Adult Pt getting sicker Vent Strategies (Mod 4) Flashcards
What should your vent goals be if the patient is unable to maintain adequate oxygenation or ventilation (or both)
Increase ventilator support must be increased while minimizing damage to the lungs
Advanced strategies for ARDS patients that are getting sicker
Lung protective ventilation (ARDSnet and Driving pressure)
- APRV
- Proning
- Optimal PEEP
- ECMO
- Independent lung ventilation
Berlin definition of ARDS
Presence of pulmonary edema not explained by cardiac issues
- Acute onset (1 week or less) w/bilateral opacities w/pulmonary edema aka “white out”
- PF ratio < 300mmHg w/min of 5 cmH2O PEEP (or CPAP)
How could edema be managed
Furosemide (lasix)
ARDS mild severity
200-300
ARDS moderate severity
100-200
ARDS severe severity
<100
ARDS treatment strategies
Peeps and FiO2s that increase together (according to ARDSnet)
- Low Vts; Start Vts at 6 and titration up; given that Plats are less than 30
Liquid ventilation
Lungs can be ventilated with liquids given there is enough oxygen content in it
- used for divers; bc air compresses under pressure; liquids don’t (as much)
What is more important aspect when managing ARDS?
Driving pressure rather than the actual Vts
Driving pressure vs mechanical power?
- why is mechanical power receiving more interesting recently?
Theory of Airway Pressure Release Ventilation (APRV)
As an elevated CPAP pressure (aids oxygenation) w/brief intermittent releases in airway pressure (aids in ventilation)
- Flow wave forms are the reverse of normal; longer Tis than Tes
- Basically CPAP w/a release
Add slides 14-20
Advantages of Airway Pressure Release Ventilation (APRV)?
Employs lung protective strategies
- Easy to manipulate both MAP and I:E
- Aids both oxygenation and ventilation
- Considered a comfortable mode as the Pt can take a Spontaneous breath as they want
Disadvantages of Airway Pressure Release Ventilation (APRV)
- Designed to be used with spontaneous breathing pts
- May cause respiratory muscle atrophy if pt is apneic for prolonged periods
- Dangerous if applied incorrectly
- Vts scare physicians who aren’t familiar with the mode
What is the theory for the benefits of elevated CPAP pressure?
High PEEPs = High mean airway pressure; improving oxygenation (at a safe plat)
- Responsible for recruiting the most difficult to recruit alveoli
What complication do you need to monitor in Airway Pressure Release Ventilation (APRV)?
- hint; Thigh and Tlow
Ensure that air trapping associated with Airway Pressure Release Ventilation (APRV) less than 15%
- deliberailty holding air, means that we are allowing air trapping/holding (even tho Tlow is set at 0, it won’t actually derecruit)
Are Vts set high or low during Airway Pressure Release Ventilation (APRV)?
Vts can be set higher IF compliance increases (lungs can expand more), but driving pressures should be set lower (they should also realistically drop)
RR needs to be ajusted when Thigh and Tlow are changed.
- Remember TCT = 60/RR; so RR = 60/TCT bc TCT = Thigh + Tlow
What is the impact of changes in lung mechanics in Airway Pressure Release Ventilation (APRV)
Maintaining Tlow so we push air back into the the lungs back in at 75%???????????
In APRV, if compliances is low should Tlow be set higher or lower?
Set lower Tlow
Check everything before slide 21: We Finished APRV
What is the goal of Prone Positioning?
Goal is to improve oxygenation by creating better v/q matching (via reduced shunt)
Inclusion Criteria for Prone positioning?
Severe ARDS as evidenced by?
- **A P/F Ratio < 100 while on FiO2 > 0.6
- OI greater than or equal to 20
DO2 formula?
Oxygen Index formula?
(FIO2 x Mean airway pressure/PaO2) (x100 if you need to convert it back)
What are the respiratory benefits of using APRV?
Improved v/q matching and better gas exchange for a given volume (improves ventilation)
What are the cardiovascular benefits of using APRV?
Retention of the thoracic pump mechanism
How does APRV impact oxygenation?
Improved through better recruitment and surface area for gas exchange
- allows for higher MAP while still at safe plats
What benefit does APRV provide regarding a patients neurological status; such as in delerium?
Reduced need of sedation
- instead of RASS levels of -4 to -5 (that are often done to reduce metabolic rate-VO2 and VCO2) patient can be more alert…RASS -2
How does aid in oxygenation and ventilation?
Makes it easier to manipulate both MAP and I:E
What is the goal of Prone positioning?
Goal is to improve oxygenation by creating better v/q matching (via reduced shunt)
Which why should a patient be turned for proning?
Towards the vent
Patient position for proning?
Reverse Trendelenburg, 30 degrees if possible
How long are patients proned according to AHS policy?
20 hours per day, 16 of which are continuous
Criteria for discontinuation of proning?
FiO2 < 0.60 or OI< 20
- Deterioration of pt status related to prone position
- Proning has no improvement to status
- Doctor says stop
What is the purpose of ECMO?
An extrapulmonary form of support that can provide oxygenation and/or ventilation of the blood
- Allows time for the lungs to recover from their acute injury
- Can be used up to 10 days
What are 2 types of ECMO?
- Venoarterial (VA): provides respiratory and hemodynamic support
- Venovenous (VV): provides respiratory support only
When would ECMO be used in adults?
severe ARDS or severe asthma
When would ECMO be used in neonates?
- PPHN (primary, or associated with pneumonia, MAS, RDS)
- CDH
Ventilator settings for ECMO?
30-30-10-10 approach
- FiO2 0.3
- Plat <30
- PEEP 10
- RR 10
ECMO risks?
- Bleeding
- Thrombosis
- Infection
- DIC
Whats Nova Lung?
A membrane ventilator
- provides arterio-venous extrapulmonary lung support
- Relies on Pts blood pressure to drive the system aka BP is needed
- uses simple diffusion to provide oxygenation and ventilation
Whats Independent Lung Ventilation?
Uses a double lumen tube with a ventilator attached to each lumen; each lung is vented independently and either synchronously or asynchronously
Synchronous independent lung ventilation (IVL)
RR of both lungs is kept the same or PEEP, VT, etc can be set independently
Asynchronous independent lung ventilation (IVL)
Lungs are inflated 180 degree out of phase
How do you use Esophageal pressure monitoring to calculate Transpulmonary Pressure (Ptp)?
Intrapulmonary pressure (Plat) - (PIP) Intrapleural pressure
- Pes is often a surrogate for PIP when using a esophageal balloon to measure pressures
What are the advantages of using a Esophageal monitoring to guide pressure settings?
- Airway Pressure alone may be misleading
- TPP offers a more accurate assessment of stress on the lung tissue
- Customization of PEEP and VT settings is possible
- Measurement of TPP is fairly non-invasive
What are the disadvantages of using a Esophageal monitoring to guide pressure settings?
- Relies on correct balloon position
- ARDS is heterogenous; Pes may not reflect TPP in whole lung
- Nobody knows how to interpret Pes in prone patients
- Pes overestimates pleural pressure in well aerated lung tissue and underestimates in in dependent regions; may relocate VILI without reducing severity.
What does airway pressure (Paw) reflect?
Pressure required to inflate both the lungs and chest wall
- Paw = Palv during pause maneuvers
What are the implications from the ventilator if Paw = Palv?
During pause maneuvers, it implies that
- Plats are measured during an insp pause
- Total PEEP is measured during an expiratory pause
What does pleural pressure (Ppl) reflect?
Pressure in the pleural space
- affected by increased intra abdominal pressure or decreased chest wall compliance
What factors affect pleural pressures?
Increased intra abdominal pressure or decreased chest wall compliance
- Obesity
- Ascites
- Ileus
- Bowel edema
- Post fluid resuscitation edema of ab tissue
How can you measure pleural pressure?
Measuring esophageal pressure
What does Transpulmonary Pressure (Ptp) reflect?
Pressure required to inflate the lung only
Safety limit for Ptp?
Keep Ptp < 25 cmH2O during inspiration for lung protective ventilation
What should you aim for Ptp settings?
Aim for a positive Ptp 0-10 cmH2O during expiration to prevent alveolar collapse.
- realistically 2-10 cmH2O tho
How is Ptp calculated?
Ptp = Paw - Pe
- Pe is thought to reflect Ppl
Insertion technique for Esophageal balloon?
Insert to 60cm…pull back 40cm
- should see cardiac oscillations on the monitors
Smallest catheter for a Esophageal balloon?
6 Fr
How can you check Esophageal balloon placement?
Should see cardiac oscillations on the monitor
- Can also push the belly as a check to see temp spike in pressure
What factors affect Esophageal Pressures (4)
- Elastic recoil of the esophagus
- Esophageal muscle tone
- Pressure transmitted from surrounding structures
- posture
What posture should patients with Esophageal balloons be in?
Supine
What pressures affect Esophageal pressures?
Pleural pressure and mediastinal pressure
What relationship does pleural pressure have with transpulmonary pressure (ptp)?
They have an inverse relationship;
- Increased pleural pressures implies a decrease in Ptp (alveolar pressure)
What factors would cause a increase in pleural pressure (and thus decrease Ptp)?
- Increase in intraabdominal pressure
- Decrease in chest wall compliance
What is a Delta Ptp is a measurement of?
Lung stress
- DeltaPtp= Ptp plat - Ptp peep
- Lung stress = k x strain
- K = 13.5 cmH2O (constant for specfic lung compliance)
What lung strain is considered lethal?
Lung strain of 2
- lung strain = Deltaptp/13.5
What needs to be ensured throughout expiration to prevent alveolar collapse when using esophageal monitoring?
Positive peep, in this case we refer to transpulmonary pressure (Ptp) to be positive throughout expiration
Why is the purpose of Inverse Ratio Ventilation (IRV) (inversed I:E ratio) like 2:1?
Purpose is to increase Mean Airway Pressure (MAP) to help increase oxygenation time
- keeps lungs recruited, big risk of air trapping and have less exhalation time for CO2 clearance
How does a inverse ratio, such as in APRV reduce shearing stress?
You reduce the shearing stress that occurs when lung units fully inflate then deflate.
- The idea is that you cause less lung tissue damage by limiting how much each alveoli deflates then there is less pressure and stress needed to reinflate the alveoli.
How do you measure spontaneous breaths?
- Measured Total MV - (set RR x Vt)
- Subtract total RR - Set RR
- Divide step 1 by spontaneous breaths (step 2 value)
Mode switch example:
- VC to PC
V in this example is Vt.
- After calculating Compliance
- Manipulate the Comliance formula to calc for whatever you need with the values goals provided (if there are any)
What waveform will display auto peep?
Auto peep will be determined in the flow time scalar waveform…NOT the pressure scalar
- Expiratory hold determines the amount of auto peep present
In VC-CMV, which of the following changes would result in an increased Te?
- Increase Te = Decreased Ti
Changes from decelerating waveform to square flow pattern
- Increased flow (increased Te = Increased flow)
- Decreased RR (TCT decreases, takes more time to cycle to next breath aka decreased RR = Increased Te) (remember Increased Ti = Decreased Te => risk of airtrapping)
- Decreased Ti pause
- Decrased I:E ratio
What does no observable pausae at the end of inspiration mean?
No Ti pause means PIP > plat (doesn’t hit baseline)
no observable pause sample
