Ventilator Modes, Alarms, and common causes

VENTILATOR MODES VCV, A/PCV, PSV, SIMV, CPAP, etc Alarms, and common causes

A medical ventilator or Ventilator Mode is a machine that supports breathing, the mechanical ventilator machine is designed to move breathable air into and out of the lungs. It is mainly used in critical care units in hospitals & rehabilitation centers. To provide breathing for a patient who is physically unable to breathe, or breathing insufficiently.


Ventilator Modes refers to the machine that will ventilate the patient concerning the patient’s respiratory efforts. there is a mode for nearly every patient situation, plus many can be used in conjunction with each other.

Volume Control Ventilation ( VCV / CV )

6 Easy Steps to ABG Analysis

VCV Mode delivers the preset volume or pressure regardless of the patient’s inspiratory efforts. This mode is used for patients who are unable to initiate a breath. If it is used with spontaneously breathing patients, they must be sedated and/or pharmacologically paralyzed so they don’t breathe out of synchronizing with the ventilator.

Assist Control Ventilation (A/PCV )

A/C delivers the preset volume or pressure in response to the patient’s inspiratory effort but will initiate the breath if the patient does not do so within the set amount of time. This means that any inspiratory attempt by the patient triggers a ventilator breath. The patient may need to be sedated to limit the number of spontaneous breaths since hyperventilation can occur. This mode is used for patients who can initiate a breath but who have weakened respiratory muscles.

Synchronous Intermittent Mandatory Ventilation (SIMV)

Allens Test

In ventilator modes, SIMV was developed as a result of the problem of high respiratory rates associated with A/C. SIMV delivers the preset volume or pressure and rate while allowing the patient to breathe spontaneously between ventilator breaths. Each ventilator breath is delivered in synchrony with the patient’s breaths, yet the patient is allowed to completely control the spontaneous breaths. SIMV is used as a primary mode of ventilation, as well as a weaning mode. (During weaning, the preset rate is gradually reduced, allowing the patient to slowly regain breathing on his or her own.) The disadvantage of this mode is that it may increase the work of breathing and respiratory muscle fatigue.

Pressure Support Ventilation (PSV)

PSV is Preset pressure that augments the patient’s spontaneous inspiratory effort and decreases the work of breathing. The patient completely controls the respiratory rate and tidal volume. PSV is used for patients with a stable respiratory status and is often used with SIMV to overcome the resistance of breathing through ventilator circuits and tubing.

Positive End Expiratory Pressure (PEEP)

Online Nursing Test For AIIMS

PEEP is a positive pressure that is applied by the ventilator at the end of expiration. This mode does not deliver breaths but is used as an adjunct to CV, A/C, and SIMV to improve oxygenation by opening collapsed alveoli at the end of expiration. Complications from increased pressure can include decreased cardiac output, pneumothorax, and increased intracranial pressure.

Constant Positive Airway Pressure (CPAP)

ventilator mode CPAP is similar to PEEP except that it works only for patients who are breathing spontaneously. The effect of both is comparable to inflating a balloon and not letting it completely deflate before inflating it again. The second inflation is easier to perform because resistance is decreased. CPAP can also be administered using a mask and CPAP machine for patients who do not require mechanical ventilation, but who need respiratory support; for example, patients with sleep apnea.

Independent Lung Ventilation (ILV)

This method is used to ventilate each lung separately in patients with unilateral lung disease or with a different disease process in each lung. It requires a double-lumen endotracheal tube and two ventilators. Sedation and pharmacological paralysis are used to facilitate optimal ventilation and increased comfort for the patient.

High-Frequency Ventilation (HFV)

HFV delivers a small amount of gas at a rapid rate (as much as 60-100 breaths per minute.) This is used when conventional mechanical ventilation would compromise hemodynamic stability, during short-term procedures, or for patients who are at high risk for pneumothorax. Sedation and pharmacological paralysis are required.

Inverse Ratio Ventilation (IRV)

The normal inspiratory: expiratory ratio is 1:2 but this is reversed during IRV to 2:1 or greater (the maximum is 4:1). This mode is used for patients who are still hypoxic even with the use of PEEP. The longer inspiratory time increases the amount of air in the lungs at the end of expiration (the functional residual capacity) and improves oxygenation by re-expanding collapsed alveoli. The shorter expiratory time prevents the alveoli from collapsing again. Sedation and pharmacological paralysis are required since it’s very uncomfortable for the patient.


Assist-Control Ventilation (A/C)Delivers breath in response to patient effort and if the patient fails to do so within a preset amount of time.Usually used for spontaneously breathing patients with weakened respiratory muscles.
Constant Positive Airway Pressure (CPAP)Similar to PEEP but used only with spontaneously breathing patientsMaintains constant positive pressure in airways so resistance is decreased.
Control Ventilation (CV)Delivers preset volume or pressure regardless of the patient’s own inspiratory efforts.Usually used for patients who are apneic.
High-Frequency Ventilation (HFV)Delivers small amounts of gas at a rapid rate (60-100 breaths/minute); requires sedation/paralysisUsed for hemodynamic instability, during short-term procedures, or if the patient is at risk for pneumothorax.
Independent Lung Ventilation (ILV)Ventilates each lung separately; requires two ventilators and sedation/paralysisUsed for patients with unilateral lung disease or different disease processes in each lung.
Inverse Ratio Ventilation (IRV)l: E ratio is reversed to allow longer inspiration; requires sedation /paralysis.Improves oxygenation in patients who are still hypoxic even with PEEP; keeps alveoli from collapsing
Positive End Expiratory Pressure (PEEP)Positive pressure applied at the end of expirationUsed with CV, A/C, and SIMV to improve oxygenation by opening collapsed alveoli.
Pressure Support Ventilation (PSV)Preset pressure augments the patient’s inspiratory effort and decreases the work of breathing.Often used with SIMV during weaning.
Synchronous Intermittent Mandatory Ventilation (SIMV)Ventilator breaths are synchronized with the patient’s respiratory effort.Usually used to wean patients from mechanical ventilation

Alarms and common causes

As mentioned earlier, the ventilator is designed to monitor many aspects of the patient’s respiratory status, and many different alarms can be set to warn healthcare providers that the patient isn’t tolerating the mode or settings. The following are common ventilator alarms and their most frequent causes.

High-Pressure LimitLow PressureHigh Respiratory RateLow Exhaled Volume
Secretions in ETT / Airway or Condensation in the tubing.Ventilator tubing not connected.Secretions in ETT/airway.Ventilator tubing not connected.
Kink in ventilator tubing.Displaced ETT or tracheal tube.Hypoxia.Occurrence of another alarm preventing full delivery of a breath
Patient Biting on ETT.HypercapniaLeak in the cuff or inadequate cuff seal.
Patient coughing, gagging, or trying to talkPatient anxiety or pain.
Increased airway pressure from bronchospasm or pneumothorax.

Also, Read

Practice Questions For Respiratory System

RUHS BSc Nursing Entrance Exam 2019

Instruments Used in Gynecology and Obstetrics pdf

Job description of nursing | duties, and responsibilities

Second Trimester in the Pregnancy Period

Thanks for reading. if you have any query please comment below. we answer your query as fast as we can.

One thought on “Ventilator Modes, Alarms, and common causes

Leave a Reply

Your email address will not be published. Required fields are marked *

Open chat
Can we help You ?