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How to Regulate Ventilator Settings (AC, SIMV, RR, FiO2)

Nurse Mike (Mike Linares)
By SimpleNursing | Published December 29th, 2017
Published December 29th, 2017
A pretty female Nursing student in scrubs, a mask, a hairnet, and gloves


Your client is on a ventilator.


  1. How are you going to regulate that?
  2. What does that even mean?
  3. How do you make sure that the ventilator installed appropriately?
  4. What are the different modes of ventilation?

Don’t panic!


With Mike’s ventilator setting memorization tips, you can easily answer those questions without second-guessing yourself.

Now, to address your predicament, think of the ventilator as an air conditioning system. You want to make sure that your client’s lungs are getting sufficient air.

Things to consider

As a medical professional assigned to safeguard the condition of your client, assessing introduced air into the lungs is one of your top priorities. You don’t your client’s lung to burst by putting in more than what the lungs can handle. However, if this happens, it could lead to over inflation.

Another factor that you have to consider as a medical provider is, you have to make sure that your client is getting adequate respirations and oxygen every minute. This is what we refer to as FiO2.

Ventilator settings

Ventilator settings have two ventilator modes – the AC mode and the SIMV mode. To differentiate, AC stands for Assist-Control while SIMV is for Synchronized Intermittent-Mandatory Ventilation. The AC mode breathes for your client, pushing air down to the respiratory tracts. The SIMV mode is the “weaning mode”.

Assist-Control Ventilator Mode

As what was previously mentioned, the AC setting is a full-pledged breathing mode that aids in breathing by pushing oxygen down your client’s lungs. Equipped with an endotracheal tube (ET) or a vent, air is pushed by shoving down the tubes inside the respiratory tract and then a balloon is inflated to keep the airway open. Another route that the tube is inserted is through an opening created directly at your throat. This mode is usually seen in clients who are technically brain dead and can no longer breathe for themselves.

Synchronized Intermittent-Mandatory Ventilation Mode (SIMV)

On the other hand, if a client underwent an operation and anesthesia was required, the client will first be placed on AC mode then, as the client’s condition improves, the ventilator will be switched to SIMV mode. It has been referred to as the “weaning mode” for the reason that you would want to gradually taper ventilation until it reaches the point when the client will resume normal breathing.

Tidal Volume/Respiratory Rate

Another ventilator setting is your tidal volume which is the one responsible for pushing a given number of milliliters into the client’s respiratory system. The tidal volume is directly proportional to your client’s weight. One of the complications of the increased tidal volume is pneumothorax which is too much volume introduced down the lungs.

Remember, your respiratory rate should be between 16 to 20 breaths per minute.

Fraction of Inspired Oxygen (FiO2)

FiO2 is the amount of oxygen invested in the ventilator itself to pump your client’s lungs up with air. Normal FiO2 is between 35% to 50%. However, in the events that your client is not compensating and is not receiving the desired amount of oxygen, the FiO2 can be increased to 75% and as much as 100%.

Variables of an open airway

Aside from what was already discussed, there are other things that influence a person’s airway and of which is the Positive End-Expiratory Pressure (PEEP). PEEP maintains the alveoli open at the end of respiration. When pushing down air into the distal portions of the respiratory tracts, sometimes, the alveoli collapse; thus, increasing the oxygen supply during the exchange.

The main goal is to decrease your CO2 and increase the pH levels, making sure that the client is not acidic and not lead to respiratory acidosis. Increasing the oxygenation in the pulmonary artery oxygen (PAO2) is another goal.

Remember, anything between 80% and 100% is desirable. If that goes down to 60%, it can be criteria for acute respiratory distress.

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Nurse Mike (Mike Linares)
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