Modes of mechanical ventilation

Modes of Mechanical Ventilation

Mechanical ventilation is a method to assist or replace spontaneous breathing. It is commonly used in intensive care units (ICUs) and during anesthesia for surgical procedures. Various modes of mechanical ventilation are employed to meet the specific needs of patients. These modes can be broadly categorized into volume-controlled, pressure-controlled, and dual modes.

Volume-Controlled Ventilation

In volume-controlled ventilation, the ventilator delivers a preset volume of air with each breath. This mode ensures a consistent tidal volume regardless of changes in the patient's lung compliance or airway resistance. Common types of volume-controlled ventilation include:

• **Assist-Control Ventilation (ACV)**: The ventilator delivers a set tidal volume at a set rate, but the patient can initiate additional breaths.
• **Synchronized Intermittent Mandatory Ventilation (SIMV)**: The ventilator delivers a set number of breaths with a preset tidal volume, but the patient can breathe spontaneously between these mandatory breaths.

Pressure-Controlled Ventilation

Pressure-controlled ventilation delivers air until a preset pressure is reached. This mode is beneficial for patients with stiff lungs or those at risk of barotrauma. Types of pressure-controlled ventilation include:

• **Pressure-Controlled Ventilation (PCV)**: The ventilator delivers breaths at a set pressure and rate.
• **Pressure Support Ventilation (PSV)**: The ventilator provides a preset pressure to assist spontaneous breaths, reducing the work of breathing.

Dual Modes

Dual modes combine features of both volume and pressure-controlled ventilation to optimize patient care. Examples include:

• **Adaptive Support Ventilation (ASV)**: The ventilator adjusts the pressure and volume based on the patient's needs and lung mechanics.
• **Proportional Assist Ventilation (PAV)**: The ventilator provides assistance proportional to the patient's effort, enhancing comfort and synchrony.

Other Modes

Several other specialized modes of mechanical ventilation are used in specific clinical scenarios:

• **High-Frequency Oscillatory Ventilation (HFOV)**: Delivers very small tidal volumes at high frequencies, used primarily in patients with severe acute respiratory distress syndrome (ARDS).
• **Airway Pressure Release Ventilation (APRV)**: Allows spontaneous breathing throughout the ventilatory cycle, maintaining alveolar recruitment and improving oxygenation.

Indications

Mechanical ventilation is indicated in various conditions, including:

• Respiratory failure
• Severe pneumonia
• Chronic obstructive pulmonary disease (COPD) exacerbations
• Neuromuscular disorders affecting respiratory muscles

Complications

While life-saving, mechanical ventilation can have complications such as:

• Ventilator-associated pneumonia (VAP)
• Barotrauma
• Volutrauma
• Ventilator-induced lung injury (VILI)

Weaning

Weaning is the process of gradually reducing ventilatory support to allow the patient to resume spontaneous breathing. Techniques include:

• **Spontaneous Breathing Trials (SBT)**: Assess the patient's ability to breathe without assistance.
• **Gradual reduction of support**: Decreasing the level of pressure support or mandatory breaths over time.

See Also

• Respiratory therapy
• Critical care medicine
• Pulmonology
• Anesthesia