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
What is the primary purpose of inflation hold control?
The primary purpose of this control is to obtain a plateau pressure to calculate static CL. It should never be used continuously on a patient who is triggering the ventilator.
____________ is used to maintain positive pressure in the airway after a ventilator breath.
PEEP
PEEP Indications
a. Atelectasis
b. PaO2 of 60 mm Hg on FiO2 of .50% O2
c. Decreased functional residual capacity (FRC)
d. Decreased CL
e. Pulmonary edema
Hazards of PEEP
a. Barotrauma
b. Decreased venous return
c. Decreased cardiac output
d. Decreased urinary output
Define optimal PEEP
The level of PEEP that improves lung compliance (CL) without cardiac compromise.
Normal PvO2
35-45 mm Hg
A decreased cardiac output (or cardiac index) caused by PEEP is indicated by a decrease in _______________________.
blood pressure and PvO2 values
How may excessive PEEP levels lead to decreases in
PaO2 and CL (lung compliance)?
by overdistending already open alveoli and shunting blood to collapsed alveoli.
A PvO2 of less than 35 mm Hg indicates a possible decrease in what?
CO
YOU SHOULD KNOW
If the PvO2 decreases after initiation of PEEP, it is an indicator of reduced venous return and cardiac output caused by PEEP.
NEVER LOOK AT PAO2 WHEN DETERMINING OPTIMAL PEEP!
What value best indicates the adequacy of tissue oxygenation?
PvO2
LOW PRESSURE ALARMS
Low pressure alarm should be set __________ below PIP
5-10 cmH2O
When would you commonly hear the low pressure alarm go off?
- leaks in the ventilator circuit
- leaks around the chest tube
- a ruptured ET tube cuff
- inadequate cuff pressure,
- patient disconnection
HIGH PRESSURE ALARM
High-pressure should be set about ____ cmH2O above PIP.
10 cmH2O
When high-pressure limit is reached with volume-control ventilation, inspiration ends prematurely, decreasing VT.
LOW PEEP/CPAP ALARM
Low CPAP/PEEP alarm should be set ____________ below baseline level.
2-4 cmH2O
APNEA ALARM
The maximum accepted level is ____________ or may be set so the patient will not miss more than two consecutive breaths
20 seconds
The alarm is activated after a set time passes with no inspiratory flow through the tubing.
LOW VT ALARM
The low VT alarm should be set approximately what percent below the set VT?
10%
MEAN AIRWAY PRESSURE, MAP OR Paw
Define the following term.
Average pressure applied to the airway over a specific time.
List a few things airway pressure is directly affected by?
- Ventilator rate
- PIP
- Inspiratory time
- Inspiratory hold
- PEEP level
- Pressure waveform
- I:E ratio
Capnography is a technique by which ____________ is measured.
Exhaled CO2
Normal PETCO2 range
Aproximately the same as alveolar CO2.
(35-45 mm Hg or 4.5-5.5%)
PETCO2 is therefore a noninvase technique to obtain PaCO2 level
PETCO2 is usually how much lower than PaCO2?
4-6 mmHg
List some instances where PETCO2 would be decreased.
- Hypoventilation
- Hyperthermia
UNDERSTANDING PETCO2
The tracing records CO2 readings during
inspiration (which should be 0) because little CO2
is in inspired air) and during expiration, when
CO2 begins to increase.
Read.
OPPOSITE OF VENTILATOR WAVEFORMS
A PETCO2 measurement by itself should not be used to predict what disease processes because it causes inaccurate descriptions under those conditions?
- LVF (decreased CO)
- Pulmonary embolism
- COPD
DEFINE THE FOLLOWING:
The portion of gas that does not take part in gas exchange.
VD - Dead space volume
Note to self: NEVER SUCTION a patient with pulmonary edema. How do you treat it?
- 100% oxygen
- Upright position
- Pressure
- Diuretics
A tracheostomy decreases the anatomic VD by ____% due to bypassing the upper airway.
50
Anatomic VD is __ mL/lb of ideal body weight.
1
___________ consists of the conducting airways from the nose and mouth to the terminal bronchioles (i.e., air that does not reach the alveolar epithelium where gas exchange occurs)
Anatomic VD
What is the term for the following?
Air reaches the alveoli but does not take part in gas exchange.
Alveolar VD
What is the most accurate measurement of VD?
Physiologic dead space
The sum of anatomic and alveolar VD
Physiologic dead space
INCREASE OR DECREASE?
Additional mechanical VD space may be added to the ventilator circuit between the ventilator Y adapter and the ET tube adapter to ________ PaCO2 levels.
increase
This results from some of the patient’s exhaled air (which contains CO2) getting trapped in the
excess tubing and being rebreathed with each ventilator breath
Cdyn Equation
VT/PIP-PEEP
Theoretically, for every 100 mL of deadspace added, the PaCO2 increases approximately ____ mm Hg.
5
Why should you NEVER add deadspace when the patient is breathing spontaneously? (E.g: SIMV, CPAP, PSV?)
Dead space would increase RAW as well as result in more CO2 being rebreathed.
Normal total CL (sum of the compliance of lung tissue and thoracic cage) is ___________________.
0.1 L/cm H2O (100 mL/cm H2O)
IMPORTANT EXAM NOTE
If compliance data and cardiac output are both given in a question regarding optimal PEEP, select the PEEP level before the drop in cardiac output even if a higher PEEP level resulted in the best CL.
DO NOT FORGET!!
Raw Equation
PIP-Pplat divided by flow rate (converted to L/s)
Normal RAW in nonintubated individuals is ____, based on a flow rate of 30 L/min.
0.6 to 2.4 cm H2O/L/s
This ratio is calculated to determine the extent of ARDS and acute lung injury (ALI).
PaO2/FiO2 ratio
“P/F ratio”
Normal P/F ratio range
400-500 mm Hg while on room air
What P/F ratio value classifies as ARDS?
<200 mm Hg
What P/F value classifies as an acute lung injury?
<300 mm Hg
The P/F ratio should be greater than ____ for ventilator weaning to be intiated.
200 mm Hg
What is normal ICP level?
<10 mm Hg
OXYGEN INDEX
What does an OI of 10-20 indicate?
Impaired oxygenation
OXYGEN INDEX
Generally, an OI of ______ is acceptable.
Less than 5
Normal static CL in the patient receiving ventilation is ____ mL/cm H2O.
60 to 70
OXYGEN INDEX
What does an OI of >25 indicate?
Severe oxygenation issues with poor clinical outcomes
VENTILATION IN THE PATIENT WITH HEAD TRAUMA
________ should be used to make inspiratory time shorter, which would lessen the time of positive pressure in the airways. The longer the time of positive pressure in the airways, the more impedance of blood flow from the head, which increases intracranial pressure (ICP).
Higher than normal flow rates
VENTILATION IN THE PATIENT WITH HEAD TRAUMA
Maintain the PaCO2 between 25 and 30 mm Hg to reduce ICP by vasoconstriction of cerebral vessels. ICP should be maintained below ____ mm Hg
15
VENTILATION IN THE PATIENT WITH HEAD TRAUMA
How would you decrease PaCO2 levels in a head trauma patient?
To decrease the PaCO2 level, always increase the ventilator rate.
VENTILATION IN THE PATIENT WITH HEAD TRAUMA
If your mechanically ventilated patient’s ICP begins to increase, what ventilator change would you make?
Increase rate to reduce cerebral blood flow thus lowering ICP.
WEANING (LIBERATING) FROM MECHANICAL VENTILATION
VC
> 10-15 mL/kg
WEANING (LIBERATING) FROM MECHANICAL VENTILATION
Spontaneous VT
4-6 mL/kg
WEANING (LIBERATING) FROM MECHANICAL VENTILATION
Spontaneous VE
<10-15 L/min
WEANING (LIBERATING) FROM MECHANICAL VENTILATION
MIP
At least -20cmH2o
WEANING (LIBERATING) FROM MECHANICAL VENTILATION
VD/VT
<0.60
WEANING (LIBERATING) FROM MECHANICAL VENTILATION
P(A-a)O2
<350 mm Hg on 100% O2
WEANING (LIBERATING) FROM MECHANICAL VENTILATION
RSBI
<105
WEANING (LIBERATING) FROM MECHANICAL VENTILATION
RR
<35 breaths/min
WEANING (LIBERATING) FROM MECHANICAL VENTILATION
PEEP
<8 cmH2O
WEANING (LIBERATING) FROM MECHANICAL VENTILATION
P/F ratio
> 200
SOMETHING TO KNOW
To consider weaning, the patient should be on an FiO2 of less than 0.40 to 0.50 with an SaO2 of at least 90%.
To consider weaning, the patient should be on an FiO2 of less than 0.40 to 0.50 with an SaO2 of at least 90%.
What is the goal of SIMV?
The goal using SIMV to wean is to continue to decrease the ventilator rate while allowing the patient to breathe more on their own, and finally put on CPAP or PSV with the patient breathing totally on their own.
HIGH-FREQUENCY VENTILATION (HFV)
HFV is a type of mechanical ventilation that utilizes high RR or frequencies, usually specified in hertz (Hz) or cycles per second. One hertz equals ________.
60 cycles/min or 60 breaths/min.
How to calculate the desired rate?
Rate (current) x PaCO2 (current)/ PaCO2 (desired)
Desired FiO2 equation
PaO2 (desired) x FiO2 (current)/PaO2 (current)
HFV is considered any form of ventilation with a breath frequency of more than ____ breaths/min.
150
HFV may be considered for patients with ALI/ ARDS if MAP exceeds _____ cm H2O on conventional mechanical ventilation.
15
High-frequency oscillation ventilation (HFOV)
________ the frequency or Hz increases delivered VT, which increases PaCO2.
Decreasing
High-frequency oscillation ventilation (HFOV)
To decrease the PaCO2, what should be increased?
the power (amplitude), or strength of the oscillation
Potential Advantages of HFV over Conventional Ventilation
- Reduced risk of barotrauma
- Reduced risk of cardiac side effects
- Improvement of mucociliary clearance
List ways the ventilator high-pressure alarm may be activated.
- Decreasing CL
- Increasing Raw
List six conditions that result in a decreased PETCO2 reading.
- Hyperventilation
- Apnea
- Total airway obstruction
- Hypotension
- Pulmonary embolism
- Decreased CO
What is indicated if PIPS are increasing but Pplat is not increasing?
Increase in Raw
FLOW WAVEFORMS
With this flow pattern, the flow remains constant throughout inspiration.
Square wave (constant flow)
Changes in RAW and compliance do not change the flow pattern under normal circumstances.
What type of flow pattern is beneficial to patients with increased RRs?
Square wave (constant flow)
Routine ventilator circuit changes vary from hospital to hospital, but the circuit does not need to be changed unless it is visibly soiled or malfunctions. The more frequently the circuit is changed, the higher the risk for __.
ventilator-associated pneumonia (VAP)
What flow pattern does this describe?
- The flow gradually accelerates from the beginning of inspiration, then decelerates toward the end of inspiration.
- This flow pattern benefits patients with increased RAW because airway turbulence produced by this flow is decreased.
Sine (sinusoidal) wave
This flow pattern usually results in optimal distribution of gas, lower transairway pressure, reduced work of breathing, and improved patient comfort.
Decelerating ramp wave
The pattern benefits patients with low compliance by allowing ventilation to occur at a decreased pressure.
The flow pattern is initially slow and accelerates to a peak flow by the end of inspiration. This pattern creates less turbulence of flow in the beginning of inspiration; therefore more volume may be delivered through narrowed or obstructed airways.
Accelerating ramp wave
On a volume-time waveform, if the volume tracing does not return to baseline at the end of exhalation, what does it indicate?
Indication of leaks in the ventilator circuit or around the ET tube cuff or chest tube; or it may result from air trapping.
On a volume-time waveform, if the volume tracing goes below baseline at the end of exhalation, what does it indicate?
Indication of either active exhalation for patients who are air trapping, or the expiratory flow sensor is out of calibration.
Obstructive lung disease causes the tracing to be flat during exhalation as a result of decreased expiratory flows.
FLOW-TIME WAVEFORM
How would correct the issue of auto-PEEPing?
Expiratory time must be increased by increasing the inspiratory flow.
When flow is increased, i-time decreases, allowing a longer e-time
VAP is pneumonia that occurs in patients who have been receiving mechanical ventilation for at least ____ hours.
48
Cstat equation
VT/Pplat-PEEP
DO NOT FORGET!!!!!!!
IMPORTANT EXAM NOTE: if a ventilator patient has an elevated PaCO2 and the question indicates the patient has dead space added to the ventilator circuit, always ________ first. Do not increase the VT or breathing rate.
remove the deadspace
Normal VC range
65-75 mL/kg
Normal P(A-a)O2
25-65 mm Hg
Normal VD/VT ratio
25-35%
Normal MIP range
-50 to -100 cmH2O
Normal PEP range
100 cmH2O
