Basics of vaporizer

1. Vaporizer
Presenter:
Dr. Tirtha Raj Bhandari
2nd year Resident
Department of Anesthesiology
PMWH, Thapathali
NAMS

2. Objectives
To understand the basic physic of vaporizer.
To classify vaporizer
Factors affecting vaporizer outflow
To discuss briefly about different types of vaporizer
Features of ideal vaporizer
To discuss hazards of vaporizer

3. Vapor??
Vapor is a phase at a temperature at which both liquid and gaseous
phase of a substance co-exist.(i.e. below critical temperature)
Gas: It the the gaseous phase of substance, which cannot be liquified
with the application of pressure.( i.e. above critical temperature)

4. Physics: Critical temperature
That temperature, above which a substance can not be
liquefied, on application of much higher pressure.
CRITICAL TEMP : O2 is -118.4 0 C
N2O is 36.5 0C
CO2 is 310 C
The pressure required to liquefy a gas at its critical temp is the
CRITICAL PRESSURE

5. Vapor/Gas

6. Vaporizer??
Vaporizer: Vapor delivery system/anesthetic gas delivery system
Anesthetic gas delivers in the vapor form by the vaporizer after mixing
with the fresh gas flow or breathing system.

7. Why??
• Inhalational agents are highly toxic and potent substance.
• Cannot be given directly.
• It has to be given in small amount along with the oxygen(FGF), and
other gases.

8. Physics
Vapor Pressure: A pressure exerted by the vapor to its surroundings.
Saturated Vapor pressure: A pressure exerted by vapor when it is in
equilibrium with the liquid state under constant temperature.
On applying heat more liquid will enter into vapor phase. Also on
passing fresh gas also causes more liquid will enter into vapor phase.
(Vapor pressure mainly depend upon the liquid and temperature not
on the ambient pressure.)

9. Physics

10. Physics
Boiling point: It is that temperature at which saturated vapor pressure
becomes equal to atmospheric pressure, also at which all the liquid
agent changes into vapor phase.
The lower the atmospheric pressure lower will be the boiling
point.(high altitude)
Most anesthetic agents has high saturated vapor pressure.

11. Physics

12. Physics
Latent heat of vaporization: It is the amount of heat/calories required
to convert 1 ml liquid into vapor. It removes the heat from the liquid so
that temp of remaining liquid falls.
Specific heat capacity: Amount of heat required to raise temp of 1
gm/1ml substance through 1 degree C.
Liquid anesthetic agent should have the low specific heat so that it can
be easily changed into vapor phase.

13. Physics
Thermal conductivity: Measures the speed with which heat flows
through the substance.
Define as amount of heat flows through unit area of a plate of unit
thickness in unit time per degree of temperature gradient.
Significance: Vaporizer constructor material should be able to conduct
heat from the surroundings to contained liquid.
Copper has moderate specific heat and high thermal conductivity , so
used in making vaporizer.
Thermal capacity: Amount of heat stored in the vaporizer body(specific
heat*mass)

14. Thermo stabilization: Aim to minimize temperature change. Construct
the vaporizer with the metal with high specific heat and high thermal
conductivity.
Wicks to be in contact with metal parts so that it will minimize heat loss
due to vaporization.
Thermo compensation: To maintain vaporizer output constant despite
alteration in temperature. Alteration in splitting ration(automatic
compensation)

15. Thermo compensation

16. Thermo compensation
When the temperature of the vaporizing chamber falls the
bimetallic strip blends and move away , which reduces the
resistance to gas flow, the gas flow rate increases.

17. Physics
Dalton’s law of partial pressure: P(total)=P1+P2+P3…....
Splitting ratio: The ratio of bypass flow to flow to the vaporizing
chamber is referred to as the "splitting ratio" . It depends on
a) Ratio of resistance in two pathways
b) Total flow to vaporizer

18. VOLUME %
Commonly used
It is the number of units of volume of a gas in relation to a
total of 100 units of volume for the total gas mixture
Is a relative ratio of gas molecules in a mixture
vol % /100 = partial pressure/total pressure OR
Vol % = pp/tp x 100

19. Splitting Ratio

20. Splitting of Gas

21. Classification
Based on method of regulating outflow;
a) Variable bypass vaporizer/ concentration calibrated
b) Measured flow vaporizer

22. Variable bypass/ Concentration calibrated
Vaporizers calibrated by agent concentration expressed in percentage of
vapor output are known as Concentration calibrated vaporizers/Direct
reading/Dial controlled / Automatic plenum/Percentage type/Tec type
vaporizers.
Vaporizer output controlled by simple knob/dial calibrated in volume
percent.
Located between flow meter and common gas outlet.
Also called variable bypass because desired concentration is achieved by
splitting the gas.

23. Variable bypass Vaporizer

24. Variable bypass Vaporizer

25. Electronic Vaporizer
Two types
a) A computer calculates the carrier gas flow that needs to pass
through vaporizing chamber to produce desired concentration of
anesthetic agent.
b) Withdraws a calculated amount of liquid agent and injects into the
breathing system / fresh gas flow.

26. Measured Flow Vaporizer
• Kettle type / flow metered / flowmeter controlled vaporizer systems.
• Use a measured flow of carrier gas–oxygen, to pick up anesthetic
vapor.
• No longer available for sale.

27. Measured flow vaporizer

28. Copper kettle

29. Classification
Depending on method of vaporization
1. Flow over
2. Bubble through
3. Injection
Depending on temperature compensation
• None,
• By supplied heat
• By flow interaction
• Computerized compensation

30. CONTD
Flow over: A stream of carrier gas passes over the surface of the liquid.
Bubble through: the carrier gas is bubbled through the volatile liquid,
further increasing the gas-liquid interface.
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.

31. Classification:
Depending on the location:
a) Outside the breathing system
b) Inside breathing system
Depending upon specificity;
a)Agent specific
b)Multiple agent

32. Classification
• Plenum vaporizers: positive pressure applied at the inlet of
the vaporizer. eg. Boyle vaporizers, copper kettle, fluotec
Mark 2 and 3.
• Inhalers or draw over vaporizers: negative pressure applied
at the outlet. eg. EMO vaporizer, Oxford miniature inhaler,
Tecota
• Simple vaporizers eg. Goldman, Rowbotham vaporizer.

33. Factors affecting vaporization of liquids
Flow through the vaporizing chamber
Efficiency of vaporization
Temperature
Time
Gas flow rate
Carrier gas composition
Volatility
Area of contact with liquid

34. Effect of Barometric Pressure(high atm)
Concentration calibrated: increase in atm pressure  change in density
of gas  provides more resistance to flow of gas through the
vaporizing chamber decreased vapor output( both partial pressure
and volume percent). The effect in the partial pressure is less dramatic.
Measured Flow: There will be lower concentration in terms of both
partial pressure as well as volume percent.

35. Effect of Barometric Pressure(low-atm)
Concentrated Calibrated: High resistance pathway through the
vaporizing chamber offers less resistance under hypobaric condition, so
that slight increase in vapor output occurs.
Measured flow: Here the delivered partial pressure and volume
percent increases. The amount of increase depends upon the
barometric pressure and agent.

36. Effect of intermittent back pressure
Pumping effects: Increase in output.
Pressurizing effect: Decrease in output
Sources of back pressure;
1)During assisted/ controlled ventilation the positive pressure
generated during inspiration transmitted from the breathing system
back to the machine and vaporizer.
2) Use of O2 flush valve, the output from O2 flush enters the circuit
downstream of vaporizers and its activation produces high pressure.

37. Pumping Effect
a) When resistance is applied to the outlet of the anesthetic machine,
as during assisted or controlled ventilation, there will be increase in
the anesthetic gas pressure, which finally transmitted back to
vaporizer.
b) This adds to the output and finally increases the vaporizer output.
c) This change is more pronounced when there is less agent, low
carrier gas flow and high and frequent pressure fluctuation, low dial
settings.

38. Pumping Effect

39. Pumping Effect

40. Pumping Effect

41. Pumping Effect

42. Pumping Effect

43. Modifications to reduce the ‘pumping effect’
• Decrease size of vapor chamber
• Increase size of bypass
• Long spiral tube leading to the
vapor chamber
• Exclude wicks from the inlet

44. CONTD

45. Pressurizing effect
a) the output of some vaporizers decreases when there is back
pressure. This effect is greater with high flows, large pressure
fluctuations and low vaporizer settings.
b) The changes in vaporizer output caused by the pumping effect is
usually greater in magnitude than those associated with the
pressurizing effect.
Pressurizing effect: with high gas flow
Pumping effect: with low gas flow

46. Pressurizing effect

47. Pressurizing effect

48. Effect of Rebreathing
• Rebreathing causes a difference between the vaporizer setting and
the inspired concentration.
• Only an agent analyzer can provide an accurate value for the inspired
agent concentration.

49. Sequence of vaporizer(Vaporizer Mounting)
• In modern anesthesia machines an interlocking system called the
SELECTATEC system incorporated so that only one vaporizer is in use
at a time.
• If selectatec system is not installed the sequence of vaporizer should
be such that least potent agent must be placed upstream and most
potent agent last in the sequence.
• Seletatec Back Bar
• Mechanical locking system
• Mechanical Inter-connecter

50. Order of Vaporizer
 Less potent – upstream
 More potent – downstream
 If equipotent
low VP – upstream
high VP – downstream
 If explosive – downstream

51. Order of Vaporizer

52. How much liquid agent does a vaporizer use per
hour?
Ehrenwerth and Eisenkraft gives the formula
=> 3 X Fresh gas flow(L/min) X Volume % = ml liquid used /hr
This formula is based on the fact that typically 1 ml of liquid volatile
agent yields about 200ml of vapor

53. Specific Vaporizers

54. Early Methods
• Open Drop Method – Inhalation anes. By vaporization of a
liquid placed drop by drop on gauze mask covering mouth
and nose
• Devices Used:
• Schimmelbusch mask
• Yankauer mask
• Bellamy Gardner mask
Fig: Yankauer mask

55. • Semi open
• Frame Added to keep ether in an enclosed area
,permitting some degree of rebreathing
• Eg: Ogston inhaler, Junkers chloroform apparatus , Flagg’s
can

56. Semi-open
Fig: Ogston mask with schimmelbusch
frame

57. • EMO (Epstein Machintosh
Oxford) vaporizer
• OMV(Oxford Miniature
vaporizer)

58. • Oxford Inflating Bellows (OIB) • Morton’s Ether Inhalar

59. Boyle’s Bottle
• Mainly for ether and
trichloroethylene
• Flow over or bubble through type.
• No temperature compensation or
calibration

60. Goldman Vaporizer
• Conc. calibrated, Flow- over
• No temp compensation
• Agent non specific
(Halothane, ether, trilene)
• In & Out of system
• Max. conc never exceeds 2%
irrespective of total gas flow

61. CONTD
• Described by Lucein Morris in
1952.
• Constructed of copper
-High heat capacity
- High thermal conductivity
-High degree of accuracy

62. TEC 2
TEC 3

63. TEC 5
• One handed dial control and
more obvious OFF position.
• Helical intermittent positive
pressure assembly to minimize
effects of positive pressure
ventilation.
TEC 5

64. Desflurane vaporizer(Tec 6)
The Tec 6 vaporizer  electrically heated, thermostatically controlled,
constant-temperature, pressurized, electromechanically coupled, dual
circuit, gas/vapor blender.
The pressure in the vapor circuit is electronically regulated to equal the
pressure in the fresh gas circuit.
At a constant fresh gas flow rate, the operator regulates vapor flow
using a conventional concentration control dial.
When the fresh gas flow rate increases, the working pressure increases
proportionally.
At a specific dial setting at different fresh gas flow rates, vaporizer
output is constant because the amount of flow through each circuit is
proportional

65. Desflurane-Tec 6 vaporizer
Schematic diagramof TEC 6

66. Desflurane vaporizer

67. TEC 7
• an improved version of the TEC
5 was introduced in July 2002 by
Datex-Ohmeda with minor
modifications
• "Easy-fil" filler mechanism
• Improved sight glass design

68. GE Datex Ohmeda Aladin Cassette Vaporizer
• 2 parts:
• Electronic control system
in anesthesia machine
• A portable cassette
containing agent
• Flow at the out let is
controlled by the CPU in the
anesthesia machine

69. Fig: Schematic of GE- Datex Ohmeda Aldin Cassette Vapor

70. Vaporizer-characteristics
Fig: Vaporizer models & Characteristics

71. Drager 2000
• Tippable vaporizers
• Transpot mode “T”
• Tortous in-let protects
against pumping effect

72. Features of Ideal Vaporizer
a) It should be simple, safe, satisfactory and more practical.
b) It should have low resistance to gas flow.
c) It should be temperature compensation for uniform vaporization.
d) It should have flow stability and should permit constant
concentration of agent at the different carrier gas flow rate.
e) It should permit precise, accurate, controllable and predictable
delivered concentration of the vapor to the patient.

73. CONTD
f) The performance of the vaporizer should not be affected by changes
in fresh gas flow, volume of liquid, ambient temperature and pressure,
decrease in temperature due to vaporization and pressure fluctuation
due to mode of respiration.
g) It should be light weight and small liquid requirement.
h) Construction should be corrosion and solvent resistant.
i) It should have good quality control.
j) The case of the vaporizer is usually made of copper which is a good
heat sink and it consists of bypass channel and vaporization chamber.

74. ASTM Standard
(1)Vap must be capable of accepting15L/min and deliver predictable vapor
conc.
(2)effects of condns of use in manual
(3)influence of temp/in flow rate so be stated
(4)must be a system to isolate vaps from each other
(5)controls to limit escape of vapor from vc so less than 0.1% is delivered in
off
(6)Knobs to turn counterclockwise to increase
(7)Must have liquid level indicator visible from front
(8)Cannot be overfilled

75. CONTD
(9) must allow calibrated flows of O2 & N2O in ON & OFF and
not discharge liquid through outlet when mounted
(10) if unsuitable for use in breathing system, non
interchangeable 23 mm fittings; inlet to be male, outlet to be
female, direction of gas flow to be marked
(11) if suitable for use in breathing system, standard 22 mm
fittings ; inlet to be female, outlet male and direction to be
marked.

76. Safety Features of Modern vaporizer
a)Keyed filling system
b)Low filling ports
c)Secured vaporizer(less ability to move)
d) Interlock devices or vaporizer exclusion systems – prevent more than one
vaporizer from being turned ON at a time.
e)Color coding system
f)Single agent
h)Interlocking
i)Anti spill Protection designs
j)Firmly attachment with vaporizer manifold

77. Filling agent color code

78. Filling devices
• Funnel fill system
• Keyed fill system
• Quik- fill system (For Sevoflurane)
• Easy-fill system (Tec 7 Vaporizers)

79. Funnel fill system

80. Keyed fill system

81. Quik Fill System

82. Easy Fill System

83. Hazards of Modern Vaporizer
a) Incorrect agent – if an agent of high potency or volatility is used in a
vaporizer intended for an agent of low potency or volatility, a
dangerously high concentration may be delivered. The vaporizer must
be completely drained and all liquid discarded.
b) Tipping – liquid from the vaporizing chamber may get into the
bypass or outlet high concentration will be delivered when the
vaporizer is first used. Prevented by keeping the vaporizer in off/travel
position while movement.

84. CONTD
c) Overfilling – liquid agent may enter the fresh gas line, and lethal
concentrations may be delivered, or no output due to complete
vaporizer failure. Agent specific filling devices prevent overfilling.
d) Reversed flow – increases output.
e) Leaks – affect fresh gas composition and flow, pollutes
OR environment.
f) Interlock malfunction , Concentration dial in wrong position , physical
damage,
g) Contaminant in vaporizing chamber, obstruction in fresh gas flow.

85. Any Questions??

86. Summary
• Vaporizer is special device for delivery of anesthetic gas.
• Vapor is the gaseous form of liquid below critical temperature.
• Its output is affected by so many factors.
• Mounting of vaporizer should be systemic.
• It should follow ASTM guidelines.
• We should know hazards of vaporizer.

87. References
• Miller’s anesthesia 8th edition
• Dorsch and Dorsch

88. THANK YOU