Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Intro to Anesthesia > Vaporizers > Flashcards

Vaporizers Flashcards

1
Q

What is vaporization

A
  • converting a liquid to a gas
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What does volatility mean?

A

-the ability of a substance to break it’s intermolecular forces

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Why do we call our inhaled agents volatile agents?

A
  • liquids are converted to vapor to be inhaled by patient and provide general anesthesia
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is the goal of the vaporizer

A

1) convert liquid to vapor at a consistent concentration with
2) tight control

so that we can deliver anesthesia safely (no underdosing or overdosing)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Vaporization is dependent on what three things?

A
  • vapor pressure of each volatile agent
  • temperature of the ambient environment (linear)
  • amount of carrier gas (FGF) increase in flows increase dilution (linear)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What gas laws apply to vaporization

A
  • Ideal Gas Law

- Dalton’s Law of Partial Pressure

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Describe the process of vaporization. How do the components of the Ideal Gas Law relate to vaporization?

A
  • in a sealed container gas molecules crash into the walls and exert a pressure
  • that pressure is:
  • directly proportional to the number of moles of gas molecules present
  • directly proportional temperature of the system
  • inversely proportional is volume
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Dalton’s Law of Partial Pressure

A

-total pressure in a given space is calculated by adding the partial pressures of each gas

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

How is vapor pressure calculated from total pressure?

How is concentration calculated from vapor pressure?

A
  • (molar fraction)(total pressure) = (vapor pressure)

- vapor pressure/barometric pressure = concentration or molar fraction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is concentration measured in?

A

V/V %

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Enflurane Vapor Pressure

A

172 mmHg

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Isoflurane Vapor Pressure

A

240 mmHg

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Halothane Vapor Pressure

A

244 mmHg

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Sevoflurane

A

157 mmHg

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Desflurane Vapor Pressure

A

669 mmHg

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

When anesthesia providers select a dose of volatile agent that the vaporizer will deliver they select what?

A
  • v/v %

- partial pressure of gas / total atmospheric pressure x 100

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is the partial pressure of oxygen, nitrogen, and other at atmospheric temp?

A
  • Oxygen = .21 x 760 = 160
  • Nitrogen = .779 x 760 = 592
  • Other = .011 x 760 = 8.4
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What effect does temperature have on the vaporization process?

A

-(direct) as temperature decreases, vapor pressure decreases

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What is the latent heat heat of vaporization?

A
  • the energy (calories or joules) at which a liquid or volatile anesthetic changes from a liquid to a gas without changing its temperature
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Why is there no change in temperature?

A

There is no temperature change because although you are adding energy to the liquid, energy is escaping in the form of kinetic energy once the molecules at the surface leave in the form of gas molecules

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

When the latent heat of vaporization is reached, what effect happens to the liquid

A

-the remaining liquid will be depleted of its energy, having a cooling effect, decreasing vapor pressure

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Why is the liquid cooling a problem?

A

Decrease in vapor pressure means decrease in anesthetic concentration means under-dose

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

How do you prevent the cooling of liquid

A

-add a constant heat source

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Liquid and vapor are _____ at vapor pressure

A

Equilibrium

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

Adding heat source shift equilibrium toward _____

at this time vapor pressure is ________

A

(Right) toward vapor

Increases

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

Adding cooling source shift equilibrium toward _____

at this time vapor pressure is ________

A

(Left) liquid

Decreasing

27
Q

Adding blow by gas shift equilibrium toward _____

at this time vapor pressure is ________

A

(Right) vapor

Decreased or constant

28
Q

Specific heat

A
  • the amount of energy required to increase the temperature of a specific volume of substance by 1 degree centigrade
29
Q

Vaporizers are made with materials with a ______ specific heat. Why?

A

High

- resists changes in temperature so resists evaporative cooling and delivers gas at a more constant concentration

30
Q

Thermal conductivity

A

-measures the speed at which heat flows through something; higher thermal conductivity the better the substance conducts heat

31
Q

Vaporizers are produced with materials with _____ thermal conductivity, why?

A

High

-to maintain a consistent temperature within the vaporizer

32
Q

What effect does altitude have on the barometric pressure?

A

(Inverse)

  • as altitude increases, barometric pressure decreases
  • as altitude decreases, barometric pressure increases
33
Q

Types of vaporizers

A
  • variable bypass
  • tech 6
  • cassette
  • injection
34
Q

How does a Variable bypass vaporizer work? How is it compensated?

A
  • has a bypass chamber and vaporizing chamber
  • portion of gas goes to vaporizing chamber to be saturated; another portion goes through the bypass chamber
  • a variable orifice at the inlet controls gas flow
  • vapor laden portion meets bypass portion to be diluted and delivered.
  • agent specific, temp pressure compensated

-this device uses:
pressure compensation mechanism
temperature compensation mechanism
split ratio to deliver a safe, consistent anesthetic vapor

35
Q

Pressure compensation mechanism

A
  • prevents major overdose
  • detects “pumping” or retrograde pressure in the system
  • does not allow it to create retrograde flow of gas into the bypass chamber
36
Q

Temperature compensation mechanism

A
  • prevents major underdose
  • metal that expands/shrinks in response to evaporative cooling
  • proportions the bypass chamber flow to the vaporizing chamber flow
37
Q

What two mechanisms control the concentration of volatile agent through the outlet

A

1) temperature compensation mechanism

2) concentration control dial

38
Q

What temperatures does the temperature compensating mechanism work in?

A

50-104 degrees F

10 - 40

39
Q

Factors that impact vaporizer output

A
  • extreme flow rates = underdose
  • temperature at boiling points
  • pumping effect = overdose
  • carrier gas composition (not clinically relevant)
  • barometric pressure = under/over
40
Q

How do extreme flow rates affect concentration of volatile anesthestic

A

-if you administer really high flow (>15L/min), and really low flow (<125mL/min) your v/v% may be slightly less than what you dialed in

41
Q

How does temperature at boiling point affect volatile anesthetic concentration?

A

-at the boiling point the volatile agent is moving into a gas too quickly, there is no control over it’s flow (~50 degrees C)

42
Q

How does the pumping effect affect volatile anesthetic concentration?

A

-this will result in a back flow of anesthetic vapor into the main inflow line increasing the concentration overall, resulting in massive overdose

43
Q

How does carrier gas composition effect the volatile agent concentration?

A

-if you add nitrous as carrier gas instead of oxygen, it is a little more soluable in liquid so it can increase concentrations

44
Q

How does barometric pressure affect the volatile anesthetic concentration?

A

At higher altitudes and lower barometric pressure, the partial pressure of the volatile agent will be a greater percentage of the barometric pressure.

45
Q

What are some potential vaporizer hazards?

A
  • wrong agent wrong vaporizer (high VP gas in low VP container = overdose + hypoxemic mixture; low VP gas in high VP container = underdose)
  • contamination (can cause bacterial growth)
  • tipping (overdose)
  • overfilling (overdose)
  • leaks (underdose)
  • pumping effect (overdose)
46
Q

In high altitudes do you have to make changes to a variable bypass vaporizer? Do you make changes in a tech 6?

A
  • no changes with variable bypass

- changes with tech 6

47
Q

Why do we need a Tech6 to give Des?

A
  • VP 669 (87%) at 1atm so need HIGH FGF to dilute des (not economic)
  • Des not very potent, requires MAC of 6.6% so has very fast evaporative cooling and requires constant heat source
  • Des boiling point 73 degrees at 1atm; will quickly boil and lose control of output
48
Q

Tech 6 vaporizer

A
  • electrically heated
  • pressurized
  • “dual gas” blender two independent gas circuits in parallel
49
Q

What two variables impact tech 6 vaporizer output?

A

1) Altitude: you have to deliver higher dialed desflurane than at sea level;
- (desired % at sea level)(760mmHg)/ (current barometric pressure)
Carrier gas: vaporizer calibrated to 100% oxygen
- lower O2 concentrations than 100% or nitrous as carrier gas can decrease output by 20%

50
Q

Aladin Cassette Vaporizers

used at georgetown

A
  • electronicallly controlled variable bypass unit in which the bypass circuit is within the anesthesia machine and the vaporizing chamber and circuit are within the cassette
  • color coded and magnetically coded for safety
  • some have warming fans that warm arm to decrease evaporative cooling effect
51
Q

Desflurane = ____

A

Blue

52
Q

Isoflurane = _____

A

Purple

53
Q

Sevoflurane = _____

A

Yellow

54
Q

What does the check valve do in a cassette vaporizer

A

-prevents against overdose by preventing retrograde pressure from O2 flush or retrograde flow by tipping etc.

55
Q

From what area does the CPU in the cassette vaporizer gather data

A
  • pressure and temperature sensors in the vaporizing chamber
  • flowmeters in the bypass chamber and vaporizing chamber
  • control dial set by the provider
56
Q

How does the CPU affect outflow of gas

A

-CPU will use the flow control valve to determine the amount of flow leaving the vaporizing chamber, dictating the percent of fresh gas saturated with volatile anesthetic at the outflow

57
Q

Safety mechanisms of the cassette vaporizer

A
  • electronic control of the carrier gas ratio
  • safety relief valve
  • when cassette removed from machine, valves close to prevent FGF loss
  • spill valve
58
Q

-Electronic control of carrier gas ratio

A

-prevents hypoxemic gas mixture

59
Q

Safety relief valve

A

-detects obstruction in system; cassette pressure up 2.5atm; valve opens

if desfluane boils; valve open up and allows pressure to escape into atm;

60
Q

Closing valves

A

-allows you to change cassettes during case

61
Q

Spill valve

A
  • prevents retrograde flow from tipping overfilling
62
Q

What happens in the desflurane cassette when desflurane boils?

A
  • when OR temp is higher than 73 degrees and pressure becomes higher in vaporizer chamber than bypass chamber, the one way check valve closes and does not allow any FGF into vaporizing chamber; CPU starts to inject desflurane
63
Q

What types of vaporizers does the Desflurane cassette function as?

A
  • variable bypass until boiling
  • switches to injector
  • controlled by CPU
64
Q

Injector Vaporizer

A
  • agent specific
  • electronically controlled
  • vaporizer output set by electronic interface on anesthesia machine
  • gas enters via drive gas inlet, pressurized liquid, moving it to injector
  • liquid injected into heat vaporizing chamber and monitored by microprocessor
  • injections continue in small amounts until desired volume is reached
  • gas analyzer downstream measures output
  • optical sensor in the chamber monitors integrity of injections

Intro to Anesthesia (15 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions