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Principles in Practice > The Anesthesia Gas Machine > Flashcards

The Anesthesia Gas Machine Flashcards

1
Q

What is an APL valve?

A

Adjustable Pressure Limiting Valve

  • found in the expiratory limb -
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2
Q

What are Pneumatic Components of the Pressure System?

A

High pressure system (exposed to cylinder pressure)

  • —Hanger yoke
  • —Yoke block with check valves —
  • Cylinder pressure gauge
  • —Cylinder pressure regulators
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3
Q

What is the pressure in the E Cylinder System?

A full tank

A

2200 psi

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4
Q

What is the pipeline pressure psi?

A

Intermediate pressure system

50 psi

  • Pipeline inlets, check valves, pressure gauges — Ventilator power inlet
  • —Oxygen pressure-failure devices
  • —Flowmeter valve**
  • —Oxygen second-stage regulator (if present) —
  • Flush valve
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5
Q

Where does the flow meter tube reside?

A

Low-pressure system

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6
Q

How much O2 does the O2 flush valve deliver?

A

35 -75 L/min of O2

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7
Q

What area are you checking when you check the low-pressure system?

A

Low-pressure system (distal to flowmeter valve) —

  • Flowmeter tubes
  • —Vaporizers
  • —Check valves (if present)
  • —Common (fresh) gas outlet
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8
Q

Where does the low-pressure bulb checker attach to?

A

common gas outlet

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9
Q

What are the types of problems that can occur in the pipeline supply?

A
  • Loss of O2 pipeline pressure
  • Circuit Breakers
  • Excessive pipeline pressure
  • Cross-connection of gases
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10
Q

What is the only monitor that can accurately detect a hypoxic mixture?

A

O2 Analyzer

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11
Q

What are the three types of safety relief valves?

A
  • Frangible disk (made of copper) that bursts under pressure
  • —Fusible plug made of Wood’s metal (consists of lead, tin , bismuth, and cadmium) that melts at temperatures b/t 157*- 220* F
  • —Spring-loaded safety relief valve that opens at extreme pressure
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12
Q

_____ occurs when gas flows from the cylinder with higher pressure into the lower pressure cylinder rather than proceeding toward the flow meters

A

Transfilling

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13
Q

Hanger yoke

A
  • Orient Cylinders
  • Provides gastight seal
  • Ensures unidirectional flow
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14
Q

Why is transfilling a potential fire hazard?

A

Because cylinder filing generates heat

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15
Q

Only Gas that does not pass through a fail-safe valve before proceeding to the flow meter

A

All gases except O2 pass through a fail- safe valve before proceeding to their flowmeters

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16
Q

Path of Gases in the Anesthesia Machine

A
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17
Q

What are the 5 tasks of Oxygen in the anesthesia machine

A
  • Proceeding through the flowmeters
  • O2 flush
  • Activation of _fail-safe (not part of oxygen lines)_mechanisms
  • Activation of low-pressure alarms
  • Driving the ventilator
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18
Q

What is a variable orifice flowmeter?

A

Tapered so it’s narrower at the bottom

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19
Q

most fragile part of the machine

A

flow tubes

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20
Q

What are the different types of flow meter indicators? How do you read it?

A

FLOWMETERS

— Rotating ball (Drager)

  • Read in the center of float

— Plumb bob (Datex-Ohmeda)

  • Read at the top of float

Auxiliary flowmeter: use for FM or NC

  • —Cannot use if pipeline pressure lost since supplied by same source
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21
Q

When do you avoid activating the Oxygen Flush? Why?

A

Avoid activating flush while the ventilator is on, especially during inspiration

–> barotrauma since the ventilator relief valve is closed during inspiration

  • If fl_ushing is necessary_ to fill bellows, use short bursts during the expiratory phase
  • may dilute inhaled agent and may lessen inhaled anesthesia
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22
Q

How does the fail-safe mechanism function?

A

FUNCTIONS ON O2 SUPPLY PRESSURE FAILURE

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23
Q

What is the fail safe called for Datex - Ohmeda?

A

Pressure sensor shutoff valve

— Flow of all other gases shut off when O2 supply pressure decreases to 20 psi

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24
Q

What is the fail-safe called for Drager?

A

Drager: oxygen failure protection device (OFPD)

  • —Reduces supply of other gases proportionately as O2 supply pressure decreases, shutting off all flow of N2O and air when O2 pressure 12 psi
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25
Q

How does a datex -ohmeda low-pressure alarm sound? when does it sound?

A
  • Datex-Ohmeda: O2 supply failure alarm whistles when the machine turned on
  • —When the pressure decreases to 28 psi** or when the machine is **turned off, whistles again
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26
Q

How does a Drager low-pressure alarm sound? when does it sound?

A
  • sounds alarm when O2 supply pressure reaches 37 psi
  • — Series of medium[you can silence], high [continuous] and low [pop-up] priority alarms
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27
Q

Where/How does hypoxic guard work?

A

The Hypoxic guard (proportioning system) works on FLOW/ CONCENTRATION that the patient is getting

  • Designed to prevent delivery of hypoxic breathing mixtures
  • All link O2 and N2O so that the final breathing mixture is at least 25% +/- 4% O2

Datex-Ohmeda: Link-25 system (pneumatic/mechanical)

—Flowmeter control knobs are linked by a chain so that O2 is increased automatically when N2O is increased

—Consists of 29 teeth 14 teeth linkage

—Second-stage regulators incorporated

  • O2 14psi
  • N2O26psi

Drager: Oxygen Ratio Monitor Controller (ORMC) or Oxygen Ratio Controller (ORC)

—Maintains at least 25% O2 by limiting N2O flow; the flow of O2 generates pressure on a diaphragm, which is linked by a rod to a second diaphragm and valve in the N2O line, which creates an appropriate ratio

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28
Q

What is the most dangerous situation that can happen in regards to the problem with the hypoxic guard system

A

Inert gas administration (third gas such as Helium) should detect with O2 analyzer

  • — Most dangerous situation
  • — Able to bypass hypoxic guard system with Drager
  • Machine has switch with 2 positions: N2O-O2 and All Gases
  • In N2O-O2 position, ORMC and alarms active
  • In All Gases position, ORMC and alarms inactivated and all gases (except N2O) may flow without hypoxic guard protection
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29
Q

this is how much fresh gas entering the vaporizer inlet is allowed to come into contact with the liquid anesthetic

A

Splitting ratio

30
Q

What are the modern vaporizers called?

A

Variable- Bypass (vaporizers)

31
Q

What is the vaporizer for Desflurane called?

What is the splitting ratio?

A

Datex-Ohmeda Tec 6 (Desflurane)

  • —Heated, dual-circuit vaporizer
  • —Fresh gas from the common manifold passes through the vaporizer; it never comes in contact with the liquid agent
  • NO SPLITTING RATIO
  • —More vapor is delivered from the vapor circuit if either the desired volume percent setting is increased or the fresh gas flow is increased
  • — Heated to 39*C; produces vapor pressure of 1500 mmHg
  • —Desflurane near boiling at room temperature; if placed in variable-bypass vaporizer, would constitute 100% of output at first, creating a hypoxic breathing mixture
32
Q

A system that can assure only one vaporizer can be turned on at a time

A

Interlock system on anesthesia machine ensures that only one vaporizer can be on and that trace vapor output is minimal when vaporizers turned off

33
Q

only vaporizer that can be

filled while turned on; the others must be in off position

A

Desflurane Tec-6

34
Q

ELECTRONIC VAPORIZERS

A
  • The volume of carrier gas necessary to produce the desired agent concentration may be determined by a computer that calculates the carrier gas flow that needs to pass through the vaporizing chamber in order to produce the desired anesthetic agent concentration
  • Another type of electronic vaporizer withdraws a calculated amount of liquid agent from the agent bottle and injects that liquid into the breathing system or fresh gas flow. The amount of liquid that is injected is adjusted to achieve the desired anesthetic agent concentration
35
Q

What are Vaporizer Hazards?

A
  • Incorrect agent administration: Must maintain diligence during filling
  • Tipping: If vaporizer tips > 45*, must contact a service agent —-> Entry of liquid agent into control assembly at the top of vaporizer can deliver unpredictable amount of agent
  • Overfilling with agent: Prevent by filling only to the top etched line on the liquid level indicator glass
  • Simultaneous inhaled agent administration: place Datex-Ohmeda vaporizers next to each other if center one removed
36
Q

What are the factors that influence vaporizer output?

A
  • Flow Rate: The output of the vaporizer is generally less than the dial setting at very low (< 200 ml/min) or very high (> 15 L/min) flows
  • Temperature: Automatic temperature compensating mechanisms in bypass chambers maintain a constant vaporizer output with varying temperatures
  • Back Pressure: Intermittent back pressure (e.g. positive pressure ventilation causes a higher vaporizer output than the dial setting)
  • Atmospheric Pressure: Changes in atmospheric pressure affect variable bypass vaporizer output as measured by volume % concentration, but not (or very little) as measured by partial pressure (lowering atmospheric pressure increases volume % concentration and vice versa)
  • Carrier Gas: Vaporizers a_re calibrated for 100% oxygen. Carrier gases other than this result in decreased vaporizer output._
37
Q

Review Potencies of Inhaled Anesthetics

A
38
Q

Breathing Circuit take-home points

A
  • delivering O2
  • eliminating CO2
39
Q

How is Co2 eliminated?

A
  • CO2 is eliminated by washout with adequate fresh gas flows or by absorption in soda lime
40
Q

How is resistance in the circuit minimized?

A

Resistance in a circuit minimized by reducing circuit’s length and increasing its diameter, avoiding sharp bends, eliminating valves, and maintaining laminar flow

41
Q

Where does the dead space end?

A
  • Dead space ends at the Y-piece of the circuit
    • — Where the inspiratory and expiratory gases diverge
42
Q

What is the. position of the APL on WHEN doing a bag mask?

A

Bag-mask Ventilation: Valve is usually left partially open. During inspiration bag is squeezed pushing gas into inspiratory limb until pressure relief is reached, opening the APL valve.

43
Q

What are the 2 common reasons for an increase inspired C02

*EXAM

A

Only 2 common reasons for an increase in inspired CO2:

exhaustion of absorbent granules or faulty unidirectional valves

Faulty unidirectional valves: increase in inspired and expired CO2

  • — Should increase fresh gas flow to 5-8 L/min–> converts system to semi-open in which rebreathing of gases minimized
  • — If this causes inspired CO2 to decrease substantially, absorbent granules are exhausted and should be replaced at end of the case
  • —If elevated inspired CO2 persists, valves are likely to be incompetenT –> anesthetist should
    • remove expiratory valve
    • inspect , dry and reassemble it while ventilating patient with an ambu bag
44
Q

What is the inspired CO2 baseline?

A

should be zero unless smoker

45
Q

CO2 WAVEFORM PHASES

A
46
Q

What is happening here?

A

LOW ETCO2 WITH GOOD PLATEAU

  • May be the result of hyperventilation or an increase in dead space ventilation. Comparison of PetCO2 with PaCO2 is necessary to distinguish these two conditions.
47
Q

What is happening here?

A

HIGH ETCO2 WITH GOOD PLATEAU

  • May be caused by hypoventilation or increased CO2 delivery to the lungs.
48
Q

What is happening here?

A

Curare Cleft/ Spontaneous Respirations

49
Q

What is happening here?

A

Obstruction: Prolonged Expiratory Upstroke

50
Q

What is happening here?

A

BASELINE ELEVATED

  • May be c_aused by an incompetent expiratory valve or exhausted absorbent in circle system_; insufficient fresh gas flow to Mapleson system; problems with inner tube of Bain system; deliberate addition of CO2 to fresh gas; an incompetent inspiratory valve.
  • May also be result of rebreathing under drapes in spontaneously breathing patient who is not intubated
51
Q

What is happening in this picture?

A

INCOMPETENT INSPIRATORY VALVE

  • The waveform shows a prolonged plateau and a slanting inspiratory downstroke
  • The inspiratory phase is shortened, and baseline may or may not reach zero, depending on fresh gas flow
  • A similar pattern may be seen with suction applied to a chest tube
52
Q

What is happening here?

A

IRREGULAR PLATEAU OR BASELINE

  • May result from displacement of tracheal tube into upper larynx or lower pharynx with intermittent ventilation of stomach and lungs or from pressure on the chest, which causes small volumes of gas to move in and out of the lungs
  • maybe its mainstem
53
Q

What is happening here?

A

Classic LEAK IN SAMPLING LINE

  • If the patient is breathing spontaneously a falsely low end-tidal carbon dioxide reading may be seen, owing to air entrainment, but no terminal hump is seen
  • An upswing at the end of Phase III may also be seen in obese and pregnant patients
54
Q

What is the use of Carbon Dioxide Absorber?

A
  • Makes rebreathing of gases possible
  • Conserves agent and gases while preventing respiratory acidosis that would result from rebreathing of CO2
55
Q

What are the patterns of exhausted CO2 absorber?

A

change it when its all violet!

56
Q

Soda Lime equation!

A
57
Q

absorbent that only has Lithium Hydroxide

does it have Compound A?

A
58
Q

absorbent that does not dessicate

recyclable; better for the earth

A

THE ONLY ONE THAT DOES NOT CHANGE IN COLOR!

BE VIGILANT WITH FICO2!

59
Q

Which one has the strongest base?

Whats the water content?

What is the mesh size?

A

SODA LYME –> strongest base

lithium product has less base; it does not have an activator

–> water content of lithium product compared to more base products has about the same of slightly higher

higher water content helps prevents dessication

–> Aside from Spiralith that does not have a mesh ; its is 4-8 for the rest

–> Spiralith does not change color

60
Q

How do the unidirectional valves work?

A

When the patient inspires: the inspiratory valve should go up

When the patient expires: the expiratory valve should go up.

61
Q

Two things that we look at for absorption and exhaustion of the absorbent

A

Channeling and wall effect

Both absorbents undergo decreases in efficiency due to channeling and the wall effect

  • — Inside edge of canister low-resistance pathway (top and along the edges)
  • —Exhaled gas follows this pathway through the canister, forming channels (angling along the pathway forms channels) whose capacity to absorb CO2 is exhausted before the capacity of the bulk of absorbent is used
  • wall effect and channeling produce exhaustion of absorbent before capacity reached
  • Prevent this by shaking canister before place in system to promote uniform packing throughout
62
Q

What are clinical signs of CO2 absorbent exhaustion?

A

CLINICAL SIGNS OF CO2 ABSORBENT EXHAUSTION

  • Increase in partial pressure of EtCO2; may also see increase in inspired CO2
  • Increase (and later decrease) in HR and BP
  • Hyperventilation
  • Respiratory acidosis
  • Dysrhythmia
  • SNS activation (flushed, dysrhythmias,sweating)
  • Increased bleeding at the surgical site (surgeon says theres alot of oozing)
  • Color of indicator at end of case
63
Q

Complications of Sevo

A

Production of Compound A

  • —Found with Sevoflurane (unstable in soda lime)in studies
  • Renal injury at 25-50 ppm in rats ¢ Lethal at 130-340 ppm
  • Theoretical concern in humans
  • Package insert recommends that after 2 MAC hours, increase FGF to a minimum of 2 L/min
64
Q

What forms the most carbon monoxide?

A

Desflurane > Enflurane > Isoflurane >> Sevoflurane and Halothane

  • — Worse in dry carbon dioxide absorbent [dessicated]
  • —Importance of using low flows and turning off flows when done
65
Q

Changing CO2 absorbent

A
  • Do not change in middle of case (ideally)
  • Increase fresh gas flow to 1-2 times MV (>5 L/min –> converts to semi-open circuit)
  • Manufacturer recommends changing
  • absorbent if it is left in machine for longer than 48 hours –> overly cautious; use clinical judgment and established practice
  • Dehydration and CO production are concerns with high gas flows used or flows left on overnight or during the weekend
66
Q

What are the typical alarms found in the anesthesia machine?

A

Alarms based on exhaled volume —

  • Disconnect, apnea; low TV
  • — High RR
  • — Reverse flow
  • — Low MV
  • —Ascending bellows

Alarms based on pressure within breathing circuit

  • — High pressure
  • — Disconnect; pressure below that expected following a mechanical breath
  • — Continuing high pressure
  • — Subatmospheric pressure

Alarms based on pressure within oxygen supply lines

  • —Low oxygen supply pressure
  • Alarms based on composition of gases in circuit
  • — Low concentration of exhaled agent
  • — Low oxygen concentration
  • — Apnea: low or absent concentration of CO2
67
Q

What are the components of the Scavenger System

A
  • Gas collection assembly –> At APL valve and ventilator relief valve
  • Transfer tubing: 19 or 30 mm; color coded yellow sometimes
  • Scavenging interface (most important part)
  • Gas disposal tubing
  • Gas disposal assembly
    • —Active disposal (more common) or passive disposal (less common)
68
Q

What does the scavenging system protect the breathing circuit from

A

SCAVENGING SYSTEMS

  • Protects the breathing circuit or ventilator from excessive positive or negative pressure.
69
Q

What are the types of Scavenger interface

A

TYPES OF SCAVENGER INTERFACE

  • Closed interface (all Datex-Ohmeda, old Drager) — Communicates to atmosphere only through valves
    • Used with passive disposal system
    • Must have positive pressure relief
    • Used with active (suction) disposal system
    • Must have positive and negative pressure relief
70
Q

What does all new Drager scavenger have?

A

Open interface (all new Drager)

—No valves; open to atmosphere (both negative and positive pressure relief “built in”

  • — Must be used only with active systems
  • — Reservoir required

—Safety

  • Safer than closed interface for the patient; no barotrauma
  • Less safe than closed interface for the anesthetist (if used improperly)
71
Q

What are the causes of critical incidents?

A

CAUSES OF CRITICAL INCIDENTS

  • Underlying causes of all critical incidents — Improper or reduced maintenance
    • — Inadequate in-service education
    • —Substandard equipment monitoring
    • — Failure to use checklists
    • —Lack of familiarity with equipment standards
72
Q

What are some MECHANISMS OF CRITICAL INCIDENTS?

A

Failure to ventilate

  • — Disconnection
  • — Failure to initiate ventilation initially or after an interruption
  • — Failure to close APL (applicable to older absorber systems that lack “bag/vent”switch)
  • — Misconnections of breathing circuit

— Occlusion or obstruction of the breathing circuit

  • Kinking or plugging of ETT
  • Incorrect insertion of flow direction-sensitive components
    • PEEP valves
    • Cascade humidifiers
  • Kinking of fresh gas delivery hoses

— Leaks

  • Failure or improper reassembly of bellows after cleaning
  • Damage to or disconnection of pressure monitoring hoses — Failure of pipeline and tank oxygen supply
  • Driving a vent with cylinders (when pipeline is unavailable) cause rapid tank depletion

— Inadvertent application of suction to breathing circuit

  • Failure of scavenger interface negative-pressure relief valve
  • Intubation of trachea with nasogastric tube, which is then connected to suction

Barotrauma

  • —Excess inflow to breathing circuit (flushing during ventilator inspiration)
  • Ventilator relief valve may stick closed —
  • Control assembly problems

Principles in Practice (19 decks)

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