Modes of Ventilation Flashcards
Continuous Mandatory Ventilation (CMV) modes
Assist Control (AC) includes Pressure Controlled (PC), or Volume Controlled (VC) ventilation.
Pressure controlled ventilation is
when a patient has a pressure setting on the ventilator and when the ventilator cycles a breath the pressure will continue to rise on the ventilator until the pre-set pressure limit is reached.
With Pressure controlled ventilation, When the pressure setting is reached the
ventilator will then cycle off and the patient will then exhale.
With pressure controlled ventilation, How much the patient’s tidal volume is
determined on how high the pressure limit is set.
If the lungs are stiff or non-compliant the pressure will build
more slowly and the inspiratory time will have to be adjusted to accommodate the need of the patient.
A longer inspiratory time will allow the
patient to obtain a full tidal volume with each breath.
If the lungs are very pliable such as a
patient with
COPD a shorter inspiratory time will be needed because the lungs will inflate very quickly.
Inspiratory time on the ventilator is a
critical factor when using pressure control ventilation.
Although inspiratory time can be
controlled with its own setting on the vent
most of time
it is determined by the
dialed in rate set on the ventilator.
Usually the inspiratory/expiratory ratio for ventilator patients is .
1:2
A patient with a rate of 10 breaths per minute would be
allowed
6 seconds for a cycled breath which would contain 2 seconds for inspiration and 4 seconds for expiration.
Volume Controlled ventilation is exactly as
it sounds. what is it?
A pre-determined volume is dialed in and every time the ventilator cycles on the patient receives that tidal
volume.
For Volume controlled, Inspiratory time is
also a factor with volume control but not as critical when using pressure control.
These modes are classified as control
modes because they do
100% of the work
for the patients while on the ventilator.
Controlled mode: These modes
are the most efficient for the patient in complete respiratory failure.
Triggering a breath in AC can be achieved by
Pressure trigger
Timed trigger
Pressure trigger
Pressure triggering for the patient is achieved by
either flow or negative pressure against the endotracheal tube to initiate the breath supplied
by the machine.
Timed trigger
The breath is given at a set time according to what the rate of the machine is, such as a rate of 10 breaths a minute means every 6 seconds a breath is initiated by the machine
AC: Patients that are
sedated, paralyzed or need to rest will need to be in this mode for proper ventilation.
AC This mode
allows the patient’s breathing to be “controlled”.
AC If the patient begins to actively participate
in breathing this mode will
become less effective and could lead to the patient
over breathing.
AC mode will give the.
full tidal volume of the breath every time it is triggered
in AC mode, If the tidal volume is set for 500 ml for each breath the waking patient will get
This can lead to
500 ml of air with each triggered breath. Can lead to “air trapping”. Air trapping results when the lungs can not fully expel the air before another breath is
initiated.
In AC mode, If the patients rate increase from 10 to 15
breaths per minute due to p
Possible poor sedation the patient has drastically
changed his I:E ratio which will accommodate air trapping.
In AC If the patient is
waking up then the mode of ventilation should change from assist control to SIMV
SIMV (Synchronized Intermittent Mandatory Ventilation) is
the most common mode of ventilation used for conscious patients who don’t require 100% of the work being done for them.
SIMV This mode allow the patient to
breathe on their own between the set rate of breaths
given by the machine
SIMV If the patient has a ventilator rate of 10
breaths a minute and the patient is able
to spontaneously breathe on his own
he can take small breaths between the cycles of the ventilator.
In SIMV, once the patient start taking breaths The machine will
sense the patient’s effort and will time the next breath around the patient’s effort thus preventing air
trapping.
SIMV The patient is not
forced a pre-set tidal volume and can have a small one of it’s own.
SIMV This can also decrease the anxiety of the
patient
by not forcing a full breath on him each time he tries to breathe on his own
If a patient is successful in the SIMV
mode he may then be placed on CPAP.
CPAP (Continuous Positive Airway Pressure) this mode of ventilation uses
pressure support and peep to allow the patient to
spontaneously breathe on his own without any mechanical breaths being given.
CPAP If a patient in this mode can maintain his
own respiratory effort without excess work,
if the ABG’s are good, and the patient has good respiratory mechanics then extubation is at
hand.
