1. Vent Modes
Education and Explanation
**Rule #1: Do not touch the vent.**
Kindly ask your Respiratory Therapist to
make the change for you.

2. IMV
 IMV stands for Intermittent Mandatory
Ventilation
– This mode of ventilation would deliver a breath
based entirely on time.
» If you set a rate of 12 a breath would be given every
5 seconds regardless of where the patient is in their
breathing cycle
– This is a mode of ventilation that is no longer
used because it can cause over stretching and
barotrauma.

3. IMV (continued)
 What can be set?
– Rate – How often the patient receives a breath
– Inspiratory Time/Flow – How quickly the patient
receives the ventilator breath. Measured in Sec, or
LPM
– FiO2 – The Fractional inspired Oxygen from 21% -
100%
– Pressure/Volume – The amount of pressure or the
volume to be received.
» Pressure measured in cmH2O
– PEEP – Positive End Expiratory Pressure
» Is used to distend the alveoli and thin the alveolar capillary (AC)
membrane.
» Improves the gas transfer for the oxygen into the capillary system.
» Increases a patients functional residual capacity (FRC)

4. AC/VC
 Assist Control or Volume Control
– Same mode of ventilation with a different name.
– Every breath is the same, and a vent breath.
– Takes all the work away from the patient.
– May be a “first choice” mode of ventilation in other
institutions.
– Can predispose a patient to atelectasis due to no change
in volume.
– If: Patient is set at a rate of 12 and a Tidal Volume (Vt)
of 500 but breathing 20 times per minute what is the
patients Minute Ventilation (MV)?

5. AC/VC (continued)
 It would be 10 LPM because every triggered
breath is a volume of 500 mL.
 The set rate is really a “back up” rate.
 If the patient is sedated the rate of 12 will kick in
and the patient will receive a breath every 5
seconds at the desired I time or flow.
 Have to make sure the I time is adequate for their
RR. Can easily become inversed if the patient is
tachypneic.

6. AC/VC (continued)
 What can be set?
– Rate
– Inspiratory Time (I time) or Flow LPM
– FiO2
– Volume
– PEEP

7. PC
 Pressure Control
– A pressure is set instead of a volume.
– Every breath is still the same, and a “back up” rate is
set.
» Same:
 Pressure
 I time or Flow
– Volume delivered is determined by the patients lung
compliance.
– Have to make sure the I time is adequate for their RR.
Can easily become inversed if the patient is tachypneic.

8. So, what is lung compliance?
 Lung compliance is how easily a breath can be
pushed into the lung.
– Expressed as mL/cmH2O
– Can be static or dynamic
» Static is preferred
 What can decrease lung compliance
– Bronchospasm
– Inflammation
– Pulmonary Edema
– Mucus
– Size of the endotube
– Auto-PEEP
– Pleural Effusion
– Pneumonia
– Pneomothorax
– Anything that makes it more difficult to push a breath into a patient

9. SIMV
 SIMV stands for Synchronized Intermittent
Mandatory Ventilation
– This mode uses a microprocessor to determine where
the patient is in their breathing cycle and will fit the
breath at the beginning of inspiration or in-between
spontaneous breaths
– Much less likely to “stack breaths” and helps encourage
comfort on the vent.
– Patient will breath spontaneous volumes unassisted by
the vent in-between the vent breaths.

10. SIMV VC
 What can be set?
– Rate
– Volume
– I time or Flow
– FiO2
– PEEP

11. SIMV PC
 What can be set?
– Rate
– Pressure
– I time or Flow
– FiO2
– PEEP

12. Now lets add PSV
 PSV or Pressure Support Ventilation
– Is a pressure that augments a patients spontaneous
breaths.
– Is set as a pressure greater than the baseline PEEP.
– Helps the patient overcome the resistance of the
endotracheal tube.
– Give the patient assistance for the work put in.
– Volume of PS breath is completely determined by the
patient effort.
– Most all “modern” modes of ventilation can have PS.
» Ie: SIMV VC + PSV, SIMV PC +PSV, SIMV PRVC + PSV

13. PRVC
 Pressure Regulated Volume Control
– Combines the best of two modes of ventilation.
» Allows the patient to breath in as much flow as they
demand…..BUT
 Is delivered over a set I time.
 Set to a target volume.
 Pressure delivered will increase or decrease to lung
compliance
 Is like having a therapist set the patient’s vent in PC and
adjusting the pressure each breath to acheave the target
volume.
 Every breath is a PRVC breath.

14. PRVC (continued)
 Not good for a patient who is breathing a lot
spontaneously.
– The vent has a difficult time reaching the target volume
when the patient’s lung compliance is changing
drastically due to spontaneous (negative pressure)
breaths.
– Works well when a patient’s overall respiratory rate is
20 or less, and their spontaneous volumes are about that
of the set volume
» Otherwise the patient could be under ventilated compared to
set MV

15. PRVC (continued)
 At Sparrow hospital it is customary to place
patients in SIMV PRVC+PSV.
 This allows the patients spontaneous
breaths to be pressure supported while
assuring a specific MV is achieved.
– This mode of ventilation is only offered on the
newest generation of vents (Servo I and Servo
S), and is better than PRVC with assuring the
set MV.

16. Normal Vent Settings
 Since the ARDS Net Study, hospitals
around the country have been setting lower
Vt to decrease mortality.
– Normal:
» Vt = 8-10 cc per Kg of Ideal Body Weight (IBW)
» RR = 10-14 breaths per minute
» FiO2 = Starts at 100% and weaned to pt tolerance
» I time = Usually set by the RT at 1 sec
 Increased or decreased based off of graphics and pt
comfort / respiratory cycle.

17. How To Change ABG’s With
The Vent
 To increase PO2
– Increase FiO2 till it is 60% then consider
increasing the PEEP.
– Increase the PEEP
» This will allow for recruitment of alveoli
» This will thin the AC membrane
» O2 exchange will become easier
» Be Aware: Too high of PEEP can cause a decrease
in venous return or tamponade the heart (decrease
BP)

18. Changing ABG’s With The Vent
(continued)
 Decrease PCO2
– Increase the rate
» Increasing the rate increases the patients MV
» Be Aware: Too high of a rate can cause air trapping
especially in those with an obstructive lung disease.
» Cuts into E time or the amount of time a patient has
to exhale.
– Increase the Vt.
» This increases MV and is only recommended in
patients with compliant lungs
» Be Aware: Too high of a Vt will cause barotrauma
and cytokine release.

19. HFOV (High Frequency
Oscillation Ventilation)
 This is the simplest mode of ventilation,
and it is placed on the sickest patients.
 Works like a speaker
 Is the only vent that works off of an active
ventilation concept.
– All other modes of ventilation we push the
breath in and the patient passively exhales.
– With the oscillator we push the breath in and
pull the breath out with a piston.

20. HFOV (continued)
 Works well as an oxygenator, but not so
well as a ventilator.
 Should be considered when a patients FiO2
is greater than 60% on a PEEP greater than
10cm H2O
 Only 4 things are set and control
ventilation.
– MAP (works like PEEP and is started
2-4cmH2O greater than that on the ventilator.

21. HFOV (continued)
– FiO2 (amount of inspired O2. Normally set at 100%
and weaned down)
– The P or d P (this is where ventilation occurs)
» Is initially set by increasing till there is jiggling in
the mid thigh. (YES REALLY)
 This is called the Chest Wiggle Factor (CWF)
» Please remember: Only about 20% of the actual
pressure set makes it to the alveoli.
– And finally the HZ. (1HZ = 60 cycles in a minute)
» Is initially set between 3HZ and 6HZ
» The Vt is determined by the amount of distance
between peaks in the waves.

22. How To Change Your ABG With
HFOV
 To increase PO2
– Increase the FiO2
– Increase the MAP
» This will thin the alveolar wall and make it easier to
move the O2 into the capillary system.
» Be aware: Just like PEEP, the higher the setting the
more likely for a decrease in venous return or
tamponade of the heart to occur. (decrease BP)

23. Changing ABGs with HFOV
(continued)
 To decrease PCO2
– Increase the P
» This increases the venilatory pressure.
– Decrease the rate
» Wait a minute this goes against everything we
know!
» The oscillator is trapping gas in the lung, by
decreasing the HZ we allow more time for CO2 to
escape. (this increases the Vt)
– As a last ditch the cuff can be deflated some to
allow a leak and more CO2 to escape.

24. Good Luck
 Remember every patient is different
– Just because a mode of ventilation works with
most patients does not always make it a fit for
all your patients.
 And lastly
– If you have a question, please ask your
Respiratory Therapist.

25. Thank You