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Principles I > Anesthesia Machine > Flashcards

Anesthesia Machine Flashcards

1
Q

What does “patient ready” imply?

A
  • APL valve is open
  • In bag mode
  • flowmeters and vaporizers are OFF
  • mask is on Y piece
  • suction is on
  • make sure monitors are ready
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2
Q

What are the primary purposes and associated risks of the anesthesia machine?

A
  • provide oxygen (may deliver a hypoxic mix)
  • blend anesthetic gas mixture (may deliver incorrect anesthetic dose)
  • allow ventilation of patient lungs (may give inappropriate ventilation)
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3
Q

Describe the oxygen analyzer?

A
  • Essential part of the machine check
  • analyzes the percentage of oxygen delivery
  • make sure it is calibrated to room air
  • do this part of the test BEFORE the positive leak test since you will have to break the closed system
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4
Q

What are some circumstances that defeat anti-hypoxic safeguards?

A
  • wrong gas in oxygen pipeline or cylinders
  • defective pneumatics or mechanics
  • leaks downstream of flow control valves
  • inert third gas administration
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5
Q

What are the five functions/paths of oxygen?

A
  • go to the flowmeter
  • go to the O2 flush
  • activate the oxygen pressure failure safety mechanism (fail-safe)
  • activate oxygen low-pressure alarm
  • power mechanical ventilator bellows
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6
Q

How does scavenging work with the different types of ventilation?

A
  • manual: gas enters scavenging system when peak pressure exceeds the opening pressure of the APL valve
  • mechanical: gas enters during late exhalation and the expiratory pause after the vent bellows have returned to full position
  • spontaneous: gas enters during late exhalation and the expiratory pause after the reservoir bag is full
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7
Q

What are the safety mechanisms of the scavenging system?

A
  • different size hoses (19mm or 30mm) as opposed to 22mm breathing hose
  • positive pressure relief mechanism if the vacuum is not high enough
  • negative pressure relief if vacuum too strong will not affect gases to be delivered to patient
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8
Q

What is the positive pressure relief valve?

A

valve that opens when there is too much pressure, allowing waste gases to vent into the room and help prevent positive pressure in the patient circuit

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9
Q

What is the negative pressure relief valve?

A

valve that opens when there is too much suction, allowing room air into the flow of waste gas to the vacuum suction in order to prevent a negative pressure in the patient circuit

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10
Q

Describe the scavenging system?

A
  • collects and disposes of excess gases for environmental safety
  • may be active or passive
    active: vacuum from hospital disposal system withdraws gas from scavenging system (uses negative pressure)
    passive: slight positive pressure of excess gases in machine moves it into evacuation hose and into a disposal system
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11
Q

What are the different parts of the scavenging system?

A
  • collection hoses: come from the APL valve and ventilator pressure valve
  • intake ports: where the hoses connect to the system (open ports should be capped!)
  • reservoir: allows waste gases which enter the system in uneven delivery to be handled in a constant, continuous manner
  • manifold: interfaces between the machine and the disposal system
  • vacuum control: used in the active system; adjusts the amount of vacuum from hospital disposal influencing scavenging system
  • exhaust port and evacuation hose: used in passive system; connects to the environment
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12
Q

Describe the correct use of vacuum suction in the scavenging system.

A
  • needle valve should be adjusted so flow out of manifold keeps the reservoir bag expanding and collapsing slightly and less than half full
  • positive pressure relief valve opens with too much pressure
  • negative pressure relief valve opens with too much suction
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13
Q

Describe the breathing system.

A 
-where fresh gas mixture passes from machine to patient
includes:
-fresh gas hose/inlet
-inspiratory/expiratory unidirectional valves
-breathing hoses
-Y piece
-APL or "pop off" valve
-CO2 absorber housing
-CO2 absorber canister
- breathing system pressure gauge
-reservoir bag
-bag/vent switch
-mechanical vent
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14
Q

what is the function of the fresh gas hose or fresh gas inlet in the breathing system.

A

delivers from the CGO to the breathing system

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15
Q

Describe the adjustable pressure limiting (APL) valve of the breathing system.

A
  • during ventilation, APL valve is closed to amount of pressure needed to deliver a breath and anything over that pressure goes to the scavenging system
  • if APL is set on “0” or “minimal”, anything above that goes to scavenging
  • totally open APL valve is used to check the scavenging system
  • totally closed APL valve is used to check the breathing system
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16
Q

Describe the reservoir (ambu) bag of the breathing system.

A
  • when full, pressure from the O2 flush starts transferring to the breathing system, creating risk for barotrauma
  • does provide some flexibility to help minimize barotrauma
  • different sizes are used for different ages
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17
Q

Describe the bag/vent switch of the breathing system.

A
  • switches between mechanical ventilation and ambu bag
  • in vent mode, APL valve and reservoir bag do not function
  • vent system has its own pressure valve
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18
Q

What are the parts of the mechanical vent?

A
  • vent drive gas tube
  • vent hose
  • vent bellows
  • vent pressure relief valve (spill valve)
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19
Q

Describe the breathing system’s positive leak test.

A
  • APL valve totally closed
  • flowmeters all off
  • Y piece occluded
  • in bag mode
  • Hit the O2 flush and drive gauge pressure >30 cmH2O
  • If the pressure stays up at least 10 seconds, there is no leak
  • to release pressure, OPEN the APL valve!
  • ALWAYS perform test after any breaks in the system and before each case
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20
Q

What are the safety features of the breathing system?

A
  • antidisconnect fresh gas hose connector
  • antidisconnect pressure sampling line connection
  • ventilator low airway pressure alarm (“apnea alarm”)
  • ventilator pressure limiting adjustment knob (prevents barotrauma)
  • ventilator pressure relief valve (any set pressure increase spills out)
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21
Q

Describe the low pressure system.

A 
-blending of gases and volatile agent based on control settings
includes:
-flowmeters
-vaporizers
-common gas outlet (CGO)
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22
Q

What are the flow control valves?

A
  • control gas flow through the flowmeter
  • used for carrier gas
  • calibrated to the density and viscosity of specific gases
    include: needle valve, flow tubes, and indicator float
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23
Q

What is the function of the needle valve of the flow control valve?

A

control gas flow

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24
Q

Describe the flow tubes of the flow control valves.

A
  • Thorpe tube
  • tapered
  • calibrated to specific gas
  • coated with a conductive substance to minimize static electricity
  • may have two tubes, first tube being smaller and more precise for doses less than 1 L/min
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25
Q

Describe the indicator float of the flow control valves.

A
  • rotates to minimize friction
  • in the center
  • ball float read at the center of the ball
  • tapered float read at the top of the float
  • a float stop at the top may cause damage if float shoots to the top, so be sure to have all flowmeters off when turning on to avoid damage
26
Q

What are safety features of the low pressure system?

A
  • touch index O2 flow control knob
  • proportioning system: link-25, ORMC
  • minimal O2 flow
  • positioning of flowmeters
  • interlock-exclusion system on vaporizers
  • antidisconnect device on the CGO
27
Q

Describe the touch index O2 flow control knob safety system.

A

O2 knob is fluted, has a big size difference, protrudes further, and is positioned most right for distinction

28
Q

Describe the proportioning safety system.

A
  • used to prevent delivery of hypoxic mixes
  • delivers at least 25% (+-4%) O2
  • maintains the ratio N2O:O2 at no more than 3:1
  • includes the link-25 and ORMC systems
29
Q

Describe the Link-25 safety system.

A
  • flow control knobs of N2O and O2 are linked by a chain
  • if N2O is turned up, O2 goes up as well to maintain the 3:1 ratio
  • O2 does not come down with N2O so you must turn O2 down
30
Q

Describe the oxygen ratio monitor controller (ORMC) safety system.

A
  • pneumatic, mechanic control
  • will not allow you to turn up N2O past O2, but will allow O2 increase which then allows you to increase N2O up to a 3:1 ratio
  • must turn back down
31
Q

Describe the minimal O2 flow safety system.

A
  • if the machine is on it will automatically deliver 150 ml/min of O2 meeting the basic needs of the patient if the operator forgets to turn on oxygen flow
  • reason machine needs to be off during low pressure leak tests
32
Q

Describe the safety mechanisms of flowmeter positioning.

A

oxygen flowmeters are always nearest to the vaporizers which is downstream, furthest right

  • minimizes the risk of delivering a hypoxic mixture if a leak occurs within flowmeter
  • will still be hypoxic if the leak is within the O2 flowmeter or downstream of it
33
Q

Describe the interlock-exclusion system of vaporizers.

A
  • prevents using more than one vaporizer at one time
  • locking lever locks in place on the manifold port valves
  • interlock rods on vaporizers will not permit more than one vaporizer to be turned on at once
34
Q

What is the manifold?

A

where gases from different flowmeters mix together and have opportunity to enter into a vaporizer which is attached here

35
Q

What is the check valve of the manifold?

A

valve that helps prevent O2 flow from going backwards (upstream)
-if a crack or leak develops in N2O flowtube, this valve helps prevent O2 flow from flowing back to N2O flowtube and leaking to the atmosphere

36
Q

Describe the common gas outlet (CGO).

A
  • supplies gas mixture to the breathing system
  • “fresh gas outlet”
  • here you perform the low pressure circuit leak test
  • includes the antidisconnect safety feature
37
Q

Describe calibrated vaporizers.

A
  • add vaporized anesthetic agent to gas flow
  • use a “keyed” system to fit
  • includes the interlock-exclusion safety feature
38
Q

Describe the low pressure circuit leak test (negative pressure leak test).

A
  • looks at vaporizers and flowmeters
  • all vaporizers and flowmeters off
  • connect bulb to CGO
  • compress suction bulb
  • want it to stay compressed for 10 seconds
  • then open each vaporizer one at a time, recompress bulb and look for each to stay compressed 10 seconds
  • vaporizers commonly have leaks
39
Q

Describe the high pressure system.

A
  • gas supplies connected to the machine

includes: pipeline, cylinder, O2 power outlet

40
Q

What is the pipeline gas inlet?

A

pipeline supply of gas through hoses from wall outlets

41
Q

What is the function of pipeline filters?

A

remove damaging debris

42
Q

What is the function of pipeline check valves?

A

prevents retrograde flow and leakage if the pipeline supply is disconnected and cylinder supply is in use
*gas can’t flow backwards and there won’t be any cross filling between the pipeline and cylinder

43
Q

what should a pipeline pressure gauge read?

A

50-55 psig

44
Q

What are some pipeline safety features?

A

Diameter index safety system (DISS)

Quick Connectors

45
Q

What is the cylinder gas inlet?

A

reserve supply of gases (O2, N2O, and air)

46
Q

what is the function of the cylinder hanger yoke?

A
  • orients the cylinder
  • provides a seal (washer)
  • directs flow
  • also contains a required filter
47
Q

what is the function of the cylinder check valve?

A

prevent retrograde flow and transfilling to a second cylinder of some gas

*transfilling occurs if both cylinders are open and gas flows from the higher to lower pressure cylinders instead of flowmeters

48
Q

what is the function of the cylinder pressure regulator?

A
  • reduces pressure to 45 psig

* if the pipeline and cylinder are open, pressure prefers to come from the pipeline since its pressure is higher

49
Q

Describe the cylinder’s pressure gauge.

A
  • Bourdon-type gauge: flexible tube within the gauge that straightens when exposed to gas pressure, causing gear mechanism to move needle pointer
  • should start at 0
  • need to bleed pressure gauge back down to 0 if cylinder has been opened
  • if baseline is not 0, gauge will only read accurately pressure higher than the baseline
50
Q

what is the cylinder’s safety system?

A

pin index safety system (PISS)

51
Q

Describe the O2 power outlet.

A

connected to the mechanical ventilator and the O2 flush valve

52
Q

Describe the O2 flush valve.

A
  • bypasses flowmeters and vaporizers directly to the breathing system (50 psig)
  • delivers 35-75 L/min
  • reinflates the reservoir when it is not full and the vent bellows
  • important to disconnect the ETT and patient and clamp the Y tube to ensure extra pressure is not sent to the pt
  • safety rim around the button to prevent accidental push
  • can cause barotrauma from high pressures
53
Q

what are safety features of the high pressure system?

A
  • low O2 supply pressure alarm
  • O2 pressure failure safety mechanism (fail-safe)

*must continue to monitor inspired O2 concentration (FiO2) since these only look at pressure and cannot verify correct gas

54
Q

Describe the low O2 supply pressure alarm safety system.

A
  • reservoir reed device sounds on initiation of pressure as O2 fills the reservoir and sounds as pressure drops and O2 begins to escape reservoir
  • must sound within 5 seconds of O2 supply pressure drop below 30 psig
  • does not prevent hypoxic mixtures
55
Q

Describe the fail-safe system.

A
  • causes a cessation of flow of non O2 gases if O2 pressure falls below 25 psig
  • prevent hypoxic mixture
  • can be overcome if pipeline/cylinder has the wrong gas since it only reads pressure
56
Q

Describe the electrical supply of the anesthesia machine.

A
  • single power cord
  • battery backup of at least 30 min
  • convenience receptacles and circuit breaker
57
Q

The “on” switch of the machine does what?

A
  • allows electricity to flow to ventilator monitors and desflurane vaporizer
  • connects the O2 supply to shutoff valves, the low O2 supply alarm, and to the flowmeters
58
Q

The “off” switch of the machine does what?

A
  • causes the system to vent O2 pressure to the atmosphere

- check valve is present, allowing for negative pressure test

59
Q

Describe proper use of convenience receptacles and circuit breaker.

A
  • unplug the last thing plugged in if circuit breaker closes
  • do not plug bear huggers or cauterizers into receptacles
  • know where the circuit breaker Is on the machine
60
Q

Describe battery back up.

A
  • at least 30 minutes
  • limited function varies with manufacturer
  • may lose patient monitors, vent function, fresh gas flow, vaporizers, and manual vent function
  • once battery power is lost, may only have delivery of O2
  • switch from vent to manual
  • switch to cylinder to preserve O2
61
Q

What devices or techniques do not rely on wall outlet electrical power?

A
  • spontaneous or manually assisted ventilation
  • mechanical flowmeters
  • scavenging
  • laryngoscope, flashlights
  • IV bolus or infusion
  • battery operated peripheral nerve stimulators or IV infusion pumps
  • patient monitoring using the 5 senses
  • variable bypass vaporizers

Principles I (18 decks)

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