1. Controlled: These breaths come at a set time. (i.e. If you set RR at 10 then every 6 seconds you get a breath. Controlled breaths will only be given if the patient is sedated/apneic/paralyzed or if you set RR higher than patients rate)

2. Assisted Breaths: Triggered by the patient but only when the patient triggers or initiates the breath they will get full tidal volume set by the doc or therapist (i.e. VC SIMV + PS). If the rate is set at 10 then patient will get a breath every 6 seconds. If they trigger a breath at second 6 the breath given will be an assisted breath. If they fail to trigger or initiate a breath then the breath is a controlled breath.

3. Spontaneous Breaths: SIMV mode allows you to take spontaneous breaths and you can add PS to these breaths. Again if rate set to 10 then every 6 sec the patient can take an assisted breath (if patient initiated) or controlled (time dependent if patient not breathing). So in between breaths the patient can take spontaneous breaths that will be pressure supported.