Perfusion Index during Endotracheal Intubation, Surgical Incision and Extubation.

The perfusion index (PI) is the ratio of the pulsatile blood flow to the non pulsatile or static blood flow in peripheral tissue. Perfusion index thus represents a non invasive measure of peripheral perfusion that can be continuously and non invasively obtained from a pulse oximeter. Perfusion index is an assessment of pulsatile strength at a  specific monitoring site( e.g hand, finger or foot), and as such perfusion index is an indirect and non invasive measure of peripheral perfusion. It is calculated by means of pulse oximetry by expressing the pulsatile signal (during arterial flow) as a percentage of non pulsatile signal,both of which are derived from the amount of infrared(940nm) light absorbed.As the sensitivity of certain pulse oximeters has improved, the fidelity and reliability of PI has improved to a level where clinicians are beginning to explore various ways they can utilize PI to care for their patients