This document discusses different modes of mechanical ventilation: - Assist control-volume control (AC-VCV) delivers breaths at a preset tidal volume and rate whether triggered by the ventilator or patient. - Assist control-pressure control (AC-PCV) delivers each breath at a preset inspiratory pressure with a variable tidal volume. - Synchronized intermittent mandatory ventilation (SIMV) attempts to synchronize mandatory breaths with spontaneous efforts and reserves time for spontaneous breaths within a preset interval. - Pressure support ventilation (PSV) provides an increase in pressure above PEEP triggered by patient effort, requiring the patient to have respiratory drive.

1. Principal indication for mechanical ventilation is to
support patients with respiratory failure, including
failure of either ventilation (hypercarbic) or
oxygenation (hypoxic) or both.

2. ASSIST CONTROL - VOLUME CONTROL
VENTILATION (AC-VCV)
 Ventilator delivers a preset tidal volume at a preset
respiratory rate when there is not respiratory effort
from the patient.
 But if the patient triggers a spontaneous respiratory
effort earlier than the time interval created by the
set respiratory rate, the ventilator will still deliver the
breath at the set tidal volume and then resets the
time interval for the next breath.
 All breaths are delivered at the set tidal volume
whether it was ventilator triggered or patient
triggered.

3. ASSIST CONTROL - PRESSURE
CONTROL VENTILATION (AC-PCV)
 Ventilator delivers each breath at a preset
inspiratory pressure with variable tidal volume.
 PCV can be set up to have all breaths delivered at
the pre-set pressure or only for the number of
preset breaths while all additional breaths are
driven by the spontaneous negative inspiratory
pressure that the patient is able to generate.

4. SIMV – SYNCHRONISED INTERMITTENT
MANDATORY VENTILATION
 In SIMV mode ventilator attempts to synchronise as
many of the mandatory breaths with a spontaneous
effort as it is able. Set rate establishes a time
interval between each breath. A pre-set fraction of
the time interval is reserved to deliver the set tidal
volume if the patient makes a spontaneous effort
within that time interval.
 If the patient is also on PSV mode, any
spontaneous effort from the patient after the preset
time interval will be supported by the ventilator
other wise spontaneous breaths will not be
supported.

5. PRSSURE SUPPORT VENTILATION (PSV)
 In PSV, the operator determines an increase in
pressure (above PEEP) which is triggered by a
patients spontaneous inspiratory effort.
 Operator cannot set a respiratory rate and mode
requires the patient to have a respiratory drive.