Modes of Ventilation: Types and Uses

Ventilation is the air movement between the environment and the lungs via inhalation and exhalation. A ventilator is a machine that supports a patient's respiratory efforts when they are very low in order to maintain saturation. Mechanical ventilation is using artificial methods to assist breathing. Ventilation types:

1. Invasive ventilation- it is done in the case of unconscious patients.
2. Non-invasive ventilation- it is done in cases of concious patients. 

There are various modes of ventilation that are important for the NEET-PG/next and FMGE examination. These ventilator modes are:

1. CMV (Controlled Mode Ventilation), also known as IPPV (intermitted positive pressure ventilation)
2. SIMV (Synchronized Intermittent Ventilation)
3. PCV- Pressure Control Ventilation
4. PS- Pressure Support
5. CPAP- Continuous Positive Airway Pressure

 Mechanical ventilation machines are available with invasive and non-invasive modes.

Read this blog further to get a quick overview of this important topic for DERMATOLOGY and gynecology and ace your NEET PG/NExT exam preparation.

Types of Modes of Ventilation

CMV (Controlled Mandatory Ventilation)

Control ventilation is a mode of ventilation in which the respirator delivers the preset volume or pressure regardless of the patient's inspiratory efforts. It is indicated in patients with severe neurological alterations, deep sedation, shock, or respiratory failure.

It is the best method of ventilation for patients who require little breathing effort. It controls the patient's total breathing. Here, the volume is fixed manually. The patient should be heavily sedated, as there should not be any breathing efforts. The drugs that can be used for sedation are fentanyl, dexmedetomidine, and midazolam. 

This is a very common way to reduce intracranial pressure in head injury. 

The disadvantages of continuous mandatory mode of ventilation are:

• If the patient is not responding, then he can fully depend on this mode.
• Can develop muscle atrophy.
• Reduced compliance of the lung can cause barotrauma (due to high pressure of CMV).

SIMV (Synchronized Intermittent Mandatory Ventilation)

Synchronized intermittent mandatory ventilation is a ventilator mode that enables partial mechanical assistance. In this mode of ventilation, The ventilator first assesses the patient's breath, and if the volume is not generated by the patient's effort, the ventilator gives the volume.

This is a Weaning mode as it allows the patient to breathe spontaneously. The patient is required to be moderately sedated.

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Pressure Control Ventilation (PCV)

Pressure is fixed manually, and the ventilator decides the volume. It is mainly used in ARDS. the main drawback of this mode of ventilation is that the Blockage of the ET tube due to secretions leads to reduced volume reaching the patient’s lungs. This results in respiratory acidosis due to poor oxygenation and increased CO.

PS Ventilation

Pressure-support ventilation (PSV) is a spontaneous mode of ventilation in which each breath is initiated by the patient but supported by constant pressure inflation. The person is spontaneously breathing. It works on two mechanisms: CPAP (continuous positive airway pressure) and PEEP (positive end-expiratory pressure), which enable the alveoli to open.

PEEP (Positive End-Expiratory Pressure)

It enables the alveoli to be open at the end of expiration. It helps improve the patient's oxygenation. An increase in intrathoracic pressure leads to a decrease in venous pressure and a decrease in carbon dioxide. BP is a decrease in the perfusion of a vital organ, resulting in a decrease in urine output. Pulmonary edema, Acute respiratory distress syndrome(ARDS), and cardiothoracic surgery are the main indications for SIMV. the main contraindication of SIMV is that it is avoided in shock and head injury patients. 

CPAP(Continuous Positive Airway Pressure)

CPAP is frequently used to evaluate a patient's chances of being extubated if they only need little ventilation support. It maintains the circuit pressure that the operator specifies throughout ventilation. PSV is frequently combined with CPAP.

High-Frequency Ventilation

This type of ventilation is used in emergencies. The main indications for this are:

• Cricothyroidotomy
• Bronchopleural fistula
• Tracheoesophageal fistula

This high-frequency ventilation is used in three main types:3 types

• As a High-frequency positive pressure ventilation, where the Rate is 60 to 120/minute.
• High-frequency jet ventilation. Here, the Rate is 120 to 180/minute.
• High-frequency oscillation. Here, the rate is 300 to 900/minute.

In this post-COVID era, we must discuss a very important mode of ventilation: Prone Ventilation.

This is used when all the lung protection strategies of ARDS fail. Here, the patient is maintained in a prone position for 18 to 20 hours. This position recruits the dorsal region of the lung, where greater lung mass is present, leading to a homogeneous distribution of breathing.

FAQs

Q1. What does a V/Q Scan detect with a mismatch between perfusion and ventilation?

Ans. pulmonary embolism

Q2. What is the best mode for initial ventilation of patients with less breathing effort?

Ans. CMV (Continuous Mandatory Ventilation).

Q3. What is Assist Control mode?

Ans. Similar to CMV but this mode also monitors for patient-triggered breaths. 2 modes

1. Volume control (Best mode)
2. Pressure control

Q4. What are the drawbacks of Pressure control mode?

Ans. Blockage of the ET tube due to secretions leads to reduced volume reaching the patient. This causes respiratory acidosis due to poor oxygenation and increased CO2 .

Q5. What are the uses of spontaneous mode?

Ans. Pressure support, Used in spontaneous breathing patients to increase tidal volume

Q6. What are the main modes of mechanical ventilation used in the ICU?

1. Controlled Mandatory Ventilation (CMV): The ventilator completely controls breathing, delivers preset tidal volume and respiratory rate. Used in heavily sedated or paralyzed patients who make no spontaneous effort.
   
2. Synchronized Intermittent Mandatory Ventilation (SIMV): Delivers a set number of mandatory breaths but also allows spontaneous breathing between them. Used when weaning from full ventilatory support, requires less sedation.
   
3. Pressure Support Ventilation (PSV): Patient initiates all breaths the ventilator provides  pressure support to reduce the work of breathing. Helps during weaning and supports spontaneous efforts.
   
4. Continuous Positive Airway Pressure (CPAP): The patient breathes spontaneously with continuous positive pressure maintained throughout the respiratory cycle. Keeps alveoli open and improves oxygenation; used in spontaneously breathing or weaning patients.
   

Q7. What is SIMV — full form and how does it work?

Synchronized Intermittent Mandatory Ventilation (SIMV)

SIMV is a ventilator mode that helps patients breathe partly on their own. The ventilator checks if the patient can take a full breath; if not, it gives a breath. This mode allows spontaneous breathing and is often used for weaning patients off the ventilator. Moderate sedation is usually needed.

Q8. How does pressure-controlled ventilation (PCV) differ from volume-controlled ventilation (VCV)?

In Pressure-Controlled Ventilation (PCV), Pressure is fixed manually, and the ventilator decides the volume. It is mainly used in ARDS. The main drawback of this mode of ventilation is that the Blockage of the ET tube due to secretions leads to reduced volume reaching the patient’s lungs. This results in respiratory acidosis due to poor oxygenation and increased CO2

In Volume-Controlled Ventilation (VCV), the tidal volume stays constant, ventilator adjusts the pressure needed to deliver

Q9. What are the indications for invasive ventilation versus non-invasive support (CPAP/BiPAP)?

Indications of invasive ventilation are airway protection, severe respiratory failure or hypoxemia not improving with oxygen, hypercapnia with acidosis, and need for full ventilatory support
Non-Invasive Ventilation (CPAP/BiPAP) is used for moderate respiratory distress with spontaneous breathing, COPD exacerbations with hypercapnia, cardiogenic pulmonary edema, and obstructive sleep apnea.

Q10. What does PEEP stand for, and how is it chosen on the ventilator?

PEEP stands for Positive End-Expiratory Pressure. It is the pressure that remains in the lungs at the end of exhalation, preventing the alveoli from collapsing. The amount of PEEP is chosen based on the patient’s oxygen needs and condition. A starting value of 5 cm H₂O is usually used in most patients. In Pulmonary edema or ARDS, higher PEEP levels may be required to improve oxygenation.

Q11. What are the common ventilator alarms, and how should staff respond?

High-pressure alarm triggers when pressure in the circuit is too high, usually due to coughing, blockage, kinks in the tube, or stiff lungs; staff should check the tube, suction secretions, and make sure the tube is not bent or blocked. 

A low-pressure or disconnection alarm happens when there is a leak or disconnection in the circuit, so staff should quickly reconnect it and check for leaks. 

A low tidal volume alarm shows the patient is not getting enough air. Look for leaks, disconnections, or patient fatigue, and fix the cause immediately.

An apnea alarm means the patient has stopped breathing, so staff should check the patient immediately and provide manual ventilation if needed. 

Bi-level Positive Airway Pressure (BiPAP): Provides two pressure levels: higher during inspiration (IPAP) and lower during expiration (EPAP). Used in pediatric or non-invasive ventilation settings to support breathing while maintaining oxygenation.

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