The two types of mechanical ventilation breaths are mandatory breaths and spontaneous breaths.
Mandatory breaths: the ventilator determines the start time (time triggering) or tidal volume (or both). In other words, the machine triggers and/or cycles the breath.
 
Spontaneous breaths: are started by the patient (i.e., patient triggered), and tidal volume delivery is determined by the patient (i.e., patient cycled). With spontaneous breaths, the volume and pressure delivered are based on patient demand rather than a value set by the ventilator operator.