**1. Introduction**

Shock is a pathological state in which there is an insufficiency in oxygen supply and demand. Ultimately it results in global hypoperfusion and a resulting increase in anaerobic respiration causing lactic acidosis. Adequate oxygen delivery is an essential requirement for the sustenance of every cell in the body, the lack of which can result from a variety of pathological disturbances and can lead to life-threatening alterations. Therefore, maintaining adequate oxygen delivery in the critical care setting is of primary importance in the management of a critically ill patient.
