Exam 3- Compressed Gases and Vaporizers (7/10/23) Flashcards
PSI stands for
Pounds per square inch
What were examples of gases that do not liquefy at ordinary ambient temperatures regardless of the pressure applied?
- Oxygen
- Nitrogen
- Air
- Helium
A liquified gas can become a liquid at ambient temperature and at pressures from ____- _____psi
- 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)
- Department of labor/ OSHA (employee safety)
- National Fire Protection Association
Name the 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
What kind of bases do the cylinders have?
- Flat Base
- Concave Base
What is the valve of the cylinder made out of?
- Bronze
- Brass
What is the function of the valve on the cylinder?
- The valve is attached to the neck of the cylinder and allows refilling and discharge of gas
O2 tanks are now refilled away from the facility.
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
Pressure relief device can be a disc or a plug.
What is the Pin Index Safety System?
- Pins protrude from yokes and fit corresponding holes in the cylinder valves, providing a mostly “fool-proof” way of connecting the appropriate gas to the appropriate valve.
How are cylinder sizes labeled?
What is the most common cylinder size on anesthesia machines?
- A (smallest) to H (largest)
- Cylinder size E on anesthesia machines
What size cylinders are used for transport?
- Cylinder size D are used for transport
What is the content and pressure of a full oxygen tank on an anesthesia machine?
- 600 L
- 1900 - 2200 psi
Non-liquefied gases: Pressure decreases as volume decreases. Half the volume, Half the psi.
For liquefied gases, the pressure depends on ______. This makes pressure NOT an indication of remaining volume.
- Vapor Pressure
Note the full and half tank of Nitrous, but tanks have a pressure of 745 psi. Pressure is not an indicator of volume for liquefied gase.
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
Associate the color with gas:
Green
Blue
Yellow
White
- Green = Oxygen
- Blue = Nitrous
- Yellow = Air
- White = Suction
Describe the 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
Things to consider when 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 (slowly) to relieve excess pressure before bringing the cylinder to pt
- Face valve outlet away from people
- Check service pressure
- Correct leaks
How do oxygen, nitrous, and air get delivered throughout the hospital?
- Pipeline Systems
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 oxygen supply is contained in large G/H cylinders, refilled on-site or transported
- Liquid oxygen supply is less expensive and more convenient to store, refilled by supply trucks, service can not be interrupted
What are the three 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
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)
DISS = Nipple and nut vary in bore and diameter
PISS for cylinders
DISS for wall units
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
Volatile anesthetics exist in a liquid state below what temperature?
- 20C (68F)
In a closed container, molecules escape liquid to __________ phase.
- Vapor
What is saturated vapor pressure (SVP)?
- When vapor molecules bombard a closed container until it has reached an equilibrium of the liquid’s surface.
- Gas phase above liquid contains all the vapor it can hold
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 _______.
- Temperature
The concentration of a gas in a mixture expressed as a percentage
- Volume percent
Partial Pressure / Total Pressure =
- Volume percent
Vapor pressure is independent of _______
- Atmospheric Pressure (Barometric Pressure)
Vapor pressure is dependent on ________
- Characteristics of liquid
- Temperature of liquid
Vapor Pressure of Halothane (Fluothane)
- 243 mmHg
Vapor Pressure of Enflurane (Ethrane)
- 175 mmHg
Vapor Pressure of Isoflurane (Forane)
- 238 mmHg
Vapor Pressure of Desflurane (Suprane)
- 669 mmHg
Vapor Pressure of Sevoflurane (Ultane)
- 157 mmHg
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)
The number of calories necessary to convert 1 gram of liquid into vapor (or 1 mL of liquid to vapor).
- Heat of Vaporization
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, causing vapor pressure to drop
- There will be an equilibrium shift, more molecules in a liquid state
- Output of vapor will decrease
More heat will be needed to increase vapor output.
Vapor pressure is dependent on heat (temperature).
Number of calories required to raise the temperature of 1 g of a substance 1 degree C
- Specific Heat
The higher the specific heat, the more heat required to raise the temp of the substance
Specific Heat of Water
The Standard
Material with higher specific heat minimizes _________.
- Temperature Variation
The ‘speed’ at which heat flows through a substance
- Thermal Conductivity
The higher the thermal conductivity, the better the substance conducts heat
Metals with high thermal conductivity minimize ____________ during vaporization.
- temperature swings
- 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 variable bypass.
- Concentration
Where is the vaporizer located?
- Between flow meter and common gas outlet
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 makes up the splitting ratio?
- Vaporizing chamber flow rate
- By pass 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)
- 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.
What factors can influence vaporizer output?
- Placing incorrect agent in the vaporizer
- 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
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 happens to the vaporizer output if the flow rate is less than 250 ml/min?
- Output will be less than 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?
- Output will be less than setting
- Failure to saturate carrier gas because the carrier gas is too fast.
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 counters the pumping effect?
- Machine Outlet Check Valve
What are 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
Effects of rebreathing with high FGF
Effects of rebreathing with low FGF
- Little exhaled gas rebreathed
- Significant rebreathing with low FGF
Vaporizers are calculated at __________
- sea level (760 mmHg)
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
How does tipping affect vaporizer output?
- There will be an excessively high output due to liquid entering the bypass chamber
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
What will be the patient consequence of a vaporizer leak?
- Patient awareness
What are vaporizer safety standards?
- Average concentrations +/- 20% of setting
- Gas may not pass through more than 1 vaporizer
- Output of vaporizer <0.05% in OFF
- All control knobs counterclockwise
- Filling levels displayed
- Can’t overfill when in use
What are the 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
