modes of ventilation

1. Volume-Controlled Ventilation (VCV):
• Trigger: VCV uses a hybrid trigger, which means it can be initiated by
both the patient's effort and a pre-set ventilator rate. The patient can
trigger a breath based on either a certain level of airway pressure or flow.
• Target: VCV focuses on maintaining a consistent flow of air during each
breath. You can set both the flow rate and the pattern of flow (like constant
or decelerating) on the ventilator.
• Cycle: In VCV, the cycle variable is volume. The ventilator delivers a
specific volume of air during each breath, and this volume determines the
inspiratory time. Patient effort or changes in respiratory system conditions
don't affect the inspiratory time.
• Summary of VCV: VCV is a mode in which the ventilator controls the
airflow by targeting a set volume of air per breath. It uses a hybrid trigger,
and the inspiratory time is fixed.

2. Pressure-Controlled Ventilation (PCV):
• Trigger: PCV, like VCV, uses the same hybrid trigger system where
both patient effort and a pre-set rate can initiate a breath.
• Target: PCV primarily targets maintaining a specific airway
pressure. The ventilator adjusts the flow of air to achieve and sustain
this pressure.
• Cycle: In PCV, the cycle variable is time. You set the inspiratory time
on the ventilator, and the breath ends once that time is reached,
regardless of patient effort or respiratory system changes.
• Summary of PCV: PCV is a mode where the ventilator maintains a
set airway pressure for a predefined time. It uses the same trigger
system as VCV, and the inspiratory time is fixed.

3. Pressure Support Ventilation (PSV):
• Trigger: PSV relies entirely on the patient's effort to initiate a breath.
There are no pre-set, time-triggered breaths.
• Target: Similar to PCV, PSV targets maintaining a specific airway
pressure. The ventilator adjusts the flow of air to achieve and
maintain this pressure.
• Cycle: In PSV, the cycle variable is flow. The breath ends when the
flow of air decreases to a specified percentage of the peak inspiratory
flow. This allows for flexibility in inspiratory time, which patients
can control by adjusting their respiratory effort.
• Summary of PSV: PSV is a mode in which the ventilator assists the
patient in maintaining a set airway pressure. Patients can control
their breathing effort, resulting in variable inspiratory times for
greater comfort and synchronization with the ventilator.

4. Figure 3.2 Flow and Pressure Waveforms in
Pressure-Controlled Ventilation (PCV) into
easy-to-understand points:
• Target Variable in PCV: In PCV, the main thing we're aiming for is to control the airway pressure.
That means we want to keep the pressure inside the patient's airway at a certain level.
• Cycle Variable in PCV: The way PCV operates is based on time. The clinician sets a specific
amount of time for each breath. When this time is up, the breath ends, regardless of what the
patient is doing.
• Setting Proximal Airway Pressure: The clinician can decide the desired airway pressure, and the
ventilator works to reach and maintain this pressure during inspiration.
• Inspiratory Time (TI): The inspiratory time is also set by the clinician. It determines how long each
breath will last.
• Flow Waveform Result: The interaction between these set variables (pressure target and time cycle)
and the patient's respiratory system leads to a specific flow pattern. In PCV, this pattern is typically
a "decelerating ramp." This means that the flow of air starts high at the beginning of the breath and
gradually decreases as the breath continues.
• PCV is all about controlling and maintaining a specific airway pressure and inspiratory time. The
way the flow of air changes during a breath is like a ramp, starting fast and slowing down. This
helps ensure that the patient receives the right amount of air at the right pressure for the set time, as
determined by the clinician.

5. figure3.3 Flow and Pressure Waveforms in
Pressure Support Ventilation (PSV):
• Target Variable in PSV: In PSV, the primary goal is to control the airway
pressure. This means maintaining a specific pressure level in the patient's airway.
• Cycle Variable in PSV: PSV operates based on flow. Unlike PCV, which uses
time as the cycle variable, PSV uses the flow of air as its cycle parameter.
• Setting Proximal Airway Pressure: Clinicians can set the desired airway pressure
that they want to achieve and maintain during the patient's breathing.
• Percentage of Peak Inspiratory Flow for Cycling: Clinicians also set a specific
percentage of the peak flow (in this case, 25%) as the threshold for ending the
breath. Once the flow decreases to this level, the breath terminates.
• Flow Waveform Result: The way air flows during a PSV breath is similar to PCV;
it's a "decelerating ramp." This means that at the start of the breath, the flow is
high and gradually decreases as the breath continues.