quiz 6 Flashcards
When using a pressure volume loop to determine the upper and lower inflection points, where should optimal PEEP be set?
2-3 cmH2O above the lower inflection point
Describe how you would get a pressure volume curve when using the low flow or quasi-static method
Automated procedure requiring a paralyzed patient
Flow introduced at 2 lpm
Not static, flow low enough to generate roughly equivalent values
Proceed to 45 cmH2O
In simple terms, what is the lower inflection point?
The point at which compliance improves
In simple terms, what is the upper inflection point?
The point at which compliance worsens
In simple terms what is the deflation point?
The point at which the alveoli close down after being inflated
What is the difference between over distension and hyperinflation?
Over-distention = overstretching of lung tissue (increased alveolar tension)
Hyperinflation = inflation of the lungs beyond their usual size
Give an example of hyperinflated lungs vs overdistended lungs
Hyperinflated lungs would be the lungs of a patient with Emphysema
Overdistended lungs could be the lungs of an ARDS patient who is receiving mechanical ventilation which is straining individual alveoli but not hyper inflating the lung
What factors are evaluated during a PEEP study?
PEEP
FiO2
PaO2
Blood pressure
PvO2
What increments should PEEP be weaned at?
Increments of 2 cmH2O
You have a patient on 10 of PEEP and 60% FiO2. Can the PEEP on this patient be weaned?
PEEP should not be weaned until FiO2 is below 40%
Why can supine positioning be problematic for some patients?
Decreases FRC
Decreases V/Q matching
What are the “minor” risks associated with proning?
Facial edema
Patient agitation
Pressure injuries
Dislocated shoulders
Pulled out ETTs, lines, catheters
Requires experienced staff
What recommendation is proning given by the ARDS net study?
Strong recommendation in patients with P/F ratios less than 150
How can the risks of proning be minimized?
Wrap patients in sheet
Support with strategic pillow placement
Memory foam pillows for face
Team approach
Practice
How does proning affect V/Q matching?
Improves V/Q matching by allowing better ventilation of previously closed portions of the lung
Lungs are bigger in the back so proning allows the ventral portions to be better ventilated which can improve oxygenation
How does proning affect pleural pressure?
Moves the heart so that it is no longer pressing down on the lungs
Pleural pressure is more uniformly distributed promoting alveolar recruitment
What are “major” risks associated with proning?
Worsening dyspnea
Hypoxemia
Cardiac arrhythmia
Increased ICP
Limited patient examination
If you have a patient with unilateral lung disease who is satting low, how should you position them and why?
Position them with the good lung down to increase perfusion to the good lung
How does mean airway pressure affect oxygenation?
A higher MAP increases oxygenation because it favors alveolar recruitment
Define Mean airway pressure
The average airway pressure during a total respiratory cycle
What is the formula to determine mean airway pressure?
Paw = (PIP-PEEP) x (Itime/Etime) + PEEP
What is the most effective way to raise Mean airway pressure?
Increase PEEP
What can you adjust to increase mean airway pressure?
PEEP
PIP
Itime
Define a recruitment maneuver
A sustained increase in airway pressure intended to open as many collapsed lung units as possible
Describe how you would perform a recruitment maneuver using CPAP
20 cmH2O for 20 seconds
30 for 30 seconds
40 for 40 seconds
30 for 30 seconds
20 for 20 seconds
What are the two properties that govern the behavior of lung tissue?
Elastic properties and viscous properties
Why is time an important factor when performing a recruitment maneuver?
The lung tissue is not homogenous
The elastic behavior of the lungs is quickly activated
The viscous behavior of the lungs slows activation resulting in slowed inhalation and exhalation
Recruitment maneuvers in PC-CMV can be performed in 2 different ways. Describe the method that requires rapid implementation of high PEEP
Place patient in PC-CMV
Set PC to 20 cm H2O above PEEP
Increase PEEP to 40 cmH2O
Sustain for 40-60 seconds
Decrease PEEP to a level that will sustain recruitment
Recruitment maneuvers in PC-CMV can be performed in 2 different ways. Describe the method that requires incremental increases in PEEP
Place patient in PC-CMV
Increase PEEP by 5 cmH2O and hold for 2-5 minutes
Repeat increase with other parameters held constant
Monitor for changes in compliance
Describe periodic recruitment maneuvers
Aka periodic hyperinflation
Larger than normal tidal volumes delivered periodically to protect again atelectasis
What correlation did one study find between sustained high PEEP and blood pressure?
One study found that the benefits of sustained high PEEP are found in the first 10 seconds of the maneuver and that blood pressure decreases after those ten seconds
What is APRV?
Airway pressure release ventilation
What is TCAV?
Time controlled adaptive ventilation
Describe the breathing pattern in APRV
Sustained inspiratory pressure to benefit oxygenation with brief releases of the pressure to release carbon dioxide
How does APRV increase alveolar recruitment?
Increases alveolar recruitment through extended inspiratory times
How does APRV maintain alveolar stability?
By only allowing for a brief period of exhalation to release carbon dioxide, APRV prevents the alveoli from being able to completely deflate and collapse
How is rate set in APRV?
By manipulating Thigh and Tlow
What are the ordered settings for APRV?
Thigh
Tlow
Phigh
Plow
FiO2
How do you set Phigh?
From VC CMV = use Pplat
From PC CMV = use peak pressure
From PRVC = use peak pressure
What do you set Plow to?
Zero
How do you set Tlow?
Read the peak expiratory flow
Take that number and multiply by 0.75
The number calculated should be where exhalation ends
Describe the slope you would see in a patient on APRV if they have normal lungs
The slope should be about 45 degrees
Describe the slope you would see in a patient on APRV if they had decreased compliance
The slope would be “steeper”
Slide calls it 30 degrees, which only makes sense if you are measuring from the y axis, so keep that in mind
How do you set Thigh?
Calculate TCT from old mode
Subtract Tlow you calculated from old TCT
The difference is Thigh
What did the study on pigs with ARDS ventilated on APRV TCAV vs ARDSnet protocols demonstrate?
Compliance was better on APRV
Why did APRV TCAV work better on pigs than ARDSnet?
Alveoli need time to recruit, the sustained inspiratory pressure of APRV with the short exhalation periods allowed for the alveoli to be recruited and stay open
In short, MAP was increased
What patients might find APRV more comfortable?
Critically ill patients with a very high respiratory rate may find APRV more comfortable
What can Tlow tell us about the compliance of the lung?
Shorter Tlow indicates lower compliance
Longer Tlow indicates higher compliance
What are the benefits of spontaneous breathing on APRV?
Aids in recruitment
Helps maintain negative pressure in pleural space
Supports venous return
What are some of the risks associated with ARPV?
Higher MAP can mean decreased cardiac output
Minute ventilation tends to be lower on APRV than on other modes creating problems with ventilation
If you want to increase the RR on APRV, what would you do?
Decrease Thigh
What are the different kinds of non-invasive respiratory support?
HHFNC
CPAP
BiPAP
Negative pressure ventilation
If you want to increase tidal volume on APRV, what would you do?
Increase Phigh
What is NPPV?
Noninvasive positive pressure ventilation
What is NIV?
Noninvasive ventilation
What is BiPAP?
Bilevel positive pressure ventilation
In order for a patient to be on CPAP, they must be what?
Spontaneously breathing
What kind of interfaces can be used with CPAP?
Oronasal mask
Hybrid mask
Total face mask
Nasal pillows
Nasal mask
CPAP can also be thought of as
EPAP
PEEP
What does the positive pressure of CPAP do?
Stent open the airways
Increase FRC by recruiting alveoli
Improve gas exchange
Reduce diaphragmatic work
What are the indications for CPAP?
Atelectasis
Acute hypoxemic respiratory failure
Acute cardiogenic pulmonary edema
How does CPAP help patients with sleep apnea?
Eliminates soft tissue obstruction in the upper airway
How does CPAP help patients with cardiogenic pulmonary edema?
Continuous pressure can help push back the fluid in the lungs
What are the initial CPAP settings for PEEP and FiO2?
PEEP = 5-10 cm H2O
FiO2 = either match what they were on previously if on supplemental oxygen or start at 100% and wean down
List the interfaces that can be used for BiPAP
Oronasal mask
Nasal mask
Helmet
Total facemask
Hybrid mask
Helmet
Nasal pillows
What are the two pressure supplied by BiPAP?
IPAP
EPAP
What is EPAP equivalent to?
CPAP
PEEP
What is IPAP equivalent to?
PIP
Pressure support
EPAP is meant to improve patient ______
Oxygenation
IPAP is mean to improve patient ______
Ventilation
How does IPAP improve patient ventilation?
Pressure support
Increases tidal volume
Decreases WOB
When is BiPAP shown to have the most useful implimentation?
COPD
ACPE
Post op respiratory failure
Prevention of post extubation respiratory failure
What are the basic initial settings for BiPAP?
EPAP = 5-10 cmH2O
IPAP = 10-15 cmH2O
FiO2 = Start high and wean
What should the minimal pressure difference between IPAP and EPAP be?
At least 5 cmH2O
What is the number one reason a patient will fail on CPAP or BiPAP?
Wont comply or tolerate mask
What are the benefits of HHFNC?
Provide precise FiO2
Flowshes CO2 from anatomic dead space
Decrease upper airway resistance
Increase pharyngeal pressure and lung volume
Added humidity
What are the clinical indications for HHFNC?
Acute hypoxemic respiratory failure
Risk of hypoxemic respiratory failure post extubation
What are the flow settings on HHFNC for adults?
1-40 lpm, 60 max
What are the flow settings on HHFNC for pediatrics?
1-20 lpm