Lung Protective Ventilation

Question 1

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

Answer 1

a positive trans-pulmonary pressure

Question 2

Ptp =

Answer 2

Ptp = Palv - Ppl

Question 3

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

Answer 3

alter the intrapleural pressure gradient

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

Question 4

How is a positive transpulmonary pressure maintained during surgery?

Answer 4

maintaining alveolar pressure

Question 5

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

Answer 5

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

Question 6

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

Answer 6

increasingly POSITIVE intrapleural pressure

increasingly NEGATIVE transpulmonary pressure

Question 7

Upright to supine is a loss of how much FRC?

Answer 7

0.8-1L

Question 8

Induction of anesthesia is a loss of how much FRC?

Answer 8

0.4-0.5L

Question 9

Total reduction of FRC during supine induction of anesthesia?

Answer 9

1.2-1.5L

Question 10

How much FRC does a patient have?

Answer 10

~ 30mL/kg of IBW

Question 11

Loss of FRC favors: (3)

Answer 11

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

Question 12

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

Answer 12

hypoxic hypoxia from alveolar shunting

Question 13

In ARDS, why are lungs non-recrutible?

Answer 13

• cellular debris

- edema

Question 14

In GA, why are lungs recruitable?

Answer 14

• loss of FRC

- atelectasis

Question 15

What are 5 factors that contribute to alveolar collapse?

Answer 15

1. position
2. induction
3. FiO2
4. Maintenance
5. emergence

Question 16

How does position contribute to alveolar collapse?

Answer 16

INCREASED closing pressure → decreased FRC

Question 17

How does induction contribute to alveolar collapse?

Answer 17

loss of muscle tone → decreased FRC

Question 18

How does FiO2 contribute to alveolar collapse?

Answer 18

resorption behind closed airways → atelectasis

*increased FiO2 → faster resorption

Question 19

How does maintenance of GA contribute to alveolar collapse?

Answer 19

progressive airway closure with decreasing compliance

Question 20

How does emergence from GA contribute to alveolar collapse?

Answer 20

high FiO2 promotes postoperative atelectasis

absence of CPAP → continued furthering of lung collapse

Question 21

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

Answer 21

1. structural

2. functional

Question 22

What is ventilation induced lung injury?

Answer 22

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

pressure or volume too high

Question 23

What is ventilation associated lung injury?

Answer 23

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

Question 24

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

Answer 24

1. volutrauma
2. barotrauma
3. atelectrauma
4. biotrauma

Question 25

What are volutrauma manifestations?

Answer 25

damaged endothelium, decreased surfactant, increased capillary leak

Question 26

What is atelectrauma?

Answer 26

damage from repeated closure and opening of small airways/alveoli *under-utilization of PEEP

Question 27

What is biotrauma?

Answer 27

damage to the lungs from the release of inflammatory mediators

Question 28

``` Conventional lung ventilation: Vt PEEP I:E FiO2 ```

Answer 28

strategy that promotes VALI - not individualized - Vt = 10-15mL/kg TBW - PEEP: 0-5cmH2O - I:E no greater than 1:2 - FiO2: provider preference

Question 29

``` Lung protective ventilation: Vt PEEP I:E FiO2 ```

Answer 29

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 ```

Question 30

LPV emergence settings:

Answer 30

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

Question 31

LPV induction strategies & goal

Answer 31

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

Question 32

LPV goal during maintenance of anesthesia

Answer 32

restore / maintain lung volume to baseline & maximize lung compliance - alveolar recruitment maneuver - individualize PEEP - use LOWEST POSSIBLE driving pressure (deltaP) - compliance = Vt / deltaP

Question 33

What is compliance equation?

Answer 33

Vt / deltaP

Question 34

What is deltaP?

Answer 34

the driving pressure deltaP = Pplat - PEEP deltaP (estimation) = PIP - PEEP

Question 35

What is the set Vt in LPV?

Answer 35

6-8mL/kg IBW

Question 36

How is oxygen maintained during LPV?

Answer 36

FiO2 <30% Goal SpO2 >= 94% *reduce resorption atelectasis [after this there is a steeper drop on the oxyhemoglobin dissociation curve]

Question 37

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

Answer 37

>10%

Question 38

When does the initial alveolar recruitment maneuver occur?

Answer 38

post-extubation CPAP or PEEP adequate to exceed critical opening pressure

Question 39

What is done post-intubation

Answer 39

alveolar recruitment maneuver

Question 40

Why is an alveolar recruitment maneuver done immediately after intubation?

Answer 40

1. pre-oxygenation = absorption atelectasis 2. induction drugs = ↓FRC *easier to open right away than wait until later

Question 41

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

Answer 41

do not let go! maintain pressure until adequate PEEP is applied *ARM through the ventilator is preferred

Question 42

What are 4 types of alveolar recruitment maneuvers?

Answer 42

1. bag squeezing 2. CPAP 3. cycling maneuver 4. stepwise Vt changes

Question 43

``` Minimum recruitment pressure required during alveolar recruitment maneuver: BMI <30 BMI 30-40 BMI 40-50 BMI >=50 ```

Answer 43

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

Question 44

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

Answer 44

TELL THE SURGEON

Question 45

What should the initial PEEP setting be?

Answer 45

BMI x 0.3

Question 46

What are the 2 purposes of PEEP?

Answer 46

1. maintain end expiratory lung volume | 2. reduce atelectasis formation

Question 47

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

Answer 47

driving pressure

Question 48

What is the initial I:E ratio BMI < 45

Answer 48

1:1.5

Question 49

What is the initial I:E ratio BMI > 45

Answer 49

1:1

Question 50

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

Answer 50

↓PIP requirement | ↓deltaP

Question 51

What is the benefit of decreased I:E ratio?

Answer 51

reduced airway pressure | increased homogenous ventilation

Question 52

2 goals of emergence from mechanical ventilation during anesthesia?

Answer 52

1. maintain open-lung throughout emergence | 2. minimize anesthesia induced changes during post-op period

Question 53

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

Answer 53

APL valve to maintain patient's PEEP

Question 54

To reach goal PEEP at LOW FGF:

Answer 54

APL valve may need to be INCREASED

Question 55

To reach goal PEEP at HIGH FGF:

Answer 55

APL valve may need to be DECREASED

Question 56

During emergence:

Answer 56

maintain peep/apl | raise HOB

Question 57

What does raising the HOB do?

Answer 57

1. decreases chest wall compression | 2. increases lung compliance

Question 58

4 concerns of using un-necessary post-op O2

Answer 58

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

Question 59

During mechanical ventilation, what should be monitored?

Answer 59

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

Question 60

What is important to note on the pressure volume loop?

Answer 60

width of the loop is the driving pressure

Question 61

What is important to note on the flow volume loop?

Answer 61

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