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Anesthesiology > Anesthetic Machine & Breathing Circuits > Flashcards

Anesthetic Machine & Breathing Circuits Flashcards

1
Q

What are the 4 primary functions of the anesthesia gas delivery system?

A
  1. Provide O2 to the patient
  2. To blend and deliver an anesthetic gas mixture
  3. To remove CO2 from breathing circuit
  4. To support ventilation of the patient
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2
Q

Name the 4 component subsystems of the anesthesia machine

A

High pressure system, low-pressure system, breathing system, and scavenging system

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3
Q

The role of the high-pressure system is to…?

A

regulate pressure before the gas enters the low-pressure system

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4
Q

What is the role of the low-pressure system?

A

it is where O2 and the anesthetic gas mixture are mixed

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5
Q

What does the breathing system do?

A

delivers the anesthetic gas mixture to the patient

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6
Q

What is the purpose of the scavenging system?

A

collects excess gas from the breathing system and transports it to the waste gas evacuation system

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7
Q

What is a pipeline gas supply and how might it differ in a large hospital vs. private practice?

A

anesthetic machine receives its gas supply (typically O2) from this via high-pressure gas hoses; central supply of liquid O2 (large hospital) vs. series of O2 tanks stored at back of private practice

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8
Q

What is the operating pressure of the pipeline gas supply?

A

50-55 psig (pounds per square inch)

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9
Q

What is the formula to determine the volume of oxygen in an E-cylinder based on the pressure gauge reading?

A

Multiply the pressure gauge by 0.3

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10
Q

Why is liquid O2 preferable to gaseous and and what temperature is it stored?

A

less expensive and large amounts of oxygen can be stored at one time; -297 degrees F

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11
Q

Why is N2O no longer used in vet clinics?

A

too great of a potential for abuse

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12
Q

What is the general purpose of the safety features installed in a high pressure system?

A

to prevent delivery of hypoxic gas to patient

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13
Q

Describe the Diameter Index Safety System (DISS)

A
  • prevents misconnection of a gas supply hose to the wrong pipeline gas inlet e.g different sized body, nipple, nut
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14
Q

What are quick connectors?

A

allow faster connection of gas supply hoses to the pipeline outlets than DISS connectors; based on matching pins and holes

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15
Q

Pin Index Safety System (PISS) Connections

A

use unique pin and receptacle combos on cylinder hanger yokes to prevent misconnection of gas cylinder to wrong cylinder inlet

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16
Q

What is the purpose of the pressure regulator? And what pressure does it reduce that of the E-tank to?

A

allows maintenance of constant flow as cylinder pressure changes, which prevents flowmeter fluctuation; 45 psig

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17
Q

What are the different safety features of the high pressure system?

A
  1. Diameter Index Safety System connections
  2. Quick connectors
  3. Pin Index Safety System connections
  4. Pressure regulator
  5. Flow control valves
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18
Q

Why should you not interchange the flowmeters from different machines?

A

because the floats and flow tubes are calibrated as a pair for a specific gas

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19
Q

How should you read the indicator of a flowmeter differently for an indicator that is a ball vs. one that is not?

A

you read the ball indicator in the center, all others are read at the top

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20
Q

What is the purpose of a manifold and why do we not use it in vet med?

A

it is the junction where gas emerging from each flow meter must be joined together; we only use O2 in vet med

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21
Q

What is the function of the vaporizer in the low-pressure system?

A

facilitates the change of a liquid anesthetic into its vapor and add a controlled amount of this vapor to the fresh gas flow

22
Q

What are the features of a precision vaporizer?

A
  • a portion of O2 flow passes through the vaporizing chamber (contains liquid anesthetic) and another portion bypasses. The gases remix prior to exiting to provide desired anesthetic concentration
  • placed out of breathing circuit to prevent breathing resistance
23
Q

What is the purpose of the oxygen flush valve and when should and shouldn’t it be used?

A

provides direct connection b/t high pressure and breathing systems (bypassing the vaporizer)

should use: in recovery when using a rebreathing system to rapidly replace gas in breathing bag

should NOT use: when using non-rebreathing system and when starting inhalation anesthesia b/c can dilute anesthetic concentration or could overpressurize lungs

24
Q

Define an open breathing system

A

no reservoir for anesthetic gas mixture and no rebreathing of expired gas; e.g. ‘open drop’

25
Q

Define a semiopen breathing system

A

with reservoir for anesthetic gas mixture, no rebreathing of expired gas, and without CO2 absorption; e.g. non-rebreathing systems (Jackson-Rees)

26
Q

What is a semiclosed breathing system?

A

with reservoir for anesthetic gas mixture, partial rebreathing of expired gas, and with CO2 absorption; e.g. circle

27
Q

Define a closed breathing system

A

with reservoir for anesthetic gas mixture, complete rebreathing of expired gas without CO2 (removed by soda lime/baralyme); O2 supplied to patient is equal to its metabolic requirement

28
Q

What are the two main breathing systems utilized in veterinary practice?

A
  1. circle breathing systems (semiclosed)
  2. non-rebreathing systems (semiopen)
29
Q

What are the components of a circle breathing system?

A
  1. CO2 absorber
  2. Unidirectional valves
  3. Breathing (reservoir) bag
  4. Breathing tubes and Y-piece
  5. Pressure gauge
  6. Negative pressure relief valve
  7. Adjustable pressure limiting valve (pop off valve)
30
Q

The main capacity for CO2 absorption of soda lime is

A

Ca(OH)2

31
Q

Why is water needed in the soda lime reaction occurring in the CO2 absorber?

A

CO2 must be dissolved before it can react

32
Q

What are the characteristics of fresh soda lime?

A
  • crumbles easily
  • white
  • CO2 canister feels warm during anesthesia
  • Bitter taste
33
Q

What are your 4 indicators that your soda lime is “old” or exhausted?

A
  • hard and chalky
  • color turns blue/violet with exhaustion
  • CO2 canister stays cool during anesthesia
  • Slightly salty taste
34
Q

What is the formula to determine breathing bag size?

A

6 x tidal volume (10-15 ml/kg)

35
Q

T or F: a circle rebreathing system can operate without a pressure gauge?

A

True

36
Q

What is the purpose of the negative pressure relief valve?

A

allows entry of room air into the circuit when there is an excessive negative pressure in the circuit as a result of the patient inspiring from an “empty” circuit (*no longer on VAB machines)

37
Q

What are the advantages of using a vaporizer out of the circuit?

A
  1. Vaporizer output isn’t affected by changes in ventilation
  2. Assisted or controlled ventilation will not greatly increase inspired anesthetic concentration
  3. Known anesthetic concentration can be delivered to the patient breathing circuit
  4. Inspired gas, esp at low fresh gas flow, is humidified resulting in decreased loss of patient’s body heat
38
Q

Disadvantages of using a vaporizer out of the circuit?

A
  1. $$$
  2. Slow changes in anesthetic concentration because the expired gas dilutes anesthetic concentration in the breathing circuit
39
Q

Why do you increase O2 flow rate from 1 L/min to 2-3 L/min immediately after anesthetic induction using an IV agent?

A

the higher flow rate minimizes the difference between inspired anesthetic concentration and the concentration set at the vaporizer, which will expedite the induction process

40
Q

What are a couple problems associated with circle breathing systems?

A
  1. resistance to breathing d/t the unidirectional valves and CO2 canister
  2. dead space - mainly d/t the Y piece

Both of these prove much more problematic in smaller patients

41
Q

Name the 2 benefits of using a non-rebreathing system?

A
  1. Provides less dead space*
  2. Provide less or no resistance to breathing*

*compared to circle breathing systems

42
Q

Describe the Jackson-Rees non-rebreathing system

A
  • the patient inspires fresh gas from the expiratory tube and the fresh gas inlet.
  • During expiration, expired gas goes down the expiratory tube.
  • During the expiratory pause, CO2 exhaled by the patient is eliminated by the high fresh gas flow via the outflow valve.
43
Q

What gas flow rate do people generally use?

A

200-300 ml/kg/min

44
Q

What are the advantages of non-rebreathing systems?

A
  • no valves, so low resistance
  • good control of anesthetic concentration which means the inspired anesthetic concentration is the concentration set on the vaporizer
  • less dead space
45
Q

What are the disadvantages of the non-rebreathing system?

A
  • very high gas flow needed in mL/kg/min and higher anesthetic consumption especially in bigger animals
  • inspired gas is not humidified - leads to greater loss of body heat
  • more pollution of the environment
46
Q

What is the Bain Coaxial System?

A
  • a modified Mapleson D system - most common non-rebreathing system used in UF SAH
  • internal tube supplies fresh gases to patient end of system minimizes mechanical dead space
  • inspires fresh gas from large bore, expiratory and inspiratory tubes, and expired gas is directed down expiratory tube and flushed out by high flow of fresh gas during expiratory pause
47
Q

What 3 elements make up the scavenging system?

A
  1. Gas collecting assembly
  2. Interface
  3. Disposal system
48
Q

What is the purpose of the interface in the scavenging system?

A
  • prevents transfer of pressure changes in the scavenging system to the breathing system
  • provides postive pressure relief to protect patient from occlusions of scavenging system
  • provides negative pressure relief to limit pressure effects of an active disposal system
49
Q

What is an active disposal system?

A

provides negative pressure to eliminate the waste gas e.g. piped vacuum and active duct systems (used at UF)

50
Q

What is a passive disposal system?

A

waste gas moves to disposal system w/o an aid of a system that provides negative pressure, e.g. nonrecirculating ventilation systems, piping directly into atmosphere and absorption devices (activated charcoal

  • used at UF when transporting a small anesthetized patient from one section of hospital to another

Anesthesiology (12 decks)

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