P - Anesthesia Machine

Question 1

Your oxygen supply has failed and you have switched to the backup tanks. Which of the following would be an appropriate measure to reduce the amount of oxygen consumed and prolong the duration of your backup oxygen supply?

Answer 1

Ventilate the patient using the reservoir bag

Most anesthesia machines utilize oxygen as the driving gas to power the ventilator. By reducing fresh oxygen flow rates and eliminating the use of the ventilator by allowing the patient to breathe spontaneously or ventilating via the reservoir bag, you will prolong the backup oxygen supply.

Question 2

The unidirectional valves in the anesthesia breathing system must be positioned between the patient and the

Answer 2

reservoir bag

Unidirectional valves are typically disc valves or rubber flap valves built into the anesthesia machine breathing circuit. A circle system anesthesia circuit contains two of them: an inspiratory valve and an expiratory valve. The unidirectional valves can be mounted anywhere in the inspiratory and expiratory limbs as long as each valve is positioned between the patient and the reservoir bag on each limb.

Question 3

You are preparing your anesthesia machine for cases in the morning. You close the pop-off valve, occlude the y-piece, and evaluate for a drop in pressure after pressurizing the circuit to 30 cm H2O using the flush valve. What test have you just performed?

Answer 3

The leak test

The leak test is performed by closing the pop-off valve, occluding the y-piece, and evaluating for a drop in pressure after pressurizing the circuit to 30 cm H2O using the flush valve.

Question 4

Which statement reflects an accurate understanding of the flowmeter tubes on an anesthesia machine?

Answer 4

A ball is less likely to stick in the presence of dirt

The ball or bobbin in a flowmeter is more likely to stick at low flows where the tube is more narrow. At low flows or in the presence of dirt, a ball is best because it is less likely to stick. The rotameter tubes must be vertical so that the ball or bobbin does not touch the sides of the tube. Flow should be read at the top of a bobbin or in the middle of a ball.

Question 5

The anesthesia machine fail-safe mechanism will

Answer 5

interrupt nitrous oxide flow if the oxygen supply pressure drops

The oxygen fail-safe device will trigger an alarm and shut off the supply of nitrous oxide in the event of loss of oxygen supply pressure.

Question 6

The nitrous oxide shutoff device on an anesthesia machine

Answer 6

turns off the nitrous oxide supply when the oxygen pressure drops

The nitrous oxide shutoff device (also known as the fail safe device) triggers an alarm and closes the supply of nitrous oxide and other gases when the oxygen pressure falls below 30 psi.

Question 7

The hanger-yoke assembly on the anesthesia machine is responsible for which of the following?

Answer 7

Providing uni-directional gas flow

The hanger yoke assembly orients the gas cylinder, provides for uni-directional gas flow, and provides an air-tight seal.

Question 8

The oxygen proportioning system on an anesthesia machine limits the FiO2 when using nitrous oxide to a minimum of

Answer 8

25%

Anesthesia machines are configured to prevent the delivery of a hypoxic mixture of gases from the flowmeters. One of the ways this is done is to link the nitrous oxide flowmeter to the oxygen flowmeter so that at least 25% oxygen is delivered when nitrous oxide is being used.

Question 9

You are using the nitrous oxide tank connected to your anesthesia machine. Your flowmeters are set to administer 1 liter per minute of oxygen and 2 liters per minute of nitrous oxide. The nitrous oxide tank just dropped below a pressure of 745 psig. About how many more minutes of nitrous oxide do you have left?

Answer 9

200 minutes

Because E-cylinder nitrous oxide tanks contain nitrous oxide in both the liquid and gas state, the only accurate way to determine the amount of gas left in the tank is by weighing it. A full E-cylinder tank will hold 1590 liters of nitrous oxide. When the pressure gauge drops below 745 psig, the liquid form has been consumed. The amount of nitrous oxide in the gas phase at that point is about a quarter of the tank or around 400 liters. At 2 liters per minute, you would have approximately 200 minutes of nitrous oxide left.

Question 10

All of the following are tasks that oxygen performs in the anesthesia machine except

Answer 10

pressurize the variable-bypass vaporizers to 2 atmospheres

Unlike other medical gases, oxygen serves multiple functions in the anesthesia machine. The five tasks of oxygen in the anesthesia machine are: supply the fresh gas flowmeter, power the oxygen flush valve, activate the oxygen low-pressure alarms, activate the fail-safe mechanism, and drive the ventilator bellows. Oxygen passes through the variable-bypass vaporizers when they are turned on, but it does not increase the pressure within them.

Question 11

Match the anesthesia machine component with the pressure system to which it belongs.
hangar yoke, flowmeters, O2 flush valve ——high, intermediate and low pressure system

Answer 11

hangar yoke - high
O2 flush valve- intermediate
flowmeters - low pressure
The anesthesia machine is divided into three pressure systems: the high-pressure system, intermediate-pressure system, and the low-pressure system.

Question 12

When the BAG/VENT selector on the anesthesia machine is set to VENT, which components are eliminated from the circle anesthetic system? (select two)

Answer 12

APL valve & Gas reservoir bag

When the BAG/VENT selector is switched to VENT, controlled ventilation is instituted and the gas reservoir bag and APL valve are eliminated from the circle system.

Question 13

On what principle do the mechanical flowmeters on anesthesia machines function?

Answer 13

Flow past a resistance is proportional to the pressure

Mechanical flowmeters function on the principle that flow past a resistance is proportion to the pressure. The flowmeter actually measures the drop in pressure that occurs when the gas flow passes through a resistance.

Question 14

Which pin configuration in the pin index safety system is used by oxygen?

Answer 14

2&5
The pin index safety system utilizes two 5 mm pins that have to align with the matching connector. This is to prevent the inadvertent connection of a wrong gas cylinder to an anesthesia machine. Each specific gas has its own pin configuration. For air, it is pins 1 and 5, for nitrous oxide, it is pins 3 and 5, and for oxygen, it is pins 2 and 5.

Question 15

What are the two components of the anesthesia machine circle system test? (select two)

Answer 15

the flow test
The leak test

The circle system test evaluates the circle breathing system from the common gas outlet to the y-piece and consists of two parts, the leak test and the flow test.

Question 16

You are testing your anesthesia machine in the morning before cases begin. You disconnect the pipeline supply and turn on the backup oxygen cylinder to make sure it functions correctly. The oxygen cylinder is full and connected correctly, but the anesthesia machine still does not pressurize. You know that the problem could be due to a

Answer 16

fault in the oxygen pressure failure device

If you have verified that the backup oxygen cylinder is full, connected properly, and opened, but the anesthesia machine still does not pressurize, then there is a problem in the high or intermediate pressure system in the anesthesia machine. The flowmeters, vaporizers, and unidirectional valves are all part of the low pressure system.

Question 17

Which component is not part of the low pressure system on an anesthesia machine?

Answer 17

Second-stage pressure regulator

The low pressure system on an anesthesia machine contains the flowmeters, hypoxia prevention devices, unidirectional valves, pressure relief devices, and the common gas outlet. The intermediate pressure system of an anesthesia machine contains the pneumatic part of the master switch, pipeline inlet connections and pressure indicators, the gas power outlet, oxygen flush valve, oxygen pressure failure devices, and flow control valves.

Question 18

Which of the following are components of the low pressure system of an anesthesia machine? (select four)

Answer 18

flowmeters, unidirectional valves, common gas outlet, vaporizers

The low pressure system on an anesthesia machine contains the flowmeters, vaporizers, hypoxia prevention devices, unidirectional valves, pressure relief devices, and the common gas outlet. The intermediate pressure system of an anesthesia machine contains the pneumatic part of the master switch, pipeline inlet connections and pressure indicators, the gas power outlet, oxygen flush valve, oxygen pressure failure devices, and flow control valves.

Question 19

The function of the vaporizer interlock system on an anesthesia machine is to

Answer 19

allow only one vaporizer to be turned on at a time

The function of the vaporizer interlock system on an anesthesia machine is to allow only one vaporizer to be turned on at a time.

Question 20

On an anesthesia machine, what components are found in the intermediate pressure system? (select four)

Answer 20

pipeline inlet connections
O2 flush valve
flow control valves
pipeline pressure indicators

The intermediate pressure system of an anesthesia machine contains the pneumatic part of the master switch, pipeline inlet connections and pressure indicators, the gas power outlet, oxygen flush valve, oxygen pressure failure devices, and flow control valves.

Question 21

Select two components of the anesthesia machine that are in the intermediate pressure system.

Answer 21

Oxygen supply failure alarm
Oxygen flush valve

The intermediate pressure system of an anesthesia machine contains the pneumatic part of the master switch, pipeline inlet connections and pressure indicators, the gas power outlet, oxygen flush valve, oxygen pressure failure devices, and flow control valves.

Question 22

The device that connects the oxygen cylinder to the anesthesia machine is known as the

Answer 22

hanger yoke

Gas cylinders are connected to the back of the anesthesia machine by the hanger yoke. It has a safety mechanism known as the pin index safety system that is designed to prevent the inadvertent connection of the wrong gas to the yoke.

Question 23

The low-pressure circuit leak test would not assess the integrity of the

Answer 23

cylinder pressure indicator

The low-pressure circuit leak test evaluates the anesthesia machine from the flow control valves to the common gas outlet. This includes the portion of the machine that is downstream from all safety devices except the oxygen analyzer. The cylinder pressure indicator is in the intermediate pressure system.

Question 24

What is the only machine safety device that detects problems downstream from the flowmeters in an anesthesia machine?

Answer 24

the oxygen monitor

The oxygen monitor is the only machine safety device that detects problems downstream from the flowmeters in an anesthesia machine.

Question 25

You are preparing your anesthesia machine for a general anesthetic on a small child. You should select a breathing bag with a volume that is approximately

Answer 25

three times the patient tidal volume

You can estimate the proper size breathing bag as a volume equal to the vital capacity of the patient, or about three times the tidal volume.

Question 26

In the event of an oxygen supply failure, the oxygen fail-safe device on an anesthesia machine will

Answer 26

turn off the nitrous oxide supply

The oxygen fail-safe device will trigger an alarm and shut off the supply of nitrous oxide in the event of loss of oxygen supply pressure.

Question 27

Your anesthesia machine has a removeable oxygen sensor. You know that this device is most likely a _____ sensor.

Answer 27

galvanic

Galvanic analyzers measure the current produced at the anode of an electrical circuit as oxygen diffuses across a membrane. Galvanic analyzers have a sensor capsule that must be replaced regularly. The removable oxygen sensors seen on anesthesia machines are most commonly galvanic sensors.

Question 28

The oxygen low-pressure alarm on your anesthesia machine begins sounding. What is the first step you should take?

Answer 28

Switch on the backup oxygen cylinder

If the pipeline pressure is lost, the first step is to open the backup oxygen cylinder, reduce oxygen flows to conserve the backup gas supply, and consider switching to manual ventilation since many ventilators use the oxygen supply to drive the ventilator bellows.

Question 29

You are preparing to purge an anesthesia machine prior to administering an anesthetic for a patient with malignant hyperthermia. When performing a purge, you should use a fresh gas flow rate of

Answer 29

10 mL/min

When purging an anesthesia machine prior to administering an anesthetic to a patient with malignant hyperthermia, you should run oxygen at 10 L/min, and ventilate a model lung (such as a breathing bag) at a rate of 10 breaths/min with a tidal volume of 500 mL. The actual amount of time you should purge the system is dependent on the type of machine and can range from about 7 minutes for an Ohmeda Excel to 70 minutes for a GE Aisus.

Question 30

When the anesthesia machine ventilator is in use, the amount of fresh gas flow that contributes to the tidal volume during inspiration is increased by

Answer 30

higher I:E ratios

Unless you are using an anesthesia machine that is designed to compensate for it, when the ventilator is being used a portion of the fresh gas flow will contribute to the tidal volume. This effect increases if the fresh gas flow rates are high, if the I:E ratio is high, and if the patient has a slower respiratory rate.

Question 31

Before installing a new oxygen cylinder on your anesthesia machine, you should

Answer 31

crack the valve open slightly for a second

Before installing a new oxygen cylinder on your anesthesia machine, you should crack the valve open slightly for a second. This will clean away any grease, dust, or debris that would otherwise be released into the anesthesia machine. Because of the serious consequences that occur should a pressurized cylinder fall and break the valve off, you should lay a tank flat on the ground if it cannot be secured in an upright position.

Question 32

Pressing the oxygen flush valve on the anesthesia machine allows oxygen gas to bypass (select two)

Answer 32

flowmeters
vaporizers

Pressing the oxygen flush valve creates a direct communication between the low and high pressure circuits and allows oxygen to bypass the flowmeters and vaporizers on its way to the outlet.

Question 33

What anesthesia machine alarms are based on the circuit pressure? (select two)

Answer 33

The disconnect alarm
The high pressure alarm

The disconnect alarm and the high pressure alarm can be triggered by circuit pressure alarms.

Question 34

What component of the hanger yoke prevents the cross-filling of gas from one cylinder to another?

Answer 34

check valve (not PISS)

Each hanger yoke contains a check valve inside it that prevents the backflow of gas out of the anesthesia machine or the cross-filling from one tank to another.

Question 35

What device on an anesthesia machine is designed to prevent the administration of a hypoxic mixture of nitrous oxide?

Answer 35

The oxygen proportioning system

Anesthesia machines are configured to prevent the delivery of a hypoxic mixture of gases from the flowmeters. One of the ways this is done is to link the nitrous oxide flowmeter to the oxygen flowmeter so that at least 25% oxygen is delivered when nitrous oxide is being used.

Question 36

Which component of the anesthesia machine can serve as a useful indicator of neuromuscular blockade in a mechanically-ventilated patient?

Answer 36

the bellows

The bellows can be a useful indicator of the degree of neuromuscular blockade because the diaphragm will recover from the blockade before the peripheral muscles. As a patient’s respiratory efforts begin to increase, movement in the bellows may be noted between ventilator cycles. The breathing bag is excluded from the circuit when the machine is set to mechanical ventilation.

Question 37

Match the pin positions for the cylinder pin index safety system with it’s corresponding gas

Answer 37

AON

The pin index safety system utilizes two 5 mm pins that have to align the matching connector to prevent the inadvertent connection of a wrong gas cylinder to an anesthesia machine. There are seven different possible pin positions. Medical air uses pin positions 1-5, oxygen uses pin positions 2-5, and nitrous oxide uses pin positions 3-5.

Question 38

Medical gas tanks connect to the anesthesia machine using a safety mechanism called the

Answer 38

pin index safety system

The pin index safety system utilizes two 5 mm pins that have to align the matching connector to prevent the inadvertent connection of a wrong gas cylinder to an anesthesia machine.

Question 39

Your patient is being mechanically ventilated with a pneumatically-driven anesthesia machine. Because of a loss of your pipeline medical gas supply, you have switched your anesthesia machine to your backup oxygen cylinders. What action could you take to prolong the amount of time you have before your oxygen cylinders are exhausted?

Answer 39

Switch to manual ventilation

The ventilator is driven by oxygen and requires a significant amount of oxygen to power it (sometimes as much as your minute ventilation). Your oxygen cylinder can become depleted quickly when using the ventilator. Switching to manual ventilation will dramatically prolong the amount of time you can administer oxygen through the backup cylinders.

Question 40

The pipeline inlet connections on the anesthesia machine are fitted with

Answer 40

diameter index safety system fittings

The pipeline inlet connections on an anesthesia machine are fitted with diameter index safety system fittings to prevent connection of a gas line to the wrong connector on the machine. They also have a unidirectional check valve.

Question 41

Which gas should be positioned last in the flowmeter sequence on an anesthesia machine?

Answer 41

oxygen

Oxygen should be placed last in the sequence of flowmeters to reduce the risk of delivery of a hypoxic mixture of gases if a leak develops in one of the upstream flowmeters.

Question 42

The oxygen supply failure alarm on the anesthesia machine

Answer 42

generates an alarm within 5 seconds of the disconnect

The oxygen supply failure alarm sets off an alarm if the oxygen pressure falls below a standard set by the manufacturer (which is typically 30 psig). It must engage within 5 seconds of the disconnect and cannot be disabled by the anesthetist. It is designed to help prevent hypoxia from lack of oxygen flow, but does not prevent the flow of anesthesia gases (and could still possibly allow a hypoxic mixture of gases to be delivered).

Question 43

Which test assesses the integrity of the unidirectional valves on an anesthesia machine?

Answer 43

Flow test

The flow test checks the integrity of the unidirectional valves by removing the y-piece and breathing through each individual hose to observe the movement of each valve. The leak test is performed by closing the pop-off valve, occluding the y-piece, and evaluating for a drop in pressure after pressurizing the circuit to 30 cm H2O using the flush valve. The positive-pressure test ascertains the ability of the circuit to achieve and maintain sufficient pressure to ventilate the patient.

Question 44

You are checking the oxygen cylinders connected to your anesthesia machine and notice that tank A has two washers in the hanger yoke connection and tank B only has one. You should

Answer 44

remove the second washer from tank A

A washer is typically present between the cylinder port and the hanger yoke. Never use more than one washer as this could potentially bypass the pin index safety system and allow the connection of the wrong gas.

Question 45

When the anesthesia machine is connected to a pipeline gas supply, the backup gas cylinder valves should be kept in the closed position so that

Answer 45

a pipeline oxygen failure will trigger an alarm more quickly

When connected to a pipeline gas source, the cylinders should be kept closed so that a pipeline pressure failure would be detected earlier and to prevent pressure variations in the pipeline from draining oxygen from the cylinders.

Question 46

Which factors would result in higher tidal volumes than are set for the patient when the anesthesia machine ventilator is in use? (select two)

Answer 46

High I:E ratio
Low Respiratory Rate

Unless you are using an anesthesia machine that is designed to compensate for it, when the ventilator is being used, a portion of the fresh gas flow will contribute to the tidal volume. This effect increases if the fresh gas flow rates are high, if the I:E ratio is high, and if the patient has a slower respiratory rate.

Question 47

Most mishaps related to the anesthesia machine scavenging system occur due to

Answer 47

User error

Waste anesthetic gases from the breathing circuit and ventilator are collected by the anesthesia scavenging system and discarded. In order for the integrity of the breathing circuit to be maintained and prevent disruption of ventilation and oxygenation of the patient, an amount that is equivalent to the fresh gas flow must be scavenged each minute. It’s important to note that most scavenging mishaps result from user error.

Question 48

All of the following are types of cylinder pressure relief valves except the

Answer 48

pin index safety system

There are three fundamental types of cylinder pressure relief valves: the fusible plug, the frangible disk assembly, and the safety relief valve. All three types are built into the cylinder and can’t be inspected by the user. The pin index safety system is a mechanism that prevents the inadvertent connection of the wrong cylinder to gas supply tubing or anesthesia machine.

Question 49

All newly manufactured anesthesia machines are supplied with _____-reservoir scavenging interface systems with a(n) _____ disposal system.

Answer 49

open, active

All newly manufactured anesthesia machines are supplied with open-reservoir scavenging interface systems. These systems are valve-less, using relief ports that remain constantly open to the atmosphere to avoid buildups in negative or positive pressure. Open-reservoir systems must, however, be used with active disposal routes because they are dependent on adequate suction in order to properly function. Joint Commission accreditors in the United States mandate the use of active disposal systems.

Question 50

When performing a leak check of the anesthesia machine breathing system, you should pressurize the system to about _____ cm H2O.

Answer 50

30 cm H2O

When performing the breathing system leak test, turn all gas flows to their minimum value, close the APL valve fully, occlude the y-piece, press the oxygen flush valve until the system pressure reaches about 30 cm H2O, and observe for the pressure to remain at 30 cm H2O for at least ten seconds.

Question 51

The low-pressure circuit leak test evaluates the integrity of the anesthesia machine between which two components? (select two)

Answer 51

Flow-control valves
Common gas outlet

The low-pressure circuit leak test evaluates the anesthesia machine from the flow control valves to the common gas outlet. This includes the portion of the machine that is downstream from all safety devices except the oxygen analyzer.

Question 52

A hospital’s pipeline delivers oxygen to the anesthesia machine at

Answer 52

50 Psig

The hospital pipeline delivers oxygen to the anesthesia machine and the operating room at 50 psig.

Question 53

A leak in the vaporizer of an anesthesia machine is most commonly due to

Answer 53

a loose filler cap

A leak in the vaporizer of the anesthesia machine is most commonly due to a loose filler cap.

Question 54

When is the low peak pressure alarm on an anesthesia machine turned on?

Answer 54

When is the low peak pressure alarm on an anesthesia machine turned on?

The low peak pressure alarm is activated when the ventilator is turned on. It is designed to help detect disconnects in the anesthesia circuit. In order to prevent the alarm from triggering, the airway pressure must exceed a preset minimum within a set amount of time (usually about 15 seconds).

Question 55

Which anesthesia machine component is not a part of the intermediate pressure system?

Answer 55

Flowmeters

The intermediate pressure system of an anesthesia machine contains the pneumatic part of the master switch, pipeline inlet connections and pressure indicators, the gas power outlet, oxygen flush valve, oxygen pressure failure devices, and flow control valves. The flowmeters are part of the low-pressure system.

Question 56

Which of the following statements regarding the gas flowmeters found on an anesthesia machine is FALSE?

Answer 56

The diameter of the flowmeter tube is smaller at the top than at the bottom

All of the statements above are true except for answer A. The diameter of the flowtube is tapered, but it is smaller at the bottom than at the top. At lower gas flows, it takes less pressure to support the bobbin and the diameter is smaller. At higher gas flows, the diameter is larger and more gas is allowed to pass around the bobbin.

Question 57

Which of the following anesthesia machine components are upstream from the flowmeters? (select two)

Answer 57

Proportioning system
Fail-safe valve

The oxygen monitor and common gas outlet are downstream from the flowmeters. The fail-safe valve, proportioning system, and the O2 supply alarm are upstream from the flowmeters.

Question 58

The fail-safe valve on an anesthesia machine is designed to engage

Answer 58

when the pressure in the oxygen delivery line drops

The nitrous oxide shutoff device (also known as the fail safe device) triggers an alarm and closes the supply of nitrous oxide and other gases when the oxygen pressure drops.

Question 59

One of the oxygen cylinders connected to your anesthesia machine is empty. Which of the following should you do?

Answer 59

remove the cylinder from the machine

Never leave empty cylinders on the anesthesia machine. If a cylinder is empty, replace it. If you do not have another tank available, place the yoke plug into the hanger yoke as a safety mechanism in case a check valve fails and allows gas to escape the anesthesia machine. Never stand a cylinder upright or lean it against a wall when not in use. The cylinder could fall and break off the cylinder valve. If a cylinder stand is not available, lay it on its side on the ground. The plastic cylinder valve sleeve indicates that a tank is full and unused and should be removed and discarded before connecting it to the anesthesia machine.