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Know the difference between controlled
ventilation and assist/control
Controlled variables: PC-CMV vs VC-CMV
Phase variables: trigger/limit/cycle
Know the breath types
Know the breath sequence
Settings and adjustment
Indications, advantages and disadvantages
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All breaths are mandatory and can be volume
or pressure targeted
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Controlled Ventilation – when mandatory
breaths are time triggered
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Assist/Control Ventilation – when mandatory
breaths are either time triggered or patient
triggered
Control
Trigger
Pressure
Or
Volume
Time
Limit
Target
Cycle
Pressure or
Volume
Time or
Volume
Time Triggered Time Cycled Ventilation
All breaths are mandatory breaths
Ventilator determines the start time (time
triggered)
 Ventilator delivers the set control (volume or
pressure target)
 Te ventilator ends the breath (time- or volumecycled)
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All breaths are mandatory breaths
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Appropriate when a patient can make no
effort to breathe or when ventilation must be
completely controlled
 Drugs
 Cerebral malfunctions
 Spinal cord injury
 Phrenic nerve injury
 Motor nerve paralysis
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In other types of patients, controlled
ventilation is difficult to use unless the patient
is sedated or paralyzed with medications
 Seizure activity
 Tetanic contractions
 Inverses I:E ratio ventilation
 Patient is fighting (bucking) the ventilator
 Crushed chest injury – stabilizes the chest
 Complete rest for the patient
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Adequate alarms must be set to safeguard
the patient
 E.g., disconnection
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Sensitivity should be set so that when the
patient begins to respond, they can receive
gas flow from the patient
Do not lock the patient out of the ventilator!
Set PC Level
Time Cycling
Pressure
(cm H2O)
Flow
(L/m)
Volume
(mL)
Time (sec)
Time Triggered, Pressure Limited, Time Cycled Ventilation
Time Cycling
Pressure
(cm H2O)
Dependent on
CL & Raw
Flow
(L/m)
Preset VT
Volume Cycling
Volume
(mL)
Time (sec)
Time Triggered, Flow Limited, Volume Cycled Ventilation
ADVANTAGES
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Decreases the work of
breathing (WOB)
Helps maintain a normal
PaCO2
DISADVANTAGES
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Not able to assist the
ventilator
Control
Trigger
Pressure
Or
Volume
Time
Or
Patient
Limit
Target
Cycle
Pressure or
Volume
Time or
Volume
Time or PatientTriggered Time Cycled
Ventilation
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A time or patient triggered CMV mode in which the operator
sets a minimum rate, sensitivity level, type of breath (volume
or pressure)
The patient can trigger breaths at a faster rate than the set
minimum, but only the set volume or pressure is delivered
with each breath
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Time or patient
triggered, volume
targeted, volume
cycled ventilation
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Graphic (VC-CMV)
 Time-triggered,
constant flow, volumetargeted ventilation
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Time or patient
triggered, volume
targeted, volume
cycled ventilation
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Graphic (VC-CMV)
 Time-triggered,
descending-flow,
volume-targeted
ventilation
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PC – CMV (AKA – Pressure control ventilation - PCV)
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Time or patient triggered, pressure targeted (limited),
time cycled ventilation
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The operator set the length of inspiration (Ti), the
pressure level, and the backup rate of ventilation
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VT is based on the compliance and resistance of the
patient’s lungs, patient effort, and the set pressure
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Airway pressure is limited, which may help guard
against barotrauma or volume-associated lung injury
 Maximum inspiratory pressure set at 30 – 35 cm H2O
 Especially helpful in patients with ALI and ARDS
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Allows application of extended inspiratory time,
which may benefit patients with severe oxygenation
problems
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Usually reserved for patient who have poor results
with a conventional ventilation strategy of volume
ventilation
Time Cycling
Pressure
(cm H2O)
Preset peak Flow
Flow
(L/m)
Volume
(mL)
Time (sec)
Patient Triggered, Flow limited, Volume Cycled Ventilation
Set PC Level
Time Cycling
Pressure
(cm H2O)
Flow
(L/m)
Volume
(mL)
Time (sec)
Patient Triggered, Pressure Limited, Time Cycled Ventilation
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Indications
 Patients requiring full ventilatory support
 Patients with stable respiratory drive
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Advantages
 Decreases the work of breathing (WOB)
 Allows patients to regulate respiratory rate
 Helps maintain a normal PaCO2
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Complications
 Alveolar hyperventilation