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Clinical Anesthesia > Anesthesia Machine > Flashcards

Anesthesia Machine Flashcards

1
Q

The anesthesia machine is divided into what 4 component subsystems?

A
  1. High pressure system
  2. Low pressure system
  3. Breathing system
  4. Scavenging system
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2
Q

What is the typical operating pressure of the pipeline gas supply?

A

50-55 psig

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3
Q

E tanks contain how many liters of gaseous oxygen compared to H tanks?

A

660 L vs. 6900 L

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4
Q

To keep oxygen in its liquid phase, what temperature must it be kept at?

A

-297 degrees F

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5
Q

What are the advantages and disadvantages of oxygen generators?

A
  • Advantage: cost saving
  • Disadvantage: noisy, needs power supply, higher cost initially
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6
Q

What gas is no longer used for anesthesia machines due to concerns about substance abuse?

A

N2O

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7
Q

What is the role of the pressure regulator?

A

facilitates constant pressure and flow (prevents flowmeter fluctuations), reducing the pressure to approx. 45 psig, forcing the pipeline supply to be used

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8
Q

What part of the anesthetic machine provides a direct connection between the high pressure and breathing systems?

A

oxygen flush valve; considered a part of the high pressure system

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9
Q

When it’s depressed, the oxygen flush valve delivers O2 at what rate?

A

35-75 L/min

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10
Q

What is the role of the flow control valve?

A
  • it separates the high and low pressure systems and adjusts the flow of gas
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11
Q

What is the part of the machine that measures the flow of gas emerging from the flow control valve called?

A

Flow meter

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12
Q

T or F: Flowmeters can be interchanged

A

False; floats and flow tubes are calibrated as a pair for a specific gas

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13
Q

A flow meter should be read how?

A

at the top of the bobbin, unless it is the ball type, which is read in the center

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14
Q

What is the function of the vaporizer?

A

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

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15
Q

Describe the characteristics of a precision vaporizer we use today?

A
  1. Concentration calibrated or variable bypass output
  2. Flow over vaporization method
  3. Thermocompensation
  4. Out of the circuit
  5. Agent specific
  6. Plenum (high) resistance
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16
Q

Describe an open breathing system

A

No reservoir for anesthetic mixture and no rebreathing of expired gas

  • e.g open drop method on a cloth
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17
Q

Describe a semi-open breathing system

A

With or without reservoir for anesthetic mixture, no rebreathing of expired gas and without CO2 absorption

  • non-rebreathing systems (Ayre’s T piece, Bain, Jackson-Rees, Mapleson)
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18
Q

Describe a semi-closed breathing system

A

With reservoir for anesthetic gas and partial rebreathing of expired gas with CO2 absorption

  • e.g. Circle with oxygen flow higher than the metabolic requirement of the patient
19
Q

What is the difference between low-flow and high-flow anesthesia?

A
  • Low-flow: fresh gas flow b/t metabolic O2 requirement and below 22 ml/kg/min
  • High -flow: fresh gas flow higher than 22 ml/kg/min
20
Q

Describe a closed breathing system

A

With reservoir for anesthetic mixture, complete rebreathing of expired gas without the CO2 (CO2 removed by soda lime canister)

  • O2 supply = metabolic requirement
  • O2 flow b/t 4-7 ml/kg/min

e.g. circle with oxygen flow equal to metabolic requirement of patient

21
Q

What are the advantages of a closed breathing system?

A
  1. Economical
  2. Conserve heat and humidity
  3. Reduced operating room/environmental pollution
  4. Can estimate O2 consumption of patient/dx hypermetabolic states
  5. Less danger of barotrauma b/c takes longer to develop high pressure with such low O2 flows
22
Q

What are the disadvantages of a closed breathing system?

A
  1. Requires knowledge of uptake
  2. More attention required (fresh gas flow must balance uptake)
  3. Inability to change inspired concentrations quickly
  4. Danger of hypercapnia if CO2 not changed regularly
  5. Accumulation of undesirable gases in breathing circuit (e.g. Compound A)
23
Q

What is Compound A?

A

a noxious compound produced by Sevoflurane reacting with soda lime which causes proximal tubular damage in the kidneys

24
Q

What is the most commonly used breathing system in most veterinary clinics?

A

A semi-closed system using a circle breathing circuit and a high flow of fresh O2

25
Q

Describe the principle of operation for a circle breathing circuit

A

animal inspires from and expires to the circuit through a Y-piece, gases are directed around the circuit by unidirectional valves, CO2 is absorbed by soda lime, and the O2 consumed by the patient is replaced by the fresh gas flow

26
Q

Describe the Unviersal F circuit

A

it is a coaxial rebreathing system (tube within a tube) that can be used in small animals up to 90 kg where the expired gas warms the inspired gas inside the smaller tube

27
Q

What are the advantages of F circuits?

A
  • Small size and light weight
  • allows heat and moisture retention to maintain body temp
28
Q

What are the disadvantages of F circuits?

A
  • smaller inner tube provides resistance to breathing in big dogs
  • elongation of outer corrugated tubing results in more dead space
  • more difficult to clean
29
Q

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

A
  • Output not affected by changes in ventilation, temp, or O2 flow rate
  • Assisted or controlled ventilation will not greatly increase inhaled anesthetic concentration
  • known anesthetic concentration delivered
30
Q

What are the disadvantages of a vaporizer out of a circuit?

A
  1. Expensive
  2. Slow changes in anesthetic concentration especially with low flow of O2
31
Q

What oxygen flow rate should dogs be started on immediately after induction with a VOC? What is the maintenance flow rate?

A

2-3 L/min (to reduce the dilution effect of the expired gas to the inspired anesthetic concentration); 1 L/min

32
Q

What are the advantages of a vaporizer in the circuit?

A
  1. Cheap
  2. Economical; less anesthetic used
  3. Less environmental pollution
  4. More humidified
33
Q

What are the diadvantages of having a vaporizer in the circuit?

A
  1. Inspired anesthetic concentration varies with changes in carrier gas flow rate, variations in temp, use of positive pressure ventilation, and patient’s ventilation
  2. anesthetic concentration in circuit is unknown
34
Q

What are the general principles of using a VIC system?

A
  1. The higher the O2 flow rate, the lower the inspired anesthetic concentration (dilution)
  2. Inspired anesthetic concentration increases with:
    • controlled or spontaneous ventilation and warm room temp
35
Q

If you wish to use a circle breathing system with a VOC for closed circuit anesthesia, what are the necessary steps for this?

A
  • Use semi closed system to achieve stable plane of anesthesia
  • lower O2 flow and increase vape setting 2-3X over maintenance
  • if patient wakes up or when vape is turned off for recovery, switch back to semi closed
36
Q

What type of non-rebreathing system do we use at UF?

A

modified Bain (Mapleson D)

37
Q

What is the usual oxygen flow rate for a non-rebreathing system?

A

200-300 ml/kg/min (ie. 2-3x minute ventilation)

38
Q

Non-rebreathing systems are indicated for small patients (<7-10 kg). The two main reasons for this are what?

A
  1. Provide less dead space than circle breathing systems
  2. Provide less or no resistance to breathing compared to circles
39
Q

What are the advantages of non-rebreathing systems?

A
  • no valves, so low resistance
  • good control of anesthetic concentration (inspired AC should = vape setting)
  • does not require CO2 absorber
  • less dead space
40
Q

What are the disadvantages of non-rebreathing systems?

A
  1. Very high gas and anesthetic consumption esp in bigger animals
  2. Inspired gas not humidified
  3. Breathing of cool/dry gas results in more fluid loss
  4. Wasteful of anesthetic
41
Q

What non-rebreathing system is used in VCOP?

A

Modified Jackson-Rees (Mapleson F)

42
Q

Circle breathing systems can be used in small patients provided what two things?

A
  1. A breathing hose with a smaller Y-piece is used (decrease dead space)
  2. Ventilation is supported to prevent the fatigue of respiratory muscles resulting from breathing against the resistance of the unidirectional valves
43
Q

What is the role of the scavenging system?

A

Collect waste gases from the breathing system and eliminate them from the workplace

Clinical Anesthesia (15 decks)

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