Most ventilators can be set to apply the delivered tidal volume in a control mode or a support mode.

 

Control mode

In control mode, the ventilator delivers the preset tidal volume once it is triggered regardless of patient effort. If the patient is apneic or possesses limited respiratory drive, control mode can ensure delivery of appropriate minute ventilation.

 

Support mode

In support mode, the ventilator provides inspiratory assistance through the use of an assist pressure. The ventilator detects inspiration by the patient and supplies an assist pressure during inspiration. It terminates the assist pressure upon detecting onset of the expiratory phase. Support mode requires an adequate respiratory drive. The amount of assist pressure can be dialed in.