Anesthesia Machine Flashcards
1
Q
What signifies a failed low-pressure leak test?
A
A bulb is attached to the common gas outlet and squeezed to create negative pressure. If bulb reinflates in less than 10 seconds
2
Q
How much negative pressure should be created for the negative pressure test?
A
-65cm H2O
3
Q
Should the vaporizer be on or off during the low-pressure leak test?
A
Both. Off first to test flowmeters and then on one by one.
4
Q
What does SPDD stand for?
A
Supply, Processing, Delivery Disposal
5
Q
3 components of supply
A
electricity, pipeline, cylinders
6
Q
Site of Supply component of SPDD
A
back of the machine
7
Q
Site of the processing component of the SPDD
A
within the machine, proximal to the common gas outlet
8
Q
Site of the delivery component of the SPDD
A
breathing circuit - both to and away from patient
9
Q
Site of disposal component of the SPDD
A
scavenger
10
Q
What organization is responsible for the compressed gas cylinders?
A
Department of Transportation
11
Q
What organization is responsible for the scavenger system?
A
OSHA
occupational safety and health administration
12
Q
Is the pipeline supply oxygen stored as a liquid or gas?
A
Liquid
13
Q
What is the boiling point of oxygen? How is it stored as a liquid?
A
BP = -184 Celcius
Held under pressure to be stored as a liquid
14
Q
How does it turn from a liquid to a gas? What pressure is oxygen supplied from the pipeline?
A
As it leaves the highly pressurized tank it almost instantaneously turns from liquid to gas and travels via pipelines at 50psi
15
Q
Normal working pressure of gas machine?
A
50 psi
16
Q
What is the DISS? How does it work?
A
Diameter Index Safety System
The pipeline inlet for the fresh gases (oxygen, air, n20) has different sizes/threads that only correspond to the appropriate gas tubing. And a check valve ensures unidirectional flow.
17
Q
The pipeline pressure gauges should read about what psi?
A
50 psi
18
Q
What is cross-connection regarding pipelines?
A
A rare mistake - but when nitrous oxide is coming out of the oxygen pipeline source
19
Q
What monitors for low oxygen pressure in the anesthesia machine?
A
oxygen pressure failure device
20
Q
What pressure system does the oxygen pressure failure device (failsafe device) reside in?
A
intermediate pressure system
21
Q
The oxygen pressure failure device (failsafe device) will not alarm in the setting of?
A
pipeline crossover
crack in glass flow meter
22
Q
What are the two components of the oxygen pressure failure device (failsafe device) that prevent a hypoxic mixture?
A
- Threshold alarm: sounds when oxygen pipeline pressure falls below 30psi
- Pneumatic system: reduces or stops the flow of n20 when the pressure in the oxygen pipeline falls below 20psi
23
Q
Who sets the standards for the required components of the anesthesia machine?
A
ASTM
American Society for Testing and Materials
24
Q
If your oxygen pipeline pressure supply fails? What do you do?
A
Switch to oxygen cylinder!
25
Newer machines switch to air to drive the ventilator if there is a loss of oxygen pressure. However, if you're on an older machine that is using bellows, what will you want to do if this loss of oxygen pressure occurs?
Hand ventilate because you will lose more oxygen from your cylinder than the flow meter says because it is still being used to drive the machine. You will chew up your oxygen much faster than you anticipate.
26
Where can a cross-connect happen?
Anywhere! Always trust an oxygen analyzer until you can prove it wrong! (you calibrate it everyday with machine check)
27
What is the pressure distal to the cylinders?
Why is this important?!
45psi
Because pipeline is supplied at 50 psi - IF you were to leave the cylinder valve open - the machine would still use the pipeline pressure however if you loose pipeline pressure your machine will now use the cylinder and you wont know until your tank is empty!
28
Will your machine alarm if it switches to cylinder oxygen instead of the pipeline if you accidentally leave the cylinder valve open?
No!
29
DISS and PISS - which goes with which gas delivery system
DISS - pipeline
PISS - cylinder
30
Describe the PISS system
Pin Index Safety System
Pins on the back of the cylinder valve are placed in a unique arrangement to so that they can only be placed in the appropriate spot
31
3 functions of the hanger yoke
1. orient the cylinders in the right direction
2. provides a gas-tight seal
3. ensures uni-directional flow
32
oxygen, air, and n20 PISS numbers
2,5 - oxygen
1,5 - air
3,5 - n20
33
What is the most fragile part of the cylinder?
cylinder valve
34
In the case of a fire near a cylinder - what are 3 safety relief devices
1. Fusible Plug
2. Pressure Valve
3. Frangible Disk
35
What does the pressure safety relief valve do in the case of a fire near a cylinder? How does it work?
releases contents at a stable rate to avoid explosion
Frangible disk bursts, the valve opens, and the plug melts
36
The fusible plug is made from?
Woods Metal - aka it melts.
37
Max Service pressure for oxygen cylinder
1900 psi (2,000 acceptable for calculations)
38
Max Capacity for oxygen cylinder
660L
39
Max Service Pressure for Nitrous Oxide
745psi
40
Max Capacity for nitrous oxide
1590L
41
Max service pressure for air
1900psi
42
Max capacity for air
625L
43
A full oxygen tank contains how many Liters of oxygen
660L
44
How do you calculate how much time you have left on an oxygen cylinder at a given flow rate?
Tank Capacity / Full Tank (service) pressure
=
contents remaining (L) / current gauge pressure
This gives you Liters remaining. Then take the Liters remaining divided by the flow rate (L/min) to give you how many minutes you have left before the tank expires
45
Is nitrous oxide stored as a liquid or gas?
Liquid and turns to gas when close to empty (1/4 left)
46
The pressure of the nitrous gas cylinder will remain at 745psi until all liquid is gone, which equates to how much is gone. When should you change the cylinder?
3/4 tank empty when the cylinder has no liquid left. This is when you should change the tank!
47
At what rate of N20 would create frost on its wall or freeze the valve?
4L/min
48
A half-full oxygen tank will have about how much gas pressure and volume left?
about 1000 psi and 330L
49
What is the oxygen "color" in the US and internationally?
Green in US
White for international
50
What is the air "color" in the US and internationally?
Yellow in US
Black and White for international
51
Anesthesia machines will have at least how many minutes of battery if loss of power occurs
30 minutes
52
The traditional flowmeter (Thorpe Tubes) are the beginning of what system? It controls and measures the fresh gas flow that travels towards the?
Low-pressure system
Vaporizers and common gas outlet
53
Why must oxygen be the furthest flow meter to the right and common gas outlet?
Safest - for the patient and reduces risk of hypoxic mixture
54
T/F : A piston-driven ventilation gas machine utilizes oxygen as the gas driver
False. If you have a piston (aka electrical) system compressing the bellows, you do not need oxygen pressure / drive to compress the bellows and deliver the gas.
55
Describe the Link-25 Proportioning System to prevent a hypoxic mixture
A mechanical system linking N2O and O2 with a chain around the flow meter knobs. It prevents a serious hypoxic mixture by limiting the ratio of N20 and O2 to a 3:1 ratio.
56
The reading of any glass flow meter should be read at what point of the float device?
at the widest point of any float within the tube.
Ball (middle)
57
Oxygen Flush can supply how much oxygen?
35-75 L/min flow
58
To avoid barotrauma - when should you activate the oxygen flush?
If a ventilator is in use, do not use it during the inspiratory phase. Flush should be utilized in short bursts during the expiratory phase.
59
Why do we prefer to use oxygen to compress the bellows?
If the bellows allows gas to enter/mix with its inner contents, you'd prefer that to be oxygen
60
Humans consume how much oxygen per minute?
2-3ml/kg
61
Thorpe Tubes / Flow Meter Tubes are in which pressure system of the anesthesia gas machine?
Low Pressure System
62
Cylinder Pressure Regulators are in which pressure system of the anesthesia gas machine?
High Pressure System
63
Hanger Yokes are in which pressure system of the anesthesia gas machine?
High-Pressure System
64
Pipeline inlets are in which pressure system of the anesthesia gas machine?
Intermediate Pressure System
65
Vaporizers are in which pressure system of the anesthesia gas machine?
Low-Pressure System
66
Flow Meter Valves are in which pressure system of the anesthesia gas machine?
Intermediate Pressure System
67
Oxygen pressure failure device (aka oxygen failsafe device) is in which pressure system of the anesthesia gas machine?
Intermediate Pressure System
68
Oxygen Flush Valve is in which pressure system of the anesthesia gas machine?
Intermediate Pressure System
69
Cylinder Pressure Gauge is in which pressure system of the anesthesia gas machine?
High-Pressure System
70
Common Gas Outlet is in which pressure system of the anesthesia gas machine?
Low-Pressure System
71
List the 5 tasks of oxygen in the anesthesia gas machine
1. O2 Pressure Alarm
2. O2 Pressure Device
3. O2 Flowmeter
4. O2 Flush Valve
5. Ventilator Drive Gas
72
The PISS system is used to?
Prevent the use of the wrong gas cylinder
73
The DISS system is used to?
Prevents the wrong gas hose from being attached to the anesthesia machine
74
The bourdon pressure gauge on an oxygen cylinder reads 500psi. If the flow rate is 2L /min, how much time do you have left?
660L/2000psi = Contents remaining/500psi
contents remaining / 2L = minutes left
83minutes
75
What are some best practices when changing the e-cylinders
1. Laying on the side when changing
2. Change o-ring
3. Remove plastic
76
Who developed the Anesthesia Machine Pre-Use Checkout Procedures
FDA
77
The oxygen pressure failure device activates when?
1. the oxygen pressure supply in the supply line is less than 20psi
2. the oxygen tank is exhausted
78
What is the purpose of the oxygen failsafe device?
to monitor for (and protect against) low oxygen pressure in the anesthesia machine
79
The oxygen failsafe device will alert you to what 3 problems?
1. Depleted O2 tank
2. A drop in pipeline pressure
3. Disconnected O2 supply hose
80
When does the oxygen failsafe device fail to detect a hypoxic mixture?
1. Pipeline Crossover
3. Flowmeter Leak
81
What is another name for the oxygen failsafe device?
Oxygen Pressure Failure Device
82
Function of the hypoxia prevention safety device on the machine will?
Limit the nitrous oxide flow to three times the oxygen flow. It's a pneumatic or mechanical device.
83
What is the difference between the oxygen pressure device and the hypoxia prevention safety device regarding nitrous oxide?
OPD is a failsafe device. It shuts off and/or proportionally reduces Nitrous Oxide flow if O2 pressure drops below 20psi
HPSD is a proportioning device. Prevents you from setting a hypoxic mixture with the flow control valves.
84
What are the two types of hypoxic prevention safety devices ?
1. Link 25 System (chain system between the n20 and O2 flowmeter controls)
2. Oxygen Ratio Monitor Controller
oxygen and nitrous are connected pneumatically. If no oxygen flow, the n20 flow shuts off
85
When does the hypoxic prevention safety device fail?
1. Pipeline crossover
2. Leaks distal to the flowmeter valve
3. Administration of a third gas (ex. helium)
4. Defective mechanic or pneumatic components
86
What is the minimum FiO2 permitted by the proportioning device?
25%
87
What is the maximum percent of N2O that can be used due to the proportioning device?
75%
88
What are the names of the 4 flowmeter floats
Skirted
Ball
Plumb Bob
Nonrotating
89
What is the annular space in the flowmeter?
The area between the float and the sidewall of the flowmeter
90
Describe the internal geometry of the flowmeter
Flowmeter is narrowest at the base and widens along its ascent. Creates a "variable orifice" architecture.
91
Equation for Reynolds Number?
(Density x Diameter x Velocity) / Viscosity
92
What is the safest position for the oxygen flow meter related to other gas flowmeters?
Positioned on the far right (closest to the manifold outlet)
93
What is the equation of finding FiO2 via flowmeters
(Air Flow Rate x 21) + (Oxygen Flow Rate x 100) / total Flow Rate
If N20 is used - add those liters to the total flow rate denominator
94
What is the sequence of FiO2 for nasal cannula from 1L to 6L?
95
What is fresh gas coupling? What is the equation?
Fresh gas coupling occurs when (usually older) machines add the FGF to the set tidal volume and deliver it to the patient.
Vt set on vent + FGF during inspiration - Volume lost to compliance.
96
If asked to calculate the total tidal volume delivered to the patient, including FGF coupling, what are the steps?
FGF = 4/L min
I:E= 1:3
RR: 10/min
Vt: 500
633mL
97
Assuming FGF is added to total tidal volume - what variables will influence tidal volume and how
98
How do you determine how much volume is lost to circuit compliance?
Compliance = change in volume/change in pressure
If you are told compliance and peak pressure, multiply those to find the volume lost and subtract from set tidal volume
99
The isoflurane dial is set to 2%, What percent of fresh gas flow exiting the vaporizing chamber is saturated with isoflurane?
100%
it then mixes with the FGF that did not pick up the anesthetic and drops to 2%
100
What are the two components of a variable bypass vaporizer that increases the surface area of anesthetic flow
Wicks and Baffles
101
What should you do if you tip the vaporizer over?
1. Drain the vaporizer to remove all the liquid anesthetic
2. Turn the dial to the highest setting and run high FHF for 20-30 minutes
102
What us the "T" setting on the vaporizer?
Setting the vaporizer to transport mode (T) eliminates the worry of tipping the vaporizer during transport or removal
103
What is the most common cause of the vaporizer leak?
Loose Filler Cap
or Needs new O-ring
104
How does the vaporizer minimize the effect of cooling on vapor pressure and vaporizer output?
The temperature compensating valve adjusts the ratio of vaporizing chamber flow to bypass flow and guarantees a constant vaporizer output over a wide range of temperatures.
105
What hazards are associated with actuating (pushing) the oxygen flush valve during a procedure?
1. Risk of Barotrauma
2. Patient awareness
106
What could occur if the first-stage oxygen regulator in the anesthesia machine is faulty?
Depletion of oxygen tank
The first-stage regulator allows the preferential use of the pipeline oxygen when the higher pressure in this system is sensed. This regulator prevents the use of cylinder oxygen even if it is left on. But if the regulator is faulty, you would deplete the cylinder because it has a higher pressure than the pipeline.
107
What is the best indicator of anesthesia circuit disconnect?
A. Absence of CO2 waveform
B. Low expired tidal volume
C. Decreased minute ventilation
D. Set pressure threshold not reached
A
108
What is the appropriate first step in managing an alarm from the oxygen analyzer low fi02
1. Fully open emergency oxygen cylinder
2. Disconnect from pipeline connections at the wall
3. Ventilate by hand with the anesthesia breathing circuit
109
What is the equation for desflurane vaporizer % when changing altitude
Required Dial Setting = (sea level v/v% x 760) / current barometric pressure
110
When using mechanical veniltation, the low inspiratory pressure alarm should be set to?
within 5cm H2O below peak pressure
thus detecting disconnection and minor to moderate leaks
111
Nitrous oxide/oxygen proportioning devices are designed to ensure minimum oxygen concentration at what percent?
25%
112
Which components of the anesthesia workstation are the most vulnerable to breakage or leaks?
1. Flow Tubes
2. Vaporizer Manifold
3. Circle Breathing System
113
When exposed to sevoflurane, which components of CO2 absorbents are implicated in the production of compound A?
Sodium Hydroxide
Potassium Hydroxide
114
What is a reason the oxygen supply failsafe device may alarm?
Pipeline pressure insuffiecient
115
What are 2 reasons the positive pressure alert system may alarm?
Expiratory Valve Malfunction (ventilator spill valve)
Faulty unidirectional valve
116
What is most likely to trigger the sub-ambient pressure alarm in the anesthesia machine
The nasogastric tube within the trachea is placed on suction
117
What are three conditions that can inadvertently cause EXCESS anesthetic vapor to be delivered to the breathing circuit with a variable bypass vaporizer?
1. Vaporizer tipped over during transport
2. Vaporizer overfilled between cases
2. Flush Valve frequently activated during low-flow anesthetic (pumping effect)
118
What is the pumping effect?
Anything that causes gas that has already left the vaporizer to re-enter the vaporizing chamber.
119
What can create the pumping effect?
Positive Pressure Ventilation
120
How do you calculate how much liquid anesthetic is used / how long your agent will last?
mL of liquid anesthetic used per hour = Vol% x FGF (L/min) x 3
121
The Tec 6 desflurane vaporizer injects gas into? How is the chamber pressurized and heated?
Injects gas into the fresh gas flow. (not a flow-over design).
Pressurized to two atmospheres and heated to 39 (not 42) degrees Celcius
122
What is the relationship between a desflurane vaporizer and elevation
Inversely related. Higher elevations require a higher dial setting because the atmospheric pressure is lower.
123
What 2 functions does the drive gas on a pneumatic ventilator serve?
1. It compresses the bellows
2. It opens and closes the ventilator spill valve
124
What is the position of the ventilator spill valve during inspiration?
Closed. This ensures that the tidal volume goes to the patient and not to the scavenger
125
How does an ascending bellows move during inspiration
it falls
126
Will a descending bellow fill during a circuit disconnect?
Yes - it can fill with entrained room air
127
How will a bellows leak affect the inspired concentration of an anesthetic agent?
It will dilute the anesthetic concentration (it goes down)
128
What are the functions of the positive and negative pressure relief valves in the piston-driven ventilator
Positive Pressure Relief Valve: opens at 75 +/- 5cm H2O. Prevents excessive pressure build up in circuit
Negative Pressure Relief Valve: open at -8cm H2O. The negative pressure relief valve opens and entrains room air when circuit pressure falls below this value. However, this will dilute the oxygen and anesthetic agents.
129
How is gas flow delivered in volume-controlled ventilation
Inspiratory flow is held constant during inspiration.
130
If airway resistance rises or lung compliance decreases, then PIP will?
Peak Inspiratory Pressure will increase
131
What are the fixed factors in Volume Controlled Ventilation
Tidal Volume
Inspiratory Flow Rate
Inspiratory Time
132
What are the fixed factors in Pressure Controlled Ventilation
Peak Inspiratory Pressure
Inspiratory Time
133
What is the dependent variable in Volume Controlled Ventilation
Peak inspiratory Pressure
134
What are the dependent variables in Pressure Controlled Ventilation
Tidal volume
Inspiratory Flow
135
Situations where PCV is better than VCV
Patient has low compliance: Pregnancy, Obesity, Laparoscopy, ARDS
High PIP would be dangerous: LMA, Neonate, Emphysema
Need to Compensate for a Leak: LMA, Uncuffed ETT in children
136
What modes of mechanical ventilation are best suited for laryngeal mask airway?
SIMV (synchronized intermittent mandatory ventilation)
PSV (pressure support ventilation)
137
Describe VCAC ventilation
Volume Control Assist Control
Machine-initiated breath delivers a preset Vt and RR
A spontaneous breath receives the full preset tidal volume. The tidal volume will be the same if the machine or patient initiates the breath.
138
Describe Pressure-Control Ventilation with Volume Guarantee (PCV-VG)
PCV-VG offers the benefits of pressure control ventilation but also guarantees a predetermined tidal volume while applying the minimum required pressure.
(useful because sometimes laparoscopic surgery or patient positioning can change the tidal volume a patient can take)
139
Describe Pressure-Support Ventilation (PSV)
Augments spontaneous breaths with a pre-set amount of pressure support. No machine-initiated breaths unless there is a back-up rate if apnea is detected (PSV-Pro)
140
What is the difference between CPAP and PSV
CPAP delivers a continuous amount of pressure throughout the respiratory cycle. Augments inspiration and reduces airway collapse during expiration.
PSV only applies pressure to the circuit when the patient initiates a breath: Used to support spontaneous breaths by decreasing the patient’s effort during inspiration. It helps increase tidal volume, reduce the workload of respiratory muscles, and improve ventilation efficiency
141
Describe Biphasic Positive Airway Pressure (BiPAP)
two levels of pressure are set
P1 = inspiratory positive airway pressure
P2 = expiratory positive airway pressure
Basically, it combines PSV and CPAP
142
Describe Airway Pressure Release Ventilation (APRV)
used for spontaneous ventilation
like BiPAP, but a high level of CPAP throughout most of the respiratory cycle. High-level pressure released at preset intervals to facilitate exhalation, Useful in ARDS pts
143
Why is Silica added to Soda Lime?
It provides hardness and minimizes dust production
144
What is the ideal mesh size for CO2 absorbent?
4-8 mesh
145
Benefits of Calcium Hydroxide Lime
No carbon monoxide production
Very little or no compound A production
Lower risk of fire when compared to soda lime
146
Drawbacks of calcium hydroxide lime
Lower CO2 absorbent capacity
Requires more frequent replacement
High cost
147
To maintain constant pressure inside the breathing circuit, the scavenger must only remove an amount of gas equal to?
Fresh gas flow minus the volume of gas lost due to the patient's oxygen consumption
148
The APL valve controls?
The amount of gas that remains in the circuit and the amount that is released to the scavenger during spontaneous ventilation
149
The ventilator spill valve determines?
The amount of gas that remains in the circuit and the amount that is released to the scavenger during mechanical ventilation
150
Does an Open scavenger system have an active or passive scavenging interface?
Active Only. Suction provides the negative pressure. If this is occluded, gas leaks into the OR via the scavengers open windows
151
An open scavenging interface interacts with the OR environment. What happens if too much or too little suction occurs?
If there is too much suction, room air is entrained(pulled) into the system.
If there is too little suction, the scavenge system will release its contents into the OR environment.
152
Does a closed scavenging interface an active, passive, or either scavenging system?
Can be either
153
What does a closed scavenging interface require for a passive scavenging system?
A positive pressure relief valve - to prevent barotrauma in the event of distal obstruction
154
What valves must be present in a closed scavenging system with an active interface?
Both a positive and negative pressure relief valve.
This protects against excess negative pressure by entraining room air if there is too much negative pressure and releasing contents into the OR if there is too much positive pressure.
155
What is the most common cause of low circuit pressure?
Circuit Disconnect at the Y-piece
The second most common - leak around the carbon dioxide absorbent
156
According to OSHA, recommended standards what is the Maximum accepted level of exposure to halogenated agents with and without nitrous oxide in use?
2ppm Halogenated Gases
When nitrous is in use, 0.5ppm halogenated and 25ppm nitrous
157
A patient is receiving controlled ventilation with a fresh gas flow of 5L/min. Which Mapleson Circuit is MOST likely to cause hypercarbia?
Mapleson A
158
Which Mapleson circuits are MOST likely to be encountered in modern anesthetic practice?
D, E, and F - The T-Piece Group
159
The Mapleson Circuits are examples of what kind of circuits?
Semiopen Circuits
160
What are the Semiopen circuits?
Mapleson A-F, Bain System, Circle System w/ FGF > Ve
161
What circuit contains a reservoir bag but does not allow rebreathing of exhaled gases?
Semiopen
162
All of the following allow fresh gas to escape into the atmosphere EXCEPT a:
Bain System
T-Piece
Nasal Cannula
Simple Face Mask
Bain System
163
What are the 4 steps to perform the Pethick test?
1. Occlude the elbow at the patient end of the circuit
2. Close the APL valve
3. Use the oxygen flush valve to fill the circuit
4. Remove the occlusion at the elbow while flushing the circuit
164
What will indicate that the Bain System is good to use after the Pethink Test? What would indicate that it is not?
If the inner tubing is patent, the venturi effect will cause the reservoir bag to collapse.
If the inner tubing is occluded, the reservoir bag will remain. Not safe to use.
