Triggering refers to the signal that causes inspiration. A ventilator breath may be time triggered or patient triggered. During patient-triggered breaths, the ventilator may detect patient effort using a variety of inputs. These include pressure, volume, flow, impedance, and motion. Ventilator operation during patient-triggered breaths varies with the trigger variable and the type of ventilator. Clinicians should understand ventilator operation during patient-triggered modes in order to maximize patient-ventilator synchrony.