There are various modes in ICU Ventilator. Volume Control Ventilation (VCV):  In volume control mode a prestel tidal volume is delivered at a set rate, primarily used when the patient has no spontaneous breathing. Pressure Control Ventilation (PCV): In PCV mode the ICU ventilator delivers a breath at a set pressure, and at a set rate. This primarily used when the patient has no spontaneous breathing, but will support the patient if they are able to trigger a breath. Pressure Support Ventilation (PSV): Pressure support provides support for every patient triggered breath and is used for patients who do not have sufficient capacity or facilitate weaning. Synchronized Intermittent Mandatory Ventilation (SIMV): This mode is used to help patients who have some, but not sufficient breathing and can be used for weaning.