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gtown nur641 > Anesthesia Systems > Flashcards

Anesthesia Systems Flashcards

1
Q

3 Essential Components of a Breathing Circuit

A

Low resistance conduit for gas flow

Reservoir for Gas that meets inspiratory flow demand

Expiratory port or valve to vent excess gas

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2
Q

Requirements of a Breathing System (5)

A
  1. Deliver the gases from the machine or device to the alveoli in the same concentration as set and in the shortest possible time
  2. Effectively eliminate carbon dioxide
  3. Minimal apparatus dead space
  4. Low resistance to gas flow
  5. Allow rapid adjustment in gas concentration and flow rate
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3
Q

Effects of hypercarbia

A

Right shift on oxygen-hemoglobin dissociation curve

  • Acidosis
  • Vasodilation -> hypotension
  • tachycardia
  • increased ICP
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4
Q

The anatomic dead space in the circle system begins at

A

The Y Piece

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5
Q

Desirable Features in a Breathing System (8)

A
  1. Economy of fresh gas
  2. conservation of heat
  3. adequate humidification
  4. light weight
  5. convenience during use
  6. efficiency during spontaneous and controlled ventilation
  7. adaptability for adults, children, and mechanical ventilators
  8. proviso to reduce environmental pollution - safe disposal of waste gas
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6
Q

Higher FGF is associated with

A

less rebreathing in any circuit

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7
Q

Dead space increases

A

The chance of rebreathing CO2

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8
Q

Apparatus Dead space ends where

A

The inspiratory and expiratory gas streams diverge (Y-piece)

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9
Q

Apparatus dead space can be minimized by

A

separating the inspiratory and expiratory streams as close to the patient as possible (hence Y piece)

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10
Q

The concentration of inspired gas most closely resembles that delivered from the common gas outlet when

A

rebreathing is minimal or absent

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11
Q

Open classification =

A

no reservoir, no rebreathing (NO VALVES)

ex. sufflation, blow by, tenting, bronchoscopy port, nasal canula

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12
Q

Semi-Open classification =

A

Reservoir, no breathing

ex. some Maplesons, FGF dependent.
circle systems if FGF > MV (i.e. no rebreathing)

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13
Q

Semi-Closed classification =

A

Reservoir, partial rebreathing

Circle systems, FGF < MV

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14
Q

Closed classification =

A

Reservoir, complete rebreathing

FGF is minimal, APL closed.

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15
Q

Advantages of open systems

(i.e. blow-by, insufflation) - 7

A 
Simple! 
Avoids direct patient contact
No rebreathing of CO2 
No reservoir bag 
No valves so less resistance and no chance of disconnection
Good for peds
Good for facial surgery
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16
Q

Disadvantages of Open Systems (blow-by, insufflation) - 5

A

No ability to assist or control ventilation
Requires high FGF to eliminate CO2 (especially with drapes/tenting)
No control of anesthetic depth/Fio2
Environmental pollution
Increased Fire Risk

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17
Q

Mapleson Components (4)

A

Connection point to a facemask or ETT
Reservoir Tubing
Fresh Gas inflow tubing
Expiratory pop-off valve / port

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18
Q

Best Measure of optimal FGF to prevent re-breathing

A

End tidal CO2

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19
Q

Fundamental ways that maplesons differ from circle systems

A

Bidirectional flow

Lack of CO2 absorber, elimination is dependent on FGF

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20
Q

Instances when maplesons are used - 5

A

Pediatrics

Transportation of patients

Procedural sedation

Weaning tracheal intubation

pre oxygenation during out of OR management

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21
Q

Three distinct functional groups of maplesons

A

A

BC

DEF

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22
Q

Structure of Mapleson A (Magill)

A

FGF is after reservoir bag,

Pop off valve is near face mask/ETT

FGF and pop valve are opposite each other

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23
Q

Best mapleson for Spontaneous Ventilation

A

All > Dogs > Can > Bite

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24
Q

With Mapleson A during Spontaneous Ventilation:

FGF = 1x MV then

A

there is no rebreathing

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25
Q

How to achieve no rebreathing with mapleson A during spontaneous ventilation

A

FGF. = 1 x MV

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26
Q

Steps of Spontaneous Ventilation with Mapleson A

A
  1. Pt takes a breath from reservoir (FGF) inhaling mostly FGF, emptying reservoir bag
  2. Pt expires alveolar gas/dead space gas into tubing. EXPIRATORY PAUSE
  3. During expiratory pause, FGF continues to flow, pressure in system is enough to open APL/pop off valve, gas escapes via valve, because this valve is closest to pt, the gas escaping is EXPIRED GAS.

Gas filling reservoir tubing is FGF.

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27
Q

Best Mapleson for Controlled Ventilation

A

Dog > Bites > Can > Ache

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28
Q

Steps of Controlled Ventilation with Mapleson A

A

With the APL valve closed, the anesthetist squeezes the reservoir bag to deliver a breath.

FGF is behind reservoir bag, gas is pushed towards pt.

Pt expires, alveolar gas/dead space gas mixes with FGF in reservoir bag.

Another breath given = not only FGF, but mixed gas. There will be rebreathing, extra pressure will allow mixed gas to leave via pop off valve.

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29
Q

To prevent rebreathing in Mapleson A with controlled ventilation

A

Much larger FGF, up to 20L/min

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30
Q

Disadvantages of Mapleson A (5)

A
  1. Inefficient for controlled ventilation (requires up to 20L/min to flush out mixed gas)
  2. Impractical design for operating room
  3. Proximal location of pop off valve makes scavenging difficult
  4. Difficult to adjust in head/neck surgery
  5. Heavy valve can dislodge small ETT
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31
Q

Structure of Mapleson B/C

A

FGF and pop off valve are located near each other and right near patient.

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32
Q

Mapleson C is used

A

For resuscitation and in patient transfer

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33
Q

Disadvantages of Mapleson B/C

A

FGF and pop off are so close to each other so mixing will always occur, requires huge FGF to wash out CO2.

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34
Q

Structure of Mapleson D

A

FGF is near patient,

pop off valve is closest to reservoir bag, they are far from each other as in A but D is the opposite of A.

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35
Q

Most efficient Mapleson for both spontaneous and controlled

A

Mapleson D

All Dogs Can Bite
Dog Bites Can Ache

Dogs are friends *

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36
Q

Steps of Spontaneous Ventilation with Mapleson D

A
  1. FGF is flowing closet to patient, so patient inhales mostly FGF,
  2. Pt exhales, expired gas mixes with FGF, goes down tube to reservoir bag.
    EXPIRATORY PAUSE allows FGF to flush tubing, pop off valve opens when pressure is high enough, mixed gas escapes via pop off valve.

A higher FGF is still required to prevent rebreathing (2-3 x MV)

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37
Q

FGF required to prevent rebreathing in spontaneous ventilation with Mapleson D

A

2-3 x MV

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38
Q

Steps of Controlled Ventilation with Mapleson D

A
  1. FGF is flowing close to patient,
    when reservoir is compressed to deliver a breath, pt receives breath that is mostly FGF.
  2. Pt exhales, reservoir bag is mixed gas. No expiratory pause to flush gas, but when reservivr bag is compressed it pushes DISTAL FGF into pt, so less FGF overall is needed.
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39
Q

FGF for no rebreathing in controlled ventilation of Mapleson D

A

1 -2 x MV

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40
Q

Critical Difference between Spontaneous and Controlled Ventilation =

A

Expiratory Pause

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41
Q

Faster rate = shorter

A

expiratory pause, less ability for FGF to flush out expired air, greater risk for rebreathing

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42
Q

Conditions that increase CO2 production

A

fever, catabolic state, malignant hyperthermia

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43
Q

How to decreased CO2 with mapleson

A

Must increase rate and also FGF

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44
Q

Advantages of Bain Circuit

A
  1. warming of FGF by inflow of exhaled gas in corrugated tubing
  2. Conservation of moisture as a result of partial rebreathing
  3. Ease of scavenging waste anesthetic gases from overflow valve
  4. Light weight, easily sterilized reusable, useful for limited access to pt as in during head/neck surgery
45
Q

Disadvantages of Bain Circuit:

A

unrecognized disconnect of inner FGF tubing

46
Q

Pethick Test:

A

Used to assess integrity of Bain circuit, assure that inner FGF tube isn’t disconnected.

Occlude patient end of circuit, flow in high flow oxygen until reservoir is filled.

Let go of patient side, if the inner tube is intact, the the bag will deflate.

If the inner tube is not intact, gas escapes from FGF line to corrugated tubing and the reservoir remains inflated.

47
Q

Only mapleson without a reservoir

A

Mapleson E

48
Q

Structure of Mapelson E

A

No reservoir!
Expiratory limb functions as reservoir.
No Pop off valve.
FGF is near patient.

49
Q

Mapleson E functions most like

A

Maplseon D

A, BC, !!DEF!!

50
Q

Ventilation with Mapelson E

A

During expiration, the tubing fills with dead space and alveolar gas which is then flushed out by FGF

Rebreathing is dependent on amount of FGF,

51
Q

In a mapleson E, If FGF is not equal to the inspiratory flow rate then

A

room air will be entrained through open end

52
Q

Recommended FGF in Mapleson E to prevent rebreathing

A

2-3 x MV

53
Q

Mapleson F (Jackson-Rees) is a modification of

A

Mapleson E
- Mapleson E + reservoir bag = Mapleson F

/DEF/

54
Q

FGF to prevent rebreathing in Mapleson F =

A

2- 3 x MV

55
Q

Mapleson F is commonly used for

A

controlled ventilation and transportation of intubated patients

56
Q

Mapleson F is ideal for

A

Pediatric anesthesia

57
Q

In Mapleson F there are no

A

moving parts except the pop valve at the end of the reservoir bag, therefor circuit dead space is minimal

58
Q

Mapleson F during spontaneous ventilation

A

Pt inhales from FGF and reservoir bag, exhales into tubing, EXPIRATORY PAUSE, FGF helps flush expired air towards reservoir bag

59
Q

Advantages of Mapleson F - 4

A

Used for both spontaneous and controlled ventilation

Inexpensive, can be used with face mask or ETT

Is light weight, can be repositioned easily

Pollution of the atmosphere with anesthetic gases while using this system can be decreased by adapting it to scavenging system.

60
Q

Disadvantages of Mapleson F

A

Requires high FGF to prevent rebreathing

Possibility of high airway pressure and barotrauma should the pop off valve become occluded

Lack of humidificaiton
-can add a humidifier

61
Q

If you’re using a volatile ambu bag with a volatile anesthetic

A

The spring in the ambu bag can break r/t the anesthetic gases

62
Q

Jackson-Rees allows you to see

A

lung compliance with inflation of bag

63
Q

Difficulty of transporting with Jackson-Rees

A

its flow inflating, so you need to carry oxygen

64
Q

CO2 rebreathing depends on (5)

A

FGF

MV of patient

Mode of ventilation (spontaneous vs controlled)

CO2 Production of individual patient

Respiratory wave form characteristics (insp. flow, I:E times, expiratory pause)

65
Q

7 components of a circle system

A
  1. FGF source
  2. Inspiratory / expiratory unidirectional valves
  3. Insp./ Exp limbs
  4. Y piece
  5. APL valve
  6. Reservoir bag
  7. CO2 absorber
66
Q

More cost effective to save on

A

anesthetic gases rather than CO2 absorbents

67
Q

Opposite of patient lung in circle system is

A

reservoir bag / counter lung

68
Q

The carbon dioxide absorber in a circle system is most often placed on

A

The inspiratory limb on the bag side.

69
Q

Preferred location for FGF inlet in circle system

A

Between CO2 absorber and inspiratory valve

  • in case there is a problem with CO2, fresh gas comes after it
70
Q

Essential characteristics of unidirectional valves in circle system

A

low resistance, high competence

71
Q

Unidirectional valves must be placed

A

On exp and insp limb. Between the reservoir bag and the patient

72
Q

properly positioned and functioning unidirectional valves prevent:

A

any part of the circle system from contributing to the apparatus dead space

73
Q

Primary sources for resistance is an anesthesia machine

A

ETT, valves, Co2 absorber

74
Q

Unidirectional valves will exert significantly more resistance when

A

When they are moist from water vapor

75
Q

3 functions of reservoir bags

A
  1. Serve as a reservoir for anesthetic gases or oxygen
  2. Visual assessment of spontaneous ventilation & rough estimate of the volume
  3. Means for manual ventilation
76
Q

A reservoir function is necessary because:

A

Anesthesia machines cannot provide the peak inspiratory gas flow needed during normal spontaneous inspiration

77
Q

Optimally sized reservoir bag :

A

Can hold a volume that exceeds the patients inspiratory capacity (3L most common)

78
Q

Spontaneous Respiration means APL valve is

A

Valve fully open

79
Q

Assisted ventilation means APL valve is

A

partially open/partially closed

80
Q

in a circle system, the pop-off/APL valve is usually located

A

between the exp valve and the bag mount

81
Q

Any circuit should be tested before use by determining the O2

A

O2 flow required to maintain 30 cm h2o of pressure in the circuit

82
Q

Advantages of the circle system - 8

A

Relative stability of concentration of inspired gases

conservation of moisture and heat

Low resistance (but not as low as mapleson)

can be used for closed-system anesthesia

Can be used with fairly low flows with no rebreathing of co2

economy of anesthetics and gases

can scavenge waste gases

prevention of OR pollution

83
Q

Disadvantages of circle system - 6

A

complex design

has at least 10 connections

potential of malfunctioning valves

increased resistance to breathing (Compared to mapleson)

less portable and convenient than mapleson system due to its bulkiness

increased dead space BUT dead space ends at Y piece

84
Q

Unidirectional valve stuck open

A

rebreathing will occur

85
Q

unidirectional valve stuck closed

A

airway obstruction will occur

86
Q

Leak test in circle system

A

Set all gas flows to zero, occlude the Y-piece, close the APL valve, pressurize the circuit to 30 cm of water pressure using the O2 flush valve, ensure pressure holds for 10 seconds, listen for sustained pressure alarm,

87
Q

Leak test does not assess for

A

integrity of unidirectional valves

88
Q

Flow test in circle system

A

Attach breathing back to Y -piece, turn on ventilator, assess integrity of system

ASSESS INTEGRITY OF UNIDIRECTIONAL VALVES

89
Q

Potential Problems in Circuit (Circle) System: (5)

A

misconnections or disconnections

leaks

valve failure

carbon dioxide absorber defect

bacterial filter occlusion

slide 54

90
Q

Basic function of a breathing circuit

A

interface between patient and anesthesia machine, to delivery oxygen and other gases , eliminates carbon dioxide

has 3 essential components

  • low resistance conduit for gas flow
  • pop off valve / port
  • reservoir for gas that meets inspiratory demand
91
Q

“Things to consider” with breathing systems (6)

A 
Low resistance
Rebreathing
Dead space
Dry gases/humidification
manipulation of inspired content 
bacterial colonization

– slides 7&8

92
Q

Recommended bacterial filter

A

One with an efficiency rating of more 95% for particles sizes 0.3 micrometers, protects the machine from colonization of airborne infectious disease.

93
Q

Pros of Maplesons (4)

A

Simplicity of design

Ability to change the depth of anesthesia rapidly

Portability

Lack of rebreathing of exhaled gases (only if FGF is adequate)

94
Q

Disadvantages of Maplesons (3)

A

lack of conservation of heat and moisture

limited ability to scavenge waste gas

high requirements for FGF

95
Q

With mapleson E, the sole determinant of wether rebreathing will occur is

A

The FGF (and the pt’s MV)

for spontaneous breathing the FGF must be 2-3 x the MV

96
Q

Steps of steal induction

A

Child is usually already sleeping (from versed or anti-anxiolytic)

Mask is primed with O2 and N2O, mask is brought near child, insufflation, when child is further anesthetized, mask is placed on childs face (now a semi-open system r/t reservoir of mask)

97
Q

Advantages of Mapleson (4)

A

simplicity of design

ability to change the depth of anesthesia rapidly (because FGF is usually higher than in circle system)

portability

lack of breathing of exhaled gases (as long as FGF is high enough)

98
Q

Disadvantages of Mapleson

A

lack of conservation of heat/humidity (unless Bain)

limited ability to scavenge waste gas (r/t where the aPL is)

high requirements for FGF

99
Q

FGF and common gas inflow site:

A

is usually between CO2 absorber and inspiratory valve

can be incorporated in housing of CO2 absorber housing or with the unidirectional inspiratory valve

100
Q

APL valve purposes (4)

A

Purpose: permits PEEP during SV or allows for pressure- limited controlled respiration

Releases gases to scavenge or to atmosphere

User-adjustable, pressure required to open it changed by user

Provides control of pressure in system

slide 40

101
Q

Semi-Open Circle system

A

No rebreathing occurs (as it is a semi-open system)

therefore, requires HIGH gas flows. High = FGF > MV
10-15 L/min

No conservation of waste gas/ heat

APL valve is all the way open or ventilator is in use with. high gas flow so CO2 absorber is doing nothing.

102
Q

Gas flow needed for a semi-open CIRCLE system

A

10-15 L/min

slide 46

103
Q

Most commonly used circle system is

A

Semi-closed circle system, partial rebreathing. Low gas flows, but not minimal.

104
Q

Semi-Closed Circle System:

A

Allows for some re-breathing of agents and exhaled gases (minus CO2 due to CO2 absorption)

Uses relatively low flow rates (about 1-3L/min)
FGF

105
Q

Gas flows for semi-closed circle system

A

1-3 L /min

slide 47

106
Q

Closed Circle system

A

Used often in long surgical cases and third world countries

Inflow gas exactly matches metabolic needs/ O2 consumption of the patient using very low flows (O2 flow rate ~ @ 250 mL/min)

Total re-breathing of all exhaled gases after absorption of CO2

APL is closed

Change in gas concentrations is VERY slow

107
Q

Closed circle systems are used most in

A

Very long surgeries or third world countries.

Minimal gas flows.

108
Q

In closed circle systems, the FGF flow =

A

Inflow gas exactly matches metabolic needs/ O2 consumption of the patient using very low flows (O2 flow rate ~ @ 250 mL/min)

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