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PMI > 6. Anesthesia Circuits > Flashcards

6. Anesthesia Circuits Flashcards

1
Q

basic parts of anesthesia circuit (9)

A
  1. inspiratory one way valve
  2. inspiratory tubing
  3. y-piece
  4. elbow adapter
  5. expiratory tubing
  6. expiratory one way valve
  7. breathing bag
  8. CO2 absorber
  9. humidifier
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2
Q

inspiratory valve

A

open during inspiration
closed during expiration

inhibits CO2 rebreathing

all inhaled gas come from inspiratory limb (free of CO2)

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3
Q

expiratory valve

A

open during expiration
closed during inspiration

inhibits CO2 rebreathing
all exhaled gas goes to expiratory limb

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4
Q

Y-Piece

A

merges the inspiratory and expiratory limbs

able to connect circuit to mask, LMA, ETT

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5
Q

humidifier

A

warms/humidifies gases
filters bacteria/viruses
prevents machine contamination

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6
Q

elbow adapter

A

connect circuit to pt airway device
not necessary
helps prevent pulling of tube

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7
Q

breathing bag

A

more compliant than lungs
- if circuit P increase, bag absorbs more P than lungs

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8
Q

types of anesthesia circuit tubing

A

circuit w/inhalation and exhalation tubing
coaxial circuit

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9
Q

circuit w/inhalation and exhalation tubing

A

most common
uses y piece

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10
Q

co-axial circuit

A

inspiratory lumen (purple) is inside expiratory lumen (clear)

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11
Q

co-axial circuit advantage

A

better conserves heat/humidity
exhaled gases in exterior lumen warm up inner lumen

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12
Q

co-axial circuit disadvantage

A

possibility of disconnecting/kinking inner fresh gas tubing
- hypoxia / hypercarbia

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13
Q

dead space

A

any portion of the airway that does not participate in gas exchange

any portion of the airway that is not alveoli (serves no respiratory function)

any portion of the airway that causes us to rebreathe CO2

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14
Q

increasing dead space

A

increases amount of CO2 rebreathed

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15
Q

anesthesia circuit dead space

A

anytime inhaled and exhaled gases occupy the same space

anything distal to the y piece:
masks
LMAs
ETT
elbow adapter
humidifier

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16
Q

inspiratory limb dead space

A

none
will not have CO2 in it

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17
Q

expiratory limb dead space

A

none
pt cant inhale CO2 from the expiratory limb

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18
Q

y-piece dead space

A

portion distal to the Y piece has inhaled and exhaled gases mixed

distal to y piece has dead space

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19
Q

3 types of dead space

A

anatomic
mechanical
physiological

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20
Q

anatomic dead space

A

portions of airway that do not participate in gas exchange

nose
trachea
bronchi
pharynx

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21
Q

normal Total anatomic dead space

A

2mL/kg

1/3 of tidal volume

upright position

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22
Q

mechanical dead space

A

anesthesia airway equipment

anything distal to y piece

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23
Q

physiologic dead space

A

alveolar space that receive air but no blood flow
damaged alveolar capillaries are dead space

lung disease pts have more dead space

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24
Q

physiology of smokers

A

alveolar sacs fuse into blebs
excess mucus in bronchioles
destroyed pulmonary capillaties

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25
Q

normal Extrathoracic anatomic dead space

A

70-75mL

nose/pharynx

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26
Q

endotracheal tube dead space

A

8.0 ETT = 12.6mL dead space

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27
Q

LMA dead space

A

90mL

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28
Q

face mask dead space

A

126mL

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29
Q

ypiece dead space

A

adult: 8mL
ped: 4mL

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30
Q

humidifier dead space

A

10-60mL

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31
Q

dead space ranking for ventilation

A

most
- facemask (162mL)
- LMA (90mL)
- ETT (12.6mL)
least

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32
Q

dead space ranking for circuit pieces

A

most
- humidifier (10-60mL)
- Y piece (4-8mL)
least

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33
Q

dead space volume

A

is fixed
(does not change)

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34
Q

how does tidal volume affect dead space

A

Tv affects the % of dead space in each breath
- larger TV = lower % of dead space
- small TV = higher % of dead space

smaller breaths are less efficient

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35
Q

peds and dead space

A

small tidal volumes
most affected by mechanical dead space (high % of ventilation)

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36
Q

pulmonary shunting

A

some blood that goes to the lungs bypasses the alveoli and dose not pickup O2

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37
Q

normal pulmonary shunt

A

3%

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38
Q

right mainstem intubation shunting

A

50%

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39
Q

V/Q ratio

A

alveolar capillary gas exchange

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40
Q

V

A

ventilation/airflow to alveoli
alveolar ventilation

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41
Q

Q

A

blood flow to alveoli

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42
Q

V/Q mismatch

A

alveolar capillary gas exchange is abnormal/decreased

causes hypoxia and/or hypercarbia

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43
Q

type of V/Q mismatch

A

v/Q: decr alveolar ventilation

or

V/q: decr alveolar blood flow

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44
Q

V/q

A

pulmonary dead space
due to reduced pulmonary blood flow
normal alveolar ventilation

larger % of the airway not participating in gas exchange

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45
Q

V/q causes

A

pulmonary embolism
profound CO drop
pulmonary vasoconstriction

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46
Q

v/Q

A

pulmonary shunting
due to reduce alveolar ventilation
normal blood flow

higher % of blood bypassing lungs w/out participating in gas exchange

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47
Q

v/Q causes

A

right mainstem intubation
pneumothorax
pulmonary edema
atelectasis

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48
Q

most common V/Q mismatch

A

atelectasis

causes hypoxemia in recovery

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49
Q

simultaneous
v/Q
and
V/q

A

lateral decubitus position
emphysema
COPD

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50
Q

lateral decubitus position
V/Q mismatch

A

upper lung: V/q
- more ventilation
- less blood flow
lower lung: v/Q
- less ventilation (compressed)
- more blood flow (gravity)

51
Q

Emphysema
V/Q mismatch

A

bullae/mucus: v/Q
- less alveolar ventilation
- shunt

destruction of capillaries: V/q
- less pulmonary blood flow
- dead space

52
Q

normal V/Q ratio

A

0.8

V/Q = (4L/min)/(5L/min)

53
Q

normal minute ventilation

A

6L/min

(tidal volume 500mL x 12 RR= 6L/min)n

54
Q

alveolar ventilation (V)

A

4 L/min
minute ventilation - dead space vent

6L/min - 2L/min == 4L/min

55
Q

normal CO (Q)

A

5L/min

56
Q

supplemental O2 circuits

A

nasal cannula
high flow nasal cannula
simple facemask
nonrebreathing mask
venturi msk

57
Q

supplemental O2 circuit uses

A

sedation (MAC anesthesia)
transport to PACU
in PACU

58
Q

nasal cannula

A

max FiO2: 44% (6L/min)

59
Q

nasal cannula FiO2 calc

A

FiO2 = 21% + 4%(L/min flow)

60
Q

nasal cannula hazards

A

> 4L/min can damage nares
increase risk of fires during sedation cases near the face w/cautery

61
Q

high flow nasal cannul

A

max: 60L/min = 95% FiO2
O2 humidified
+ airway pressure: 3cmH2O

62
Q

simple face mask

A

5L/min = 40% FiO2
10L/min = 60% FiO2

must be at least 6L/min to prevent CO2 rebreathing

63
Q

nonrebreathing mask

A

attached bag minimizes CO2 rebreathing
10L/min = 80% FiO2
15L/min = 90% FiO2

slight rebreathing does occur (cannot reach 100% FiO2)

64
Q

venturi mask

A

specific FiO2 between 24-60%
adapter-specific

65
Q

preventing rebreathing in partial rebreathing circuits

A

increase O2 flow rate

66
Q

O2 flow rates vs CO2 rebreathing

A

inversely proportional

67
Q

supplemental O2 compensates for:

A

anesthetic induced hypoventilation
atelectasis

68
Q

supplemental O2 during GA

A

ETT or LMA connected to anesthesia circuit

69
Q

supplemental O2 outside OR under GA

A

mapleson circuit

70
Q

mapleson circuit

A

delivers O2
positive pressure ventilation

w/LMA or ETT

for general anesthesia

71
Q

supplemental O2 for MAC sedation

A

use mask or nasal cannula
cannot provide PPV

72
Q

mapleson A

A

best for SV (pt breathing on own)
worst for CV

breathing bag
APL valve near mask

73
Q

mapleson D

A

best for CV (breathe for pt)
worst for SV

breathing bag
APL valve near bag

74
Q

bain circuit

A

modified mapleson D
co-axial design
inner lumen: FGF
outer lumen: expired gas

75
Q

mapleson E

A

ayres T-piece
- hooks up to ETT
- only for SV pts

inspiratory: right
expiratory: left

minimal rebreathing of CO2

no breathing bag or APL valve

76
Q

mapleson’s commonly used today

A

D
E
Fm

77
Q

mapleson’s not commonly used

A

A
B
C

78
Q

mapleson E advantage

A

minimal to no rebreathing

79
Q

mapleson E disadvantage

A

positive pressure ventilation not possible

must be for SV pt only

80
Q

common mapleson E use

A

transporting pt to PACU who is SV but not ready to be extubated
- good tidal volume
- not responding to commands

81
Q

mapleson F

A

jackson-rees’ modification

t-piece w/breathing bag for PPV
tail = APL valve

peds pts for assist ventilation during transport

82
Q

mapleson circuit advantages

A
  1. supp O2 via ETT or LMA
  2. PPV w/breathing bag
83
Q

mapleson circuit disadvantages

A
  1. inspiratory/expiratory gases in same tubing (incr dead space)
  2. no CO2 absorber
  3. high dead space
    • possibly high CO2 rebreathing
84
Q

semi-closed breathing circut

A

anesthesia machine

minimal CO2 rebreathing

85
Q

semi-open breathing circuit

A

mapleson circuit

more dead space = CO2 rebreathing

86
Q

prevent rebreathing CO2 in mapleson circuits

A
  1. use high flow of O2
  2. shorten circuit volume
    • decr dead space
87
Q

open circuit

A

open to atmosphere
gas freely disperses around face/room

nasal cannula
O2 insufflation (mask)
open drop anesthesia

88
Q

open drop anesthesia

A

soaking gauze in volatile agent
placing over pt face

89
Q

open circuit uses

A

O2 delivery

90
Q

O2 insufflation

A

blow by

blowing O2 across pt face/airway

claustrophobic pts
infants
sedation case w/scope in mouth
- EGD
- TEE
bronchoscope
facial surgery

91
Q

EGD/TEE O2 mask

A

POM mask
procedural O2 mask

conduit for scope to pass through

92
Q

bronchoscope insufflation

A

O2 hooks up to bronchoscope
typically dont need to use blow by method w/scope O2

93
Q

facial surgery insufflation

A

facial drape catches CO2
place breathing circuit under drape
high AIR flow (not O2)

prevents CO2 buildup under drape

94
Q

open circuit fire hazard

A

higher [O2] can kindle fire during procedure w/cautery

95
Q

managing facial surgery under sedation

A

supp O2 via cannula/mask contraindicated

2 options:

  1. minimal sedation
  2. ETT or LMA for higher sedation
    • higher FiO2 via tube
96
Q

CO2 absorber

A

soda lime granules that absorb CO2 and eliminate from circuit

converts CO2 into H2O and heat

97
Q

can you eliminate CO2 w/out absorber?

A

yes

use FGF >5L/min
minimal rebreathing

98
Q

CO2 larger granules

A

less absorptive capacity
- less surface area
lower circuit resistance

99
Q

CO2 smaller granules

A

more absorptive capacity
- more surface area
more circuit resistance

100
Q

why is silica added to CO2 granules

A

increase granule hardness
minimize dust inhalation
minimize airway irritation

101
Q

dessicated old school absorbent

A

degrade volatile agents into CO
accelerate degradation of sevo into compound A

102
Q

which agent produces most CO with desicated CO2 absorbers?

A

Des

103
Q

minimum FGF rate for Sevo with old CO2 absorbers

A

2L/min

to avoid compound A formation

104
Q

old school absorbant

A

double cannister
decreases circuit resistance

changing absorbant = circuit leak
- cannot change during case

105
Q

new school absorbent brands

A

sodasorb
drager sorb

105
Q

new school absorbent advantages

A
  • do not degrade agents into CO or compound A
    • can run low/min flow w/sevo
  • optimal resistance to dusting
  • reduced resistance to gas flow
  • single canister
  • reduced induction and emergence time
  • can be change out mid-operation w/out circuit leak
106
Q

new school absorbant

A

single canister
reduced induction and emergence time
can be change out mid-operation w/out circuit leak

107
Q

exhausted new school absorbant

A

stays purple once exhausted

108
Q

when to replace old school CO2 absorbant

A

weekly
when 50-70% color changed

109
Q

when to replace new school CO2

A

after 8 hrs of surgical use
inspiratory CO2 >1 mmHg

110
Q

circuit humidifier

A

AKA
heat moisture exchanger (HME)

111
Q

airway humidity normal person

A

air humidified by upper airway
air in alveoli is warm/moisturized

112
Q

airway humidity w/ETT

A

air not humidified by airway
air in alveoli is cold/dry

113
Q

impacts of cold/dry air (4)

A
  1. decrease pt body temp
    (absorb heat from airways)
  2. dehydrate airway
  3. mucus plugging
  4. atelectasis
114
Q

Relative humidity in OR

A

30-60% (AIAAAH reccomends)

50-60% inhibits bacterial grow/static electricity

115
Q

Humidifier properties

A
  1. humdifies dry OR gases
  2. filters bacteria/viruses
  3. adds 10-60L deadspace
116
Q

weight recs for humdifier/filter deadspace in peds

A

HME: body weight >2.5kg
filters: body weight >3kg

117
Q

humidifier locations on circuit

A
  1. distal to Y piece
    • incr dead space
    • incr resistance to gas flow
    • best humidification
    • best for adults
  2. inspiratory or expiratory limbs
    • no dead space
    • less humidification
    • best for peds
118
Q

Ambu bag: clinical uses

A
  1. mask vent in emergency
  2. transfer mech vent pts from OR to PACU/ICU
119
Q

Steps when transporting w/Ambu bag

A
  1. call RT to have vent in PACU/ICU
  2. vent pt w/self-inflating Ambu
  3. place pt on vent in PACU
  4. admin propofol if paralyzed
120
Q

self-inflating ambu bag
without reservoir

A

connected to supp O2
fills w/mix of O2 and air during exhale

121
Q

self-inflating ambu bag
with reservoir

A

connected to supp O2
fills w/mostly O2 during exhale

highest FiO2

122
Q

ambu bag

A

does not require O2
can be hooked to O2
may have reservoir bag

123
Q

flow inflating anesthesia bag

A

requires O2 to operate
pressure controlled by APL valve

infant: 450-500mL
older child/adolescent: 1000mL

PMI (18 decks)

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