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CHEM PHYS > Exam 4: Lecture 4.1 - Ventilators > Flashcards

Exam 4: Lecture 4.1 - Ventilators Flashcards

1
Q

lung function?

A

ventilation, oxygenation
-filtration, drug administration

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2
Q

what is minute ventialtion?

A

alveolar ventilation + total dead space ventilation

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3
Q

what is anatomic dead space?

A

volume of air that fills conducting zones
do not participate in gas exchange

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4
Q

what are conducting zones?

A

nose, trachea, bronchi

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5
Q

how much of normal tidal volume is considered dead space?

A

30%

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6
Q

physiologic dead space?

A

anatomic dead space + alveolar dead space

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7
Q

what is alveolar dead space?

A

at the lung apices where alveolar pressure is high and perfusion is low
considered negligible in healthy adults

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8
Q

arterial partial pressures that measure ventilation and oxygenation?

A

PAO2 and PACO2

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9
Q

what is the oxygen consumption rate of a 70 kg adult?

A

250 mL/minute
may be lower under anesthesia

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10
Q

apneic oxygenation?

A

passive flow without ventilation
nc in the nose on a patient you’re about to intubate

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11
Q

what is denitrogenation?

A

pre-oxygenation
increasing the oxygen ratio over nitrogen ratio in the lungs

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12
Q

when the patient is breathing oxygen the pulmonary reservoir represents how many minutes of metabolic consumption?

A

12 minutes

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13
Q

what is the respiratory quotient?

A

Respiratory quotient is the ratio of the volume of carbon dioxide produced to the volume of oxygen consumed in respiration over a period of time

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14
Q

what is the respiratory quotient equal to?

A

VQ ratio
produce 200 mL CO2 and consume 250 mL O2 per minute
200/250=0.8

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15
Q

what do you need in order to denitrogenate?

A

a good mask seal, will reset if they breath room air

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16
Q

apparatus dead space?

A

ETT, HME, circuit, anything added like connectors

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17
Q

what is the work of breathing?

A

overcoming resistance aspects of circuit, ETT, and the large (upper) and small (lower) airways

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18
Q

does compliance mean expansion or contraction of the lungs?

A

expansion

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19
Q

does elasticity contract or expand the lungs?

A

contract

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20
Q

what is flow a function of?

A

resistance

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21
Q

what is a change in pressure proportional to?

A

a change in volume

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22
Q

is pressure a measure of force?

A

yes

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23
Q

is exhalation active or passive during mechanical ventilation?

A

passive

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24
Q

is exhalation active or passive during spontaneous ventilation?

A

active

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25
Q

is inhalation active or passive during spontaneous ventilation?

A

passive

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26
Q

is inhalation active or passive during mechanical ventilation?

A

active

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27
Q

what is cycle time?

A

how long it takes for a breath to complete
RR 10 breath/min=6 sec cycle time

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28
Q

peak inspiratory pressure

A

under 35 cm H2O

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29
Q

plateau pressure

A

below 30 cm H20
protective under 16 cm H2O

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30
Q

tidal volume

A

6-8 mL/kg ideal body weight

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31
Q

minute volume/ventilation

A

tidal volume x RR
OR [tidal volume - dead space (20 or 30%)] x RR

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32
Q

peak airway pressure

A
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33
Q

frequency

A

respiratory rate

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34
Q

I:E ratio

A

inspiratory: expiratory ratio of cycle length

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35
Q

normal I:E

A

1:2

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36
Q

what does it mean to expand I:E ratio?

A

increase expiratory phase, without adding time to cycle time
1:2 to 1:3 or 1:4

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37
Q

who needs an expanded I:E ratio?

A

copd, asthma

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38
Q

what will have to increase to expand the I:E ratio?

A

pressure
and shorten inspiratory phase to get the same volume in

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39
Q

what is dead space?

A

ventilation without oxygenation/perfusion

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40
Q

what is shunt?

A

perfusion without ventilation

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41
Q

how does anesthesia affect lung function?

A

adversely

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42
Q

how does anesthesia adversely effect lung function?

A

-physical insult by ETT
-retention of secretions
-suppression/damage to mucociliary expectoration system
-dehumidification
-cooling

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43
Q

how does anesthesia increase WOB?

A

ETT is smaller than normal trachea
-breathing through a straw

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44
Q

how does airway suctioning effect lung function?

A

-negative pressure
-atelectasis
-airway irritation
-coughing can place cardiovascular strain on the patient and the surgical wound

45
Q

post nasal surgery coughing? good or bad?

A

bad
-increase in intrathoracic pressure
-pressure feeds back to jugular
-increased pressure in nose/brain
-increased bleeding

46
Q

where can you get the most accurate EtCO2 reading?

A

sample line from ETT/LMA

47
Q

why do you inflate the cuff in an ETT?

A

protect airway from gastric secretions

48
Q

is an LMA a protected airway?

A

No

49
Q

why is a face mask a less accurate measure of EtCO2?

A

dilutional from room air and flow

50
Q

how can you reduce WOB?

A

mechanical ventilation

51
Q

what does MAC stand for?

A

monitored anesthesia care

52
Q

what is lung protective strategy?

A

to avoid baro and volutrauma with lower Vt
-atelectrauma, shear trauma of the parenchyma, distruptions of alveolar-capillary membrane

53
Q

how does PEEP lessen lung injury?

A
54
Q

how does PEEP increase physiologic dead space?

A

the positive pressure holding the alveoli open can lead to capillary occlusion - increases intrathoracic pressure - reduce RV capacity to pump to pulm circuit - decreased CO
-overall less perfusion

55
Q

what is recommened Vt for lung protective strategy ventilation?

A

6-8 mL/kg ideal body weight

56
Q

what alveolar pressures may be associated with lung injury?

A

greater than 30-40 cm H2O
alveolar pressure may be lower than Paw

57
Q

how does peep improve oxygenation?

A

more positive pressure pushed through thickened membrane (pna, secretions, fibrosis) to better perfuse
-holds alveoli open longer to increase oxygenation
-maximized FRC

58
Q

what are conservative recommendations for plateau pressure?

A

< 16 cm H2O and PEEP 5

59
Q

how does permissive hypercapnia reduce ventilatory complications?

A

allows patients to keep their respiratory drive

60
Q

what examples of humans tolerating respiratory acidosis well?

A

pH 7.15 and PaCO2 80 mm Hg

61
Q

what patients should you avoid high PaCO2?

A

-high ICP
-recent MI
-pulm htn

62
Q

how would you have to actually measure alveolar pressure?

A

with a sensor in the actual alveoli, we just estimate

63
Q

what is the spill valve?

A

-pressure relief valve similar to APL valve on the manual circuit
-spill valve only on ventilation mode

64
Q

what does the spill valve do during inspiration?

A

closed during inspiration so the ventilator can generate positive pressure

65
Q

what does the spill valve do during exhalation?

A

valve is open to allow the driving gas to be released from the plastic housing of the bellows

66
Q

what happens if the spill valve gets stuck in the closed position?

A

results in high airway pressures
(similar to a patient breathing against a closed/tightened APL valve)

67
Q

what is peak inspiratory pressure?

A

highest circuit pressure measured during inspiration

68
Q

what is an indication of dynamic compliance?

A

peak inspiratory pressure

69
Q

what peak air way pressure puts patient at risk of barotrauma?

A

> 30 mmH2O

70
Q

what is a conservative, lung protective peak airway pressure?

A

< 16 mm H2O and a PEEP 5

71
Q

when is plateau pressure measured?

A

during the inspiratory pause
-between inspiration and expiration when no ventilatory movement is occuring

72
Q

what is plateau pressure a measure of?

A

static compliance

73
Q

what does the pressure do during the inspiratory pause?

A

drops slightly before dropping with exhalation

74
Q

when is the low peak pressure alarm activated?

A

when the ventilator is turned on

75
Q

what do low Vte and low EtCO2 alarms detect?

A

circuit disconnect

76
Q

two types of bellows ventilators?

A

ascending and descending

77
Q

which bellow ventilator is preferred?

A

ascending

78
Q

how do bellow ventilators work?

A

pressurized oxygen from the anesthetic machine is fed into the plastic housing at 50 psi to compress the bellows with inspiration
the bellows expand when the patient exhales

79
Q

if a leak exists in the bellows, the ventilator could transmit the high gas pressure to where?

A

the patients airway and you would see higher than expected FiO2

80
Q

how do some bellow ventilators use a venturi device?

A

to draw air into the plastic housing
-oxygen sparing and FiO2 would not increase in the evnet of a leak

81
Q

how do piston ventilators work?

A

substitute an electrically driven piston for the bellows and do not require pneumatic (oxygen, gas) power for ventilation

82
Q

advantages to piston ventilators?

A

accuracy, ability to deliver accurate tidal volumes in patients with poor lung compliance or very small patients

83
Q

what is a turbine ventilator?

A

electric motor powers a spinning turbine fan to produce drive gas pressure

84
Q

what is the fixed input and variable output in volume control ventilation?

A

volume is fixed
output is variable

85
Q

how do airway pressures rise with time as gas volume is pushed into the lung?

A

linearly

86
Q

pressure control

A

pressure is fixed input
volume is a variable output

87
Q

pressure control volume guarantee

A

the vent will dynamically titrate pressure (up to a specified limit) until a particular tidal volume is achieved

88
Q

what is assist control ventilation?

A

patient will trigger a breath by pulling negative pressure (flow trigger)

89
Q

when will a breath not be delivered in ACV?

A

as long as the patient triggers the ventilator more than the defined interval set by the control rate a control breath will not be delivered

90
Q

what happens if the patient has a long pause or goes apneic in ACV?

A

the backup rate will kick in

91
Q

what is pressure support ventilation?

A

clinician sets the peak airway pressure to be delivered and the flow trigger

92
Q

what it the flow trigger?

A

how much work patient has to do to get a supported breath from the vent

93
Q

what is a low flow trigger?

A

0.6
means the patient has to do less work before the vent gives a supported breath
less work - smaller breath or lower trigger that the vent will notice and finish with a supportive breath

94
Q

what is a normal flow trigger that would show you’re closer to extubation?

A

1-3 L/min

95
Q

if PSV fails and a backup mode will turn PSV off and completely take over, do you have to turn PSV back on?

A

yes

96
Q

what is SIMV?

A

update of IMV
synchronizes patient breaths with automatic breaths

97
Q

SIMV reduces risk of what?

A

breath stacking

98
Q

when does SIMV place a time observation window of each respiratory interval?

A

at the beginning

99
Q

in SIMV what does the ventilator monitor for?

A

pressure or flow changes

100
Q

in SIMV if parameters are not exceeded , the mandatory breath is delivered when of the respiratory interval?

A

at the beginning

101
Q

what does CPAP represent?

A

the airway pressure between exhalation and inhalation

102
Q

how is CPAP dialed on the ventilator?

A

APL valve, lets pressure build up to this limit

103
Q

what recruitment does CPAP serve?

A

alveolar

104
Q

Does CPAP increase intrathoracic pressure?

A

yes

105
Q

high frequency jet ventilation

A

high frequencies and small volumes

106
Q

where are jet ventilators used?

A

NICU and thoracic surgery

107
Q

ventilator concerns

A

-over pressurization of the airway
-hypothermia
-dry secretions
-hypercarbia, hypocarbia
-hypotension in the airway
-excess PEEP
-trauma
-tracheal tube cuff herniation
-bronchospasm
-cross-infection

108
Q

what can cause over pressurization of the airway?

A

dis-synchrony
coughing against vent
O2 flush valve pushed when patient is in the inspiratory phase
bad input parameters

CHEM PHYS (7 decks)

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