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NURA 641 Intro to Nurse Anesthesia > Week 5 Anesthesia Machine Intro > Flashcards

Week 5 Anesthesia Machine Intro Flashcards

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1
Q

Describe the purposes of using a circle system with the vaporizers.

A
  • patient safety - always #1
  • minimize waste of anesthetic (financial concern)
  • minimize contamination of the OR
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2
Q

How is the volatile anesthetic stored?

A

Store as a liquid, delivered as a vapor.

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3
Q

Name contemporary components of an anesthesia machine.

A
  • electrical supply
  • battery back up
    • 30 minutes
  • alarms
    • high, medium, low
  • required monitors
    • inspired oxygen/CO2
    • expired oxygen/CO2
    • oxygen supply failure
    • hypoxic guard system
    • anesthetic vapor concentration
    • vital signs
  • oxygen supply
    • pipeline supply (medium pressure)
    • cylinder (high pressure)
  • flowmeter
  • oxygen flush valve
  • vaporizers
    • calibrated
  • waste gas system
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4
Q

Name some features that attempt to ensure a safe gas mixture.

A
  • color coded pressure gauges
  • color coded flowmeters
  • an oxygen flowmeter controlled by a single touch coded knob
  • oxygen is the last gas to be added to the mixture
  • oxygen concentration monitor or analyzer
    • **most critical monitor**
  • nitrous oxide is cut off when the oxygen pressure is low
  • oxygen : nitrous oxide ratio monitor and controller
  • pin index safety system for cylinders and diameter index safety system for pipelines
  • alarm for failure of oxygen supply
    • cannot silence alarm
    • alarms after 5 second
    • **most critical alarm on machine**
  • ventilator disconnection alarm
  • at least one reserve oxygen cylinder should be available on machines that use pipeline system

****Key: The alarm for failure of oxygen supply is a pressure alarm, so keep in mind that this could be the wrong gas with low pressure. This is why the oxygen concentration monitor/analyzer is so critical.****

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5
Q

Despite safety features in place on the anesthesia machine, what are some errors that could still occur?

A
  • cross over of gas pipelines
  • filling of cylinders with wrong gases
  • wrong connectors
  • incorrect tanks from the central manifolds
  • accidents during installation of routine maintenance of pipelines
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6
Q

Describe the high pressure system of the anesthesia machine. What are the components?

A
  • includes segments exposed to high pressure of auxillary gas cylinders
    • <2000 psi
  • Components
    • auxillary E cylinder
    • yoke assembly
    • bourdon gauge
    • high pressure regulator
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7
Q

Most common cyclinder used.

A

Size E (E cylinder)

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8
Q

True of False: Many mishaps have happened because of the wrong cylinder or the wrong gas being filled in the indended cylinder.

A

True

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9
Q

Tanks are both available in steel and aluminum. Which is safe for MRI?

A

Aluminum is for MRI environment

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10
Q

Gas color code for CO2, both U.S. and International.

A

US: Grey

International: Grey

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11
Q

Gas color code for HeO2, both U.S. and International.

A

US: Brown and Green

International: Brown and white

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12
Q

Gas color code for Intstrument Air, both U.S. and International.

A

US: Red (USA only)

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13
Q

Gas color code for Medical Air, both U.S. and International.

A

US: yellow

International: black and white

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14
Q

Gas color code for Nitrogen, both U.S. and International.

A

US: black

International: black

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15
Q

Gas color code for Nitrous Oxide, both U.S. and International.

A

US: blue

International: blue

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16
Q

Gas color code for Oxygen, both U.S. and International.

A

US: green

International: white

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17
Q

Gas color code for Vacuum (Suction), both U.S. and International.

A

US: white

International: yellow

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18
Q

Gas color code for WAGD (Evac), both U.S. and International.

A

US: purple

International: purple

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19
Q

Describe the purpose and components of the yoke assembly.

A

​The cylinders are attached to the machine by yokes.

  • orient tanks
  • gas tight seal
  • unidirectional flow of gases
    • dont want tanks exchanging air
    • don’t want tank leaking out to atmosphere
  • contains a filter
    • when tanks are refilled they can be contaminated with metallic parts
  • some have check valve
    • stops leaking into atmosphere
    • stops transfer between tanks
  • Pin index safety system (PISS)
    • ​only one particular cylinder type will fit into the back of the machine
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20
Q

Describe the pin index safety system.

Where is it? What does it do? What are the pin positions for the commonly used gases?

A
  • The hanger yokes of the machine, which supports the cylinder, have the pin index safety system
  • Prevent the attachment of the wrong cylinder to the yokes
  • Pins are on the yoke assembly and the cylinders have corresponding holes

Oxygen: 2, 5

Nitrous Oxide: 3, 5

Air: 1, 5

****Note: PISS is a safeguard, but it is not fool proof, pins can break off, so you can still fit the wrong cylinder to the back of the machine****

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21
Q

INFO CARD

Properties of Compressed Gases and Color Coding of E-Cylinders

A
22
Q

What is the total volume of a full tank of nitrous and what will the psi read?

A

Full tank: 1590 L

psi: 750

23
Q

What are the critical temperatures of both oxygen and nitrous and what does this mean for the state of nitrous at room temp?

A

Oxygen: -118 C

Nitrous Oxide: 36.5 C

Nitrous will be in both liquid and gas form at room temperature.

24
Q

Describe the relationship between volume and pressure in a tank of O2.

A

As the volume decreases, the psi goes down proportionally.

25
Q

Describe the relationship between volume and pressure in a tank of N2O.

A

As volume decreases, psi remains the same.

The psi will remain about 750 psi until almost empty.

26
Q

0 pressure on a bourdon gauge is actually equal to ____, not 0 atm.

A

1 atm

27
Q

How does a bourdon gauge work?

A
  • The high-pressure gas causes the tube to uncoil
  • the movement of the tube causes the needle pointer to move on the calibrated dial indicating the pressure
28
Q

In a tank of N2O, pressure remains constant until all of the liquid has turned to gas. Pressure does not start to drop until about ____ of the tank is used.

A

75%, then about 250-400 mls of liquid remain.

29
Q

What is the purpose of the cylinder safety systems?

A

Prevents explosion dues to overfilling or mis filling

*ASTM standards require all cylinders to have pressure relief devices, which vent the contents of the cylinder to the atmosphere should dangerous pressures develop inside the cylinder.*

30
Q

Describe the two types of cylinder safety systems.

A
  • frangible disk
    • bursts under extreme pressure
  • fusible plug
    • melts at a predetermined temperature
    • made of bismuth, lead, tin and cadmium
    • *protects again high temperature, but not pressure*

A combination of these two is sometimes used: pressure relief valves which re-close after the dangerous pressures have been vented, thus saving the contents and not entirely discharging the cylinder.

ASTM (American Society for Testing and Materials) standards required all cylinders to have pressure relief devices, which vent the contents of the cylinder to the atmosphere should dangerous pressures develop inside the cylinder.

31
Q

Explain how the high pressure regulator works.

A
  • reduces the high and variable pressure delivered from a cylinder to a lower and more constant pressure suitable for the anesthesia machine
  • pressure regulators are preset at the factory
    • 40-45 psi
      • this is slightly lower than pipeline pressure so this ensure that pipeline gas is used preferentially to the cylinder
32
Q

What is the working pressure of the anesthesia machine?

A

50 psi

O2 is supplied to the hospital as a gas @ 50 psi

33
Q

Name the 5 components of the intermediate pressure system.

A
  • hospital supply (pipeline inlet)
  • oxygen flush valve
  • pneumatic safety systems/electrical system (on switch)
    • oxygen supply failure alarms
    • oxygen failure protection devices
  • auxiliary oxygen flowmeter
  • second stage regulator
34
Q

What kind of cylinder is nitrous typically stored in?

A

H cylinder

35
Q

The hospital supply of oxygen is typically stored as a liquid at what temperature?

A

-184 C

36
Q

Describe the hospital supply connections of gases.

A
  • diameter index safety system (DISS)
    • ensures only the correct anesthesia gas can be connected
    • sized and threaded differently
      • body, nipple, and nut combination
  • Contains
    • filter
      • stop contaminants
    • check valve
      • ensures unidirectional flow
    • pressure gauge
      • pipeline pressure
  • gas specific
  • typically to wall outlets
  • manufacturer specific
37
Q

When you press the O2 flush valve, what percentage of O2 does it provide to the anesthesia circuit and at what flow rate?

A

100% O2 @ 35-75 L/min

38
Q

How is the O2 flush valve protected so that we don’t press it by accident?

A

protected by rim in a recessed setting and will deactivate as soon as the finger activating the switch is removed

39
Q

What is the oxygen flush valve?

A
  • Provides high pressure flow of oxygen direct to the common gas outlet from the source, either pipeline or cylinder, bypassing all intermediate meters and vaporizers.
40
Q

When you press the O2 flush valve, what is something to be aware of in regards to your anesthestic gases?

A

Will dilute your anesthetic gases

41
Q

What is the potential hazard of pressing the O2 flush valve when connected to the patient?

A

BAROTRAUMA

  • especially if valve becomes stuck!
  • If used during inspiratory phase of mechanical ventilation
    • ventilator relief valve closes & APL out of circuit - older machines
    • fresh gas decoupling valve - newer machines
      • ​makes it so that if you press this valve the high pressure will not be delivered to the patient
42
Q

Describe the electrical system of the anesthesia machine? How many power cords? In event of a power loss, what can you expect? What else should you plug into it?

A
  • uses single power cord
  • in case of power outage
    • always plugged into red outlet - emergency generator
    • battery back up
      • at least 30 minutes (machine specific)
  • Do not plug anything else into the back of the machine
    • may trip circuit breakers on back of machine
43
Q

What is the Auxillary Oxygen Flowmeter?

A
  • not a mandatory requirement, but on almost all anesthesia machines
  • allows for the use of low flow oxygen without using the anesthesia circuit
    • typical used for MAC cases
  • most often accessible when the pneumatic power switch is off
    • can be used in an emergency, even without machine power
    • however uses ame pipleine supply or attached e cylinder
      • even if contaminated…
  • may serve as potential source of oxygen for jet ventilaiton
44
Q

Describe the second stage pressure regulator.

A
  • located downstream from the gas supply sources in the intermediate pressure system
  • supply contstant pressure to the flow control valves and the proportioning system
    • protects against fluctuations of pipeline pressure
  • lowers the pressure to 14-35 psi
    • ​depends on the workstation
    • typically
      • ​oxygen: 14 psi
      • nitrous oxide: 26 psi
  • ensures that oxygen is the last gas flowing
45
Q

List the components of the low pressure system.

A
  • flowmeters
  • unidirectional valves
  • hypoxia prevention safety devices
  • pressure relief devices
  • anesthesia vaporizers/vaporizer manifold
  • commong gas outlet
  • located between the flow control devices and common gas outlet
  • pressure in this section is slightly above atmospheric
  • pressure in this section is variable
46
Q

What are the 5 pathways of oxygen?

A
  1. flow to the fresh gas flowmeter
  2. powers the oxygen flush valve
  3. activate the fail safe valve/mechanism
  4. activates the oxygen supply low pressure alarm
  5. compresses the bellows of the ventilator
47
Q

Describe the common gas outlet.

A
  • receives all the gases and vapors from the machine and delivers the mixture to the breathing circuit
  • 15 mm female slip joint fitting
  • should not be used to administer supplemental oxygen to a patient
  • where the machine ‘ends’
48
Q

Describe the flowmeter.

A
  • contains
    • flow control valves
    • flow tubes
  • regulates the flow of gases entering the breathign circuit
  • traditional are mechanically controlled
  • newer are an electronic interface
  • oxygen and nitrous flow valves are linked mechanically or pneumatically to prevent a hypoxic mixture
  • selected flows are directed into the vaporizer
49
Q

What are the components of a flowmeter?

A
  1. flow control knob
  2. a tapered needle valve
  3. valve seat
  4. valve stops
  5. flow
  6. float stops
50
Q

Regarding flowmeter arrangement, where is oxygen always placed and why? What are additional safety measures are taken to distinguish the oxygen flowmeter?

A
  • Oxygen flowemter is always positioned downstream or last in a sequence of flow meters so that if there is a leakage anywhere upstream of any other gas, still oxygen will be delivered in a sufficient concentration to the CGO
  • flow control knob for oxygen is the largest, most protruding and has tactile differentiating features like a fluted profile

NURA 641 Intro to Nurse Anesthesia (10 decks)

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