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Vaporizers Flashcards

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1
Q

What is the function of a vaporizer?

A

Change liquid anesthetic into vapor, adds controlled amt of vapor to FGF/BS

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2
Q

What is a vapor?

A

volatile liquid in closed container, molecules enter space above it

Dynamic equilibrium forms if container kept at constant temperature

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3
Q

What is saturated vapor pressure?

A

highest partial pressure vapor can achieve at certain temperature

At constant temp, dynamic equilibrium reached btw liquid, vapor

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4
Q

What is the proportional effect of temperature on vapor pressure?

A

Increased temp = increased VP, more molecules added to vapor phase

decreased temp = decreased VP

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5
Q

What is VP affected by?

A

Liquid, Temp

IS NOT AFFECTED BY AMBIENT PRESSURE

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6
Q

Halothane SVP (torr, 20*C)

A

243mm Hg

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7
Q

Enflurane SVP (torr, 20*C)

A

172mm Hg

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8
Q

Isoflurane SVP (torr, 20*C)

A

240mm Hg

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9
Q

Desflurane SVP (torr, 20*C)

A

700 mm Hg

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10
Q

Sevoflurane SVP (torr, 20*C)

A

160mm Hg

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11
Q

Boiling Point

A

Where vapor pressure = atmospheric pressure

BP decreases with lower atmospheric pressure (?)
Agents with lower BPs: more susceptible to changes in Patm

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12
Q

BP (*C) Halothane at 760mm Hg

A

50.2

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13
Q

BP (*C) Enflurane at 760mm Hg

A

56.5

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14
Q

BP (*C) Isoflurane at 760mm Hg

A

48.5

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15
Q

BP (*C) Desflurane at 760mm Hg

A

22.8

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16
Q

BP (*C) Sevoflurane at 760mm Hg

A

59

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17
Q

Partial Pressure

A

part of total pressure in container DT one gas in mixture of gases

Dalton’s Law: partial pressure exerted by gas

Depends only on temperature, NOT total pressure above liquid

Absolute value

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18
Q

How is partial pressure related to patient depth?

A

Directly

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19
Q

What is vapor pressure?

A

Highest partial pressure that can be exerted by a gas at a given temperature

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20
Q

Volumes percent

A

Number of units of vol of gas IRT total of 100 units of vol for total liquid

Percentage of vol (V/V%) of gas = (Partial pressure of gas/total pressure of air)*100

Vol % = relative ratio

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21
Q

How is vol percent related to patient depth?

A

Indirectly

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22
Q

Heat of Vaporization

A

Energy needed for molecules in liquid phase to move into gas phase

Number of calories needed to convert 1g of liquid into vapor

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23
Q

What happens as vaporization proceeds?

A

As vaporization proceeds, liquid temp drops

Gradient forms, heat flows from surroundings to liquid to equilibrate temperature

Lower liquid temperature, greater the gradient, greater flow of heat from surroundings

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24
Q

Specific Heat

A

Quantity of heat required to raise temp of 1g of substance by 1*C

Higher specific heat, more heat required to raise temperature of given quantity of that substance

Alternative definition: amt of heat required to raise temp of 1mL of substance by 1C, standard = H2O at 1cal/g/C (1cal/mL/*C)

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25
Q

Why is specific heat important to anesthesia vaporizers?

A

How much heat must be supplied to liquid ax to maintain stable temp during vaporization?

Choosing material for vaporizer: materials with high specific heat experience more gradual temperature changes

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26
Q

Thermal Conductivity

A

Measure of speed with which heat moves through substance

Greater thermal conductivity means substance better conducts heat

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27
Q

Thermostabilization

A

best achieved by constructing vaporizer with high thermal conductivity ie bronze, copper

If vaporizer has wicks, must be in contact with metal part so heat loss through vaporization can be quickly replaced

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28
Q

What are examples of measured flow vaporizers?

A

Copper kettle, Desflurane, Ohio #8

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29
Q

What are three components of measured flow vaporizers?

A

vaporizer, vaporizer flow meter, bypass flowmeter

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30
Q

Measured Flow Settings, Compensation

A
  • Require temperature compensation via flow control
    -Often require algebraic conversion or slide rule to determine ratio of vaporizer setting to bypass flow
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31
Q

What are the methods of vaporization?

A
  1. Variable Bypass
  2. Flow Over
  3. Bubble Through
  4. Injection
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32
Q

What is the main purpose of a variable bypass vaporizer?

A

VP anesthetic agents > partial pressure required to produce ax
* Must have way to dilute amt of VA being delivered to patient
* Accomplished by splitting gas through vaporizer

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33
Q

MOA variable bypass: splitting valve

A
  • determines how much of FGF goes through bypass vs into vaporizing chamber
  • Come together at vaporizer outlet to enter BS
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34
Q

Splitting ratio

A

vaporizing chamber FR/bypass FR

Depends on ratios btw two pathways, which in turn depends on adjustable orifice = outlet of vaporizing chamber

Also depends on total flow to vaporizer

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35
Q

MOA: flow over

A

Carrier gas passes over surface of liquid

Requires compensation: changes in gas FR through vap = changes in output

Ex: if excessively high flow, complete saturation of gas moving through vaporizing chamber may not occur so decreases output

Increased surface area of gas-liquid interface, increased efficiency of vaporization

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36
Q

Strategies of flow rate compensation?

A

–Increase surface area of carrier gas-liquid interface to ensure full saturation of gas exiting vap chamber

MOA:
–Baffles, spiral tracks – used to lengthen gas pathway over liquid (Tec 5)
– Wicks increase SA of liquid through capillary action, must have bases IN liquid anesthetic

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37
Q

MOA bubble through

A

Carrier gas bubbled through liquid via diffuser

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38
Q

MOA injection

A

Inject known amt of liquid anesthetic into known vol of gas

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39
Q

VOC?

A

High resistance, prevents pressurizing effect

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40
Q

VIC?

A

Low resistance
Agents with low VP (methoxyflurane) or potency (ether)
Affected by minute vol, FGF, PPV, temp

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41
Q

3 ways achieve temp compensation

A
  1. Construct vaporizer out of materials that supply/conduct heat efficiently so act as ‘sink’ from atmosphere, greater thermostability
  2. Suppled heat
  3. Alter splitting ratio so that increase GF as temperature decreases/decrease GF as temp increases
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42
Q

MOA supplied heat

A

electric heater used to supply heat to vaporizer

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43
Q

Computerized thermocompensation

A

Changing amt of liquid injected, heat loss DT vap may not be important

Altering flow of carrier gas through vaporization chamber

All done electronically

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44
Q

Mechanical Thermocompensation

A
  • Compensates by altering splitting ratio
    -Main principle: liquids/metals contract when get cold, expand as warm

So as vaporizer cools, the thermal element allows more carrier gas to pass through vaporizer

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45
Q

Why does the vaporizer decrease in temperature?

A

For vaporization to occur, anesthetic molecules have to escape from liquid and become vapor –> reduces energy of remaining liquid

More molecules escape (become vapor), more energy lost from liquid

As vaporization happens, falling temp/lowering energy of liquid = less vaporization = decrease concentration of anesthetic being delivered

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46
Q

What are the 3 strategies of mechanical thermocompensation?

A
  1. Liquid bellows
  2. Metal rod
  3. bimetallic strip (Tec series)
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47
Q

Agent Specificity

A

Most modern vaporizers = agent specific

Multipurpose: Ohio #8, Stephens

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48
Q

Resistance

A
  1. Plenum
  2. Draw Over
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49
Q

Plenum

A

High resistance, unidirectional, agent specific, variable bypass vaporizers, VOC

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50
Q

Draw Over

A

Low resistance
inefficient vs plenum
Robust, portable - good for field ax

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51
Q

Concentration Calibrated

A

Calibrated by agent concentration expressed in % of vapor output

Vaporizer output controlled by single knob or dial that calibrated in volumes percent

Designed to be btw FM, common gas outlet
o NOT for use btw common gas outlet, BS – cannot handle high FGFs of O2 flush, will increase resistance

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52
Q

Effects of barometric pressure

A

Most calibrated at sea level, ASTM standards: effects of changes in ambient pressure on performance included in manual

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53
Q

What happens with back pressure?

A

Occurs during IPPV, O2 flush activation

positive pressure transmitted back from BS to machine, vaporizers = increased or decreased outflow from vaporizer

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54
Q

What is the pumping effect?

A

Increased vaporizer outflow due to : positive pressure breath causes transmission of back pressure to vaporizer, thus back pressure opposes gas flow out of vaporizer chamber and bypass

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55
Q

MOA Pumping Effect

A

FGF entering vaporizer retrograde gets compressed

Size of vapor chamber > bypass, more gas gets compressed in vaporizer chamber

That excess gas in vap chamber collects vapor

When pressure released, goes all directions including retrograde into bypass tract so now, delivering vapor from both vaporizing chamber and bypass tract = OVERDOSE

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56
Q

Contributing factors to pumping effect

A

less agent in vap chamber (vaporizer less full), carrier gas flow low, pressure fluctuations high/frequent, dial setting low

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57
Q

Which type of flow is Assoc with pumping effect?

A

LOW carrier gas flows

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58
Q

Strategies to reduce pumping effect

A

Reduce size of vaporizing chamber relative to bypass chamber
 decreases amt of pressurized gas reaching vaporizing chamber

Long spiral, small-diameter tube to connect vap chamber to bypass channel (Drager 19.1)
 amt of pressurized gas reaching vaporizing chamber

One way check valves immediately upstream from vaporizer
 Sometimes used downstream O2 flush: prevent back pressure assoc with use

Exclude wicks from area where inlet tube joins vaporizing chamber

Overall increase resistance (?) of gas flow through vaporizer

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59
Q

Pressurizing Effect

A

essentially dilutes out anesthetic agent, decreases outflow

pressure to vaporizer outlet causes increased pressure to vaporizer chamber -> compression of carrier gas molecules so that more molecules of carrier gas per mL

Number of vapor molecules in chamber DOES NOT CHANGE bc vapor pressure depends solely on temperature, NOT ambient pressure

Same molecules of vapor in more molecules of carrier gas = decreased concentration of anesthetic in chamber/outlet

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60
Q

Contributing factors to pressurizing effect

A

high flows, large pressure fluctuations, low vaporizer settings

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61
Q

Which type of flow is assoc with pressurizing effect?

A

High flows

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62
Q

Effects of Rebreathing?

A

Vaporizer dial setting = reflects concentration of inhalational agent delivered to BS

If little to no rebreathing: Fi(inhal) ~ Et(inhal)

As decrease FGF, exhaled gases = more significant portion of inspired gases –difference btw vaporizer setting, inspired concentration

Increased minute volume -> increased rebreathing = greater effect

Need agent analyzer to determine inspired agent concentration

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63
Q

3 ways to fill vaporizers

A
  1. Standard screw capped filler port/funnel fill system - pour into vaporizer chamber
  2. Agent specific keyed port - prevents inadvertent filling of vap with wrong ax, grooves specific to agent
  3. Quik-Fill system (sevo, maybe iso): bottle pushed into vaporizer component, valve opens allowing filling
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64
Q

How to fill desflurane vaporizer

A

All vaporizers use same bottle to fill vaporizer

Crimped on adapter that has spring loaded valve that opens when bottle pushed into filling port

When bottle removed, valve on bottle closes to prevent agent spill

Filling port has spring valve to prevent agent from escaping

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65
Q

Mounting Systems

A

Back bar, rail or mounting system used to hold vaporizers on machine

Cagemount systems in vet med: 23mm taper push fittings (inlet, outlet; female, male) to attach vaporizer to gas delivery system, vaporizer bolted directly to back bar

  1. Permanent
  2. Proprietary Systems
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66
Q

Pros of permanent mounting

A

Less physical damage to vaporizers
fewer leaks
always filled in vertical position

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67
Q

Cons of permanent mounting

A

Machine may not have enough mounting locations to accommodate all needed vaporizers

Malfunctioning vaporizer cannot easily be exchanged

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68
Q

Pros of proprietary mounting systems

A

–More compact machine with fewer mounting locations
–Vaporizers can be easily removed, replaced even during a case
–Can remove vaporizer if have MH

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69
Q

What are the two proprietary mounting systems?

A
  1. Selectatec
  2. Drager
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70
Q

Cons of proprietary mounting systems

A

–Partial or complete obstruction to gas flow from problems with mounting system
–Leaks, absent/damaged o-ring
–Leaving walking lever in unlocked position
–Compatibility challenges among different manufacturers

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71
Q

MOA Selectatec Mounting System

A

–Two vertically situated male valve ports
–Btw inlet, outlet port = accessory pin, locking recess
–Compatible vaporizers: two female ports with recessed assembly to receive accessory pin
–Vaporizer lowered onto male port, locked into place via locking knobs > cannot turn vaporizer on if not locked
–O rings on male valve ports ensure gas-tight seal between vap, Selectatec mount
–Loss, deformation of rings: leaks btw vaporizer, mount
–When vap turned on, retractable spindle depresses ball valve in male valve ports  allows gas to flow from vap to ax machine

72
Q

Safety Interlock System

A

(vap exclusion/isolation) : horizontal push rod system, ensures only one vap turned on at a time

73
Q

What are the safety checks that should be performed following attachment of a vaporizer?

A

–vaporizers should be level, at the same height; –attempt to lift each off without unlocking
–can only turn on one at a time

74
Q

Maintenance

A

Required – model specific, follow manufacturers recommendations, responses of patients, suspicion that dialed concentrations erroneous, any component improperly functioning
o Evaluation of operation
o Cleaning
o Changing of filters
o Replacement of worn parts
o Calibration

75
Q

What is important about maintenance of vaporizers specifically for halothane, methoxyflurane?

A

preservatives that not highly volatile, collect in vaporization chambers/on wicks (gunk up vaporizer)
o Potential to affect ax output
o Vaporizers must be periodically drained to remove preservative accumulation

Previously: recommended flushing vaporizer with diethyl ether to dissolve
 No longer recommended: 100% oxygen as carrier gas, diethyl ether = flammable

76
Q

What is the preservative in halothane?

A

Thymol

77
Q

What is the preservative in methyloxyflurane?

A

butylated hydroxytoluene

78
Q

ASTM Standards: effects of variations?

A
  • Effects of variations in ambient temp and pressure, tilting, back pressure, input flow rate, gas mixture composition on performance must be stated in accompanying documents
79
Q

ASTM Standards: settings

A

Shall not deviate >20% or 5% of maximum setting without backpressure

Shall not deviate more than +30/-20% or more than +7.5/-5% of maximum setting with pressure fluctuations at common gas outlet of 2kPa with total flow of 2L/min or 5kPa with 8L/min

80
Q

ASTM standards: how much emit in off position?

A

<0.05%

81
Q

ASTM standards: vaporizer filling

A
  • Max and min filling level must be visible
  • Cannot be overfilled in operating position
82
Q

ASTM standards: in what direction should a vaporizer open?

A

Counter clockwise

83
Q

ASTM Standards: fittings

A
  • Out of circuit must have 23mmfittings, male on inlet, female on outlet
  • In circuit must have 22mm fittings, female on inlet, male on outlet; must be marked for use in breathing system
  • Direction of gas flow must be marked
84
Q

ASTM Standards: flow of gas btw vaporizers

A
  • Must prevent gas from going through one and then another vaporizing chamber
85
Q

Hazards: tipping

A

o If tip sufficiently, liquid from vaporizing chamber may get into bypass or outlet - high concentration delivered when vaporizer first used

o Should tipping occur high flow of gas run through vaporizer with concentration dial at low concentration until output shows no excessive agent

o Many new vaporizers: mechanism that blocks entrance/ exit from vaporizing chamber prevents problems associated with tipping

86
Q

How prevent tipping

A

 Mounting vaporizers securely, handling with care when not mounted
 Turn off or in travel setting before movement

87
Q

Hazards: overfilling

A

–If overfilled, liquid agent may enter fresh gas line -> Deliver high concentrations or cause complete vaporizer failure (no output )

Most vaporizers: filling port situated so that cannot occur, liquid pours out of funnel first
–can happen with agent specific filling devices

Always fill in vertical position securely attached to anesthesia machine

88
Q

Hazards: what happens if put anesthetic with lower SVP in a vaporizer made for an agent with a higher SVP?

A

lower than indicated ax output (=underdose)

89
Q

Hazards: what happens if put anesthetic with higher SVP in a vaporizer made for an agent with a lower SVP?

A

higher than indicated ax output (=overdose)

90
Q

Since halothane and isoflurane have similar SVP, can you use halothane and isoflurane vaporizers interchangeably?

A

SVP halothane = 243, iso = 240

halothane vaporizers can produce concentrations of iso reasonably close to dial settings for halothane

–Iso in halo vap 20-50% more vapor than expected
–Halo in iso vap lower than expected delivered concentration
–Vap needs to be completely recalibrated for iso

91
Q

Hazards: reverse flow

A

In most cases will be increased output

Consequences of reversed flow particular to vaporizer

92
Q

Hazards: leaks

A

Effect depend on size, location; whether have check valve at vaporizer outlet

Common cause of leaks equals failure to replace or adequately tightened filler cap
o Leak will result when vaporizer turned on

Vaporizer may not be mounted properly, fitting btw vaporizer and inlet/outlet connection may become loose or broken

93
Q

What if have leak in vaporizer connection or mount?

A

machine function normally until turn vap on

At that point, FGF from machine lost through leak -> total flow reduced

Consider leak if refilling vaporizer with unusual frequency, odor detected, or loss/reduction of FGF into breathing system after vaporizer turned on

94
Q

Hazards: vapor leak into FG line

A

Some vaporizers leak small amounts of vapor into bypass when turned off

Amount of leak depends on ambient temperature, sizes/configuration of internal ports

Leaks reduced by not turning vaporizer from off to the zero setting unless being used

95
Q

Hazards: physical damage

A

shock excessive vibration or mistreatment may lead to malfunction

Less common with permanently mounted vaporizers

96
Q

Hazards: contaminants in vaporizing chamber

A

Water, other substances cause corrosion - contact manufacturer to determine action

97
Q

hazards: projectile

A

Vaporizer may be MRI compatible but only when attached to machine

98
Q

Tec 3 classification

A

Variable bypass, flow-over with wick
Automatic thermocompensation
Agent specific
High resistance
Back pressure compensated

99
Q

Tec 3: thermal compensation

A

bimetallic strip

100
Q

Tec 3: back pressure compensation

A

long tube leading to vaporization chamber, expansion area in tube, exclusion of wicks from area of vaporization chamber near inlet

101
Q

Tec 3 accuracy

A

Output = nearly linear over range of concentrations, flow rates: 250mL/min-6L/min

102
Q

Tec 5 classification

A

Variable bypass, flow over the wick
Automatic thermocompensation
Agent specific
high resistance
Back pressure compensated

103
Q

Differences btw Tec 3 and Tec 4?

A

o Safety interlock system: vaporizer isolation/exclusion when multiple vaporizers mounted in series

104
Q

Accuracy of Tec 5

A

Greatest accuracy <5Lmin, <3% setting, 15-35*C
 Less output if higher flow or dial setting)
 Less output if <15, more output if >35

105
Q

Tec 5 temp compensation

A

bimetallic strip located in bypass channel

As temp decreases, less gas allowed through bypass channel (bypass channel is on bottom)

106
Q

Tec 5 internal baffle system

A

keep liquid from reaching outlet if vaporizer tipped, inverted

107
Q

Tec 5 Spiral Wicks

A

Gas flowing into vap chamber first passes through central part of rotary valve

Directed through helical channel past spiral wick in contact with wick skirt that dips into liquid agent

Gas with vapor leaves chamber via channel in concentration rotary valve, flows to outlet

108
Q

Tec 5 Agents

A

enflurane, isoflurane, sevoflurane, halothane

109
Q

Tec 4

A

Isoflurane only

Temp compensation = bimetallic strip
has Selectatec mounting bar

110
Q

Tec 5 filling mechanisms

A

2 - keyed system, drain plug

111
Q

Tec 5 Hazards

A

gas leak if locking lever loose or filling port open; overfilling possible if bottle adaptor loose/control dial on

Tilting -> overfilling -> increased vapor output

Reversed flow through vaporizer increases output

112
Q

Tec 7 Classification

A

Variable bypass, flow over the wick
Automatic thermocompensation
Agent specific
High resistance
Back pressure compensated

Obligatory Selectatec mounting bar
o Essentially same MOA as Tec 5
Safety interlock system

113
Q

Filling Mechanisms Tec 7

A

Three filling mechanisms: funnel fill, Quik-Fil, easy-Fil

~300mL liquid needed to fill vaporizer with dry wicks, ~75mL retained in wicks when drained

114
Q

Tec 7 Vaporizer Identification Label

A

on back: used by systems with vaporizer identification units

115
Q

Accuracy of Tec 7

A

Greatest accuracy: FGF 5L/min, <3%, 15-35*C
o Higher flows, higher dial settings: decreased output below set value

Thermostat does not respond to <15C
Temp >35C = unpredictably high output

116
Q

Maintenance of Tec 7

A

drain 1x yr, halothane drained Q2 weeks if additives/stabilizing agents; service 3yr from purchase then Q6mo
o Clean external surfaces with damp cloth

117
Q

Penlon Sigma Delta Classification

A

Variable bypass, flow over with wick
temperature compensated
high resistance
agent specific
VOC

118
Q

Penlon Sigma Delta Agents

A

sevo, iso, des, enflurane

119
Q

Penlon Sigma Delta Filling

A

Three different filling devices: funnel fill, keyed fill, Quik-Fil

Liquid capacity 250mL, 60mL remains in wick after drain
o When filled to minimum mark = 35mL

120
Q

Penlon Sigma Delta Accuracy

A

Accuracy: 15-35*C, FGF 0.2-15L/min
o Temp-compensating mechanism slow, may need minimum 1-2hr to compensate
o Steady back pressure of 10-15kPa/100-150 cm H2O decreases vaporizer output
Effect greatest at low vaporizer settings, low FRs

121
Q

Calibration of Penlon Sigma Delta

A

Calibrated with 100% oxygen
o Nitrous oxide: decreases output
o Air: decreases output <5%

122
Q

Penlon Sigma Delta Maintenance

A

Calibration with suitable agent gas analyzer – must service if outside limits

Major service Q10yrs, halothane Q5yr with periodic draining

123
Q

Hazards: pennon sigma delta

A

Store btw -20C and 50C, malfunction if exposed to higher temperatures

Control dial zero, vaporizer upright during filling – otherwise possible to overfill

Overfilled vaporizer requires manufacturer eval

124
Q

How to transport/manage the Penlon Sigma Delta while filled

A

0 (ideal): sit for 10’ once reconnected to machine
* Ax agent overdose if not enough time for any liquid to drain to normal position

Open: 5L/min x >10min

Tipped, interverted: dial max, 5L/min, >10min

125
Q

Fluotec Mark 2

A

Poor Performance

126
Q

Tec 3

A

Variable bypass, flow-over with wick, automatic thermocompensation, agent specific, high resistance, back pressure compensated
o Temp: bimetallic temp-sensitive element assoc with chamber
o Back pressure: long tube leading to vaporization chamber, expansion area in tube, exclusion of wicks from area of vaporization chamber near inlet

127
Q

Examples TEC 3

A

Flutec Mark 3, Pentec Mark 2

128
Q

What did the TEC4 introduce?

A

Safety Interlock System

129
Q

General MOA of variable bypass vaporizers?

A

Split carrier gas to flow in vaporizing chamber where picks up ax vapor or goes to bypass change

130
Q

Percentage vol of a gas

A

= partial pressure of gas/total pressure of air x 100%

Ex: iso SVP 240mm Hg, atmospheric pressure = 760mm Hg
240/760 x 100 = 31%

131
Q

What type of vaporizer are the Desflurane vaporizers?

A

Measured flow

132
Q

Are most vaporizers electronically powered?

A

No - mechanical devices, no external power to function normally

133
Q

Electronic Vaporizers

A

Aladin cassette vaporizer (human med)
Vetland EX3000 Electronic Vaporization System

Electronic variable bypass or electronic injection type

134
Q

Electronic Variable Bypass vaporizers

A

splitting ratio of carrier gas determined electronically instead of mechanically
 Rely on properly operating electronics to function
 Computer calculates carrier gas flow needed to pass through vaporizing chamber in order to produce desired anesthetic agent concentration

135
Q

Electronic Injection Type Vaporizers

A

withdraws calculated amount of liquid agent from agent bottle, injects liquid into breathing system or fresh gas flow
 Amount of liquid injected  adjusted to achieve desired anesthetic concentration

136
Q

In a variable bypass vaporizer, what is the final concentration of gas determined by?

A

Ratio of amt of gas that picks up inhalant to gas to gas that bypasses inhal

Vapor pressure of VA

137
Q

Drager Vaporizer 19.1

A
  • Variable bypass, flow over the wick, automatic thermocompensation, high resistance, agent specific, pressure compensated
138
Q

Inhalants used with Drager 19.1

A

Iso, enflur, sevo, halothane

139
Q

Accuracy of Drager 19.1

A
  • 10-40oC operating range, accuracy 10%
  • Accurate FGF 0.3-15L/min, complete saturation may not occur at higher flow (output falls)
140
Q

Does mounting effect output with Drager 19.1?

A

No

141
Q

What gas is used to calibrate the Drager 19.1?

A

Air
With 100% oxygen, delivered concentration 4-10% higher than set

142
Q

Drager 19.1 Hazards

A
  • Hazards: tilting  spill into control device, increase or decrease delivered concentration
143
Q

Drager 19.1 - why increase in popularity?

A

1st popular in large animal – significantly larger inhalant reservoir capacity vs Tec 3, 4

144
Q

Difference btw Drager 19.1 and 19.3?

A

19.3 – interlock model

145
Q

Maintenance of Drager 19.1

A

outside wipe down damp cloth with detergent, maintenance Q6mo, chamber cleaned/wicks changed Q2yrs
o Halothane: rinse with fresh halothane when liquid in sight glass shows discoloration, particles

146
Q

Drager Vapor 2000 - main difference

A

Handwheel: “T” transport position – used when vaporizer removed from ax machine
o Pin on locking lever must engage with groove in top of handwheel to release vaporizer, only happens in T position

Three isolation valves

Vents excess FGF to outside when vaporizer not on

147
Q

Ohio Calibrated Vaporizer

A
  • NOT same as Ohio #8 (Boyle’s Bottle)
  • Variable bypass, flow over with wick, automatically temperature compensated, agent specific, VOC, high resistance
148
Q

Agents used in Ohio Calibrated Vaporizer?

A
  • Isoflurane, halothane, sevoflurane
149
Q

Accuracy of Ohio Calibrated Vaporizer?

A
  • Accuracy at FGF 0.3-10L/min, temp compensation btw 16-32*C
150
Q

Tipping with Ohio Calibrated Vaporizer

A

o No problems if tilt up to 20* while in use, up to 45* not in use
o More tipping > delivery of higher concentrations

151
Q

Other Considerations with Ohio Calibrated Vaporizer

A

Plastic spacers btw paper wicks, may react with enflur or iso > discoloration of liquid, not problematic

152
Q

Measured Flow Vaporizers

A

No longer being manufactured, not covered by ATSM standards for equipment – precursors to today’s modern variable bypass vaporizers

Measured -flow, bubble-through, high resistance, VOC, temperature compensated (thermally stable with manual flow adjustments based on temperature of liquid, multipurpose

153
Q

Features of Measured Flow Vaporizers

A

Back pressure – check valves

Can vaporize halothane, isoflurane, sevoflurane, or methoxyflurane in same vaporizer > need to be clearly labeled for the agent in use

Able to retrofit check valves

Manual adjustments required for variations in total gas flow, day to day temperature changes, changes in liquid temp during use, especially with high FGF

154
Q

Functions of the two flowmeters in a measured-flow vaporizer?

A

One routes all oxygen through vaporization chamber where it is fully saturated

The other bypasses to meet patient requirements

Operator must manipulate both to achieve the proper anesthetic concentration

155
Q

What are the two historical measured flow vaporizers?

A

copper (Copper Kettle) or silicon bronze (Verni-Trol)

156
Q

What are the three Desflurane vaporizes?

A

Tec 6, Drager D, Penlon Sigma Alpha

157
Q

Classification of Desflurane Vaporizer

A

Measured-flow, automatic thermocompensation, agent specific, high resistance, back-pressure compensated

158
Q

Why does desflurane need a special vaporizer?

A

Des = low potency, low boiling point (~23*C, near room temp) > requires heating to ensure complete, stable vaporization of liquid + accurate vaporizer output

DT low potency, lrg amts required to be vaporized

Warmed to 39*C, pressurizes to 2atm (1500mmHg) – two heaters in base

Injects ax into FGF

159
Q

Role of Electronics in Desflurane Vaporizer (LJ)

A

Indicate operational status, level of agent, control pressure balance btw diluent/bypass + vaporized inhalant, to heat liquid desflurane, charge backup battery

Can only turn on once electronics deemed it to be operable

Performs self check every time turns on

Solenoid interlock allows dial, rotary valve to be turned on

160
Q

Concentration dial of desflurane vaporizer

A

Concentration dial: 1-18%, 1% gradations up to 10%, 2% btw 10-18

Release to turn on vaporizer cannot be depressed until operational LED on
 Release used if >12%

161
Q

Liquid Level Indicator on Desflurane

A

Liquid crustal display (LCD), visible when vap on

Indicates amt of liquid in vap btw 50-425mL (total vol of sump = 425mL)
 20 bars, 1 bar = ~20mL

162
Q

Desflurane Vaporizer Filling

A

while in use if FGF <8L/min/dial <8% (no high back pressure) or while warming up

Only desflurane-specific bottle inserted into filler port

163
Q

Accuracy of desflurane vaporizer (not in LJ)

A

0.2-10L/min, temps 18-30*C
o Tilting does not render vaporizer inactive/dangerous to operate
o No effect from fluctuating back pressure unless high while filling
o Carrier gas affects output: air, N2O  output
o Electricity consumption low

164
Q

What is important about the desflurane injection rate vs FGF?

A

THEY MUST BE MATCHED

165
Q

Hazards of Desflurane Vaporizer

A

–Vapor can leak into FGF when off
–If used on ax machine that turns off FGF during inspiration (FG decoupling, eg Fabius), intermittent flow will trigger alarm if software to avoid not in place
–Assoc with electronics:
 Sparks, smoke if plug loose
 Mounted on R side of back bar of machine so power cord does not interfere with vaporizer interlock mechanism for other vaporizers

Humans: CPA following massive overdose DT defective control valve

166
Q

Maintenance of Technicians 6

A

service Q1yr at authorized center, wipe external surface with cleaning agent

167
Q

Advantages VIC

A

low cost
Simple design
Portability
Nonspecific to agent
Low resistance to air flow
Low gas flows (minimizes amt of agent required, cost, atmospheric pollution)

168
Q

Disadvantages VIC

A

Not precise
unpredictable
Nonspecific to an agent
No compensatory mechanisms

Inhalants with high SVPs not good candidates
o Lower SVPs (methoxyflurane) less likely to produce overdose

169
Q

Vaporiing Chamber

A

simple reservoir with a glass, allows provider to determine amount of liquid present +/- temperature compensation

170
Q

VIC: what affects output?

A

vaporizer dial setting, FGF, composition/concentration of gas entering vaporizer next line

In turn, depends on patient minute vol, oxygen-ax agent uptake, BS configuration

171
Q

Where VIC usually located in circuit?

A

Btw inhalation valve, patient

172
Q

Ambient Air in VIC

A

Ambient air often used as principal carrier gas, can use oxygen with T piece
o Inspired oxygen [ ] depends on oxygen flow, reservoir volume, ventilatory volume

173
Q

Two MOA of VIC?

A
  1. Push Through
  2. Draw Over
174
Q

Stephens Vaporizer

A

glass bottle, flow through or bypassing controlled by central control graded in settings 0-8
 At 0, all gas bypasses vaporizer
 At 8, all gas passes through vaporizer
 Adjustable metal sleeve – altered to  proximity of gas entering vap chamber to surface of liquid anesthetic (similar to a wick)

175
Q

Komesaroff vaporizer

A

no adjustable sleeve, smaller liquid anesthetic surface area

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