Basics about anesthesia vaporizers for Anesthesia residents.

1. Dr Saneesh P J
Dept of Anaesthesiology & ICU,
Sultan Qaboos University Hospital
Facebook.com/AnesthesiaTOOLS https://www.youtube.com/c/saneeshpj

3. Its not my cup of tea?????

4. Objectives
 Physics – theory question
 Problem solving
 Historical vaporizers – Viva
 Vaporizer – identification, classification
 Comparison of TEC vaporizers
 Safety features
 Filling systems

5. Vapour
 Gaseous phase of a substance below its critical
temperature

6. Vaporizer
 Instrument designed to facilitate the change of a
liquid anesthetic into its vapor and add a
controlled amount of this vapor into the fresh gas
flow or the breathing system

7. Physics
 Vapor Pressure
 Boiling Point
 Partial Pressure
 Volumes Percent
 Heat of Vaporization
 Specific Heat
 Thermal Conductivity

8. Vapor Pressure
 Pressure exerted by the vapor molecules in
dynamic equilibrium with the liquid phase on the
walls of the container (SVP)
 Depends only on the liquid and the temperature
 Not affected by ambient pressure

9. Boiling Point
 A liquid’s boiling point is the temperature at which
its vapor pressure is equal to the atmospheric
pressure.

10. Partial Pressure
 The part of the total pressure due to any one gas
in the mixture
 P total = P1 + P2 + P3 ….
 Depends only on the temperature of the agent
 Unaffected by the total pressure above the liquid
 The highest partial pressure that can be exerted by
a gas at a given temp is its vapor pressure

11. Volumes Percent
 Number of units of volume of a gas in relation to a
total of 100 units of volume for the total gas
mixture
 Volumes percent = Partial Pressure
Total Pressure
 When a give partial pressure represents the same
anesthetic potency under various barometric
pressures, this is not the case with volumes
percent

12. Heat of Vaporization
 Number of calories required to convert 1 gm of
liquid into a vapor
 Liquid temp decreases as vaporization proceeds –
flow of heat from the surroundings down the
gradient – equilibrium is established

13. Specific Heat
 A substance’s specific heat is the quantity of heat
required to raise the temp of 1 gm of the
substance by 1⁰C
 For water - 1cal/g/°K
 The higher the specific heat, the more the heat
that is required to raise the temp of a given
quantity of the substance
 Material to construct vaporizer
 Temp changes more gradually for materials with a
high sp heat

14. Thermal Conductivity
 A measure of the speed with which heat flows
through a substance
 Thermostabilization is achieved by constructing
vaporizer with a metal with high thermal
conductivity
 Cu > Al > brass > steel >> glass
 Wicks – in contact with metal part – so that the
heat lost due to vaporization quickly replaced

15. Materials used in the construction
of vaporizers
 Copper
 Aluminum – MRI compatible vaporisers
 Brass
 Steel
 Glass

16. Physical properties of potent
inhaled volatile agents
Hal Iso Sevo Des
Molecular wt 197.4 184.5 200 168
Boiling Pt 50.2 48.5 58.5 23.5
SVP at 20C 243 238 160 666
MAC 0.75 1.15 1.7 6
ml of vapor per ml
of liquid at 20C
226 195 182 207

17. Classification of Vaporizers
 Method of regulating output conc
 Variable bypass
 Variable Bypass, fully saturated vapour chamber
 Mechanical -TEC, Penlon
 Electronic: GE Aladdin
 Variable Bypass, variably saturated vapour
chamber
 Boyle's bottle, Goldman
 Measured flow
 Copper kettle

18. Classification of Vaporizers
 Method of vaporization
 Flow over
 TEC, Penlon, Vapor 19.1(with wicks)
 Goldman (without wicks)
 Bubble-through
 Copper kettle
 Flow over or bubble-through
 Boyle’s bottle
 Injection type
 TEC 6, Siemens

19. Classification of Vaporizers
 Location
 Out of Circuit / high resistance / plenum type
 TEC, Penlon, Aladdin
 In-circuit / low resistance / draw over
 OMV, EMO

20. Classification of Vaporizers
 Temperature compensation
 Automatic thermocompensation
 TEC- bimetallic strip (bronze, nickel)
 Vapor 19.1 – metal rod
 EMO – ether filled bellows
 Penlon – fluid filled bellows
 Mercury expansion devices
 Supplied heat
 TEC 6

21. Classification of Vaporizers
 Temperature compensation
 No thermocompensation
 Boyle’s bottle, Goldman, Siemens
 Manual
 Copper Kettle
 Electronic
 Aladdin

22. Classification of Vaporizers
 Specificity
 Agent-specific
 TEC, Vapor 19.1, Penlon
 Multiple agent
 Goldman

23. Classification of Vaporizers
 Plenum Vaporizer
 carrier gas is pushed through the vaporiser at higher
than ambient pressure
 Draw over vaporizer
 A negative pressure may be developed in the gas stream
distal to the vaporizer, thus drawing gas through
 Eg, Tecota, EMOTRIL, Cardiff vaporizer, EMO

24. Precision Vaporizers
 Vaporizing chamber incorporates a network
of internal channels and wicks which
ensures that the gas emerging from the
chamber is fully saturated with anesthetic
vapor

25. Variable bypass
 Concentration-calibrated
 Direct reading
 Dial controlled
 Automatic plenum
 Percentage type

26. Variable bypass
 Accept the total gas flow from the anesthesia
machine flowmeters and in turn deliver the gas
flow along with a predictable conc of vapor to the
common gas outlet
 Control of the vapor conc - provided by a single
calibrated knob or dial
 Open counterclockwise
 Incoming gas flow is divided into 2 portions
 Splitting ratio
 Portion going into vap chamber – “carrier gas”

27. Variable bypass
Carrier gas
Bypass Chamber
Vaporizing
chamber
Liquid agent

29. Effects of intermittent back
pressure
 IPPV
 Oxygen flush
 Intermittent back pressure may either increase
the vaporiser output (pumping effect) or decrease
it (pressurizing effect)

30. Pumping effect

31. Pumping effect

32. Pumping effect

33. Pumping effect

34. Pumping effect

35. Pumping effect

36. Large bypass channel

37. Long inlet tube

38. Increased resistance

39. One way valve

40. One way valve

41. Pressurizing effect
P R
P

42. Pressurizing effect
P+p R+p’
P+p
Lower
concentration

43. Pumping effect

44. Modifications to minimise
pumping effect
 Alterations to vaporizer
 Keep vaporizing chamber small
 Employ a long, spiral or large-diameter tube to lead to
VC
 Exclude wicks at VC inlet
 Overall increase in resistance to gas flow through
vaporizer
 Alterations to anesthesia machine
 Check valve
 Near machine outlet, but upstream of the jn with O2 flush

45. Pressurizing effect

46. Pressurizing effect
 The pressure in the vaporizing chamber and the
bypass is P
 As gas flows to the outlet, the pressure is reduced
to R
 The number of molecules of anesthetic agent
picked up by each milliliter of carrier gas depends
on the density of the anesthetic vapor molecules
in the vaporizing chamber

47. Pressurizing effect

48. Pressurizing effect
 The increased pressure applied to the vaporizer
outlet will compress the carrier gas so that there
will be more molecules per milliliter
 The number of anesthetic vapor molecules in the
vaporizing chamber will not be increased
 Net result is a decrease in the concentration of
anesthetic in the vaporizing chamber and the
vaporizer outlet

52. Boyle’s Bottle
 simplest type of vaporiser
 Volume of gas diverted into the
Boyle's bottle can be controlled by
adjusting a lever
 Vaporisation of the liquid can be
further increased by depressing a
"cowl“ (Ether)

53. Boyle’s Bottle
 No thermocompensation
 Not calibrated - we cannot know
how much is delivered
 Can be used for ether and
trichloroethylene
 Not recommended for Halothane
 Halothane is very potent

54. Goldman Vaporiser
 Simple glass bowl which will
hold up to 20 ml of liquid
 The bowl is attached to a head
 3 positions between the OFF
and ON positions in the Mark I
and Mark II models
 Mark III model has two
settings only

55. Goldman Vaporiser
 Simple
 May be used as vaporizer in-ckt
 Easy to clean
 Can be used with multiple agents, e.g.
halothane, trilene

56. Goldman Vaporiser
 Relatively safe
 it cannot yield a vapour strength greater than 3%
halothane
 Small vaporising chamber prevents a
dangerously high concentration of vapour
being delivered to the circuit when the
vaporiser is first turned on
 Tipping

57. Goldman halothane vaporiser
 Very simple splitting device
 No temperature compensation
 output varies decreases during use as the temperature
falls
 With halothane the maximum output is 3%
 small vapour chamber; absence of wicks
 It can be used in a circle system
 Output varies dramatically depending on whether the
patient is spontaneously breathing (lower), or ventilated
by positive pressure (higher)

58. DRAWOVER VAPORISERS
 Low internal resistance to gas flow
 Gas is drawn through the vaporiser into the
anaesthetic circuit
 only in inspiration
 by the use of a self inflating bag or bellows
 flow is not constant (peak inspiratory flow rates
30-60l/min), but ‘pulsatile’
 Do not require a pressurised gas supply

59. DRAWOVER VAPORISERS
 Open drop techniques (ether and chloroform)
 e.g. Schimmelbusch mask and Ogston’s inhaler
 Goldman halothane vaporiser
 Oxford Miniature Vaporiser (OMV)
 (drawover / plenum)
 EMO ether inhaler (Epstein, Macintosh, Oxford)

60. Open drop techniques
(ether and chloroform)
 e.g. Schimmelbusch mask and Ogston’s inhaler
 Drop rate gives inspired concentration
 Number of layers of gauze or lint important (wick)
 Freezing may occur (latent heat)
 Eye protection needs to be considered (freezing)

61. Oxford Miniature Vaporiser
(OMV)
 Portable
 Multi-agent
 Easliy cleaned and serviced
 Wire-gauze wick
 No temperature compensation
 Small heat sink containing glycol

62. EMO ether inhaler
(Epstein, Macintosh, Oxford)
 Robust
 Water-bath heat sink
 Ether bellows temperature compensator
 Level indicator

63. EMO ether inhaler
(Epstein, Macintosh, Oxford)

64. PLENUM VAPORISERS
 Plenum (Latin)= “full” (opposite to vacuum)
 In air conditioning terminology it applies to air
that is forced in, cleaned and temperature
adjusted.
 Plenum vaporisers are designed for use with
continuous flow of pressurised gas, and have high
internal resistance.

65. PLENUM VAPORISERS
 Modern versions are universally agent specific,
and referred to as “flow stabilised”
 ie. perform equally well over a large range of fresh gas
flow (FGF) (±20% accurate 0.5-10 l/min)

66. Copper Kettle Vapourizer

67. Copper Kettle Vapourizer
 The world's first precision
vaporizer
 More "idiot-proof" with
the side-filling port
precluding overdose from
overfilling.

68. Copper Kettle Vapourizer
 Measured-flow
 Method of vaporization
 Bubble-through
 Temperature compensation
 Manual (i.e., by changes in carrier gas
flow)
 Non-calibrated
 Multi-agent
 Out of circuit

69. Copper Kettle Vapourizer

70. Copper Kettle Vapourizer
Saturated vapor
Carrier gas
Flowmeter for
anesthetic gases

71. Measured -flow Vaporizers
 Kettle-type
 Flowmeter controlled vaporizer system
 Utilizes a measured flow of carrier gas, usually
oxygen, to pick up the anesthetic vapor
Saturated vapor
Carrier gas
Flowmeter for
anesthetic gases

72. Vernitrol Flow Calculator
(Whiz wheel)

73. TEC 2 vaporizer
Classification:
variable bypass,
flow over with wick
out of system
temperature compensated – automatic flow alteration
agent specific
Construction:
Vaporizing chamber- round
Concentric wicks
Filling tap at the side; drain at the bottom
Viewing window on the side
Dial in front

74. TEC 2 vaporizer
 Gasflows: controlled by spindle- rightward
movement
 Control dial must be pulled forward prior to being turned
on by counterclockwise rotation

75. TEC 2 vaporizer
 Temp compensating mechanism
 Bimetallic strip
 Located at the OUTLET of VC
 Note: in most other variable bypass vaporizers in which
the temp compensation element is located in the bypass
Bimetallic strip

76. TEC 2 vaporizer
Evaluation:
Not accurate at flows below 4L/ min
Low flow rates, low dial settings - less than set
concentration
Carrier gas composition; back pressure; tipping
Care & Cleaning
Yearly servicing
Halothane – drained every 2 wks; drained agent
discarded

77. TEC 3 vaporizer
Classification:
variable bypass
flow over with wick
out of system
temperature compensated
automatic flow alteration
agent specific

78. TEC 3 vaporizer
Construction:
Metal body – alloy steel
Conc dial on top; opening – counterclockwise; upto 5%
Locking lever on the left of conc dial (red)
Vaporizing chamber- round
Bottom: viewing window (lt); filling device (rt)
To empty the vaporizer:

79. TEC 3 vaporizer

80. TEC 3 vaporizer
Internal structure:
Lower vaporizing chamber
Upper duct and valve system

81. TEC 3 vaporizer
Internal structure:
Bimetallic temp-sensitive element is located
concentrically within VC so that its temp is close to that
of the anesth agent
Thymol can alter thermocompensation if the bimetallic
strip is kept in the agent
Polytetrafluoroethylene coating (TEC 3 onwards)
prevents contact with thymol
Control channel – long and wide in relation to its depth
Rotation of control dial increase its depth
Wicks absent from inlet (from TEC 3 onwards)

82. TEC 3 vaporizer
 Evaluation:
 Accurate at low dial settings
 Carrier gas
 Negligible pumping effect
 Hazards
 Dial can be turned beyond OFF position
 Tipping on inversion to 180⁰

83. TEC 4 vaporizer
 Classification:
 variable bypass
 flow over with wick
 automatic thermocompensation
 agent specific

84. TEC 4 vaporizer
 Construction:
 Control dial at the top with release button to left and
locking lever at the rear
 Designed to be attached to
back bar by Select-a-Tec
manifold system
 Baffle system
 Filling mechanisms
- screw cap & keyed system

86. TEC 4 vaporizer
 Hazards:
No effect of tipping
Leaking of agent from drain port
Overfilling
 Maintenance:
Drained at 2 weekly intervals.
If incorrect agent filled- drain and flush vaporizer at
5l/min flow till no trace of agent in vapor

87. TEC 5 vaporizer
 Classification:
 variable bypass
 flow over with wick
 automatic thermocompensation
 agent specific

88. TEC 5 vaporizer
 Construction:
 control dial is at the top
 release button located at the rear of the dial
 at the rear is a locking lever
 bottom right front is a sight glass

89. TEC 5 vaporizer
 Construction:
 Internal baffle system
 Thermostat- bimetallic strip at the bottom; in a separate
chanber
 Spiral wick; wick skirt dips into liquid agent
 IPPV assembly present
 Pumping effect - MORE (cf- TEC4)

90. TEC 5 vaporizer

92. TEC 5 vaporizer: Filling
devices
 Keyed system
 The filling/draining port is at the front of the vaporizer
on the left near the bottom
 A locking lever to secure the filler block is located on the
left side of the vaporizer
 A small lever at the base allows liquid to be added to or
drained from the vaporizer

93. TEC 5 vaporizer: Filling
devices
 The other filling device is a funnel fill that has a
drain plug that can be loosened to drain the
vaporizer

94. TEC 5 vaporizer
 Evaluation:
 Greatest accuracy at flows of 5l/min & Dial setting less
than 3%
 Greatest accuracy between 15°C and 35°C
 More prone for pumping effect than Tec 4
 Hazards:
 Loss of liquid agent if filling port open when vaporizer is
on
 Tilting the vaporizer can result in overfilling
 Increased output in reversed flow

95. TEC 5 vaporizer: Maintenance
 Exterior of the vaporizer may be wiped with a
damp cloth
 No other cleaning or disinfection should be
attempted
 Halothane - vaporizer should be drained every 2
weeks or when the level is low
 Returned to a service center every 3 years

96. Differences between Tec 4 & Tec 5
vaporizers:
TEC 4
 Capacity-135(dry
wick),100(wet wick)
 Output conc.-non-
linear
 Thermostat at centre
 Dial
 Annual service
TEC 5
 Capacity-300(dry
wick), 225(wet wick)
 Output conc.- linear
 Thermostat at base
 Dial
 Triannual service

97. TEC 6 VAPORIZER
 Classification:concentration caliberated,
INJECTION,thermocompensation by supplied heat,
agent specific-Desflurane, electronic display
 Why the need for separate vaporizer for
Desflurane?
Extremely volatile with vapour pressure of 664
mmHg @20’C @ 760mmHg , boiling point of
22.8’C

98. TEC 6 CONT…
Cont..Temperature cannot be compensated by
regular vaporizers due to rapid temperature fall.
Very high gas flow neede to dilute the vapor to
required concentration
Special features:
Fresh gas flow does not enter the vaporizing
chamber.
Tilting alarm.
LCD for liquid level

99. TEC 6 CONT..
Power cord.
Supplied heat-heated to 39’C
Agent specific filling system-since it boils @ room
temp, cannot be poured into a funnel.
Maintains constant output conc. but variable
vapor pressure with change in atm. Pressure.

107. Tec 7 vaporizers
 On top is the concentration control dial
 At the rear -release button
 Locking lever
 At the bottom right front - sight glass
 Schematic diagram of the Tec 7 vaporizer is
essentially the same as for the Tec 5

108. Tec 7 vaporizers
 Three filling devices:
 A funnel filler
 Quik-Fil
 Easy-Fil system
 Approximately 300 mL of liquid is needed to fill a
vaporizer with dry wicks
 Approximately 75 mL is retained in the wicks when
the vaporizer is drained

109. Tec 7 vaporizers
 Special features:
 Output consistent with dial setting between
200ml/min to 15l/min and in temp ranges of 18’
to 35’
 Easy to turn dial, fine graduations
 Easy fill, funnel fill & quik fill techniques
 Equipped with non spill mechanism.

110. Tec 7 vaporizers
 Evaluation:
 Greatest accuracy at flows of 5l/min & Dial setting less
than 3%
 Greatest accuracy between 15°C and 35°C
 Changes in barometric changes are compensated for
automatically
 Intended to be operated in the upright position
 If a vaporizer is inverted, it should be connected to
a scavenging system, the dial set to 5%, and the
vaporizer purged with carrier gas at 5 L/minute for
5 minutes

111. DRAGER VAPOR VAPORIZER
 Classification:
 concentration calibrated
 flow over with wick
 automatic thermocompensated
 agent specific
 Construction:
Pressure compensation tube
Control cone controlled by concentration dial.
Filling system- keyed and funnel type

115. DRAGOR VAPOR CONT…
Special features:
 Resistant to pumping effect-pressure
compensation tube
 Temperature compensation by bypass cone &
expansion element.
 No effect of reverse flow
 Hazards:spilll occurs even when tipped to 45’

116. HAZARDS OF VAPORIZERS
 Incorrect agent
 Tipping
 Foaming
 Overfilling
 Discharge of agent into delivery system
 Reversed flow
 Contaminants.

118. Thymol
 Stabilizing agent with Halothane
 A waxy substance
 May reduce the vaporizer performance
 Clog the felt/cotton wick (older models)
 ‘Gum up’ the vaporizer
 difficult to adjust the control knob
 Compromise internal mechanism
 Advised to drain off the liquid agent and replenish
at intervals

119. Filling of vaporizers
 ‘Screw-fill systems’
 Wrong agents?
 Agent-specific filling devices
 Fraser Sweatman pin safety system
 ‘Key fill’ system

120. AGENT SPECIFIC FILLING
SYSTEMS
 FRASER SWEATMAN pin safety system
 Components:
Keyed bottle collar
Adaptor tube
Vaporizer filler receptacle
 .

122.  Problems:
Difficulty in filling
Lost adapter
Overfilling
 Advantages:
Agent specificity
Prevents spillage, if properly fixed

125.  Saf-T-Fil : Desfulrane
 Quik-Fil : Sevoflurane
 Agent in sealed bottles to which the agent specific filling
device is already fitted and made tamper proof with a
crimped metal seal.

126. “Easy-fil” filler

127. A B C
O2O2
N2O
O2
5
4
3
%Halothane
Carrier gas composition

128. Vaporizer - Out of circuit

129. Vaporizer – In circuit

130. Volume of liquid agents
Vaporizer Volume
TEC 4 125
19.1 200
TEC 5; TEC 7 225
Aladin 250
2000 300
Tec 6 Plus 375