Lung Protective Ventilation (LPV) Flashcards
physiologic respiration
- occurs through negative pressure
- negative Ppl (intrapleural pressure) provides a positive transpulmonary pressure to minimize atelectasis at baseline [Ptp = Palv - Ppl]
- anesthetic and surgical factors alter chest wall muscle tone which alters Ppl pressure gradient
- maintaining positive Ptp during surgery is dependent on maintaining Palv
anesthesia/surgical effects on lungs
- loss of muscle tone
- elevated intraabdominal pressure
- reduction in FRC
loss of muscle tone
- upper airway muscles –> lead to obstruction
- chest wall and diaphragm - abdominal contents cephalad displacement, alveolar compression
elevated intraabdominal pressure
- increased BMI
- pneumoperitoneum
- trendelenburg or lithotomy position
FRC decrease with supine position
transition from upright to supine decreases FRC by 0.8-1L
FRC decrease with induction agents
further reduce FRC by 0.4-0.5 L
total FRC reduction
1.2-1.5 L, brings lung volume closer to residual volume
normal FRC
30 mL/kg of IBW
recruitable lung area
- general anesthesia
- loss of FRC
- atelectasis
non-recruitable lung area
- ARDS
- cellular debris
- edema
factors that contribute to alveolar collapse
- position
- induction
- FiO2
- maintenance
- emergence
position on alveolar collapse
increased closing pressure –> decreased FRC
induction on alveolar collapse
loss of muscle tone –> decreased FRC
FiO2 on alveolar collapse
- resorption behind closed airways –> atelectasis
- increased FiO2 –> faster resorption
maintenance on alveolar collapse
progressive airway closure with decreasing compliance
emergence on alveolar collpase
- high FiO2 promotes post-operative atelectasis
- absence of CPAP –> continued lung collapse
ventilation induced lung injury (VILI)
ventilator does not cause injury but the settings of the ventilator do
ventilation associated lung injury (VALI)
ventilator induced lung injury specific to the OR setting
volutrauma
lung injury associated with high volumes on the ventilator, even in the presence of moderate peak inspiratory pressures; damaged endothelium, decreased surfactant, increased capillary leak
barotrauma
lung injury associated with high pressures on a mechanical ventilator; damage from positive pressure effects
atelectrauma
injury specifically to the alveoli that results from repeated atelectasis and re-inflation of the alveoli; damage from repeated collapse and re-inflation
biotrauma
damage from release of inflammatory mediators; refers to the the release of various inflammatory mediators due to injury from different ventilatory modes which can cause injury to the lungs and other distal organs
conventional lung ventilation
- strategy that promotes VALI
- not individualized
- Vt 10-15 mL/kg TBW (YIKES)
- PEEP 0-5 cmH2O
- I:E ration no greater than 1:2
- FiO2 provider preference (but usually 60% or higher)
lung protective ventilation (LPV)
- protects against VALI
- individualized to patient and surgery
- adjust settings based on patient monitors and ventilator data
LPV initial maintenance settings
- low VT 6-8 mL/kg IBW
- minimize FiO2 < 30%
- individualized PEEP 30% of BMI (usually 8-10 as starting)
- alveolar recruitment maneuvers after induction
- I:E ratio 1:1.5
LPV emergence settings
- FiO2 < 80%; decreases amount of atelectasis, 100% has been shown to have MORE atelectasis
- positive pressure ventilation –> maintenance of lung volume; PEEP must be greater than closing pressure
- elevate HOB to shift contents caudad
induction LPV strategies
- goal - attenuate anesthesia related changes
- initial FiO2 100%
- elevated HOB > 30 degrees; reverse trendelenburg > back up
- tightly sealed face mask - apply CPAP; use APL valve or CPAP mode on ventilator
- OPA or NPA as needed
maintenance LPV strategies
- restore lung volume with alveolar recruitment maneuver (ARM)
- maintain lung volume and minimize atelectasis formation (individualize PEEP)
- maximize lung compliance - use lowest possible driving pressure (Pplat - PEEP); look at compliance curves/loops
TV LPV
- initial setting 6-8 mL/kg
- purpose - maintain physiologic tidal volume
maintenance FiO2 LPV
- initially 30%
- maintain SpO2 >/= 94%
- purpose - reduce resorption atelectasis; use SpO2:FiO2 curve as monitor to assess if we are maintaining open-lung ventilation
high FiO2 dangers
- at 21% if saturation less than 97% we known that greater than 10% intrapulmonary shunting is occurring
- high FiO2 has the potential to mask what is occurring in the lungs; could be shunting or have atelectasis and don’t know it
alveolar recruitment maneuvers (ARM) definition
- initial performance post intubation
- need sufficient CPAP to exceed critical opening pressure
- purpose - to create an open-lung state
types of ARMs
- bag squeezing technique
- vital capacity maneuver - CPAP
- cycling maneuver
- stepwise Vt changes
minimum recruitment pressure required for BMI <30
40 cmH2O
minimum recruitment pressure required for BMI 30-40
40-50 cmH2O
minimum recruitment pressure required for BMI 40-50
50-55 cmH2O
minimum recruitment pressure required for BMI >/=50
50-60 cmH2O
minimum recruitment pressure required for BMI >/=50
50-60 cmH2O
PEEP
- initial setting BMI x 0.3 (between 27-33%); max starting usually 15
- purpose - maintain end expiratory lung volume, reduce atelectasis formation, BMI specific levels of be must be proceeded by ARM
PEEP LPV
- initial setting BMI x 0.3 (between 27-33%); max starting usually 15
- purpose - maintain end expiratory lung volume, reduce atelectasis formation, BMI specific levels of be must be proceeded by ARM
I:E Ratio LPV
- initial setting BMI < 45 1:1.5; BMI >/= 45 1:1
- purpose - reduce airway pressure, increase homogenous ventilation
I:E Ratio LPV
- initial setting BMI < 45 1:1.5; BMI >/= 45 1:1
- purpose - reduce airway pressure, increase homogenous ventilation
emergence goals of LPV
- maintain open-lung throughout emergence
- minimize anesthesia induced changes during post-operative period
emergence FiO2
- maintain FiO2 = 80% throughout
- purpose - reduce atelectasis formation
positive pressure ventilation in emergence
- maintain CPAP and PEEP throughout
- purpose is to prevent atelectasis formation and maintain open lung state
HOB elevation in emergence
- elevated HOB >/= 30 degrees
- purpose is to decrease chest wall compression and increase lung compliance
monitoring lung compliance
- trend of compliance throughout the case
- a down trend represents atelectasis or anything favoring poor ventilation of lungs
pressure volume loop
- assessment of driving pressure <15 cmH2O; pressure required to deliver set volume
- want to maximize volume delivered at lowest pressure
flow volume loop
- representation of expiratory flow
- acute angle represents expiratory flow limitation
Bag squeezing technique ARM
squeeze bag with APL closed to allow you to deliver enough pressure to keep the lungs open; need to make sure you maintain pressure on your bag while you flip over to the vent so that you don’t get collapse
Vital capacity or CPAP maneuver ARM
put patient on the ventilator, hit procedures button, tell vent to give a certain amount of pressure for a specified period of time
cycling maneuver ARM
set inspiratory pressure and step PEEP up in a cyclic fashion to open up the patients lungs; then step PEEP back down
stepwise Vt changes ARM
set PEEP then gradually increase the tidal volumes (so that you get enough pressure) to open the lungs up; make sure to bring Vt back down
