Vaporizers

Vapor

vaporization

• 1. vapor pressure of agent
• 2. temp of environment
• 3. amount of carrier gas used (N20, Air, O2)

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

• 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)

a liquid that has the tendency to change into a vapor at a standard temp and pressure

it has a stronger tendency to change into a vapor.. it has a higher Saturated Vapor Pressure (SVP)

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)

heat: more molecules enter gas phase, less molecules reenter liquid phase


cooling: less molecules enter gas phase, more molecules reenter liquid phase

decrease the SVP


it cools the liquid

HEAT

Boiling point


if low atmospheric pressure --- low boiling point

first blank - boiling point

therefore you need to increase the rate of your vapor administration to increase the SVP

copper kettle and vernitrol

• Ohmeda Tec 4&5
• and
• Drager 19.1 and 19.3

Desflurane

Blender--injectable vaporizer

• -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

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

they compensate for pressure changes

Wicks provide an increased surface area for the vapor

increased surface area = increase # of molecules exposed

• 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

less flow

more flow

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

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

• 1. heat
• 2. decreases
• 3. decreases
• 4. less
• 5. heat

by electric... must be plugged in to maintain a constant heat

39 degrees Celsius

2 atm

• 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

an injection vaporizer

bc a known amount of an agent is injected into the flow stream

• 1. less than 20ml of agent left
• 2. agent has been tilted > 10 degrees
• 3. Power failure
• 4. Internal malfunction

There is less than 50cc of agent in the vaporizer

22.8 degrees C


which is only slightly above room temp.

• 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

barometric pressure

• --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!

concentration x barometric pressure

partial pressure (or tension) not concentration affects the brain.

decreased

viscosity

--ex.. vaporizer output is 20% less with nitrous than with oxygen

TAKE HOME----- may have to increase dialed concentration with low flow anesthesia

??? need to read more on this

turn on the vaporizer when not connected to the patient at very high flows to flush out vaporizer for 20-30 mins

• 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

• 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

bottle is always amber with white label and blue writing

• monitor what they are exhaling..
• what they are exhaling is more important to tell you how much they are actually getting