Lung Protective Ventilation Flashcards by Shannon desmond

Physiological respiration occurs through

negatice pressure

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Negative intrapleural pressures provides

a positive transpulmonary pressure to minimize atelectasis at baseline

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Positive transpulmonary pressures=

Palveolar- intrapleural pressure

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Anesthetic and surgical factors alter

chest wall muscle tone

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Chest wall muscle tone from anesthesia and surgical factors alter

intraplueral pressure gradient

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Maintaining a positive transpulmonary pressure during is dependent on

maintain alveolar alveolar pressure

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Anesthesia and surgical effects on the lungs include:

loss of muscle tone

elevated intraabdominal pressure

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Loss of muscle tone effects on the lungs includes

upper airway muscles (obstruction)

chest wall and diaphragm (abdominal contents cephalad displacement and alveolar compression)

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Elevated intra-abdominal pressure on lungs in surgery

increased BMI
pneumoperitoneum
trendelenburg positioning

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Induction of anesthesia causes

reduction in FRC

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Transitioning from upright to supine position

decreases FRC by 0.8-1L

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Induction agents

further reduce FRC by 0.4-0.5L

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Total reduction after induction is

1.2-1.5L

bring lung volume close to residual volume

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Recruitable lungs

general anesthesia

loss of FRC and ateletasis

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Non-recruitable lungs

ARDS
cellular debris
edema

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Factors that contribute to alveolar collapse

position
induction
FiO2
maintenance
emergence

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Position as a factor that contributes to alveolar collapse

increased closing pressure leads to decreased FRC

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Induction as a factor that contributes to alveolar collapse

loss of muscle tone leads to decrease FRC

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FiO2 as a factor that contributes to alveolar collapse

resorption behind closed airways leads to atelectasis

increased FiO2 causes faster re-absorption

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Maintenance as a factor that contributes to alveolar collapse

progressive airway closure with decreasing compliance

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Emergence as a factor that contributes to alveolar collapse

high FiO2 promotes postoperative ateletasis

absence of CPAP causes continued lung collapse

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Ventilator Induced Lung injury includes

Mechanical ventilation can induce lung injury
ventilation induced lung injury
ventilation associated lung injury

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Adverse effects of mechanical ventilation

leads to potentially irreversible structural and functional damage

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What is ventilation induced lung injury?

ventilator does not cause injury but the settings of the ventilator do

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What is ventilation associated lung injury?

specific to OR setting

Ventilation Associated Lung Injury Examples

volutrauma barotrauma atelectrauma biotrauma

Volutrauma

damaged endothelium, decreased surfactant, increased capillary leak

Barotrauma

damage from positive pressure effects

Atelectrauma

damage from repeated collapse and re-inflation

Biotrauma

damage from release of inflammatory mediators

Conventional Lung Ventilation includes

``` strategy that promotes VALI not individualized PEEP- 0-5cmH2o Vt- 10-15m TBW I:E no greater than 1:2 FiO2- provider preference ```

Lung Protective Ventilation (LPV)

strategy that protects against VALI individualized to patient and surgery adjust setting based on: pt monitors and ventilator data

LPV Initial Maintenance Settings

Low Vt 6-8ml/kg IBW minimize FiO2 < 30% of BMI alveolar recruitment Maneuvers inspiratory: expiratory (I:E) ration 1:1.5

LPV Emergence Settings

FiO2 < 80% Positive Pressure Ventilation (maintenance of lung volume and must be greater than closing pressure) Elevate Head of BEd

Induction Strategies

``` Initial FiO2: 100% elevated HOB >30% RT> Back up Tightly sealed face mask- apply CPAP OPA or NPA as needed ```

Goal of Induction

attenuate anesthesia related changes

Goals of Mainteance LPV Sequence

restore lung volume via ARM maintain lung volume and minimize atelectasis formation (individualize PEEP) Maximize lung compliance

How can you maximize lung compliance during the maintenance phase?

use lowest possible driving pressure | compliance = Vt/change in pressure

Initial Setting of TV

6-8ml/kg of IBW

Purpose of TV

maintain physiologic tidal volume

Maintenance of FiO2 (initial setting)

30%

Maintain SpO2 during maintenance phase

> 94%

Purpose of Maintenance FiO2

to reduce resorption atelectasis | use SpO2: FiO2 curve as monitor to assess if we are maintaining "open-lung ventilation"

Maintenance FiO2

low FiO2 can be used as a surrogate monitor to assess ventilation at 21% less then 97% we know greater than 10% intrapulmonary shunting is occurring

Alveolar Recruitment Maneuvers- initial performance

post intubation | sufficient CPAP to exceed critical opening pressure

Purpose of alveolar recruitment

create an open lung state

Alveolar recruitment maneuvers

bag squeeze technique | vital capacity maneuvers

Bag squeezing technique

arm through ventilator is ideal | APL close need to maintain pressure on bag while you switch to ventilator mode

CPAP

VC maneuver place patient on ventilator procedure mode where amt of pressure and amt of time set to recruit lung

Cycling Maneuver

set inspiratory pressure @ 20cm then and PEEP then slowly decrease PEEP

Stepwise Vt changes

set PEEP and increase Pinspiratory circuit then decrease pressure

Minimum recruitment pressure required BMI <30

40cmH20

Minimum recruitment pressure required BMI 30-40

40-50cmH20

Minimum recruitment pressure required BMI 40-50

50-55cmH20

Minimum recruitment pressure required BMI >50

50-60cmH20

initial setting of PEEP

BMI x 0.3

Purpose of PEEP

maintain end expiratory lung volume reduce ateletasis formation BMI specific levels of PEEP must be proceeded by ARM (max starting PEEP is 15)

Initial Setting of I:E ratio for BMI < 45

1:1.5

initial setting of I:E ratio for BMI > 45

1:1

Purpose of setting I:E ratio

reduce airway pressures | increase homogenous ventilation

Goals of LPV for Emergence

maintain open lung throughout emergence | minimize anesthesia induced changes during postoperative period

Emergence FiO2

Maintain FiO2 < 80 throughout

Purpose Emergence FiO2

reduce atelectasis formation

Positive Pressure Ventilation

maintains CPAP and PEEP throughout

Purpose of PPV

prevent atelectasis formation | maintain open-lung state

Purpose of HOB >30

decrease chest wall compression | increase lung compliance

Oxygen therapy post-operatively

does everyone need O2? | excessive O2

Concerns of excessive O2?

activation of ROS (reactive oxygen species) peripheral/coronary vasoconstriction decreased CO absorption atelectasis

What does down trending compliance represent?

poor ventilation of lungs

Pressure Volume Loops

assessment of driving pressure "width of loop" pressure required to deliver a set volume want to maximize volume delivered at lowest pressure

Flow Volume Loop

representation of expiratory flow | acute angle represents expiratory flow limitation