATION OR USE OF THE OXYGEN FLUSH FUNCTION
• THE PUMPING EFFECT IS MORE PRONOUNCED AT LOW FLOW RATES , LOW DIAL SETTINGS
AND LOW LEVELS OF LIQUID ANESTHETIC IN THE VAPORIZING CHAMBER AND IT IS ALSO
INCREASCED BY THE RAPID RESPIRATORY RATES, HIGH PEAK INSPIRATORY PRESSURES (PIPS),
THE USE OF ANESTHESIA MACHINES WITHOUT FRESH GAS DECOUPLING, AND RAPID DROPS
IN PRESSURE DURING EXPIRATION
• SERPENTINE PASSAGE ALSO DAMPENS PRESSURE FLUCTUATIONS AND COMPENSATES FOR
FLUCTUATIONS IN GAS SUPPLY PRESSURE.
• A ONE-WAY CHECK VALVE CAN BE INSERTED AFTER THE VAPORIZERS AND BEFORE THE
BREATHING CIRCUIT INLET TO MINIMIZE THE PUMPING EFFECT

59. IMPACT OF CARRIER GAS COMPOSITION:
• . THIS EFFECT IS MOST PRONOUNCED WHEN NITROUS OXIDE IS INTRODUCED OR REMOVED
AS A CARRIER GAS.

60. IMPACT OF HIGHER ALTITUDE:
• VAPOR PRESSURE IS INDEPENDENT OF BAROMETRIC PRESSURE
• THEREFORE AS ALTITUDE INCREASES AND BAROMETRIC PRESSURE DECLINES, THE PARTIAL
PRESSURE OF ANESTHETIC AGENT IN THE VAPORIZING CHAMBER REMAINS CONSTANT
DESPITE DECREASES IN THE PARTIAL PRESSURES OF OTHER CONSTITUENT BREATHING
GASES AND THE TOTAL AMBIENT PRESSURE.
• THIS SITUATION RESULTS IN SIGNIFICANTLY INCREASED VOLUME PERCENT
CONCENTRATION OF ANESTHETIC AGENT WITHIN THE VAPORIZING CHAMBER AND AT THE
OUTLET OF THE VAPORIZER
• HOWEVER, BECAUSE ANESTHETIC DEPTH IS DETERMINED BY THE PARTIAL PRESSURE OF
VOLATILE AGENT IN THE BRAIN, THE CLINICAL IMPACT IS MINOR

61. • FOR EXAMPLE:{MOVING A VAPORIZER FROM SEA LEVEL TO HIGHER ALTITUDE}
• WITH DIAL SETTING OF 0.89% ISOFLURANE,1 ATM.
• A WELL-CALIBRATED ISOFLURANE VARIABLE BYPASS VAPORIZER WOULD DELIVER 0.89 V/V%
ISOFLURANE, AND THE PARTIAL PRESSURE OF ISOFLURANE OUTPUT WOULD BE 6.8 MM HG.
• ASSUME THAT WE MAINTAIN THE SAME DIAL SETTING AND LOWER THE ATMOSPHERIC
PRESSURE TO 0.66 ATM OR 502 MM HG (ROUGHLY EQUIVALENT TO AN ELEVATION OF
10,000 FEET)
• THIS RESULTS RESULT IN AN INCREASE IN THE ISOFLURANE CONCENTRATION OUTPUT TO
1.75% (A 97% INCREASE), BUT THE PARTIAL PRESSURE INCREASES TO ONLY 8.8 MM HG (A
29% INCREASE)
• A SIMILAR CHANGE IN OUTPUT PARTIAL PRESSURE AT SEA LEVEL, IN TERMS OF VOLUME
PERCENT, WOULD CORRESPOND TO AN ISOFLURANE CONCENTRATION INCREASE OF ONLY
0.2%.
• SO WHILE THE ANESTHETIC CONCENTRATION (V/V%) CHANGES SIGNIFICANTLY IN THIS
EXAMPLE, IT IS THE PARTIAL PRESSURE OF VOLATILE AGENT IN THE BRAIN THAT IS
ULTIMATELY RESPONSIBLE FOR ANESTHETIC DEPTH, AND THAT CHANGE IS MINIMAL.

62. • PARTIAL PRESSURE OUTPUT OF A VARIABLE BYPASS VAPORIZER CHANGES PROPORTIONALLY LESS
THAN THE VOLUME PERCENT CONCENTRATION AS ALTITUDE INCREASES.
• BECAUSE THE PARTIAL PRESSURE OF VOLATILE AGENT DETERMINES ANESTHETIC DEPTH, THE
OPERATOR DOES NOT NEED TO ADJUST THE DIAL TO A HIGHER SETTING TO COMPENSATE FOR
BAROMETRIC PRESSURE.
• THIS HOLDS TRUE FOR VARIABLE BYPASS VAPORIZERS, BUT NOT FOR THE DESFLURANE TEC 6–

63. • OTHER SAFETY FEATURES:
• AGENT SPECIFIC, KEYED FILLING DEVICES HELP PREVENT FILLING WITH THE WRONG
AGENT.
• OVERFILLING IS MINIMIZED BY LOCATING THE FILLER PORT AT THE MAXIMUM SAFE
LIQUID LEVEL.
• MODERN VAPORIZERS ARE FIRMLY SECURED TO A MANIFOLD ON THE ANESTHESIA
WORKSTATION TO PREVENT TIPPING.
• CONTEMPORARY INTERLOCK SYSTEMS PREVENT THE ADMINISTRATION OF MORE
THAN ONE INHALED ANESTHETIC AGENT
• THE DRÄGER VAPOR AND D-VAPOR SERIES VAPORIZERS HAVE A TRANSPORT (“T”)
DIAL SETTING THAT ISOLATES THE VAPORIZER CHAMBER FROM THE BYPASS
CHAMBER TO ELIMINATE THE POSSIBILITY OF INTERNAL OVERFLOW DURING
TRANSPORT

64. DESFLURANE VAPORIZER
• THE DATEX-OHMEDA TEC 6 VAPORIZER WAS RELEASED INTO CLINICAL USE IN THE EARLY
1990S.
• THE TEC 6 IS AN ELECTRICALLY HEATED, THERMOSTATICALLY CONTROLLED, CONSTANT
TEMPERATURE, PRESSURIZED, ELECTROMECHANICALLY COUPLED DUAL-CIRCUIT, GAS
VAPOR BLENDER SPECIFICALLY DESIGNED TO DELIVER DESFLURANE
• DRÄGER MEDICAL RECEIVED APPROVAL FROM THE U.S. FOOD AND DRUG
ADMINISTRATION (FDA) FOR THE D-VAPOR, ITS VERSION OF THE DESFLURANE VAPORIZER
IN 2004
THREE REASONS FOR SPECIAL DESFLURANE VAPORIZER
1.DESFLURANE’S HIGH RATE OF EVAPORATION WOULD REQUIRE EXCESSIVE DILUTING GAS
(BY PASS CHAMBER) FLOW
2. DESFLURANE’S HIGH RATE OF EVAPORATION WOULD CAUSE SUBSTANTIAL ANESTHETIC
COOLING
3. DESFLURANE IS MORE LIKELY TO BOIL.

65. • THE DELIVERED DESFLURANE CONCENTRATION IS DETERMINED BY THE
RELATIONSHIP B/W THE BYPASS RESISTANCE AND FLOW CONTROL CONE, WHICH
IS DETERMINED BY CONTROL DIAL SETTING.
• CARRIER GAS COMPOSITION WILL AFFECT THE VAPORIZER OUTPUT, CALIBRATED
USING O2. THE OUTPUT REDUCED WHEN AIR/N2O USED.
• PERFORMANCE BETTER AT 18-300C.
• CELLULAR PHONES SHOULD NOT BE USED WITHIN 10M OF THE VAPORIZER.

67. FACTORS THAT INFLUENCE TEC 6 DESFLURANE VAPORIZER OUTPUT
1)BAROMETRIC PRESSURE :REGARDLESS OF AMBIENT PRESSURE, THE TEC 6 MAINTAIN A
CONSTANT VOLUME PERCENT OUTPUT (V/V%), NOT A CONSTANT PARTIAL PRESSURE.
REQUIRED DIAL SETTING (%) = NORMAL DIAL SETTING ×(760 MM HG) / [AMBIENT PRESSURE
(MM HG)]
FOR EXAMPLE,
AT AN ALTITUDE OF 2000 M, OR 6564 FEET, WHERE THE AMBIENT PRESSURE IS 608 MM HG,
THE OPERATOR MUST ADVANCE THE CONCENTRATION CONTROL DIAL FROM 10% TO 12.5% TO
MAINTAIN THE REQUIRED ANESTHETIC PARTIAL PRESSURE.
IN HYPERBARIC SETTINGS, THE OPERATOR MUST DECREASE THE DIAL SETTING TO PREVENT
DELIVERY OF AN OVERDOSE. AT 2 ATM OR 1520 MM HG OF PRESSURE, THE DESFLURANE OUTPUT
IN MM HG IS TWICE THAT AT SEA LEVEL (91.2 VS. 45.6 MM HG)

68. 2) CARRIER GAS COMPOSITION:
• VAPORIZER OUTPUT MOST CLOSELY MATCHES THE DIAL SETTING WHEN OXYGEN
IS THE CARRIER GAS BECAUSE THE TEC 6 VAPORIZER IS CALIBRATED WITH 100%
OXYGEN
• WHEN A CARRIER GAS OTHER THAN 100% OXYGEN IS USED AT LOW FLOW RATES,
A CLEAR TREND TOWARD REDUCTION IN VAPORIZER OUTPUT EMERGES.
• AT LOW FLOW RATES WITH NITROUS OXIDE AS THE CARRIER GAS, VAPORIZER
OUTPUT IS APPROXIMATELY 20% LESS THAN THE DIAL SETTING.

69. SAFETY FEATURES:
• EACH DESFLURANE BOTTLE HAS A “SAF-T-FILL” ADAPTER INTENDED TO PREVENT USE WITH
TRADITIONAL VAPORIZERS.
• THE SAF-T-FILL IS ESSENTIALLY A SPRING-LOADED VALVE THAT SEALS THE BOTTLE UNTIL
THE BAYONET FITMENT IS FULLY ENGAGED IN THE FILLER PORT OF A DESFLURANE
VAPORIZER
• THE SAF-T-FILL SYSTEM HELPS PREVENT BOTH MIS FILLING OF VARIABLE BYPASS
VAPORIZERS AND LEAKAGE OF DESFLURANE TO THE ATMOSPHERE
• SHUT-OFF VALVE CLOSES, AND A NO OUTPUT ALARM IS ACTIVATED, IF ANY OF THE
FOLLOWING CONDITIONS OCCUR:
(1) THE ANESTHETIC LEVEL DECREASES TO LESS THAN 20 ML
(2) THE VAPORIZER IS TILTED
(3) A POWER FAILURE OCCURS
(4) THE PRESSURE DIFFERENCE BETWEEN THE VAPOR AND FRESH GAS CIRCUITS EXCEEDS A
SPECIFIED TOLERANCE

70. GE/DATEX-OHMEDA ALADIN AND ALADIN2 CASSETTE VAPORIZERS
(COMPUTER CONTROLLED VARIABLE BYPASS VAPORIZER)
• IT IS UNIQUE IN THAT A SINGLE ELECTRONICALLY CONTROLLED VAPORIZER IS DESIGNED
TO DELIVER SEVERAL DIFFERENT INHALED ANESTHETIC AGENTS.
TWO PARTS
1)PERMANENT INTERNAL CONTROL UNIT HOUSED WITHIN THE WORKSTATION
2)INTERCHANGEABLE COLOR CODED CASSETTES THAT CONTAIN ANESTHETIC LIQUID AND
SERVE AS VAPORIZING CHAMBERS.
RED(HALOTHANE),ORANGE(ENFLURANE),PURPLE(ISOFLURANE),YELLOW(SEVOFLURANE),AND
BLUE(DESFLURANE)
• THEY ARE ALSO MAGNETICALLY CODED TO ALLOW THE ANESTHESIA WORKSTATION TO
IDENTIFY WHICH CASSETTE HAS BEEN INSERTED

71. • IT IS EQUIPPED WITH CPU WHICH RECEIVES INPUT FROM MULTIPLE SOURCES:THE
CONCENTRATION CONTROL DIAL, CARRIER GAS COMPOSITION PRESSURE AND
TEMPERATURE SENSORS INSIDE THE VAPORIZING CHAMBER, AND FLOW SENSORS IN THE
BYPASS AND VAPORIZING CHAMBERS.
• TO OFFSET THIS COOLING EFFECT, SOME WORKSTATIONS ARE EQUIPPED WITH A FAN,
WHICH IS ACTIVATED DURING TWO COMMON CLINICAL SITUATIONS:
(1) DESFLURANE INDUCTION AND MAINTENANCE
(2) SEVOFLURANE INDUCTION.
• ALADIN CASSETTE IS IMMUNE TO TIPPING AND HAS NO RESTRICTIONS ON ORIENTATION
DURING HANDLING OR STORAGE

74. • INJECTION-TYPE VAPORIZERS: MAQUET AND DRÄGER DIRECT INJECTION OF VOLATILE
ANESTHETIC
• THE MAQUET VAPORIZER IS AN ELECTRONICALLY CONTROLLED, INJECTION-TYPE
VAPORIZER THAT IS USED EXCLUSIVELY WITH MAQUET FLOW-I ANESTHESIA
WORKSTATIONS
• THE MAQUET INJECTION VAPORIZERS ARE AGENT-SPECIFIC AND AVAILABLE FOR
ISOFLURANE, SEVOFLURANE, AND DESFLURANE
• IT HAS NO CONCENTRATION CONTROL DIAL EXTERNALLY, VAPORIZER OUTPUT
ADJUSTMENTS
ARE ACCOMPLISHED THROUGH AN ELECTRONIC INTERFACE ON THE WORKSTATION
• THE VAPORIZER IS NOT VULNERABLE TO TIPPING BECAUSE IT HAS NO WICKS TO
SATURATE, AND AGENT CANNOT SPILL INTO THE VAPORIZING CHAMBER

77. • DRAW-OVER VAPORIZERS IN CONTEMPORARY PRACTICE:
• COMPRESSED MEDICAL GASES (OXYGEN OR AIR) ARE NOT AVAILABLE IN MANY
RESOURCE-CONSTRAINED ENVIRONMENTS LIKE DURING MILITARY FIELD
OPERATION
• THEY ARE CHARACTERIZED BY
(1) IN-CIRCUIT LOCATION
(2) LOW-RESISTANCE TO GAS FLOW
(3) GAS FLOW THAT IS DRIVEN BYNEGATIVE DOWNSTREAM PRESSURE (TYPICALLY
ARISING FROM THE PATIENT’S RESPIRATORY EFFORT, BUT POTENTIALLY FROM A
BELLOWSOR COMPRESSIBLE BAG)
• THE OXFORD MINIATURE VAPORIZER (OMV) IS A STAINLESS STEEL,VARIABLE-
BYPASS, DRAW-OVER VAPORIZER THAT HAS BEEN IN USE SINCE 1968 AND IS
PARTICULARLY POPULAR IN THE BRITISH ARMED FORCES.
• FOR MORE ACCURATE RESULTS ACROSS A RANGEOF DIAL SETTINGS AND AMBIENT

79. VOLATILE ANESTHETIC REFLECTORS: ANACONDA AND SIMILAR DEVICES:
• ONE POSSIBLE SOLUTION FOR ICU DELIVERY OF VOLATILE ANESTHETICS ARE
REFLECTOR-STYLE DEVICES SUCH AS THE ANESTHETIC CONSERVING DEVICE
(ANACONDA) AND MIRUS DEVICE
• THE ANACONDA IS A SINGLE-USE DEVICE BASED ON A HEAT AND MOISTURE
EXCHANGER (HME) FILTER AND DOES NOT REQUIRE A POWER SOURCE OR AN
ANESTHESIA WORKSTATION
• LIQUID VOLATILE ANESTHETIC (EITHER ISOFLURANE OR SEVOFLURANE) IS
INJECTED INTO THE DEVICE USING A STANDARD SYRINGE PUMP AND VAPORIZED
THROUGH A POROUS EVAPORATOR ROD
• THE MIRUS DEVICE WORKS ON A SIMILAR CONCEPT, BUT IS CAPABLE OF
DELIVERING DESFLURANE, AND INCORPORATES AUTOMATIC CONTROL OF END-
TIDAL CONCENTRATIONS.

81. Thank You..