Mechanical ventilation has been known to produce changes in the flow of blood through the major blood vessels in the body. These changes may go undetected, but with continuous arterial blood pressure measurements, changes in the arterial waveform can be visualized. Although we know that these arterial pressure variations occur during mechanical ventilation, little is known about the effects of various modes of mechanical ventilation on these changes. The most common modes of ventilation used in ICU are Volume control, Pressure control and Airway pressure release ventilation.