title: Foot pulse oximeter perfusion index correlates with calf muscle perfusion measured by near-infrared spectroscopy in healthy neonates.
abstract: OBJECTIVE
  In critically ill neonates, peripheral perfusion and oxygenation assessment may provide indirect information on the circulatory failure of vital organs during circulatory shock. The development of pulse oximetry has recently made it possible to calculate the perfusion index (PI), obtained from the ratio between the pulsatile and nonpulsatile signals of absorbed light. The main goals of this study were: (1) to study foot PI; and (2) to evaluate the relationship between foot PI, obtained continuously by pulse oximetry, and a number of variables, i.e. blood flow (BF), oxygen delivery (DO(2)), oxygen consumption (VO(2)), and fractional oxygen extraction (FOE), measured indirectly by near-infrared spectroscopy (NIRS) on the calf in 43 healthy term neonates (weight 3474.6 +/- 466.9 g; gestational age 39.1 +/- 1.4 weeks).
  
  
  METHODS
  Calf BF, DO(2) and VO(2) were assessed by NIRS on short-lived venous and arterial occlusion maneuvers. PI was measured on the contralateral foot.
  
  
  RESULTS
  Foot PI was 1.26 +/- 0.39. There was a positive correlation between foot PI and both calf BF (r = 0.32, p = 0.03) and DO(2) (r = 0.32, p = 0.03), but no correlation was found between foot PI and calf FOE and between foot PI and VO(2).
  
  
  CONCLUSIONS
  In the neonatal intensive care unit, continuously measuring foot PI by pulse oximetry seems clinically more feasible for peripheral perfusion monitoring than spot measurements of the calf BF and/or VO(2) by indirect NIRS.
authors.affiliation: Department of Pediatrics, Neonatal Intensive Care Unit, University of Padova, Italy.
authors.forename: Patrizia
authors.initials: P
authors.lastname: Zaramella
authors.forename: Federica
authors.initials: F
authors.lastname: Freato
authors.forename: Valentina
authors.initials: V
authors.lastname: Quaresima
authors.forename: Marco
authors.initials: M
authors.lastname: Ferrari
authors.forename: Andrea
authors.initials: A
authors.lastname: Vianello
authors.forename: Diego
authors.initials: D
authors.lastname: Giongo
authors.forename: Lorena
authors.initials: L
authors.lastname: Conte
authors.forename: Lino
authors.initials: L
authors.lastname: Chiandetti
mesh_terms: D005528:Foot / Q000098:blood supply*; D006801:Humans; D007231:Infant, Newborn / Q000502:physiology*; D007866:Leg / Q000098:blood supply*; D010092:Oximetry; D010100:Oxygen / Q000378:metabolism; D010101:Oxygen Consumption; D019265:Spectroscopy, Near-Infrared
chemical_list: D010100:Oxygen