Vaporizers Flashcards
Vaporization
- changing liquid to gas
- molecules of volatile agent in closed container are in the liquid and gas phase
- gas molecules bombard surface of liquids and walls of container and create vapor pressure
Sevoflurane
160mmHg
Enflurane
172mmHg
Isoflurane
240mmHg
Halothane
244mmHg
Desflurane
669 mmHg
Vapor pressure
vapor pressure is dependent on temperature
liquids with high vapor pressures at room temp are Volatile
Latent heat of vaporization
of calories required to change 1 gram of liquid to vapor WITHOUT temp change
*1g=1mL
Energy for vaporization
vaporization is the change from liquid to gas
- if the energy to change states comes from the liquid
1. then liquid loses energy and the temperature of the liquid decreases
2. decreased temp of the liquid decreases the rate of vaporization - why we have a system to keep temp of liquid constant so rate of vaporization is not affected
Specific heat
of calories needed to increase the temp of 1 gram of substance( liquid, solid, or gas) by 1 degree celsius
**helps us design, operate and construct vaporizers
How concept of specific heat is applied to vaporizers
- tells us how much heat must be applied to liquid (loses energy when changing to gas) during vaporization to maintain a constant temp
- materials with high specific heat are used to manufacture vaporizers bc they are better at resisting the change in temp during vaporization
Thermal conductivity
rate at which heat passes through a specific material
higher the thermal conductivity, better the substance is at absorbing heat
Why is Thermal conductivity relative to the manufacturing of vaporizers
vaporizers are made of metals because they have a high thermal conductivity, they are able to absorb heat from environment or from liquid when it evaporated to a gas, maintaining a constant temp
Vaporizers
- key index safety system (KISS)
- agent specific
- temp compensated
- variable bypass chamber
Variable Bypass
- portion of gas flow passes into variable bypass chamber and be comes saturated with vapor
- then rejoins the gas flow to dilute vapor to a safe deliverable concentration
temperature compensating valve
- senses the temp in the system and bends right or left
- a bend to the Right occurs with a higher temp and allows more gas to escape and less to variable bypass chamber
- bend to the Left occurs with. a lower temp and allows more FGF down the variable bypass chamber to get saturated with vapor
Tec 6
-vaporizer specific only to desflurane
- *gas -vapor blender
- not a variable bypass chamber
-des is heated to 39 degrees celsius so we can pressurized it to 2 atm
(increased temp increased pressure)
-this is done bc des VP is 669mmHh which is very close to 1atm = 760 mmHg
when VP = atmospheric pressure boiling occurs
Copper Kettle
- out of circuit vaporizer
- NOT agent specific
- need to calculate vapor output and % concentration
- measured flow, bubble through
- dedicated flowmeter (measured flow)
Vapor output equation
Vapor Output =
CG x VP/ BP – VP
BP= atmospheric pressure VP= vapor pressure CG = carrier gas flow rate (this is what you can manipulate)
Anesthetic Concentration equation
% = Vapor output/ Total gas flow
*can manipulate total gas flow
How a copper kettle works
- measured flow -bubble through
- dedicated flowmeter just for kettle (measured flow)
1. gas comes up through central tube inside vaporizer to loving cup
2. gas flow forced down toward liquid (bubble through)
3. highly concentrated vapor then exits vaporizer and gets diluted by FGF
Altitude on vaporization
increased altitude decreased atmospheric pressure
decreased altitude increased atmospheric pressure
- Variable bypass vaporizers are independent to the atmospheric pressure change, depth of anesthesia given at dial setting remains constant
- this does not apply for Tec 6 (desflurane)
Altitude and Tec 6
*not a variable bypass chamber
New % = normal (dial setting) % x 760 / current atmospheric pressure
Potential hazards of Vaporizers
- Wrong agent in calibrated vaporizer
- high VP agent in lower VP vaporizer = overdose
- low VP agent in higher VP vaporizer = under dosed - Containment when open
- open and close as quick as possible
- reduce exposure to self
- dust/ particles can get in - Tipping
- Overfilling
- too high concentration
- fill to black fill line - Leaks
- check during machine low pressure check with negative pressure check using bulb suction - Pumping effect
- fluctuation in pipeline pressure (all Ors start at same time) - Administration of more than one vapor at same time
- Interlock system prevents this (cant open more than one vaporizer at a time)
