Gas systems and Vaporizers Flashcards
Thermal conductivity
a measure of speed with which heat flow through a substance
*higher thermal conductivity, the better the substance conducts heat
PISS for Oxygen
2-5
Isoflurane (20°C)
240 mmHg
Critical temp of O2
- 118.6°C
- bc ambient/room temp (20C) is above oxygens CT, it CANNOT be stored as liquid, no matter how much pressure we apply.
- HOWEVER, the main supply of oxygen in a hospital is in liquid oxygen stores. The containers are insulated from the outside and the temp is kept at -160C.
- ie: ambient temp is below O2’s CT, so if you apply enough pressure, you can make it a liquid.
Enflurane Vapor pressure (20°C)
172 mmHg
Changes in altitude
Increase altitude, decrease barometric pressure
decrease altitude, increase barometric pressure
Gas/tank color blue
Nitrous oxide
Latent heat of vaporization
Number of calories required to change one gram of liquid into vapor without a temperature change
- the energy comes from the liquid itself or an outside source
Halothane (20°C)
244 mmHg
Changes in altitude
Increased altitude, decreased barometric pressure, increased concentration of inhaled gas put out through vaporizer
Safe handling of cylinders
- never stand cylinder upright without support
- never leave empty cylinders on the machine
- lever leave the plastic tape on the port while installing the cylinder
- never rely only on the cylinder’s color for id of contents
- never oil valves
- “crack” the valve first to remove particles of dust or other crap.
- valve should always be fully open when a cylinder is in use
gas/tank color yellow
air
Vaporization
Conversion of a liquid to a gas
molecules combard the surface of the liquid and the walls of the contaner creating a vapor pressure
Dependent on:
- vapor pressure
- temperature
- amount of carrier gas used
Cylinder tag
Gas/tank color brown
Helium
Nitrous oxide:
liters
pressure
1590 L
750 psi
copper kettle
- measured flow, bubble through
- dedicated flowmeter for kettle
- gas comes up through central tube inside vaporizer to the loving cup
- flow of gas is then directed down toward the liquid (bubble through)
- highly concentrated vapor then exits the vaporizer and is diluted into the fresh gas flow
Air cylinder:
liters
pressure
625 L
1800 psi
Changes in Altitude- Effects on Vaporization
- vaporizers must be re-calibrated to assure accurate % delivered aneestheic gas
- the % delivered is relative to the agent’s vapor pressure in comparison to the barometric pressure:
Vapor pressure
barometric pressure
Gas/tank color grey
CO2
Altitude effect on Vaporizers
(variable bypass vs TEC 6)
Variable Bypass
- effect is that you are delivering a higher concenration of volatile agent at higher altitudes (lower barometric pressure), but maintaining the same partial pressure
- automatic
TEC 6
- Effect is that you would have to deliver higher dialed concentration of Des at higher altitude/lower baro pressure
-
you would alter your concetraiton dial to decrease output in lower altitude to avoid delivering overdose of anesthetic
- you must change the concentration dial
Vapor pressure
Caused by the gas molecules hitting the surface of the liquid and the walls of the container
Oxygen cylinder:
liters
pressure
625 L
2000 psi
PISS for CO2
1-6
Desflurane (20°C)
669 mmHg
variable bypass vaporizer
- a portion of the gas flow will pass into the vaporizing chamber where it will become saturated with vapor
- vapor-laden portion then rejoins the gas flow for dilution to deliverable concentrations
- altitude effect: deliver a higher concentration at higher altitued/lower barometric pressure but mainain same partial pressure
DOT permanent markings
- serial number
- service pressure in psig
- manufacturer and serial number
- “SPUN” indicates the end of cylinder was closed by a spinning process
- initial qualifying date
- ”+” indicates cylinder is authorized for charging up to 10% above marked service pressure.
- Star indicates cylinder may be retested every 10 years instead of 5
critical temp of N2O
36.4°C
- bc abient room temp (20C), is below N2O’s CT, it can be liquified with enough pressure applied to it
- that’s why we store N2O at room temp as liquid under 745psi (in the cylinder)
Sevoflurane (20°C)
160 mmHg
PISS for air
1-5
potential vaporizer hazards
- wrong agent in the vaporizer
- contamination- close lid quickly to keep crap out
- tipping
- overfilling
- simultaneous admin of more than one vapor
- leaks
- pumping effect- sputtering, like when sinks are off and turned back on again.
Specific heat
The number of calories required to increase the temperature of one gram of a substance one degree C
*can be liquid, solid, or gas
specific heat of an anesthic agent indicates how much heat must be added in order to maintain a constant rate of vaporization
boiling point
when vapor pressure = barometric pressure
PISS for Nitrous oxide
3-5
Cylinder labels
- hazard class
- type of gas
- statement of hazard and measures to avoid injury
gas/tank color green
(international white)
Oxygen
Temperature and vaporization
direct relationship
increased Temp, increased vaporization
critical temperature
the temp above which a gas cannot be made into a liquid no matter how high the pressure
** a gas CANNOT be liquified if the ambient temp is greater than the cricital temp (ex: oxygen: CT -118C)
** A gas CAN be liquified if the ambient temp is below the cricical temp (ex: Niitrous Oxide: CT 36.5C or 39.5C depending on slide)
TEC 6
- special vaporizer for desflurane
- “atmospheric pressure” within vaporizer increased to 2 atm by using heat (39C)
- requires a plug, will feel warm compared to other vaporizers
- altitude effect: you have to deliver higher dialed concentration of Des at higher altitude.
Gas/tank color black
Nitrogen
DISS
Diameter index safety system
- provides non-interchangeable connections for the medical gas lines
- consists of body, nipple, and nut
- only properly mated parts will fit together and allow the threads to engage
- required on every anesthesia machine.
PISS for heliox
2-4
Regulatory Agencies (3)
- FDA- enforces purity of medical gases
- United States Pharmacopoeia- specifies purity of medical gases
-
Department of Transportation- establishes requirements for medical gas cylinders and containers
- manufcturing
- filling
- qualification
- transportation
- storage
- handling
- maintenance
- re-qualification
- disposition
- labeling
