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SRNAProfessionalGuide II > Anesthesia Vaporizers > Flashcards

Anesthesia Vaporizers Flashcards

1
Q

Vapor Pressure (VP)

A

Created by molecules in the vapor phase bombarding the walls of a container

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2
Q

Saturated Vapor Pressure (SVP)

A

Gas phase above the liquid usually at 20C

Increase Temp –> Increase SVP

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3
Q

VP is independent of

A

atmospheric pressure if the temperature remains constant

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4
Q

Boiling Point

A

The temperature at which the vapor pressure equals atmospheric pressure

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5
Q

Units of Vapor Concentration

A 
Absolute pressure (mmHg) 
Volumes percent
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6
Q

Volumes Percent is volume of vapor per 100 volumes of

A

total gas the partial pressure due to vapor/total ambient pressure X 100%

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7
Q

Dalton’s Law of Partial Pressures

A

The total pressure exerted by a gas mixture is the sum of the individual pressures of its constituents

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8
Q

Latent Heat of Vaporization

A

The # of cal required to change 1 g of liquid into vapor without a temp change.

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9
Q

Specific Heat

A

The # of cal required to increase the temp of 1 g of a substance by 1 deg C

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10
Q

Dalton’s Law of partial pressure summary

A

In a mixture of gasses the pressure exerted by each gas is the same as that which it would exert if it alone occupied the container.

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11
Q

Diffusion Can take place

A
  • thru membrane
  • thru gas/liquid interface
  • between gasses
  • between liquids
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12
Q

Application of Fick’s Law

A

Oxygen diffuses in
CO2 diffuses out
Diffusion respiration - pre-oxygenation and emergencies

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13
Q

Henry’s Law

A

At a gas/liquid interface, some of the gas will dissolve in the liquid.

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14
Q

Relative amount dissolved in solvent depends on the

A

chemical nature of the gas and solvent

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15
Q

Molecules of the gas within the liquid will exert

A

the same amount of pressure as the molecules overlying the liquid (at equilibrium)

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16
Q

PP will the same, but the number of molecules needed to exert the pressure depends on

A

the gas and solvent

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17
Q

Effect of pressure

A

As pressure of gas overlying liquid increases, pressure of gas in liquid and number of molecules of the gas increase proportionally

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18
Q

Temperature must be named in anesthesia,

A

37 degrees is used

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19
Q

blood:

A

gas most important

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20
Q

gas:

A

oil is next most important

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21
Q

Solubility Coefficient

A

Ostwald - the volume of gas which dissolves in one unit volume of the liquid at the temperature concerned
Useful in anesthesia

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22
Q

Does the Oswald solubility coefficient dependent on pressure

A

Independent of pressure

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23
Q

Vaporizers: Measured Flow

A

Copper Kettle, Vernitrol

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24
Q

Vaporizers: Variable Bypass

A

Ohmeda Tec 4 & 5, Drager 19.1, 19.3

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25
Q

Vaporizers: Blender

A

Ohmeda Tec 6 (Desflurane)

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26
Q

What happens to SVP with increased temperature?

A

More in the vapor phase

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27
Q

Difference MEASURED FLOW (COMM)

A 
Carrier gas (CG) bubbles through agent
Manual Temp. conversion
Multi-agent
Operator determines CG split
No longer manufactured (but still present on field machines)
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28
Q

Different Variable Bypass

CH - AAA

A 
CG flows over agent
Auto adjust for Temp & Pressure
Agent specific
Auto CG split
Higher safety standards
29
Q

Decrease Temperature–> Decrease Vapor Pressure

A

Sluggish/not hitting the sides of the vaporizer

More flow must go through the vaporizing chamber so that the patient receives the same concentration of agent

30
Q

As liquid is vaporized energy is lost in the form of

A

Heat

31
Q

Increase Temperature–> Increase Vapor Pressure

A

Hitting the sides of the vaporizer rapidly

Less flow must go through the vaporizing chamber so that the patient receives the same concentration of agent

32
Q

Increase temp will______vapor pressure

A

Increase

33
Q

TEC 6

A 
No Output Alarm
    Agent < 20 ml (1 bar)
    Tilt > 10 degrees
    Power Failure
     Internal malfunction
Low Agent
       Illuminates with 50cc of agent
Warm-Up
10 minutes to reach operating temp of 39C
34
Q

Why a different vaporizer for Desflurane?

A

Requires an external heat source

  • 4-9 times more Des is required than other IA
  • Absolute amount of Des vaporized is much higher than other IA which would cause excessive cooling
  • Traditional vaporizers could not compensate adequately
35
Q

Traditional vaporizer would cause an

A

anesthetic overdose Des = 735 ml/min opposed to Iso = 47 ml/min

36
Q

VP of Desflurane

A

VP of 669 mmHg – near 1 atm

37
Q

Working pressure is affected by

A

FGF and viscosity of the carrier gases

38
Q

Increase in FGF increase

A

vapor flow as well

39
Q

Factors That InfluenceTec 6 Vaporizer Output

A

Varied Altitudes

Carrier Gas Composition

40
Q

Tec 6 – Effects of Varied Altitudes

A

Requires manual adjustments of the concentration dial with changes in barometric pressure

    • It is a pressurized vaporizer
  • –It works at an absolute pressure
  • —Partial pressure of Des changes with changes in ambient pressure
41
Q

Required setting =

A

Normal setting (%) X 760 mmHg /ambient pressure (mm Hg)

42
Q

Tec 6 – Carrier Gas Composition

A
  • Decreased concentration output can occur with low flows of gases other than oxygen due to changes in viscosity
    Vaporizer output is 20% less with nitrous than with oxygen
  • Nitrous oxide is less viscous than oxygen resulting in a lower working pressure at the differential pressure transducer
  • Take home – May have to increase dialed concentration with low flow anesthesia
  • Careful with low FIO2
43
Q

Variable Bypass Vaporizers -

A

Varied Altitudes and the effects on agent output

44
Q

***HypoBaric take home

A

The high resistance pathway through the vaporizing chamber offers less resistance thereby increasing vaporizer output.
Decrease Barometric Pressure –> INCREASED Vapor administered = Give more vapor than you have dialed on the vaporizer
Opposite of changes in temperature

45
Q

***HYPERBARIC TAKE Home

A

Changes in the density of vapors/gases cause more resistance to flow through the vaporizing chamber and a decrease in vaporizer output
INCREASE Barometric Pressure –>DECREASED Vapor administered = Give less vapor than you have dialed on the vaporizer

46
Q

HAZARDS (FOISTIP)

A 
Incorrect agent
Simultaneous agent administration
Free Standing 
Overfilling
Tipping
Intermittent Back Pressure 
“Pumping Effect”
47
Q

Safety Mechanisms (VPICK)

A 
Push/Turn
Interlock
Color Codes
“Keyed” filler system
Vigilance+Vigilance+Vigilance+…
48
Q

Never fill the vaporizer with the

A

dial in the ON position

49
Q

Be careful to keep the amount of liquid in the vaporizer

A

between the black lines.

50
Q

Tipping the Vaporizer during Transport

A

Agent enters the bypass chamber
Causes High Output Concentrations
OVERDOSAGE
Less of a problem with vaporizers that have extensive baffles (Tec 4)

51
Q

If Tipping occurs:

A
  • In hardened facilities turn in to maintenance
  • Flush for 20-30 minutes with high FGF and set the vaporizer concentration low
  • End-tidal agent monitoring
52
Q

Intermittent Back PressurePumping Effect

A
  1. Associated with positive pressure ventilation or oxygen flushing
    Oxygen flush is at __ psig-transmitted back
    Occurs during the inspiratory phase - PPV
  2. Reverse flow through the vaporizing chamber back into the bypass chamber (Bypass has diluted vapor and vaporizing chamber is also saturated with vapor)
  3. Causes higher than expected vapor concentrations
53
Q

Intermittent Back PressurePumping Effect

A
  1. Associated with positive pressure ventilation or oxygen flushing
    Oxygen flush is at (50) psig-transmitted back
    Occurs during the inspiratory phase - PPV
  2. Reverse flow through the vaporizing chamber back into the bypass chamber (Bypass has diluted vapor and vaporizing chamber is also saturated with vapor)
  3. Causes higher than expected vapor concentrations
54
Q

Pumping Effect is more Pronounced with

A 
Low flow rates
Low dial settings
Low levels of agent in the chamber
Rapid respiratory rates
High peak inspired pressures
Rapid drops in pressure during expiration
55
Q

Vigilance Steps

A
  • Make sure the vaporizer is in the OFF position after the machine check
  • Make sure that all filler ports are in place and secured tightly
  • Minimize possible leaks
  • Don’t overfill the vaporizer
  • Make sure the vaporizer has at least liquid up to the bottom line to minimize the pumping effect
  • Keep extra agent bottles in the drawer
56
Q

Calculate % of oxygen or nitrous oxide given a total FGF

A

Ex: 1 L/min of O2 , 1 L/min of N2O

1/1+1 = ½ = 50% O2 % 50% N2O

57
Q

How to determine flow %

A

Flow of particular gas/Total gas flow

58
Q

Commonalities – Modern Vaporizers

BALT- C

A 
“Button” must be pressed
Counterclockwise
Agent specific
T&amp;P compensated
Lock-out mechanism
59
Q

Less soluble

A

WIll dissolve quicker

60
Q

The temperature at Mount everest is about

A

220 mmHg so HIGHER gas will be delivered then set

61
Q

Boiling point of each VA, and MAC of each And Coefficients

A

Volatile

62
Q

Only Electronic vaporizer

A

TEC 6

63
Q

Higher you go the LOWER

A

ATMOSPHERIC PRESSURE

64
Q

TEC 6 has to reach

A

39 degrees C

65
Q

WHy do we need so much DESFLURANE

A

because the solubility is so low
INhale maybe 5.5, exhale could be 5.4
Meaning it’s not BEING ABSORBED

66
Q

The colder the patient

A

Their solubility is affected, slower metabolism

WIll take LONGER TO wake, NMB reversal more slowly

67
Q

Higher atmospheric pressure _______output

A

LOWER

68
Q

Lower atmospheric pressure _______output

A

HIGHER

69
Q

Running sevo with less oxygen like (0.5L) can lead to

A

Compound A

SRNAProfessionalGuide II (13 decks)

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