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.

Frequently Asked Questions

1. What is mechanical ventilation?

   - Mechanical ventilation is the use of a machine (ventilator) to assist or replace spontaneous breathing in patients who cannot breathe adequately on their own.

2. What are the main types of ventilation modes?

   - The main types include Assist-Control (AC), Synchronized Intermittent Mandatory Ventilation (SIMV), Continuous Positive Airway Pressure (CPAP), Pressure Support Ventilation (PSV), and Pressure Control Ventilation (PCV).

3. What is Assist-Control (AC) ventilation?

   - Assist-Control ventilation is a mode where the ventilator delivers a set number of breaths per minute at a predetermined volume or pressure, and can also assist with additional breaths if the patient initiates them.

4. When is Assist-Control (AC) ventilation used?

   - AC is used in patients who need full ventilatory support, such as those with acute respiratory failure or severe respiratory distress.

5. What is Synchronized Intermittent Mandatory Ventilation (SIMV)?

   - SIMV is a mode where the ventilator provides a set number of mandatory breaths at a set volume or pressure, while allowing the patient to breathe spontaneously between these breaths.

6. When is SIMV used?

   - SIMV is often used during weaning from mechanical ventilation or in patients who need partial ventilatory support but can also breathe spontaneously.

7. What is Continuous Positive Airway Pressure (CPAP)?

   - CPAP provides a continuous level of positive airway pressure throughout the breathing cycle, helping keep the alveoli open and improve oxygenation.

8. When is CPAP used?

   - CPAP is used in patients with obstructive sleep apnea, acute respiratory distress syndrome (ARDS), or to improve oxygenation in patients with chronic respiratory conditions.

9. What is Pressure Support Ventilation (PSV)?

   - PSV is a mode where the ventilator provides support to each spontaneous breath based on a set pressure, reducing the work of breathing.

10. When is Pressure Support Ventilation (PSV) used?

    - PSV is used to assist patients who are breathing spontaneously but need additional support to overcome respiratory muscle weakness or increased work of breathing.

11. What is Pressure Control Ventilation (PCV)?

    - PCV is a mode where the ventilator delivers breaths at a set pressure, regardless of the volume of air delivered.

12. When is Pressure Control Ventilation (PCV) used?

    - PCV is used in patients with conditions that cause high peak airway pressures or when precise pressure control is needed, such as in ARDS.

13. What is the difference between volume-controlled and pressure-controlled modes?

    - In volume-controlled modes, the ventilator delivers a preset volume of air per breath, while in pressure-controlled modes, the ventilator delivers air until a preset pressure is reached.

14. What is the significance of the I:E ratio in ventilation?

    - The I:E ratio refers to the ratio of inspiratory time to expiratory time, which affects the ventilatory pattern and can be adjusted to optimize gas exchange.

15. How is weaning from mechanical ventilation managed?

    - Weaning involves gradually reducing ventilatory support while monitoring the patient’s ability to breathe independently, often using modes like SIMV or PSV during the process.

16. What are the common complications associated with mechanical ventilation?

    - Complications can include barotrauma, volutrauma, ventilator-associated pneumonia, and hemodynamic instability.

17. How does a ventilator’s alarm system help in managing ventilation?

    - The alarm system alerts healthcare providers to issues such as high or low pressure, low tidal volume, or disconnected tubing, allowing for timely intervention.

18. What role does sedation play in mechanical ventilation?

    - Sedation can help ensure patient comfort, reduce the work of breathing, and prevent ventilator-ventilator asynchrony during mechanical ventilation.

19. What are some indicators that a patient is ready to be weaned from mechanical ventilation?

    - Indicators include improved respiratory function, stable vital signs, adequate gas exchange, and the ability to tolerate reduced ventilatory support.

20. How is the choice of ventilation mode determined for a patient?

    - The choice is based on the patient’s clinical condition, respiratory needs, and underlying pathology, with considerations for the mode’s ability to provide appropriate support and facilitate recovery.

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