Ch. 11: Ventilator Management Flashcards
List the indications for mechanical ventilation.
- Apnea
- Acute ventilatory failure
- Impending acute ventilatory failure
- Oxygenation
COMMON CRITERIA FOR INITIATION OF MECHANICAL VENTILATION
* VC
* P(A-a)O2
* VD/VT
* MIP
* PEP
* RR
* PaO2/FiO2
- A. VC of less than 10 to 15 mL/kg
- B. P(A-a)O2 of greater than 450 mm Hg with the use of 100% O2
- C. Dead space/tidal volume (VD/VT) ratio of greater than 60%
- D. Unable to obtain an MIP of at least -20 cm H2O
- E. Positive expiratory pressure (PEP) of less than 40 cm H2O
- F. RR of >35/min
- G. PaO2/FiO2 (P/F ratio) <300 mm Hg (acute lung injury); <200 mm Hg (ARDS)
Patients not able to achieve an MIP of at least ______ cm H2O cannot generate an adequate cough to maintain secretion clearance.
-20
COMPLICATIONS OF MECHANICAL
VENTILATION
- Barotrauma
- Pulmonary infection
- Atelectasis
- Pulmonary O2 toxicity
- Tracheal damage
- Decreased venous blood return to the heart
- Decreased urinary output
- Lack of nutrition
COMPLICATIONS OF MECHANICAL
VENTILATION
Tracheal damage may occur as a result of excessive cuff pressure, greater than _____.
30 cmH2O
PaCO2 > _____ and a pH < _____ indicate ventilatory failure and a need for mechanical assistance.
> 50 and <7.30
A patient on an O2 mask at 50% to 60% or more whose lungs are being ventilated well (normal or low PaCO2) but are not being oxygenated adequately (low PaO2) is probably exhibiting a large intrapulmonary shunt. How can this be corrected?
This may be corrected with CPAP or high-flow nasal cannula. Mechanical ventilation may not be necessary initially.
Describe Volume-Controlled Ventilation (VCV).
A preset VT is delivered to the patient in each machine breath, and once it is delivered, inspiration ends.
Describe Pressure-Controlled Ventilation (PCV).
A preset inspiratory pressure is delivered to the patient, and once it is reached, inspiration ends.
VOLUME VARIES, PRESSURE IS CONSTANT
EXAM NOTE
Peak inspiratory pressure (PIP) should be set to obtain a specified exhaled VT, generally 6 to 8 mL/kg of ideal body weight, or 4 to 6 mL/kg on patients with acute respiratory distress syndrome (ARDS). In other words, if the target exhaled VT is 600 mL and the actual exhaled VT is 500 mL, what could be increased?
PIP - Peak inspiratory pressure
List some benefits of PCV.
Studies have shown that PCV improves gas exchange, increases oxygenation, reduces PIP, increases mean airway pressure (MAP), reduces required PEEP levels, and decreases minute ventilation.
________ may be detected by monitoring flow waveforms, which reveal the expiratory flow not returning to baseline before the next breath.
Auto-PEEP
What are the two trigger variables for NPPV?
- Time -triggered
- Patient-triggered
A/C Mode
In this mode, each breath is either ____________ triggered
patient-triggered or time-triggered.
What is the normal I:E ratio for an adult?
1:2
It means expiration takes twice as long as inspiration
The I:E ratio is established by the use of what three ventilator controls?
- VT
- Flow rate
- Respiratory rate
Respiratory rate
Normal intial settings
10-16 breaths/min
Inspiratory Flow Control
Normal setting
40-80 L/min
If an inverse I:E ratio of greater than 2:1 is used, what may occur?
Intrinsic PEEP, also referred to as auto-PEEP
List the ARDS network guidelines and lung protective strategies.
1) Target VT of 6 mL/kg of ideal body weight (IBW).
(2) Alveolar (plateau) pressure <30 cm H2O.
(3) Use of relatively high PEEP levels (up to 24 cm H2O).
(4) Permissive hypercapnia
(5) Oxygenation target: PaO2, 55 to 80 torr; SpO2, 88% to 95%; PEEP/FiO2 adjustments should be assessed at least every 4 hours.
(6) Target pH of 7.30 to 7.45.
(7) Avoidance of excessively high FiO2 levels (try to maintain below 0.60).
Criteria for NPPV include:
- Stable hemodynamics
- A cooperative patient
- Minimal airway secretions
- No need for airway protection
Pressure support is a ______________-triggered, ___________-limited, ____________- cycled breath, which may be augmented with SIMV or used by itself in the CPAP mode.
Pressure support is a patient-triggered, pressure-limited, flow-cycled breath, which may be augmented with SIMV or used by itself in the CPAP mode.
What patient population benefits the most from NPPV?
COPD and CHF patients with pulmonary edema
NPPV may buy time for the patient to get past the initial ventilatory crisis and avoid intubation and ventilation.
NPPV
EPAP is the equivalent of ________.
PEEP
NPPV
IPAP is the equivalent of ________.
VT
NPPV
A minimum EPAP of _____ cm H2O should be used to avoid CO2 buildup in the mask.
4
NPPV
The initial IPAP setting is usually ____ cmH2O
10-15
NPPV
The initial EPAP setting is usually ____ cmH2O
4-5
What is difference between IPAP and EPAP called?
Pressure support (PS)
Pressure support ventilation
What level of pressure supprort should be used for weaning so that Raw is overcome while breathing is spontaneous?
5 to 10 cmH2o
Pressure support ventilation
The inspiratory pressure level may be set to achieve a specific what?
VT - Tidal volume
Pressure support ventilation
An inspiratory pressure is set (usually 5 to 10 cm H2O for weaning purposes). As the patient initiates inspiration, the preset pressure is reached and held constant until a specific inspiratory flow is reached. Then the pressure is terminated.
Just read.
What does this describe?
A preset pressure is maintained in the airways and alveoli as the patient breathes totally on his or her own. No positive pressure breaths are delivered.
CPAP
What is the IBW equation for males?
106 + [6 x height in inches - 60 inches)/2.2
What is the IBW equation for females?
105 + [5 x height in inches - 60 inches)/2.2
What does increasing VT do to PaCO2?
Decreases
To decrease PaCO2, what is more effective. Manipulating the VT or ventilatory rate?
EXAM NOTE
The most effective way to improve alveolar ventilation and decrease PaCO2 is by increasing the VT, not by increasing the ventilator rate. If the VT is already set at 8 mL/kg, then increasing the rate would be more appropriate
What is the most accurate method of measuring delivered VT on the ventilator?
To most accurately measure the VT delivered by the ventilator, place a respirometer directly on the ventilator outlet.
Initial RR setting for COPD patients
10-12 breaths/min
Initial RR setting for ARDS patients
20-35 breaths/min
Increasing the rate ________ expiratory time.
Decreases
Decreasing the rate ________ expiratory time.
Increases
Adjusting the flow alters the ________.
Inspiratory time
Increasing the flow ________ inspiratory time.
Decreases
Decreasing the flow ________ inspiratory time.
Increases
What is this called?
A comparison of the inspiratory time with the expiratory time.
I:E ratio
What is the normal I:E ratio for an infant?
1:1
Increasing the RR ____ expiratory time.
Decreases
Decreasing the RR ____ expiratory time.
Increases
I:E equation
I:E = Inspiratory flow rate (L/min)/Minute volume (L/min) - 1 (for inspiration)
I:E = Inspiratory flow rate (L/min) DIVIDED BY Minute volume (L/min) MINUS 1 (for inspiration)
Inspiratory time should not exceed expiratory time, except in specific situations. This is known as _________________.
Inverse I:E ratio, utilized to increase PaO2 when FiO2 and PEEP are already high
EXAM NOTE
What is the most common adjustment to
correct for an inverse I:E ratio?
Increasing flow
- If the I:E ratio alarm is sounding on the ventilator
indicating an inverse I:E ratio, three controls may
be altered to correct it.
a. Rate: decrease to lengthen expiratory time.
b. Volume: decrease to shorten inspiratory time.
c. Flow: increase to shorten inspiratory time.
IMPORTANT NOTE
O2 percentage should be increased to a maximum of ________ to maintain normal PaO2 levels. Once this FiO2 level is reached, PEEP should be added or increased.
50% to 60%
IMPORTANT NOTE
O2 percentage should be reduced first to a level of 50% to 60% before decreasing PEEP levels in
hyperoxygenated patients.
O2 percentage should be reduced first to a level of 50% to 60% before decreasing PEEP levels in hyperoxygenated patients.
Once the FiO2 level is at 50% to 60%, begin reducing PEEP, except in patients with ____________. PEEP is very beneficial to aid in oxygenating patients with these conditions; therefore continue to decrease the FiO2 and leave the PEEP at around 10 cm H2O
ARDS and/or pulmonary edema
RSBI equation
f/VT
EXAM NOTE
When given a scenario on the exam where a ventilator patient has a normal or low PaCO2 with hypoxemia and the PEEP and FiO2 levels are high, ________________ to increase the PaO2.
increase the inspiratory time (by decreasing flow)
Longer inspiratory times increase MAP, thus oxygenation as well
This determines the amount of patient effort required to trigger the ventilator into inspiration.
Sensitivity control
Sensitivity control should be set so that the patient generates ____________ cm H2O pressure. This is referred to as pressure triggering.
-0.5 to -2.0 cmH2O
If the ventilator self-triggers, is the sensitivty is too high or low?
Too high, decrease the sensitivity
If it takes more than -2.0 cmH2O pressure to trigger the ventilator into inspiration, what should be done?
Increase the sensitivity
Trigger flow is generally set at what?
1-3 L/min