Mechanical Ventilation Modes for Prolonged Ventilation

Introduction to Ventilation Modes

The American Thoracic Society recommends using ventilation modes that allow spontaneous breathing, such as Assist Control Ventilation (ACV) or Pressure Support Ventilation (PSV) with adequate PEEP levels, for prolonged mechanical ventilation 1, 2

ACV ensures a set number of mandatory breaths per minute in the absence of patient breathing efforts, allowing patients to initiate additional breaths with the ventilator delivering an identical set tidal volume 4, 6
PSV triggers the ventilator on both inhalation and exhalation based on patient breathing effort, with the patient determining the breathing frequency and duration of each breath 7, 2
ACV prevents central apneas during sleep due to the presence of a backup respiratory rate, and improves sleep quality and reduces sleep fragmentation compared to PSV 1, 3

The British Journal of Anaesthesia suggests using volume-controlled ventilation (VCV) for patients with obesity, as it is associated with lower peak airway pressures and less dead space ventilation 8, 9
The American Journal of Respiratory and Critical Care Medicine recommends targeting a tidal volume of 6-8 ml/kg ideal body weight to minimize complications 8, 10, 11

The Intensive Care Medicine society recommends using ACV at night to improve sleep quality and prevent central apneas, and carefully adjusting the level of support in PSV to prevent hyperventilation and central apneas 1, 3
The British Journal of Anaesthesia suggests maintaining a SpO2 between 88-94% to avoid hypoxemia and hyperoxia, and ensuring adequate expiratory time (inspiratory-to-expiratory ratio of 1:2 or 1:3) to prevent air trapping 8, 9, 3

The Thorax journal notes that terminology for ventilation modes may vary between ventilator manufacturers, potentially causing confusion 2, 5
The Intensive Care Medicine society warns that excessive support levels in PSV can cause hyperventilation, hypocapnia, and central apneas, especially during sleep 1, 3