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
What are the flow settings on HHFNC for infants?
1-8 lpm
What are the benefits of increasing the flow when using a HHFNC?
Decrease WOB
Improve oxygenation
Improve ventilation
What is an example of some devices that uses negative pressure ventilation?
The iron lung
Chest cuirass
Hayek ventilator
Pneumosuit
What are the initial settings when using a negative pressure ventilation device?
Rate of 12-24 bpm
Inspiratory pressure of -10 to -35 cm H2O
What are the advantages of NPV?
Simplicity of device
Maintenance of the airway
Allows patient to eat and talk
What are the disadvantages of NPV?
Bulky large machine
Access to patient is limited
Reduced venous return
Upper airway soft tissue obstruction
what driving pressure has been associated with increased survival in patients with ARDS?
less than or equal to 15 mmHg
How do you calculate driving pressure?
Driving pressure = Plat - PEEP
How do you calculate compliance?
Change in volume / change in pressure
How do you calculate resistance?
Change in pressure / flow in liters per second
When using NIV what are the two sources of leaks?
Leak around mask
Leak built into the circuit
What are some possible indications for NIV?
COPD
Acute asthma
Cardiogenic pulmonary edema
Immunocompromised patients in respiratory failure
Post extubation vent support
Preintubation vent support to avoid acute desaturation
What are some contraindications for NIV?
Inability to protect airway
Inability to clear secretions
Poor neurological status
Significant facial trauma
Cardiac or respiratory arrest
Unstable hemodynamic status
Untreated pneumothorax
What is APAP?
Autopostive airway pressure
A mode of CPAP
Auto titrates pressure and adjusts to changes in phrayngeal wall vibrations, inspiratory flow limitation, hypopnea, apnea
What is ramp time in regards to CPAP?
Amount of time the machine takes to reach maximum set pressure
Lets patients acclimate
What are the three modes on BiPAP (V60)?
Spontaneous/Timed
PCV
AVAPS
Describe the spontaneous/timed BiPAP mode
Pressure support with backup rate
Flow cycled (if triggering breaths) time cycled if not
What are the ordered setting in Spontaneous/timed?
IPAP
EPAP
FiO2
Rate
Itime
Rise
Ramp
If a patients breaths are blue, what does that mean? (bipap V60)
Spontaneous breathing
If the patients breaths are orange, what does that mean? (BiPAP V60)
Timed breaths
What is PCV on a V60 BiPAP?
Pressure control Ventilation
All breaths are mandatory
Can be patient or time triggered
What are the ordered settings for PCV on BiPAP V60?
IPAP
EPAP
FiO2
Rate
I time
Rise
Ramp
What is AVAPS?
Average volume assured pressure support
What mode on a ventilator do AVAPS mimic?
PRVC
What are the ordered settings for AVAPS?
Rate
EPAP
Itime
Minimum P
Maximum P
Rise
FiO2
What can cause asynchrony when a patient is on a BiPAP?
Inappropriate cycling
Trigger asynchrony
Autotriggering if vent is too sensitive
What can cause inappropriate cycling on a BiPAP?
Inspiratory times that are too long/short
Leak that cannot be compensated for by the machine
What can cause trigger asynchrony on a BiPAP?
Inappropriate trigger thresholds
Leak around the mask
What factors can affect NPPV compliance?
Poor patient understanding/education
Improper interface size, selection and fit
Drying of nose and mouth
High inward flow during exhalation
High fear and anxiety
What are the most common complications of using NPPV?
Skin issues
Besides skin issues, what are other complications associated with NPPV?
Nasal irritation
Dry mouth
Painful pressure in ears
Gastric bloating
Claustrophobia
Eye irritation
Air leak
What are some ways to avoid skin breakdown when using NPPV?
Routinely check site
Apply barrier
Rotation of masks (different mask types
What questions should we be asking ourselves when determining if a patient is ready to be weaned from the vent?
Has the underlying cause for respiratory failure been reversed?
Is the patient adequately oxygenating and ventilating?
Is the patient hemodynamically stable?
Is the patient capable of spontaneous effort?
How can we determine whether or not the underlying cause of intubation has been reversed?
The best way is to check a patients progress in their chart. Information like their history of vent settings, past xrays, ABGs, labs, vital signs medications and fluid balance all play a part in determining if they are ready for an SBT or extubation
What signs that a patient on NPPV should be intubated?
Maxed out NVVP settings
Patient fatigue
Continuing acidosis or hypoxemia
Hemodynamic instability
A patient who is adequately oxygenating should have a P/F ratio of?
Greater than 150-200
A patient who is adequately oxygenating and ventilating should have a PEEP of
Less than or equal to 8 cmH2O
A patient who is adequately oxygenating should have an FiO2 on the ventilator of
Less than or equal to 40%
A patient who is adequately ventilating should have a pH of
Greater than 7.25
What is weaning
The gradual reduction of ventilatory support from a patient whose condition is improving
What does it mean if a patient is capable of spontaneous effort?
That the chemoreceptors in their brain are successfully signaling their respiratory muscles to inhale and exhale
T/F: A patient can require ventilatory support and weaning can begin
True
What are the 3 primary options for weaning?
IMV
PSV
T-piece trials
T/F: the majority of patients who have been intubated cannot be extubated for at least a week
False. 80% of patients do not require gradual weaning
Patients who are able to be extubated without gradual weaning are frequently
Post op patients
Uncomplicated drug overdose
Non respiratory cause for intubation
What was the original strategy when using SIMV to wean patients?
Gradual reduce mandatory breaths to increase patients spontaneous breaths while giving them support and rest with mandatory breaths
What have we learned about weaning using IMV?
IMV extends the patients time on the ventilator
What unintended consequences did IMV have?
Increased patient effort
Increased asynchrony
Increased respiratory rate
Describe PSV weaning
Clinician adjusts the ventilatory workload for spontaneous breaths
Describe T-piece weaning
Place patient on t-piece for 5-10 minutes and gradually increase the time spent on the t piece
What is the goal of PSV weaning
Enhance the endurance of the respiratory muscles while limiting fatigue
What controls the frequency timing and depth of each breath in PSV?
The patient
What triggers the breath in PSV?
The patient
What cycles the breath in PSV
Flow
What limits the breath in PSV?
Pressure support
What score on a MIP should a patient be able to accomplish in order for weaning?
MIP> -20
What vital capacity should a patient be capable of in order for weaning?
> 15 mL/kg
What frequency should a patient be breathing at in order to be considered for weaning?
<35
What should the patients RSBI be in order to be weaned?
<30-105
What are the general settings that a patient on a SBT should be placed on?
PS 5-8 cmH2O
PEEP 5-8 cmH2O
FiO2 <40-50%
How should you screen patients for extubation (besides checking all the normal parameters)?
Place patient on SBT for 2-5 minutes and see how they respond while assessing breathing pattern, vital signs and comfort
How long should a SBT last for?
30-120 minutes
What gas exchange parameters indicate that the SBT is successful?
SpO2 > 85-90%
PaO2 of 50-60 mmHg
Increase in PaCO2 of less than 10 mmHg
What hemodynamic indices are acceptable for a successful SBT?
HR < 120-140 with less than 20% change
Systolic BP < 180 and >90
What ventilatory pattern is indicative of a successful SBT?
RR < 30-35
Change in rate of < 50%
What are indications of a failed SBT?
A change in mental status
Discomfort
Increased WOB
What are common post extubation complications?
hoarseness
Sore throat
Cough
What medications can be used to control swelling post extubation if the patient’s airway is swollen?
Racemic epinephrine
Steroids
What are some more serious post extubation complications?
Subglottic edema
Airway obstruction
Laryngospasm
Secretion management
What are some non invasive strategies for extubating patients?
Extubate to bipap
Extubate to HHFNC
Why might a recently intubated patient receive heliox?
Helium has a lower density than nitrogen which allows it to flow past obstructions with less resistance making breathing easier
Why could the termination of invasive mechanical ventilation increase stress on the cardiovascular system?
The positive pressure from the ventilator decreased venous return to the heart decreasing cardiac output and making the amount of work the heart had to do decrease. By removing the positive pressure, the venous return increases and therefore the amount of work the heart will have to do also increases
What factors may cause a patient to fail a SBT?
Cardiac factors
acid-base/metabolic factors
Drugs
Nutritional status
Psychological factors
Describe how issues with acid base balances can be caused by mechanical ventilation and how they can result in failure of SBTs or extubations
It is easy to hyperventilate patients who had previously been hypercapnic
This can result in a respiratory alkalosis or their kidneys decreasing the output of bicarbonate
Can also cause apnea due to removal of hypoxic drive post extubation
What does hypophosphatemia cause?
Muscular weakness
< 1.2 mmol
What does hypomagnesemia cause and who is at risk for having it?
Muscle weakness
Alcoholics
What does hypothyroidism cause?
Impairment of respiratory muscle function
Blunts central chemoreceptors to hypercapnia and hypoxemia
How do drugs affect a patient ability to be liberated from mechanical ventilation?
Some patients are unable to effectively metabolize sedatives and neuromuscular blockers making them difficult to wean
What physiological problems can result in poor drug metabolism?
Renal and liver function
Sepsis
Multisystem organ failure
What can cause acute myopathy in mechanically ventilated patients?
High dose steroids
Long terms NM blocking agents
What are the complications associated with overfeeding a MV patient?
Increase O2 consumption
Increase CO2 production
Increase minute ventilation
Why is malnutrition an important consideration for ventilated patients?
May occur prior to hospitalization resulting in a weaker patient that will have a harder time being liberated from the ventilator
Some patients also do not tolerate tube feeds well
Tube feeds tend to be carb heavy which doesnt support muscle growth or repair
What percentage of ICU patients will receive a trach?
10-15%
What psychological factors may prevent liberation from MV?
Fear
Anxiety
Delirium
ICU psychosis
Depression
Anger
Denial sleep deprivation
How can psychological factors that affect MV patients be potentially mitigated
Reassurance
Positivity
Treat patient like human
When is a tracheostomy considered early?
Within 7 days of mechanical ventilation
When is a tracheostomy considered late?
After 7 days of ventilation
Is there evidence to suggest that an early or late tracheostomy is beneficial in preventing VAP?
No
What should be considered prior to traching a patient?
Whether or not it will require high levels of sedation for the patient to tolerate the trach
Whether or not they have the necessary respiratory mechanics to justify a trach
What are the benefits of traching a patient?
Improved psychological benefit
Increased mobility
Lower WOB
Easier facilitation of discontinuation of MV
Why does getting a trach decrease the work of breathing?
Shorter tube = less resistance
Less tubing means less dead space
What can you look at on the vent screen to determine whether or not there is a leak in the system
The volume waveform will not return to zero on exhalation
What are the steps to discontinuing mechanical ventilation post tracheostomy?
PSV trials to strengthen respiratory muscles
Trach collar trials
Capping trials
Decannulation
What alarms could a leak provoke?
Low pressure
Low tidal volume
Low minute ventilation
Low peep
If you think there is a leak, what should you check?
All connections
Filters for cracks
Connection to the water bag
Temp probe in place?
Humidity probe in place?
HME
Closed suction catheter
You get a call from the nurse saying they hear a gurgling in the back of the patients throat. What is your first thought
Leaking cuff
ETT tube movement out of place
What should you do if you hear a gurgle in the back of the patients throat?
Check ETT for proper depth
Verify cuff is inflated
Verify cuff/pilot line/pilot balloon are not leaking
Change tube if problem cant be resolved
What does autotriggering look like on the vent?
Repetitive rapid identical breaths
How can you resolve autotriggering?
Find the leak that repeatedly triggers delivery
What is artifact triggering?
Triggering caused by fluid in circuit
Triggers settings being too sensitive and picking up the movement of artifacts
How can you resolve artifact triggering?
Remove artifact triggering the vent
Change trigger type
Make trigger less sensitive
What do missed triggers look like on the vent?
Irregularities in the pressure and flow waveforms
Waves going in the wrong direction
What causes missed triggers?
Patient efforts that are not recognized by the vent
What can result from repeated missed triggers?
Patient agitation
Increased WOB
Unnecessary sedation
How can you resolve issues with missed triggers?
Change trigger type
Make trigger more sensitive
Reduce respiratory rate
Check for autopeep
Confirm triggered breaths are indeed triggered
What does double triggering look like on the vent?
Pressure and flow going negative in the middle of breath delivery
Patients maximum inspiratory effort doesnt match the vents breath delivery
What are some ways to resolve a double trigger?
Adjust trigger
Change modes
Increase Itime
Increase Vt
What is a paradoxical or reverse trigger?
Ventilator delivers a breath which stimulates the patients diaphragm and they take a breath in the middle of the breath triggering the vent again
How can you resolve a reverse trigger
Decrease respiratory rate
Trial PC-CSV
Reduce sedation
Paralyze patient
What does flow asynchrony look like on the vent?
A dip in the pressure wave in the middle of the breath
What causes a flow asynchrony?
A patient not being happy with the amount of flow they are receiving
What can a flow asynchrony cause?
Shifts WOB from vent to patient
Leads to respiratory muscle fatigue
Increased O2 consumption
How can you resolve flow asynchrony?
Change mode to pressure control (delivers more flow up front)
Decrease Itime to increase flow
Change flow waveform in VC
What is flow overshoot?
A spike in pressure at the beginning of the pressure wave
What causes a flow overshoot?
Flow being given faster than the patient wants it
Flow is driven faster than airway resistance or lung compliance can receive it
How can you resolve a flow overshoot?
Lengthen Itime in volume modes
Lengthen rise time in pressure modes
How can you resolve delayed cycling?
Increase expiratory flow cycle sensitivity
Increase pressure support
Patient may need to be put on a rate
What does delayed cycling look like on the vent?
A spike at the end of the pressure wave indicating that the patient is trying to exhale will indicate delayed cycling
A downward slope in the flow wave prior to official exhalation will indicate delayed cycling
What can autopeep cause?
Increase PIP
Make triggering more difficult
Volutrauma
