Ventilatory Modes

Mechanical ventilation modes fall into three main categories: full support modes, where the ventilator governs volume or pressure; partial support modes, which combine machine-assisted and spontaneous breaths; and spontaneous modes, where patients manage most breathing with minimal assistance. Each category serves different patient needs based on respiratory capability and clinical condition.

Controlled mechanical ventilation delivers a preset tidal volume and respiratory rate regardless of patient effort, primarily for apneic patients. Assist-control ventilation delivers a preset tidal volume or pressure at a preset rate, but if the patient initiates a breath between machine breaths, the ventilator delivers an assisted breath at the preset volume or pressure, ensuring every breath meets the preset parameters.

Synchronized intermittent mandatory ventilation (SIMV) allows patients to breathe spontaneously between ventilator-delivered breaths without assistance. As the patient's spontaneous breathing ability improves, the preset number of ventilator breaths decreases, enabling patients to gradually assume more breathing work and transition toward independence.

Proportional assist ventilation (PAV) generates pressure in response to the patient's inspiratory efforts, synchronizing with the patient's own ventilatory efforts. As the patient generates higher inspiratory pressure, the ventilator increases pressure proportionally, amplifying breathing effort without targeting a specific pressure or volume, ensuring optimal support and synchronization.

Pressure support ventilation (PSV) applies a pressure plateau to the airway during patient-triggered inspiration to decrease resistance within the tracheal tube and ventilator tubing. Pressure support is gradually reduced as the patient's strength increases, making it ideal for patients transitioning from full ventilator support to spontaneous breathing.

Continuous positive airway pressure (CPAP) is a spontaneous mode where the ventilated patient controls almost all breathing aspects. Only FIO2 and PEEP are preset; there is no set respiratory rate, tidal volume, or peak inspiratory pressure. The patient determines their own respiratory rate and tidal volume, making it suitable for patients capable of managing their breathing independently.

Neurally adjusted ventilatory assistance (NAVA) uses an esophageal catheter to monitor the diaphragm's electrical activity, delivering assisted breaths in synchrony with the patient's breath. This specialized mode provides precise synchronization between ventilator support and the patient's own neural respiratory drive, optimizing ventilation timing and patient-ventilator interaction.