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 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

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