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What is the gas phase of a substance that is liquid at room temp and atmospheric pressure??
What is the conversion of a liquid to a gas??
Vaporization depends on what 3 things??
- 1. vapor pressure of agent
- 2. temp of environment
- 3. amount of carrier gas used (N20, Air, O2)
What is the saturated vapor pressure??
it is the pressure of the molecules that have broken away from the liquid inside a closed container to form a vapor
*pressure created when molecules "bombard" walls of the container
At a constant temp...what 3 things are true of the molecules in a vaporizer??
- 1. # molecules entering and leaving liquid are the same
- 2. # molecules in vapor phase stays constant
- 3. saturated vapor pressure is present (pressure created when molecules "bombard" the walls of the container)
What is a volatile anesthetic agent??
a liquid that has the tendency to change into a vapor at a standard temp and pressure
If an agent has a high volatility what can be said about the agent??
it has a stronger tendency to change into a vapor.. it has a higher Saturated Vapor Pressure (SVP)
What does Dalton's Law state??
Dalton's Law of Partial Pressure states that the PP of each gas in a mixture occupies a given volume as though it is alone -- other gases do not effect the pressure (each gas has its OWN pressure)
What increases SVP? what decreases it??
heat: more molecules enter gas phase, less molecules reenter liquid phase
cooling: less molecules enter gas phase, more molecules reenter liquid phase
What happens to the liquid as a carrier gas flows over the liquid??
decrease the SVP
it cools the liquid
What is required to continuously vaporize anesthetic agents and maintain constant SVP?
What is the temperature at which an agents vapor pressure is equal to the atmospheric pressure??
if low atmospheric pressure --- low boiling point
Denver has a very low pressure which makes agents have lower _______ which means you would need to do what to deliver a correct amount of vapor to the patient..
first blank - boiling point
therefore you need to increase the rate of your vapor administration to increase the SVP
What are two kinds of measured flow vaporizers?
copper kettle and vernitrol
What are two examples of a variable bypass vaporizer?
- Ohmeda Tec 4&5
- Drager 19.1 and 19.3
What vapor uses the Tec 6 to administer the vaporizer??
and what type of vaporizer is this??
What is the importance of the vaporizer interlock system?? (4)
- -It ensures that:
- 1. only one vaporizer is turned on at a time...you don't want to be given a patient two different anesthetics at the same time
- 2. gas will only enter the vaporizer that is on
- 3. vapor will not leak out when the vaporizer is off
- 4. vaporizers will be locked into the gas circuit, ensuring that they are seated on the machine correctly
How should you seat your vaporizers on your machine??
If you have two vaporizers on your machine.. put them side by side to ensure that only 1 vaporizer will release a vapor at a time.
--on some older machines, when you have a space between two different vaporizers, the vapors can leak from both vaporizers and even leak into eachother
What do baffles in a vaporizer do??
they compensate for pressure changes
What are the purpose of Wicks in a vaporizer???
Wicks provide an increased surface area for the vapor
increased surface area = increase # of molecules exposed
Name 5 differences between measured flow vaporizers and variable bypass vaporizers...
- measured flow variable
- -CG bubbles thru vs CG flows over agent
- -manual temp. conversion vs Auto adjusted temp
- -can use multi agents vs only one agent
- -operator determines CG split vs auto CG split
- -No longer used vs used often
Bypass chambers receive ____ flow with lower temps.
Bypass chambers receive ____ flow with higher temps.
If you were not using a vaporizer that automatically compensated for changes in temp and pressure what would you need to do to ensure the patient receives the correct amount of anesthetic if the temp and pressure of the vaporizer is decreased??
you would need to increase your flow so that your patient would receive the same concentration of the agent
you would do just the opposite if you have an increased temp and pressure -- decrease your flow to administer the same amount of the agent at a constant temp and pressure
What is contained within vaporizers that is used to compensate for changes in temperature??
bi-metallic strips -- two metals with very different coefficients of thermal expansion are fixed together to compensate for changes in temperature. The strips will bend with hot/cold temps
This is a very important concept to understand...
In a vaporizer, as the liquid turns into a vapor, ____ is lost, as the temp ____, vapor pressure _____, which means that there is ____ volatile agent for the carrier gas to take away. Without ____ the patient will wake up.
- 1. heat
- 2. decreases
- 3. decreases
- 4. less
- 5. heat
How does a blender vaporizer maintain a constant temp??
by electric... must be plugged in to maintain a constant heat
What temperature does the blender vaporizer stay heated to to maintain a constant temp?
and what is the atm pressure at this temp?
39 degrees Celsius
How long does it take for the blender vaporizer to get warm enough to operate??
- 10 mins..
- must be warmed or it will not work
- will stay warm as long as it is plugged in
- can leave plugged in all the time
Blender vaporizers.. the tec6 vaporizer is also know as.....
an injection vaporizer
bc a known amount of an agent is injected into the flow stream
On a Tec 6 what 4 things can a no output alarm mean??
- 1. less than 20ml of agent left
- 2. agent has been tilted > 10 degrees
- 3. Power failure
- 4. Internal malfunction
What does a low agent alarm mean on the tec 6 vaporizer??
There is less than 50cc of agent in the vaporizer
What is the boiling point of des??
22.8 degrees C
which is only slightly above room temp.
Des Tec 6 Vaporizer is different than the other vaporizers because....
- 1. it does not have a splitting ratio
- 2. it is a dual circuit -- the carrier gas and vapor do not mix till the very end
- 3. requires an external heat source
- 4. more des is required than other agents to anesthetize patient
- 5. absolute amount of des vaporized is much higher than other agents which would cause excessive cooling
The Tec 6 does not compensate for changes in _____.
- --The concentration of des is unaffected by elevation but the partial pressure decreases. At high elevations where the pressure is decreased, you must increase the concentration of the control dial to deliver equivalent partial pressures.
- --decreased pressure need more vapor!
Partial pressure =??
concentration x barometric pressure
Remember, ______ not ______ affects the brain.
partial pressure (or tension) not concentration affects the brain.
_______ concentration output can occur with low flows of gases other than oxygen due to changes in ______.
--ex.. vaporizer output is 20% less with nitrous than with oxygen
TAKE HOME----- may have to increase dialed concentration with low flow anesthesia
Hypobaric vs. hyperbaric
??? need to read more on this
If you don't have another vaporizer and it has been tilted what can you do to fix the problem??
turn on the vaporizer when not connected to the patient at very high flows to flush out vaporizer for 20-30 mins
List some causes of overdose of vapors:
- 1. tipping of vapor - more vapor in bypass area
- 2. vapor inadvertently turned on or never turned off from previous use
- 3. overfilled vaporizer
- 4. use of 2 vapors at the same time (machines without interlock system)
- 5. incorrect calculations with measured flow vaporizers
- 6. n20 flowmeter bobbin stuck at top of thrope tube
- 7. pumping effect
List some causes of inadequate doses of vapors:
- 1. o2 flowmeter bobbin or float stuck at top of Thorpe tube
- 2. disconnect that allows air to be entrained into breathing system
- 3. repeatedly using of flush valve diluting concentration
- 4. leak in bellows
- 5. empty vaporizer or leak in vaporizer
- 6. incorrect calculations
- 7. pressurizing effect
What color is a des bottle??
bottle is always amber with white label and blue writing
If you tip a vaporizer and flush it out using high flows, what should you monitor when using the vaporizer on a patient??
- monitor what they are exhaling..
- what they are exhaling is more important to tell you how much they are actually getting