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N928 - Basic Principles > Lung Protective Ventilation > Flashcards

Lung Protective Ventilation Flashcards

1
Q

Negative intrapleural (intrathoracic) pressure provides ____ trans-pulmonary pressure

A

a positive trans-pulmonary pressure

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2
Q

Ptp =

A

Ptp = Palv - Ppl

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3
Q

Alteration of the chest wall muscle tone from anesthesia & surgical do what?

A

alter the intrapleural pressure gradient

  1. cephalad shift of diaphragm
  2. chest wall pushing down
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4
Q

How is a positive transpulmonary pressure maintained during surgery?

A

maintaining alveolar pressure

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5
Q

What are three major effects anesthesia / surgery have on the lungs?

A
  1. loss of muscle tone
    1a. upper airway obstruction
    1b. chest wall & diaphragm; alveolar compression
  2. elevated intra-abdominal pressure
    - increased BMI
    - pneumoperitoneum
    - trendelenburg
    - insuflation
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6
Q

What change in intrapleural P and transpulmonary P favor atelectasis developmene?

A

increasingly POSITIVE intrapleural pressure

increasingly NEGATIVE transpulmonary pressure

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7
Q

Upright to supine is a loss of how much FRC?

A

0.8-1L

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8
Q

Induction of anesthesia is a loss of how much FRC?

A

0.4-0.5L

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9
Q

Total reduction of FRC during supine induction of anesthesia?

A

1.2-1.5L

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10
Q

How much FRC does a patient have?

A

~ 30mL/kg of IBW

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11
Q

Loss of FRC favors: (3)

A
  1. atelectasis development
  2. alveolar shunting
  3. V/Q mismatch
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12
Q

What does a loss of FRC lead to? and by what mechanism?

A

hypoxic hypoxia from alveolar shunting

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13
Q

In ARDS, why are lungs non-recrutible?

A
  • cellular debris

- edema

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14
Q

In GA, why are lungs recruitable?

A
  • loss of FRC

- atelectasis

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15
Q

What are 5 factors that contribute to alveolar collapse?

A
  1. position
  2. induction
  3. FiO2
  4. Maintenance
  5. emergence
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16
Q

How does position contribute to alveolar collapse?

A

INCREASED closing pressure → decreased FRC

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17
Q

How does induction contribute to alveolar collapse?

A

loss of muscle tone → decreased FRC

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18
Q

How does FiO2 contribute to alveolar collapse?

A

resorption behind closed airways → atelectasis

*increased FiO2 → faster resorption

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19
Q

How does maintenance of GA contribute to alveolar collapse?

A

progressive airway closure with decreasing compliance

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20
Q

How does emergence from GA contribute to alveolar collapse?

A

high FiO2 promotes postoperative atelectasis

absence of CPAP → continued furthering of lung collapse

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21
Q

Lung injury from mechanical ventilation presents as what types of potentially irreversible damage? (2)

A
  1. structural

2. functional

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22
Q

What is ventilation induced lung injury?

A

ventilator does not cause the injury,
the SETTINGS of the ventilator do..

pressure or volume too high

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23
Q

What is ventilation associated lung injury?

A

lung injury that is specific to the OR; not just the ventilator

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24
Q

What are the 4 types of trauma that can occur with mechanical ventilation?

A
  1. volutrauma
  2. barotrauma
  3. atelectrauma
  4. biotrauma
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25
Q

What are volutrauma manifestations?

A

damaged endothelium, decreased surfactant, increased capillary leak

26
Q

What is atelectrauma?

A

damage from repeated closure and opening of small airways/alveoli

*under-utilization of PEEP

27
Q

What is biotrauma?

A

damage to the lungs from the release of inflammatory mediators

28
Q 
Conventional lung ventilation: 
Vt
PEEP
I:E
FiO2
A

strategy that promotes VALI

  • not individualized
  • Vt = 10-15mL/kg TBW
  • PEEP: 0-5cmH2O
  • I:E no greater than 1:2
  • FiO2: provider preference
29
Q 
Lung protective ventilation:
Vt
PEEP
I:E
FiO2
A

protects against VALI

  • individualized
  • settings adjusted base upon patient monitors & ventilator data
  • Vt based on patient
  • RR to maintain ETCO2
  • individual PEEP to keep lungs inflated
Vt 6-8mL/kg
minimize FiO2 <30%
PEEP 30% of BMI
**alveolar recruitment maneuvers
I:E 1:1.5 (minimize time for atelectasis to occur
30
Q

LPV emergence settings:

A

FiO2 <80%
Positive Pressure Ventilation - PEEP must be greater than closing pressure

Elevate HOB

31
Q

LPV induction strategies & goal

A

attenuate anesthesia related changes

FiO2 100%
HOB 30% or reverse trendelenburg
tightly sealed face mask to provide CPAP
OPA or NPA as needed

32
Q

LPV goal during maintenance of anesthesia

A

restore / maintain lung volume to baseline & maximize lung compliance

  • alveolar recruitment maneuver
  • individualize PEEP
  • use LOWEST POSSIBLE driving pressure (deltaP)
  • compliance = Vt / deltaP
33
Q

What is compliance equation?

A

Vt / deltaP

34
Q

What is deltaP?

A

the driving pressure

deltaP = Pplat - PEEP
deltaP (estimation) = PIP - PEEP

35
Q

What is the set Vt in LPV?

A

6-8mL/kg IBW

36
Q

How is oxygen maintained during LPV?

A

FiO2 <30%

Goal SpO2 >= 94%
*reduce resorption atelectasis
[after this there is a steeper drop on the oxyhemoglobin dissociation curve]

37
Q

At room air, SpO2 < 97%, how much shunting is occurring?

A

> 10%

38
Q

When does the initial alveolar recruitment maneuver occur?

A

post-extubation

CPAP or PEEP adequate to exceed critical opening pressure

39
Q

What is done post-intubation

A

alveolar recruitment maneuver

40
Q

Why is an alveolar recruitment maneuver done immediately after intubation?

A
  1. pre-oxygenation = absorption atelectasis
  2. induction drugs = ↓FRC

*easier to open right away than wait until later

41
Q

If the bag-squeezing technique is used for an alveolar recruitment maneuver what is imperative to remember?

A

do not let go!
maintain pressure until adequate PEEP is applied

*ARM through the ventilator is preferred

42
Q

What are 4 types of alveolar recruitment maneuvers?

A
  1. bag squeezing
  2. CPAP
  3. cycling maneuver
  4. stepwise Vt changes
43
Q 
Minimum recruitment pressure required during alveolar recruitment maneuver:
BMI <30
BMI 30-40
BMI 40-50
BMI >=50
A

BMI < 30 = 40 cmH2O
BMI 30-40 = 40-50 cmH2O
BMI 40-50 = 50-55 cmH2O
BMI >=50 = 50-60 cmH2O

44
Q

What do you need to do before performing an alveolar recruitment maneuver?

A

TELL THE SURGEON

45
Q

What should the initial PEEP setting be?

A

BMI x 0.3

46
Q

What are the 2 purposes of PEEP?

A
  1. maintain end expiratory lung volume

2. reduce atelectasis formation

47
Q

Is PEEP or driving pressure more important in regard to lung injury?

A

driving pressure

48
Q

What is the initial I:E ratio BMI < 45

A

1:1.5

49
Q

What is the initial I:E ratio BMI > 45

A

1:1

50
Q

What does an increase in the I:E ratio to 1:1.5 or 1:2 do?

A

↓PIP requirement

↓deltaP

51
Q

What is the benefit of decreased I:E ratio?

A

reduced airway pressure

increased homogenous ventilation

52
Q

2 goals of emergence from mechanical ventilation during anesthesia?

A
  1. maintain open-lung throughout emergence

2. minimize anesthesia induced changes during post-op period

53
Q

When a patient is “flipped” from vent to bag mode what should be checked BEFORE?

A

APL valve to maintain patient’s PEEP

54
Q

To reach goal PEEP at LOW FGF:

A

APL valve may need to be INCREASED

55
Q

To reach goal PEEP at HIGH FGF:

A

APL valve may need to be DECREASED

56
Q

During emergence:

A

maintain peep/apl

raise HOB

57
Q

What does raising the HOB do?

A
  1. decreases chest wall compression

2. increases lung compliance

58
Q

4 concerns of using un-necessary post-op O2

A
  1. activation of ROS
  2. peripheral/coronary vasoconstriction
  3. decreased CO
  4. absorption atelectasis
59
Q

During mechanical ventilation, what should be monitored?

A

Lung compliance
Pressure volume loop
- maximize volume delivered at the lowest possible pressure
Flow volume loop
- acute angle represents expiratory flow limitation

60
Q

What is important to note on the pressure volume loop?

A

width of the loop is the driving pressure

61
Q

What is important to note on the flow volume loop?

A

an acute angle represents an expiratory flow limitation.
(very steep line)
*most likely from atelectasis development

N928 - Basic Principles (22 decks)

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