Table of modes of mechanical ventilation

Modes of Mechanical Ventilation are diverse settings and techniques used in mechanical ventilation to support or replace spontaneous breathing in patients who are critically ill or undergoing surgery. Mechanical ventilation is a key component of intensive care medicine, emergency medicine, and anesthesiology. Understanding the various modes is crucial for tailoring ventilation to the individual needs of patients, optimizing oxygenation and carbon dioxide removal while minimizing potential harm.

Overview

Mechanical ventilation can be categorized based on several factors, including the mechanism of ventilation (volume-controlled vs. pressure-controlled), the timing of ventilator support (continuous vs. intermittent), and the level of patient control over the breathing cycle (fully controlled vs. partially assisted).

Volume-Controlled Ventilation (VCV)

In Volume-Controlled Ventilation, the ventilator delivers a preset tidal volume (VT) to the patient at a predetermined frequency. The primary advantage is the assurance of adequate minute ventilation. However, the pressure required to deliver the set volume can vary, potentially leading to high airway pressures that can cause lung injury.

Pressure-Controlled Ventilation (PCV)

Pressure-Controlled Ventilation involves setting a maximum airway pressure and allowing the tidal volume to vary based on the patient's lung compliance. This mode is often used to limit airway pressures and reduce the risk of barotrauma.

Assist-Control Ventilation (ACV)

In Assist-Control Ventilation, each breath is either initiated by the patient (assisted breath) or by the ventilator (controlled breath) if the patient's spontaneous breathing is below a certain threshold. This mode ensures a minimum number of breaths while allowing the patient to breathe above the set rate if able.

Synchronized Intermittent Mandatory Ventilation (SIMV)

Synchronized Intermittent Mandatory Ventilation delivers a preset number of mandatory breaths synchronized with the patient's spontaneous breathing effort. Between mandatory breaths, the patient can breathe spontaneously with or without additional support. SIMV can be used to wean patients from mechanical ventilation.

Continuous Positive Airway Pressure (CPAP)

Continuous Positive Airway Pressure maintains a constant positive pressure in the airways throughout the breathing cycle. CPAP is often used for patients who require respiratory support but do not need assistance with breathing efforts.

Bi-level Positive Airway Pressure (BiPAP)

Bi-level Positive Airway Pressure provides two levels of pressure: a higher pressure during inhalation and a lower pressure during exhalation. BiPAP is beneficial for patients with chronic obstructive pulmonary disease (COPD) or heart failure who require assistance with ventilation and oxygenation.

Adaptive Support Ventilation (ASV)

Adaptive Support Ventilation is a form of closed-loop control ventilation that automatically adjusts ventilation parameters based on the patient's lung mechanics and effort. ASV aims to optimize patient comfort and reduce the work of breathing.

Choosing the Appropriate Mode

Selecting the appropriate mode of mechanical ventilation depends on the patient's respiratory status, underlying disease, and the goals of care. Factors to consider include the need for full ventilatory support versus assistance, the desire to minimize sedation, the need to protect against lung injury, and the goal of facilitating weaning from mechanical ventilation.

Conclusion

Modes of mechanical ventilation are critical tools in the management of patients with respiratory failure. Understanding the advantages and limitations of each mode allows healthcare providers to tailor ventilation strategies to meet the individual needs of their patients, improving outcomes and minimizing complications.