ANESTHESIA EQUIPMENT: PRINCIPLES AND APPLICATIONS, 3RD EDITION — COMPLETE
27-CHAPTER REVIEW QUESTION BANK
,Table of Contents
Anesthesia Equipment: Principles and Applications, 3rd Edition
Complete 27-Chapter Review Question Bank
Chapter Chapter Title
1 Medical Gases: Storage and Supply
2 The Anesthesia Machine and Workstation
3 Anesthesia Vaporizers
4 Breathing Circuits
5 Waste Anesthetic Gases and Scavenging Systems
6 Anesthesia Ventilators
7 Humidification and Filtration
8 Respiratory Gas Monitoring
9 Monitoring Ventilation
10 Capnography
11 Pulse Oximetry
12 Hemodynamic Monitoring
13 Temperature Monitoring
14 Airway Equipment
15 Preventing Transmission of Infectious Diseases
16 Infusion Pumps
17 Vigilance, Alarms, and Integrated Monitoring Systems
18 Ergonomics of the Anesthesia Workspace
19 Closed-Circuit Anesthesia
20 Anesthesia Delivery in the MRI Environment
21 Anesthesia at High Altitude
22 Anesthesia in Difficult Locations and in Developing Countries
23 Hazards of the Anesthesia Delivery System
24 Electrical and Fire Safety
25 Machine Checkout and Quality Assurance
26 Risk Management and Medicolegal Aspects of Anesthesia Equipment Use
27 Standards and Regulatory Considerations
Part I — Gases & Ventilation
Chapter 1 — Medical Gases: Storage and Supply
,Question 1
During the preanesthetic checkout, an oxygen E-cylinder pressure gauge reads approximately 1,000 psi.
Assuming the cylinder initially contained about 660 L at 2,000 psi, approximately how much oxygen remains?
A. 165 L
B. 220 L
C. 330 L
D. 500 L
Answer: C
Rationale: Oxygen is stored as a compressed gas, so the amount remaining is approximately proportional to
cylinder pressure. A reading of 1,000 psi represents about one-half of a nominally full 2,000-psi cylinder.
Therefore, approximately one-half of 660 L, or 330 L, remains.
Clinical Pearl: Oxygen-cylinder pressure provides a useful estimate of remaining contents because oxygen
remains gaseous at ordinary room temperature.
Exam Strategy: For compressed oxygen, calculate the fraction of full pressure remaining and multiply it by
the full cylinder volume.
Keywords: Oxygen cylinder, E-cylinder, cylinder pressure, compressed gas, remaining volume
Question 2
Which safety system is specifically designed to prevent the wrong small medical-gas cylinder from being
attached to an anesthesia-machine yoke?
A. Pin Index Safety System
B. Diameter Index Safety System
C. Oxygen failure protection device
D. Pressure-relief valve
Answer: A
Rationale: The Pin Index Safety System (PISS) uses gas-specific combinations of pins on the hanger yoke and
corresponding holes on the cylinder valve. This arrangement prevents properly manufactured cylinders
containing one gas from fitting a yoke designed for another. DISS is primarily associated with pipeline
connections.
Clinical Pearl: A simple memory aid is pins for cylinders; diameter-specific fittings for pipelines.
Exam Strategy: When the stem refers to an E-cylinder, cylinder valve, or hanger yoke, think first of the Pin
Index Safety System.
Keywords: PISS, hanger yoke, cylinder safety, gas-specific connection, cylinder identification
Question 3
A full nitrous oxide E-cylinder has been used for some time, but its pressure gauge continues to read
approximately 745 psi. What is the best explanation?
A. The pressure gauge is defective.
B. Nitrous oxide cannot be measured with a pressure gauge.
C. The cylinder regulator maintains the internal cylinder pressure.
D. Liquid nitrous oxide continues to vaporize and maintain nearly constant vapor pressure.
Answer: D
Rationale: Nitrous oxide is stored primarily as liquid with vapor above it. As vapor leaves the cylinder, additional
liquid nitrous oxide vaporizes, maintaining an approximately constant saturated vapor pressure while liquid
,remains. Cylinder pressure therefore does not reliably indicate the quantity remaining until nearly all liquid has
vaporized.
Clinical Pearl: A nitrous oxide cylinder may be substantially depleted while its pressure gauge still appears
nearly full.
Exam Strategy: When dealing with liquefied gases, think weight rather than pressure for estimating
remaining contents.
Keywords: Nitrous oxide, liquefied gas, vapor pressure, cylinder contents, N₂O
Question 4
The oxygen cylinder yoke on an anesthesia workstation contains pins at positions 2 and 5. What is the primary
purpose of this arrangement?
A. Regulate oxygen pressure
B. Prevent attachment of an incorrect gas cylinder
C. Measure oxygen-cylinder contents
D. Prevent excessive pipeline pressure
Answer: B
Rationale: Oxygen cylinders use the 2-5 pin configuration of the Pin Index Safety System. Cylinders containing
other gases have different hole configurations and should therefore not properly fit the oxygen hanger yoke. The
system is designed for gas identification and misconnection prevention, not pressure regulation.
Clinical Pearl: A frequently tested association is oxygen = pins 2 and 5.
Exam Strategy: Memorize the most commonly tested combinations together: oxygen 2-5 and nitrous oxide
3-5.
Keywords: Oxygen, pin index 2-5, PISS, cylinder identification, safety system
Question 5
Central hospital medical-gas pipelines usually deliver oxygen to an anesthesia workstation at approximately:
A. 5 psi
B. 15 psi
C. 50 psi
D. 2,000 psi
Answer: C
Rationale: Hospital pipelines generally supply medical gases to anesthesia workstations at approximately 50–55
psi. Oxygen stored in cylinders may initially be near 2,000 psi, but this high pressure must be reduced before
entering downstream machine components. Pipeline pressure is therefore far below cylinder storage pressure.
Clinical Pearl: Remember the general progression: cylinder ≈2,000 psi → regulated cylinder ≈45 psi →
pipeline ≈50 psi.
Exam Strategy: Distinguish high-pressure storage pressure from intermediate working pressure.
Keywords: Pipeline pressure, oxygen supply, central gas system, 50 psi, anesthesia workstation
Question 6
During routine anesthesia, both a full oxygen E-cylinder and a functioning oxygen pipeline are connected to the
workstation. Which source normally supplies the oxygen?
A. Both sources contribute equally.
B. The cylinder supplies oxygen first.
,C. The source alternates according to fresh-gas flow.
D. The pipeline supplies oxygen because its pressure exceeds regulated cylinder pressure.
Answer: D
Rationale: The oxygen-cylinder regulator generally reduces cylinder pressure to approximately 45 psi, whereas
pipeline pressure is usually around 50 psi. Because the pipeline has the higher downstream pressure, it normally
supplies the machine. The cylinder consequently remains available as an emergency reserve.
Clinical Pearl: A properly connected backup cylinder should not normally empty while adequate pipeline
pressure is present.
Exam Strategy: When two supplies feed the same system, compare their effective downstream pressures.
Keywords: Pipeline priority, oxygen regulator, cylinder reserve, working pressure, gas supply
Question 7
During anesthesia, the provider suspects that the oxygen pipeline has been cross-connected and may be
delivering another gas. What is the most appropriate immediate action?
A. Open the backup oxygen cylinder and disconnect the suspect pipeline.
B. Increase pipeline flow to flush the contaminating gas.
C. Close the backup cylinder and continue using the pipeline.
D. Silence the oxygen alarm and monitor pulse oximetry.
Answer: A
Rationale: A pipeline crossover may deliver an incorrect gas despite apparently normal pipeline pressure. The
immediate priority is to establish a known independent oxygen source by opening the backup oxygen cylinder
and isolating the suspected pipeline. Pressure-based safety devices cannot determine gas identity.
Clinical Pearl: Normal pipeline pressure does not guarantee that oxygen is actually flowing through the
oxygen connection.
Exam Strategy: For suspected crossover, choose the action that provides known oxygen and isolates the
questionable source.
Keywords: Pipeline crossover, backup oxygen, pipeline contamination, emergency response, oxygen safety
Question 8
Which method is most appropriate for determining the quantity of nitrous oxide remaining in a cylinder while
liquid nitrous oxide is still present?
A. Read the cylinder-pressure gauge.
B. Weigh the cylinder.
C. Measure pipeline pressure.
D. Measure cylinder temperature alone.
Answer: B
Rationale: Nitrous oxide exists partly as liquid in the cylinder, so pressure remains relatively constant while liquid
is present. The remaining quantity is best determined by weighing the cylinder and subtracting its tare weight.
Pressure begins falling substantially only after the liquid phase is exhausted.
Clinical Pearl: The tare weight represents the weight of the empty cylinder and its valve assembly.
Exam Strategy: Remember the contrast: compressed gas → pressure; liquefied gas → weight.
Keywords: Nitrous oxide, cylinder weight, tare weight, liquid gas, cylinder contents
Question 9
,A full oxygen E-cylinder contains approximately 660 L. Its pressure has fallen from 2,000 psi to 500 psi.
Approximately how much oxygen remains?
A. 55 L
B. 110 L
C. 330 L
D. 165 L
Answer: D
Rationale: A pressure of 500 psi represents approximately one-quarter of a nominal full pressure of 2,000 psi.
Therefore, 660 L × 0.25 equals approximately 165 L. This proportional relationship is applicable because oxygen
remains a compressed gas within the cylinder.
Clinical Pearl: Actual values are approximate because cylinder pressure can vary somewhat with
temperature and filling conditions.
Exam Strategy: Calculate the fraction remaining first: 500 ÷ 2,000 = 0.25, then multiply by full cylinder
capacity.
Keywords: Oxygen calculation, E-cylinder, remaining volume, cylinder pressure, compressed gas
Question 10
Which component reduces the extremely high pressure of oxygen leaving an E-cylinder to a level suitable for
use within the anesthesia machine?
A. Cylinder pressure regulator
B. Flowmeter
C. Common gas outlet
D. Vaporizer
Answer: A
Rationale: Oxygen within an E-cylinder may be stored near 2,000 psi, which is too high for downstream machine
components. The pressure regulator reduces this high, variable pressure to a much lower and relatively stable
working pressure. Flowmeters and vaporizers function farther downstream.
Clinical Pearl: The regulator transforms high and variable pressure into lower and more stable pressure.
Exam Strategy: When the stem asks what reduces cylinder pressure before gas enters the machine, select
the pressure regulator.
Keywords: Pressure regulator, high-pressure system, oxygen cylinder, working pressure, anesthesia machine
Question 11
Which connection system is commonly used to prevent incorrect attachment of medical-gas pipeline hoses?
A. Pin Index Safety System
B. Bodok system
C. Diameter Index Safety System
D. Oxygen ratio controller
Answer: C
Rationale: The Diameter Index Safety System (DISS) uses gas-specific threaded connections that differ in
diameter and configuration. This makes pipeline connections noninterchangeable under normal circumstances.
PISS serves a similar purpose for small compressed-gas cylinders.
Clinical Pearl: Gas-specific connectors should never be bypassed or modified simply to make incompatible
fittings connect.
Exam Strategy: Associate DISS with pipelines and hoses and PISS with cylinders and yokes.
,Keywords: DISS, pipeline connector, gas hose, noninterchangeable fitting, gas safety
Question 12
Which component located between an E-cylinder valve and the anesthesia-machine yoke helps create a gas-
tight seal?
A. Fusible plug
B. Bodok washer
C. Flow-control valve
D. Pressure gauge
Answer: B
Rationale: The Bodok washer is a specialized sealing gasket positioned between the cylinder valve and the
hanger yoke. It helps prevent leakage from the high-pressure cylinder connection. Omission, damage, or
inappropriate duplication of the washer may compromise the connection.
Clinical Pearl: Only one appropriate washer should be present at the cylinder-yoke connection.
Exam Strategy: When a question describes the seal between a cylinder valve and hanger yoke, choose
Bodok washer.
Keywords: Bodok washer, hanger yoke, cylinder seal, oxygen leak, gasket
Question 13
During suspected oxygen-pipeline contamination, the backup oxygen E-cylinder is opened. Why should the
pipeline subsequently be disconnected?
A. To increase cylinder pressure
B. To activate the oxygen flush valve
C. To decrease fresh-gas flow
D. To prevent potentially incorrect pipeline gas from continuing to enter the machine
Answer: D
Rationale: Opening a cylinder establishes a known oxygen source, but leaving a contaminated or cross-
connected pipeline attached may allow the incorrect gas to continue entering the machine. Disconnecting the
pipeline physically isolates that unsafe source and prevents further contamination of the gas-delivery system.
Clinical Pearl: In a gas-supply emergency, establishing an alternative supply and isolating the failed source
are both important.
Exam Strategy: Differentiate loss of pressure from loss of gas identity. A suspected crossover requires
isolation.
Keywords: Pipeline failure, crossover, pipeline isolation, backup cylinder, gas contamination
Question 14
Which characteristic best explains why liquid oxygen is advantageous for a large hospital central-supply system?
A. It requires no specialized storage container.
B. It can be stored indefinitely without evaporation.
C. A large amount of oxygen can be stored in a relatively compact volume.
D. It remains at approximately 2,000 psi during storage.
Answer: C
Rationale: Liquefying oxygen greatly increases storage density, permitting large quantities of oxygen to be
maintained in a relatively compact central storage system. Liquid oxygen requires specialized cryogenic storage
vessels and insulation. It is not stored under the same conditions as compressed oxygen in E-cylinders.
, Clinical Pearl: Bulk liquid oxygen systems are well suited to hospitals because of their very high oxygen-
storage capacity.
Exam Strategy: When asked why a gas is stored as a liquid in bulk systems, think greater storage density.
Keywords: Liquid oxygen, bulk storage, cryogenic system, central supply, storage density
Question 15
Why is an oxygen E-cylinder normally kept closed while an anesthesia workstation is connected to a functioning
pipeline?
A. To preserve the cylinder as an emergency reserve and facilitate recognition of pipeline failure
B. Because opening the cylinder automatically shuts down the pipeline
C. Because cylinder pressure can damage the hospital pipeline
D. Because oxygen becomes contaminated when both supplies are connected
Answer: A
Rationale: Keeping the oxygen cylinder closed preserves its contents for emergencies. If the cylinder remains
open, it may temporarily maintain system pressure after pipeline failure, potentially delaying recognition of the
problem and consuming the reserve supply before it is actually needed.
Clinical Pearl: During normal pipeline operation, the backup oxygen cylinder should generally be adequately
filled, attached, and closed.
Exam Strategy: Questions about keeping the cylinder closed usually test reserve preservation and early
recognition of pipeline failure.
Keywords: Backup oxygen, pipeline failure, cylinder reserve, anesthesia checkout, emergency supply
Question 16
The Pin Index Safety System positions for a nitrous oxide cylinder are:
A. 1 and 5
B. 3 and 5
C. 2 and 5
D. 4 and 6
Answer: B
Rationale: Nitrous oxide uses the 3-5 pin configuration in the Pin Index Safety System. Oxygen uses positions 2-
5. These unique arrangements decrease the likelihood that a cylinder containing one medical gas will be
connected to a yoke intended for another gas.
Clinical Pearl: Two high-yield associations are O₂ = 2-5 and N₂O = 3-5.
Exam Strategy: Memorize commonly tested pin-index configurations rather than trying to derive them
during an examination.
Keywords: Nitrous oxide, PISS, pin positions 3-5, cylinder safety, N₂O cylinder
Question 17
An oxygen E-cylinder contains approximately 330 L of oxygen, and the gas is being delivered at 6 L/min. Ignoring
any safety reserve, approximately how long will the cylinder last?
A. 30 minutes
B. 45 minutes
C. 55 minutes
D. 90 minutes
Answer: C
,Rationale: Cylinder duration equals available gas volume divided by the rate of consumption. Dividing 330 L by 6
L/min gives approximately 55 minutes. In actual clinical practice, a reserve should be maintained instead of
intentionally using the cylinder until completely empty.
Clinical Pearl: Always allow additional oxygen for transport delays, increased flow requirements, or
unexpected deterioration.
Exam Strategy: Use available liters ÷ liters per minute = minutes remaining.
Keywords: Cylinder duration, oxygen consumption, flow rate, transport oxygen, calculation
Question 18
Which physical property allows an oxygen-cylinder pressure gauge to provide a reasonable estimate of the
quantity remaining?
A. Oxygen is stored entirely as compressed gas at ordinary room temperature.
B. Oxygen exists mainly as a liquid-vapor mixture.
C. Oxygen maintains a constant saturated vapor pressure.
D. Oxygen pressure remains constant until the cylinder is almost empty.
Answer: A
Rationale: Oxygen remains gaseous inside a conventional compressed-gas cylinder at room temperature.
Consequently, cylinder pressure decreases approximately in proportion to the amount of oxygen remaining. This
contrasts with liquefied gases such as nitrous oxide, whose pressures remain relatively constant while liquid
remains.
Clinical Pearl: The physical state of the gas determines whether pressure can estimate cylinder contents.
Exam Strategy: Compare oxygen and nitrous oxide whenever the examination tests interpretation of cylinder
gauges.
Keywords: Compressed oxygen, pressure-volume relationship, cylinder contents, oxygen storage, gas physics
Question 19
Normal pressure is present at an oxygen wall outlet, but the anesthesia provider suspects a pipeline crossover.
Which monitor provides the most direct confirmation that oxygen is actually present in the delivered gas
mixture?
A. Pipeline pressure gauge
B. Cylinder pressure gauge
C. Flowmeter
D. Oxygen analyzer
Answer: D
Rationale: Pressure gauges reveal that gas pressure is present but cannot determine which gas is producing that
pressure. An oxygen analyzer directly measures oxygen concentration in the delivered mixture and therefore
provides critical protection against pipeline crossover and other wrong-gas situations.
Clinical Pearl: Pressure identifies pressure; an oxygen analyzer identifies oxygen concentration.
Exam Strategy: Whenever a question asks how to confirm the identity or concentration of oxygen, select the
oxygen analyzer.
Keywords: Oxygen analyzer, pipeline crossover, gas identity, oxygen concentration, monitoring
Question 20
Why must medical oxygen cylinders and equipment be kept free from oil, grease, and other combustible
substances?
, A. Oil decreases oxygen concentration.
B. Oxygen strongly supports combustion and can accelerate fire.
C. Grease causes oxygen to liquefy.
D. Hydrocarbons reduce cylinder pressure.
Answer: B
Rationale: Oxygen is not itself combustible, but it vigorously supports combustion. Oils, grease, and other
hydrocarbons may ignite violently when exposed to concentrated oxygen, especially under high-pressure
conditions. Oxygen equipment must therefore remain free of inappropriate lubricants and combustible
contamination.
Clinical Pearl: Never apply ordinary oil or grease to oxygen-cylinder valves, regulators, or connectors.
Exam Strategy: Oxygen plus hydrocarbon contamination should immediately suggest fire and combustion
risk.
Keywords: Oxygen safety, combustion, hydrocarbons, fire hazard, cylinder storage
Question 21
An oxygen-cylinder valve is opened rapidly, and an upstream component becomes markedly hot. Which
phenomenon most directly explains this temperature increase?
A. Adiabatic compression
B. Joule-Thomson cooling
C. Vaporization
D. Critical-point transition
Answer: A
Rationale: Rapid pressurization causes gas to be compressed before significant heat can dissipate, producing
adiabatic heating. In a high-pressure oxygen system, this may generate temperatures sufficient to promote
ignition if contaminants or combustible materials are present.
Clinical Pearl: High-pressure oxygen-cylinder valves should be opened slowly to reduce rapid compression
and heating.
Exam Strategy: Rapid gas compression accompanied by heating strongly indicates adiabatic compression.
Keywords: Adiabatic compression, rapid pressurization, oxygen fire, cylinder valve, heat generation
Question 22
What is the primary function of a check valve within a cylinder-yoke or gas-supply assembly?
A. Increase cylinder pressure
B. Measure oxygen concentration
C. Control vaporizer output
D. Prevent reverse flow of gas
Answer: D
Rationale: A check valve permits gas to flow in one direction while limiting retrograde flow toward the original
gas source. This function becomes particularly important when multiple supplies with different pressures are
connected to the anesthesia workstation.
Clinical Pearl: A check valve can be remembered simply as a one-way valve.
Exam Strategy: When the question emphasizes prevention of backflow, choose the check valve.
Keywords: Check valve, one-way valve, reverse flow, gas supply, hanger yoke
Question 23
27-CHAPTER REVIEW QUESTION BANK
,Table of Contents
Anesthesia Equipment: Principles and Applications, 3rd Edition
Complete 27-Chapter Review Question Bank
Chapter Chapter Title
1 Medical Gases: Storage and Supply
2 The Anesthesia Machine and Workstation
3 Anesthesia Vaporizers
4 Breathing Circuits
5 Waste Anesthetic Gases and Scavenging Systems
6 Anesthesia Ventilators
7 Humidification and Filtration
8 Respiratory Gas Monitoring
9 Monitoring Ventilation
10 Capnography
11 Pulse Oximetry
12 Hemodynamic Monitoring
13 Temperature Monitoring
14 Airway Equipment
15 Preventing Transmission of Infectious Diseases
16 Infusion Pumps
17 Vigilance, Alarms, and Integrated Monitoring Systems
18 Ergonomics of the Anesthesia Workspace
19 Closed-Circuit Anesthesia
20 Anesthesia Delivery in the MRI Environment
21 Anesthesia at High Altitude
22 Anesthesia in Difficult Locations and in Developing Countries
23 Hazards of the Anesthesia Delivery System
24 Electrical and Fire Safety
25 Machine Checkout and Quality Assurance
26 Risk Management and Medicolegal Aspects of Anesthesia Equipment Use
27 Standards and Regulatory Considerations
Part I — Gases & Ventilation
Chapter 1 — Medical Gases: Storage and Supply
,Question 1
During the preanesthetic checkout, an oxygen E-cylinder pressure gauge reads approximately 1,000 psi.
Assuming the cylinder initially contained about 660 L at 2,000 psi, approximately how much oxygen remains?
A. 165 L
B. 220 L
C. 330 L
D. 500 L
Answer: C
Rationale: Oxygen is stored as a compressed gas, so the amount remaining is approximately proportional to
cylinder pressure. A reading of 1,000 psi represents about one-half of a nominally full 2,000-psi cylinder.
Therefore, approximately one-half of 660 L, or 330 L, remains.
Clinical Pearl: Oxygen-cylinder pressure provides a useful estimate of remaining contents because oxygen
remains gaseous at ordinary room temperature.
Exam Strategy: For compressed oxygen, calculate the fraction of full pressure remaining and multiply it by
the full cylinder volume.
Keywords: Oxygen cylinder, E-cylinder, cylinder pressure, compressed gas, remaining volume
Question 2
Which safety system is specifically designed to prevent the wrong small medical-gas cylinder from being
attached to an anesthesia-machine yoke?
A. Pin Index Safety System
B. Diameter Index Safety System
C. Oxygen failure protection device
D. Pressure-relief valve
Answer: A
Rationale: The Pin Index Safety System (PISS) uses gas-specific combinations of pins on the hanger yoke and
corresponding holes on the cylinder valve. This arrangement prevents properly manufactured cylinders
containing one gas from fitting a yoke designed for another. DISS is primarily associated with pipeline
connections.
Clinical Pearl: A simple memory aid is pins for cylinders; diameter-specific fittings for pipelines.
Exam Strategy: When the stem refers to an E-cylinder, cylinder valve, or hanger yoke, think first of the Pin
Index Safety System.
Keywords: PISS, hanger yoke, cylinder safety, gas-specific connection, cylinder identification
Question 3
A full nitrous oxide E-cylinder has been used for some time, but its pressure gauge continues to read
approximately 745 psi. What is the best explanation?
A. The pressure gauge is defective.
B. Nitrous oxide cannot be measured with a pressure gauge.
C. The cylinder regulator maintains the internal cylinder pressure.
D. Liquid nitrous oxide continues to vaporize and maintain nearly constant vapor pressure.
Answer: D
Rationale: Nitrous oxide is stored primarily as liquid with vapor above it. As vapor leaves the cylinder, additional
liquid nitrous oxide vaporizes, maintaining an approximately constant saturated vapor pressure while liquid
,remains. Cylinder pressure therefore does not reliably indicate the quantity remaining until nearly all liquid has
vaporized.
Clinical Pearl: A nitrous oxide cylinder may be substantially depleted while its pressure gauge still appears
nearly full.
Exam Strategy: When dealing with liquefied gases, think weight rather than pressure for estimating
remaining contents.
Keywords: Nitrous oxide, liquefied gas, vapor pressure, cylinder contents, N₂O
Question 4
The oxygen cylinder yoke on an anesthesia workstation contains pins at positions 2 and 5. What is the primary
purpose of this arrangement?
A. Regulate oxygen pressure
B. Prevent attachment of an incorrect gas cylinder
C. Measure oxygen-cylinder contents
D. Prevent excessive pipeline pressure
Answer: B
Rationale: Oxygen cylinders use the 2-5 pin configuration of the Pin Index Safety System. Cylinders containing
other gases have different hole configurations and should therefore not properly fit the oxygen hanger yoke. The
system is designed for gas identification and misconnection prevention, not pressure regulation.
Clinical Pearl: A frequently tested association is oxygen = pins 2 and 5.
Exam Strategy: Memorize the most commonly tested combinations together: oxygen 2-5 and nitrous oxide
3-5.
Keywords: Oxygen, pin index 2-5, PISS, cylinder identification, safety system
Question 5
Central hospital medical-gas pipelines usually deliver oxygen to an anesthesia workstation at approximately:
A. 5 psi
B. 15 psi
C. 50 psi
D. 2,000 psi
Answer: C
Rationale: Hospital pipelines generally supply medical gases to anesthesia workstations at approximately 50–55
psi. Oxygen stored in cylinders may initially be near 2,000 psi, but this high pressure must be reduced before
entering downstream machine components. Pipeline pressure is therefore far below cylinder storage pressure.
Clinical Pearl: Remember the general progression: cylinder ≈2,000 psi → regulated cylinder ≈45 psi →
pipeline ≈50 psi.
Exam Strategy: Distinguish high-pressure storage pressure from intermediate working pressure.
Keywords: Pipeline pressure, oxygen supply, central gas system, 50 psi, anesthesia workstation
Question 6
During routine anesthesia, both a full oxygen E-cylinder and a functioning oxygen pipeline are connected to the
workstation. Which source normally supplies the oxygen?
A. Both sources contribute equally.
B. The cylinder supplies oxygen first.
,C. The source alternates according to fresh-gas flow.
D. The pipeline supplies oxygen because its pressure exceeds regulated cylinder pressure.
Answer: D
Rationale: The oxygen-cylinder regulator generally reduces cylinder pressure to approximately 45 psi, whereas
pipeline pressure is usually around 50 psi. Because the pipeline has the higher downstream pressure, it normally
supplies the machine. The cylinder consequently remains available as an emergency reserve.
Clinical Pearl: A properly connected backup cylinder should not normally empty while adequate pipeline
pressure is present.
Exam Strategy: When two supplies feed the same system, compare their effective downstream pressures.
Keywords: Pipeline priority, oxygen regulator, cylinder reserve, working pressure, gas supply
Question 7
During anesthesia, the provider suspects that the oxygen pipeline has been cross-connected and may be
delivering another gas. What is the most appropriate immediate action?
A. Open the backup oxygen cylinder and disconnect the suspect pipeline.
B. Increase pipeline flow to flush the contaminating gas.
C. Close the backup cylinder and continue using the pipeline.
D. Silence the oxygen alarm and monitor pulse oximetry.
Answer: A
Rationale: A pipeline crossover may deliver an incorrect gas despite apparently normal pipeline pressure. The
immediate priority is to establish a known independent oxygen source by opening the backup oxygen cylinder
and isolating the suspected pipeline. Pressure-based safety devices cannot determine gas identity.
Clinical Pearl: Normal pipeline pressure does not guarantee that oxygen is actually flowing through the
oxygen connection.
Exam Strategy: For suspected crossover, choose the action that provides known oxygen and isolates the
questionable source.
Keywords: Pipeline crossover, backup oxygen, pipeline contamination, emergency response, oxygen safety
Question 8
Which method is most appropriate for determining the quantity of nitrous oxide remaining in a cylinder while
liquid nitrous oxide is still present?
A. Read the cylinder-pressure gauge.
B. Weigh the cylinder.
C. Measure pipeline pressure.
D. Measure cylinder temperature alone.
Answer: B
Rationale: Nitrous oxide exists partly as liquid in the cylinder, so pressure remains relatively constant while liquid
is present. The remaining quantity is best determined by weighing the cylinder and subtracting its tare weight.
Pressure begins falling substantially only after the liquid phase is exhausted.
Clinical Pearl: The tare weight represents the weight of the empty cylinder and its valve assembly.
Exam Strategy: Remember the contrast: compressed gas → pressure; liquefied gas → weight.
Keywords: Nitrous oxide, cylinder weight, tare weight, liquid gas, cylinder contents
Question 9
,A full oxygen E-cylinder contains approximately 660 L. Its pressure has fallen from 2,000 psi to 500 psi.
Approximately how much oxygen remains?
A. 55 L
B. 110 L
C. 330 L
D. 165 L
Answer: D
Rationale: A pressure of 500 psi represents approximately one-quarter of a nominal full pressure of 2,000 psi.
Therefore, 660 L × 0.25 equals approximately 165 L. This proportional relationship is applicable because oxygen
remains a compressed gas within the cylinder.
Clinical Pearl: Actual values are approximate because cylinder pressure can vary somewhat with
temperature and filling conditions.
Exam Strategy: Calculate the fraction remaining first: 500 ÷ 2,000 = 0.25, then multiply by full cylinder
capacity.
Keywords: Oxygen calculation, E-cylinder, remaining volume, cylinder pressure, compressed gas
Question 10
Which component reduces the extremely high pressure of oxygen leaving an E-cylinder to a level suitable for
use within the anesthesia machine?
A. Cylinder pressure regulator
B. Flowmeter
C. Common gas outlet
D. Vaporizer
Answer: A
Rationale: Oxygen within an E-cylinder may be stored near 2,000 psi, which is too high for downstream machine
components. The pressure regulator reduces this high, variable pressure to a much lower and relatively stable
working pressure. Flowmeters and vaporizers function farther downstream.
Clinical Pearl: The regulator transforms high and variable pressure into lower and more stable pressure.
Exam Strategy: When the stem asks what reduces cylinder pressure before gas enters the machine, select
the pressure regulator.
Keywords: Pressure regulator, high-pressure system, oxygen cylinder, working pressure, anesthesia machine
Question 11
Which connection system is commonly used to prevent incorrect attachment of medical-gas pipeline hoses?
A. Pin Index Safety System
B. Bodok system
C. Diameter Index Safety System
D. Oxygen ratio controller
Answer: C
Rationale: The Diameter Index Safety System (DISS) uses gas-specific threaded connections that differ in
diameter and configuration. This makes pipeline connections noninterchangeable under normal circumstances.
PISS serves a similar purpose for small compressed-gas cylinders.
Clinical Pearl: Gas-specific connectors should never be bypassed or modified simply to make incompatible
fittings connect.
Exam Strategy: Associate DISS with pipelines and hoses and PISS with cylinders and yokes.
,Keywords: DISS, pipeline connector, gas hose, noninterchangeable fitting, gas safety
Question 12
Which component located between an E-cylinder valve and the anesthesia-machine yoke helps create a gas-
tight seal?
A. Fusible plug
B. Bodok washer
C. Flow-control valve
D. Pressure gauge
Answer: B
Rationale: The Bodok washer is a specialized sealing gasket positioned between the cylinder valve and the
hanger yoke. It helps prevent leakage from the high-pressure cylinder connection. Omission, damage, or
inappropriate duplication of the washer may compromise the connection.
Clinical Pearl: Only one appropriate washer should be present at the cylinder-yoke connection.
Exam Strategy: When a question describes the seal between a cylinder valve and hanger yoke, choose
Bodok washer.
Keywords: Bodok washer, hanger yoke, cylinder seal, oxygen leak, gasket
Question 13
During suspected oxygen-pipeline contamination, the backup oxygen E-cylinder is opened. Why should the
pipeline subsequently be disconnected?
A. To increase cylinder pressure
B. To activate the oxygen flush valve
C. To decrease fresh-gas flow
D. To prevent potentially incorrect pipeline gas from continuing to enter the machine
Answer: D
Rationale: Opening a cylinder establishes a known oxygen source, but leaving a contaminated or cross-
connected pipeline attached may allow the incorrect gas to continue entering the machine. Disconnecting the
pipeline physically isolates that unsafe source and prevents further contamination of the gas-delivery system.
Clinical Pearl: In a gas-supply emergency, establishing an alternative supply and isolating the failed source
are both important.
Exam Strategy: Differentiate loss of pressure from loss of gas identity. A suspected crossover requires
isolation.
Keywords: Pipeline failure, crossover, pipeline isolation, backup cylinder, gas contamination
Question 14
Which characteristic best explains why liquid oxygen is advantageous for a large hospital central-supply system?
A. It requires no specialized storage container.
B. It can be stored indefinitely without evaporation.
C. A large amount of oxygen can be stored in a relatively compact volume.
D. It remains at approximately 2,000 psi during storage.
Answer: C
Rationale: Liquefying oxygen greatly increases storage density, permitting large quantities of oxygen to be
maintained in a relatively compact central storage system. Liquid oxygen requires specialized cryogenic storage
vessels and insulation. It is not stored under the same conditions as compressed oxygen in E-cylinders.
, Clinical Pearl: Bulk liquid oxygen systems are well suited to hospitals because of their very high oxygen-
storage capacity.
Exam Strategy: When asked why a gas is stored as a liquid in bulk systems, think greater storage density.
Keywords: Liquid oxygen, bulk storage, cryogenic system, central supply, storage density
Question 15
Why is an oxygen E-cylinder normally kept closed while an anesthesia workstation is connected to a functioning
pipeline?
A. To preserve the cylinder as an emergency reserve and facilitate recognition of pipeline failure
B. Because opening the cylinder automatically shuts down the pipeline
C. Because cylinder pressure can damage the hospital pipeline
D. Because oxygen becomes contaminated when both supplies are connected
Answer: A
Rationale: Keeping the oxygen cylinder closed preserves its contents for emergencies. If the cylinder remains
open, it may temporarily maintain system pressure after pipeline failure, potentially delaying recognition of the
problem and consuming the reserve supply before it is actually needed.
Clinical Pearl: During normal pipeline operation, the backup oxygen cylinder should generally be adequately
filled, attached, and closed.
Exam Strategy: Questions about keeping the cylinder closed usually test reserve preservation and early
recognition of pipeline failure.
Keywords: Backup oxygen, pipeline failure, cylinder reserve, anesthesia checkout, emergency supply
Question 16
The Pin Index Safety System positions for a nitrous oxide cylinder are:
A. 1 and 5
B. 3 and 5
C. 2 and 5
D. 4 and 6
Answer: B
Rationale: Nitrous oxide uses the 3-5 pin configuration in the Pin Index Safety System. Oxygen uses positions 2-
5. These unique arrangements decrease the likelihood that a cylinder containing one medical gas will be
connected to a yoke intended for another gas.
Clinical Pearl: Two high-yield associations are O₂ = 2-5 and N₂O = 3-5.
Exam Strategy: Memorize commonly tested pin-index configurations rather than trying to derive them
during an examination.
Keywords: Nitrous oxide, PISS, pin positions 3-5, cylinder safety, N₂O cylinder
Question 17
An oxygen E-cylinder contains approximately 330 L of oxygen, and the gas is being delivered at 6 L/min. Ignoring
any safety reserve, approximately how long will the cylinder last?
A. 30 minutes
B. 45 minutes
C. 55 minutes
D. 90 minutes
Answer: C
,Rationale: Cylinder duration equals available gas volume divided by the rate of consumption. Dividing 330 L by 6
L/min gives approximately 55 minutes. In actual clinical practice, a reserve should be maintained instead of
intentionally using the cylinder until completely empty.
Clinical Pearl: Always allow additional oxygen for transport delays, increased flow requirements, or
unexpected deterioration.
Exam Strategy: Use available liters ÷ liters per minute = minutes remaining.
Keywords: Cylinder duration, oxygen consumption, flow rate, transport oxygen, calculation
Question 18
Which physical property allows an oxygen-cylinder pressure gauge to provide a reasonable estimate of the
quantity remaining?
A. Oxygen is stored entirely as compressed gas at ordinary room temperature.
B. Oxygen exists mainly as a liquid-vapor mixture.
C. Oxygen maintains a constant saturated vapor pressure.
D. Oxygen pressure remains constant until the cylinder is almost empty.
Answer: A
Rationale: Oxygen remains gaseous inside a conventional compressed-gas cylinder at room temperature.
Consequently, cylinder pressure decreases approximately in proportion to the amount of oxygen remaining. This
contrasts with liquefied gases such as nitrous oxide, whose pressures remain relatively constant while liquid
remains.
Clinical Pearl: The physical state of the gas determines whether pressure can estimate cylinder contents.
Exam Strategy: Compare oxygen and nitrous oxide whenever the examination tests interpretation of cylinder
gauges.
Keywords: Compressed oxygen, pressure-volume relationship, cylinder contents, oxygen storage, gas physics
Question 19
Normal pressure is present at an oxygen wall outlet, but the anesthesia provider suspects a pipeline crossover.
Which monitor provides the most direct confirmation that oxygen is actually present in the delivered gas
mixture?
A. Pipeline pressure gauge
B. Cylinder pressure gauge
C. Flowmeter
D. Oxygen analyzer
Answer: D
Rationale: Pressure gauges reveal that gas pressure is present but cannot determine which gas is producing that
pressure. An oxygen analyzer directly measures oxygen concentration in the delivered mixture and therefore
provides critical protection against pipeline crossover and other wrong-gas situations.
Clinical Pearl: Pressure identifies pressure; an oxygen analyzer identifies oxygen concentration.
Exam Strategy: Whenever a question asks how to confirm the identity or concentration of oxygen, select the
oxygen analyzer.
Keywords: Oxygen analyzer, pipeline crossover, gas identity, oxygen concentration, monitoring
Question 20
Why must medical oxygen cylinders and equipment be kept free from oil, grease, and other combustible
substances?
, A. Oil decreases oxygen concentration.
B. Oxygen strongly supports combustion and can accelerate fire.
C. Grease causes oxygen to liquefy.
D. Hydrocarbons reduce cylinder pressure.
Answer: B
Rationale: Oxygen is not itself combustible, but it vigorously supports combustion. Oils, grease, and other
hydrocarbons may ignite violently when exposed to concentrated oxygen, especially under high-pressure
conditions. Oxygen equipment must therefore remain free of inappropriate lubricants and combustible
contamination.
Clinical Pearl: Never apply ordinary oil or grease to oxygen-cylinder valves, regulators, or connectors.
Exam Strategy: Oxygen plus hydrocarbon contamination should immediately suggest fire and combustion
risk.
Keywords: Oxygen safety, combustion, hydrocarbons, fire hazard, cylinder storage
Question 21
An oxygen-cylinder valve is opened rapidly, and an upstream component becomes markedly hot. Which
phenomenon most directly explains this temperature increase?
A. Adiabatic compression
B. Joule-Thomson cooling
C. Vaporization
D. Critical-point transition
Answer: A
Rationale: Rapid pressurization causes gas to be compressed before significant heat can dissipate, producing
adiabatic heating. In a high-pressure oxygen system, this may generate temperatures sufficient to promote
ignition if contaminants or combustible materials are present.
Clinical Pearl: High-pressure oxygen-cylinder valves should be opened slowly to reduce rapid compression
and heating.
Exam Strategy: Rapid gas compression accompanied by heating strongly indicates adiabatic compression.
Keywords: Adiabatic compression, rapid pressurization, oxygen fire, cylinder valve, heat generation
Question 22
What is the primary function of a check valve within a cylinder-yoke or gas-supply assembly?
A. Increase cylinder pressure
B. Measure oxygen concentration
C. Control vaporizer output
D. Prevent reverse flow of gas
Answer: D
Rationale: A check valve permits gas to flow in one direction while limiting retrograde flow toward the original
gas source. This function becomes particularly important when multiple supplies with different pressures are
connected to the anesthesia workstation.
Clinical Pearl: A check valve can be remembered simply as a one-way valve.
Exam Strategy: When the question emphasizes prevention of backflow, choose the check valve.
Keywords: Check valve, one-way valve, reverse flow, gas supply, hanger yoke
Question 23
