Vaporizers are included in this part of the gas distribution system?
Low pressure
List the vaporizer functions
–Change liquid anesthetic into vapor
–Deliver set dosage
–Deliver consistent concentration of agent vapor into anesthetic gas mixture
A __________ is an instrument designed to change a liquid anesthetic agent into its vapor and add a controlled amount of this vapor to the fresh gas flow
Vaporizer
What is the partial pressure of an agent in vapor phase?
Vapor pressure
The boiling point of a liquid is what?
The temperature at which vapor pressure equals atmospheric pressure
What is the amount of heat (calories) required to convert 1 g of liquid agent to a vapor?
Heat of vaporization
The speed at which heat flows through a substance is what?
Thermal conductivity
Vapor pressure is dependent on what 2 factors?
Temperature and liquid (substance)
True or False: Currently there are no ideal inhalational anesthetics
TRUE
For a blood/gas partition coefficient, the higher the number means ________
It is more potent because it wants to stay in the blood
For a oil/gas partition coeffecient, the _______ the number means more of the agent wants to stay in the tissue
higher
What is isoflurane’s VP, Blood/gas coefficient, and MAC values?
238 vp
- 36 blood/gas
- 15 MAC
What is sevoflurane VP, Blood/gas coefficient, and MAC values?
157 vp
- 6 blood/gas
- 05 MAC
What is desflurane VP, Blood/gas coefficient, and MAC values?
669 vp
0.45 blood/gas
6 MAC
Which anesthetic agent is the most potent?
Isoflurane
Which anesthetic agent is least potent?
Desflurane
T or F: More potent means the agent has slower onset and means slower it comes off
TRUE
What are the 2 effects of intermittent back pressure?
Pumping effect– increases vaporizer output
Pressuring effect– decreases vaporizer output
What is vaporizer formula?
Fa = Qv x Pa / (Pb - Pa) x Qt
What is percent of Isoflurane when fresh gas flow is 2L (Carrier gas flow is 100mL)
Pb= 760 Pa=240 Qt=2000 Qv= 100
Fa= 100 x 240 / (760-240) 2000
Fa= 0.023
2.3%
What device on vaporizer ensures that only one vaporizer can be used at a time.
vaporizer interlock
What are the 2 main purposes of the vaporizer manifold
–Provides places where vaporizers are mounted on the machine
–Provides passageway for fresh gas flow
The first vaporizer was?
Ether inhalation–rag soaked in ether and then placed over patients nose and mouth
Done by Dr. Crawford Long in 1842
T or F: Do you have to dilute a copper kettle?
TRUE
T or F: All the gas passes through a copper kettle
FALSE
Are modern vaporizer’s part of the breathing circuit (in circuit) or are they not part of the actual breathing circuit (out of circuit)
Out of circuit
Classification of modern vaporizers.
- Variable bypass
- Flow over
- Temperature compensated
- Agent specific
- Out of circuit
Tec 5 vaporizers can hold approximately how much liquid anesthetic and how often do they need to be recallibrated?
~300 ml
Every 3 years
How do Tec 6 vaporizers differ from the rest of the vaporizers?
Injection
What is main difference from Tec 5 to the Tec 7 vaporizers?
Filling configurations include agent specific funnels or Easy-fil adapters
Which anesthesia machine uses the aladin cassette vaporizers?
Aisys
What color is associated with isoflurane?
purple
What color is associated with sevoflurane?
Yellow
What color is associated with desflurane?
Blue
Why is it that the Tidal Volume you set is never what is actually delivered to the patient?
The circuit itself holds compliance
What are the circle system components?
CO2 Absorbent, Reservoir Bag, Bag/Vent Switch, Ventilator, Pressure Gauge, Gas monitor sensor
airway pressure monitor, CO2 Absorbers, respirometer, Unidirectional Valve
Inspiratory / Expiratory Ports, Breathing Tubes
Y-piece, Fresh Gas inlet, APL Valve
What is the function of the CO2 absorbent and what are the main types?
Neutralize carbonic acid
Soda lime (primary) and barium hydroxide lime
What are 3 CO2 absorbent properties?
Granule size (smaller granules have high absorptive surface area)
Hard (prevents dust formation)
Moistness (Dry granules will absorb and degrade volatile anesthetics more)
When do you need to change the CO2 absorbent?
When you see FiCO2 in the inspired gas
Color change from white to purple
Heat in the cannisters (reaction with CO2 produces heat)
T or F: Tube length doesn’t affect dead space because of unidirectional gas flow
TRUE
On the Y-piece what size connectors lead to the breathing tubes?
22 mm
On the Y-piece, what size connector leads to the ETT tube?
Female 15 mm
Name 2 functions of the APL valve
Controls pressure in breathing system
Releases gases to scavenging system
Explain fresh gas flow when using low flows
Require CO2 absorber
Vary O2 & anesthetic concentrations
Prolong induction & recovery
Explain fresh gas flow when using high flows
> 5 L/min don’t require CO2 absorber
Accelerate induction & recovery
Compensate for circuit leaks
Decrease unanticipated gas mixture risk
Resistance is increased in the circuit by what?
Unidirectional valves
CO2 absorber
Coaxial tubings
No matter how long the circuit is, the dead space remains the same as long as you have __________ flow
unidirectional
T or F: When flow becomes bidirectional, then dead space will increase
TRUE
What gases is in the reservoir bag?
Expired gas including CO2 because hasn’t been scrubbed yet by CO2 absorber
When does CO2 get absorbed?
Just before inhalation, just prior to mixture with fresh gas flow
Define scavenging
Collection of excess gases from equipment used to administer anesthesia or exhaled by the patient & the removal of these gases to an appropriate place of discharge outside the work environment
What are the parts of the scavenging system?
- Gas-collecting assembly (collects excess gases)
- Transfer tubing (carries collected gas to interface)
- Interface (Provides positive and negative pressure relief)
- Gas-disposal tubing (carries gas from interface to disposal system)
- Gas-disposal system (discharges gases)
The gas collecting assembly uses what size outlet connection?
30 mm
Transfer tubing uses what size connection fittings?
19 mm inlet
30 mm outlet
What is the main function of the interface?
Prevents pressure increases/decreases in scavenging system from being transmitted to breathing system or ventilator
Features of an open interface
Has 1 or more openings to the atmosphere
Contains no valves
Used only with active disposal
Reservoir needed to hold gas surges
What is the design of an open interface scavenging system?
- Parallel tubes inside canister (1 carries waste gases to bottom of canister, 1 carries gases from bottom to disposal system)
- Open ports at top of canister provide positive and negative pressure relief
- Flow control valve regulates scavenging flow
What are the features of the closed interface system?
Connects to atmosphere through valves
Positive pressure valve required
Negative pressure valve required only if active scavenging
Reservoir not required
T or F: Passive disposal systems have piping directly to the atmosphere
TRUE
What is the gas that cannot be absorbed by passive disposal systems?
N2O (nitrous oxide)
An open interface should only be used with what type of gas disposal?
Active
What is always required with a closed interface?
Positive pressure relief valve
What gas can not be absorbed?
Nitrous
What is always required with an active duct system?
Negative pressure relief valve
Positive pressure relief valve
What colors are associated with scavenging?
Purple and yellow
Which CO2 cannister will you change out first, the top or the bottom?
TOP
Why do you change out top cannister first?
Because flow starts are top and distributes down
What is the fresh gas inlet?
Where fresh gases with/without anesthetics enter the breathing circuit
Name some functions of the reservoir bag?
Allows gas to accumulate during exhalation
Provides method for generating positive-pressure vent
Provides way to monitor spontaneous respiration
Protects pt from excessive pressure in breathing system
What is the gas called that pushes the bellows down during __________?
Drive gas
Inspiration
What is the primary gas that pushes the bellows up during __________?
Patients expiratory breath
Expiration
What does the repirometer measure?
Ventilatory volumes
What are the circle system design objectives?
Maximize inclusion of fresh gas
Maximize venting of alveolar gases
Minimize absorbent dessication
Minimize absorbent consumption
Provide accurate repirometer readings
List the order of the circuit system from patient expiration to when the gas gets the inspiratory limb (spontaneous breathing)
Pt lungs, Y-piece, Expiratory limb, expiratroy check valve, reservoir bag until full, excess flows out APL valve
AT START OF INSPIRATION
Reservoir bag, CO2 canister, fresh gas inlet, inhalation check valve, inspiratory limb, Y piece, Pt lung
List the order of the circuit system from fresh gas inlet to fresh gas inlet when on mechanical ventilation
Fresh gas inlet, inhalation check valve, Inspiratory limb, Y-piece, pt
During expiration
Y-piece, expiratory limb, exhalation check valve, Ventilator (bellows), CO2 canister, Fresh gas inlet
What is the difference in the drager circle system and datex circle system?
Drager has piston ventilation, so patients expiration does not push bellows up during mechanical ventilation. FRESH GAS FLOW FILLS THE PISTON IN DRAGER
Name the advantages of the circle system
Economy
Reduced OR pollution / reduced environmental pollution
Good estimation of anesthetic agent uptake / O2 consumption
Heat and humidity conservation
Reduced barotrauma risk
What are the disadvantages to the circle system?
Larger overall circuit size / increased complexity
Less portable
Increased resistance
Canot predict inspired gas concentrations with low FGF
Faster absorbent exhaustion
Hypercarcbia risk
What are the main locations for gas collecting assemblies?
Breathing systems
Ventilators
Respirtory gas monitor
Leak sites
What organization is responsible for the standards associated with scavenging?
ASTM
American society of testing and materials
Open interface can only be used with what type of disposal?
Active disposal
All of the following are true about closed interface except:
A) Positive pressure relief valve always required
B) Negative pressure required only with active disposal
C) Reservoir not required
D) All are true
D) all are true
With a passive disposal system, what type of interface should be used?
A closed interface with only positive pressure relief
T or F : With passive disposal system, the negative pressure relief valve is always closed
TRUE
What are the advantages of passive disposal ?
Simpler
Less expensive
What are some disadvantages to passive disposal?
Not as effective in lower trace gas levels because positive pressure promotes outward leaks
What are some advantages to active disposal?
More effective at keeping pollution levels low
Allows small bore tubing
No excessive resistance
Aid in room air exchange
What are some disadvantages to active disposal?
Expensive
Not automatic
More complex
Requires interface to have negative pressure relief
What is the size of the waste gas reservoir bag?
3 L
