Perfusion index in preterm infants during the first 3 days of life : Reference values and relation with clinical variables

Background: The perfusion index (PI) derived from pulse oximetry readings represents the ratio of pulsatile (arterial blood) and nonpulsatile contributors to infrared light absorption. PI has been shown to correlate with cardiac performance. In theory, PI is readily available on every pulse oximeter; therefore, no additional sensors or infant handling are required. Currently, reference values are lacking in (preterm) neonates and the association with common clinical conditions is unclear. Objectives: To establish reference values for the PI in premature infants and at the same time determine the influence of common clinical conditions. Methods: PI was prospectively monitored on the lower limb for 72 h in 311 neonates born with a gestational age