E3- Compressed Gases and Vaporizers Flashcards
PSI stands for
Pounds per square inch
Cylinder - primary vs emergency source
o Primary – used for transport
o Emergency – if pipeline fails + use tanks on back of machine
What are the colors of each gas?
o Oxygen = green
o Air = yellow
o Nitrous = blue
o Vacuum = white
- Define Non-Liquified gas.
- What were examples?
- gases that do not liquefy at ordinary ambient temperatures regardless of the pressure applied
- Oxygen
- Air
- Helium
A liquified gas can become a liquid at _________ temperature and at pressures from ____- _____psi
- ambient
- 25 to 1500 psi
What were examples of liquified gases?
- Nitrous oxide
- Carbon dioxide
What government agencies are involved with compressed gases used in the OR?
- FDA (purity of substance)
- DOT (marking, labeling, storage, handling)
- OSHA (employee safety)
- National Fire Protection Association
Name 4 components of the cylinder:
- Body
- Check Valve
- Handle
- Pressure Relief Device
What is the body of the cylinder made out of?
- Steel
- Steel Carbon Fiber
- Aluminum - for MRI
What kind of bases do the cylinders have?
- Flat Base
- Concave Base
What is the check valve of the cylinder made out of?
- Bronze
- Brass
What is the function of the valve on the cylinder?
- The valve is attached to neck of the cylinder
- allows refilling and discharge of gas
What is used to open/close the cylinder?
- Handle
- Handles should be attached to EVERY cylinder*
What component vents cylinder contents to the atmosphere if pressure increases to a dangerous level (overheating or filling)?
- Pressure relief device
- (Safety relief)
What is the Pin Index Safety System?
- Prevents crossover of the wrong tank into the wrong fitting
- Holes on cylinder valve positioned in an arc below outlet port
- Pins on the yoke or pressure regulator are positioned to fit into these holes
Oxygen = 2, 5 … Nitrous = 3, 5
What are 3 methods a pressure relief device works?
- Disc that bursts
- Fusible plug melts
- Valve opens + raises to let gas out or compresses a spring
How are cylinder sizes labeled?
What is the most common cylinder size on anesthesia machines?
- Letter code :: A-H
- A = smallest
- H = largest - for refilling smaller tanks
- E = most commonly on back of anesthesia machines
- D = for transport
What size cylinders are used for transport?
- Cylinder size D are used for transport
Pressure decreases as volume decreases .. with what type of gas ?
Non-Liquified
oxygen, air, helium
- what is the approx psi of cylinder?
- must remain ______. why?
- 45 psi
- closed - audible alarm that signals changing from wall to tank
Non-Liquified Gas
Pressure and volume when full?
Half full?
Quarter full?
Empty?
- 600 L @ 1900 psi
- 330 L @ 950 psi
- 165 L @ 475 psi
- 0 L @ 0 psi
- With liquified gas, pressure depends on what?
- the ___________ is not an indication of remaining ________________
- vapor pressure
- pressure ,, volume
Liquified Gas
What are the weight, volume, + pressure of nitrous oxide at….
* Full?
* Half Full?
* No liquid remaining (vapor only)?
* Nearly empty (no vapor either)?
- 20.7 lb ,, 1590 L ,, 745 psi
- 17.3 lb ,, 745 psi
- 14.2 lb ,, 250 L ,, 745 psi
- 14.1 lb ,, 125 L ,, 350 psi
PSI doesnt fall until nearly empty
What are the Department of Transportation (DOT) regulations for cylinders?
- Service pressure
- Test date
- Diamond shaped label indicating hazard of gas…danger, warning, or caution
- Name and address of manufacturer
- Expiration date of contents
Cylinder Standards: Valves, regulators, gauges never come into contact with what?
- Oil
- Grease
- Lubricants
Cylinder Standards: Never subject cylinder to temps above ______
- 54 C (130 F)
Cylinder Standards: Never cross use what?
- Hoses
- Regulators
- Gauges
Cylinder Standards: What must not be altered?
- Original Markings on Cylinder
- Original Labels
Cylinder Standards
- connections always ______
- cannot be ________
- valve kept ______ at all times
- properly ________ to revent fall
- tight
- dropped, drug, slid
- closed
- secured
Associate the color with gas:
Green
Blue
Yellow
White
- Green = Oxygen
- Blue = Nitrous
- Yellow = Air
- White = Suction
Describe the 6 conditions of storage rooms for cylinder tanks.
- Adequate ventilation
- “No smoking,” or “No Combustibles” signs
- Cylinders are not exposed to corrosive chemicals, fumes
- Stored upright in bins
- Full tanks separated from empty tanks
- Do not wrap or drape cylinders
8 things to consider prior to using gas cylinders.
- Inspect label, pin index holes, regulator, valve outlet
- Check if tamper seal is removed
- Check if washer is in place
- Open the valve to relieve excess pressure before bringing cylinder to pt
- Face valve outlet away from people
- open slowly
- Check service pressure
- Correct leaks
Pipeline systems are used to deliver what kind fo gas?
Non-flammable gases
nitrous, oxygen, air
What are the 3 components of pipeline systems?
- central supply
- piping - receiving at 50 psi
- terminal units - maintains approx 50 psi
Where are possible locations for the Central Supply?
- Outdoors in an enclosure
- Indoors in secure area
A Central Supply “bank” must contain gas for at least how many days?
- 2 days
What cylinder size would an oxygen bank be?
- G and H cylinders
Differentiate between a gaseous and liquid oxygen supply source.
- Gaseous supply = contained in large G/H cylinders + refilled on-site or transported
- Liquid supply = less expensive and more convenient to store, refilled by supply trucks, service not be interrupted
What are the 3 classes of piping?
- Main lines = connect gas source to risers
- Risers = vertical pipes connecting main line with branch lines on each level of the facility
- Branch = sections supplying a room or group of rooms on one level of the facility (horizontal)
Permit specific areas of the piping system to be isolated for problems /maintenance.
- Shut-off Valves
The area alarm system must be in at least how many places?
What places will have the gas alarm system?
- 2 places
- The affected unit, critical life support area, maintenance, engineering
The area alarm system will be triggered if pressure increases/decreases ____ % from normal.
- 20%
Area system alarm must be ________ AND ________.
- audible
- visible
What are terminal units?
- Point in piped gas distribution where user connects and disconnects by hose
What safety system does the terminal unit use?
- Diameter Index Safety System (DISS)
- “quick connects”
DISS = Nipple and nut vary in bore and diameter
differentiate bw PISS + DISS
PISS = cylinders :: hanger yoke pins + holes
DISS = terminal wall units :: nipple + not vary in bore + diameter
What allows convenient connection with one/both hands to terminal units?
What is the drawback to this?
- Quick Connectors
- Drawback: Quick Connectors leak more
Where are possible locations for Quick Connects?
- Wall
- Ceiling -mounted
- Ceiling column
Define Vaporizer.
- A device that
- changes a liquid anesthetic agent to a vapor
- adds controlled amt of vapor to FGF breathing system
Volatile anesthetics exist in a liquid state below what temperature?
- 20C (68F)
- In a closed container, molecules escape liquid to __________ phase.
- These molecules borbard container walls + create _____________________
- Vapor
- vapor pressure
What is saturated vapor pressure (SVP)?
- When equillibrium is achieved bw liquie + vapor phase @ constant temp … from molecules hitting walls of container
- Gas phase above liquid contains all the vapor it can hold
- highest amt of vapor pressure
Saturated Vapor Pressure
What is SVP dependent on?
What is SVP independent of?
- characteristics + temperature of liquid
- atmospheric pressure - altitude does not change vapor pressure
Part of the total pressure of any one gas in a mixture
Partial pressure
State Dalton’s Law
- Sum of Partial Pressure = Total Pressure
- Part of the total pressure of any one gas in a mixture
Partial pressure is dependent on _______.
NOT dependent on ___________
- Temperature
- atmospheritc pressure
The concentration of a gas in a mixture expressed as a percentage
- Volume percent
Formula for volumes percent
Partial Pressure / Total Pressure = vol percent
Vapor pressure is independent of _______
- Atmospheric Pressure (Barometric Pressure)
Vapor pressure is dependent on ________
- Characteristics of liquid
- Temperature of liquid
Vapor Pressure of Fluothane
- 243 mmHg
Halothane
Vapor Pressure of Forane
- 238 mmHg
Isoflurane
Vapor Pressure of Suprane
- 669 mmHg
Desflurane
Vapor Pressure of Ultane
- 157 mmHg
Sevoflurane
What are the trade names for Halo, Iso, Des, + Sevo?
- halo = fluothane
- iso = forane
- des = suprane
- sevo = ultane
%%%
The temperature at which vapor pressure equals to atmospheric pressure.
- Boiling point
Which volatile anesthetic has a vapor pressure almost equal to atmospheric pressure?
- Desflurane (Suprane)
- Boiling point of Desflurane 22.8C (73F)
Define Heat of Vaporization
The number of calories necessary to convert 1 gram of liquid into vapor (or 1 mL of liquid to vapor).
What happens to the liquid temperature and vapor pressure as carrier gas flows through the vaporizer, causing the vapor molecules to leave?
- Liquid temperature drops»_space; vapor pressure drop
- > > equilibrium shift - more molecules in a liquid state
- > > Output vapor decrease
More heat needed to increase vapor out - Vapor p dependent on temp
Define specific heat
Number of calories required to raise the temperature of 1 g of a substance 1 degree C
The higher the specific heat, the __________ heat required to raise the temp of the substance
more
Specific Heat of Water
1 cal/g
The Standard
- Specific heat is considred when choosing ________ for vaporizer.
- Material with higher specific heat minimizes _________.
- material
- Temperature Variation
Define thermal conductivity
The ‘speed’ at which heat flows through a substance
The _________ the thermal conductivity, the better the substance conducts heat
higher
Metals with high thermal conductivity minimize ____________ during vaporization.
Examples??
- temperature swings
- Copper + aluminum
- Copper and Aluminum have the best thermal conductivity
A device that changes a liquid anesthetic agent to a vapor and adds a controlled amount of that vapor to fresh gas flow in the breathing system.
- Vaporizer
Modern vaporizers are
_________-calibrated and _______ bypass.
- Concentration
- variable
Where is the vaporizer located?
- Between flow meter and common gas outlet
Where can a caporizer NOT be placed? Why?
after common gas outlet ,
bc not calibrated for high flows of oxygen flush
What happens if the vaporizer is before the flow meter?
What happens if the vaporizer is after the common gas outlet?
- Carrier gas will be on the wrong side and will not be able to pick up adequate vapor molecules
- There will be less stability and flow of vapor molecules delivered to the patient
What regulates the concentration of the volatile in the vaporizer (variable bypass)?
- The concentration dial
What is the splitting ratio?
ratio depends on size of adjustable orfice (hole)
* determines how much FGF bypaasses or goes into vaporizer chamber
What makes up the splitting ratio?
-
Vaporizing chamber flow rate
* Bypass pathway flow rate
Higher splitting ratio means more flow will go through vaporizing chamber, higher anesthetic gas delivery.
What are the two types of vaporizers?
- Flow-over (modern) - wicks
- Bubble through (older)
%%%%%%%%%%
Why is desflurane heated in the vaporizer when its boiling point is at room temperature?
- There is a lot of variability at room temperature.
- Desflurane is heated to a precisely controlled temperature and stable vapor phase.
- The heated vapor is then “injected” into the fresh gas flow to deliver a precise anesthetic concentration.
- in modern vaporizers, there are electronic temperature _______.
- what changes as temperature changes?
- ____________ temperature leads to more vapor amt
- sensor
- splitting ratio nchanges as temperature changes
- high
What are 8 vaporizer hazards?
- Placing incorrect agent in the vaporizer
- FGF Flow Rate
- Pumping Effect
- Effects of Rebreathing
- Barometric Pressure
- Tipping
- Overfilling
- Leaks
Why is placing the incorrect volatile agent in the vaporizer unlikely?
- Filling systems are agent-specific
- each type has different “key” hole for each gas type
- monitor will show 2 different vapors
How do you fix this issue if you somehow get the wrong agent in the vaporizer?
- Vaporizer must be completely drained, and all liquid discarded
- Run FGF at 8-10 L/min until no vapor is detected
The monitor will detect 2 vapors if incrorect agent is added to the vaporizer
What does FGF have to be between to have no vaporizer problems?
250 mL/min – 15 L/min
What happens to the vaporizer output if the flow rate is less than 250 ml/min?
- vaporizer Output < setting
- High density of volatile prevents upward movement of molecules
What happens to the vaporizer output if the flow rate is greater than 15 L/min?
- vaporizer Output < setting
- Failure to saturate carrier gas
What are two common causes of the anesthesia machine’s intermittent back pressure (pumping effect)?
- Positive Pressure Ventilation
- Oxygen Flush Valve
The pumping effect is more pronounced with:
- Low flow rates
- Low dial settings
- Low levels of liquid in the vaporizing chamber
What problem does the pumping effect have on vaporizer output?
- Inconsistency in maintaining alveolar pressure of anesthetic vapors
Negate the pumping effect by maintain adequate flow rate and dial setting
What object in the anesthesia machine fixes/inhibits the pumping effect?
- Machine Outlet Check Valve
What are 4 measures to attenuate the pumping effect besides the machine outlet check valve?
- Smaller vaporizing chamber
- Baffle system
- Longer tube for the inlet of the vaporizing chamber
- addition of check valve
Effects of rebreathing with high FGF?
Effects of rebreathing with low FGF/high Vm?
- Little exhaled gas rebreathed
- Significant rebreathing with low FGF
Remember :: vapor pressure is _________ of barometric/atm pressure
independent
Vaporizers are ALWAYS calculated at __________
- sea level (760 mmHg)
Unless requesed to be another level - denver
%%%
Why will an increase in altitude not affect the delivery of Isoflurane or Sevoflurane?
- Isoflurane and Sevoflurane are not pressurized. They operate as a function of atmospheric pressure.
- At sea level, atm = 760 mmHg. This pressure keeps molecules down in the liquid phase.
- So, in higher elevations, there will be less atmospheric pressure. Which means more molecules can escape as a gas.
- The decrease in atmospheric pressure and the increase in the volume percent of gas will equal the partial pressure of gas delivered at sea level.
- Refer to the math below or watch the YouTube link.
- https://www.youtube.com/watch?v=UgViWCNVgOA&ab_channel=CountBackwardsFrom10
Why is altitude increase controversial?
- volumes % increase significtnly
- partial pressure changes lesser
- anesthetic dpeth is partial pressure in brain
How does tipping affect vaporizer output?
Fix?
what type of vaporizer isolates vaporizer + bypass chamber with transport dial?
- There will be an excessively high output due to liquid entering the bypass chamber
- hook up to FGF + dry it up
- drager
What problem is seen when liquid enters bypass chamber + excess dose delivered to pt? Now fixed with preventative design.
Overfilling
Vaporizer leaks can be caused by:
- Loose filler caps
- Drain valves
- Vaporizer/mounting bracket interface
What would be indicators of vaporizer leaks?
- Odor of gas
- Lower than expected inhaled concentration (Fi)
What will be the patient consequence of a vaporizer leak?
- Patient awareness
What are 5 vaporizer safety standards?
- Average concentrations +/- 20% of setting
- Gas may not pass through more than 1 vaporizer - INTERLOCK
- Output of vaporizer <0.05% in OFF
- All control knobs counterclockwise
- Filling levels displayed
What are 4 mounting standards of the vaporizer?
- Detachable
- Weight of vaporizer and “O” ring creates seal
- Locking lever on the back
- Easily removed and replaced (especially for MH)
What prevents more than 1 vaporizer from being turned on at a time?
- Interlock Device
