title: Characterisation of the Oxygenation Response to Inspired Oxygen Adjustments in Preterm Infants.
abstract: BACKGROUND
  Oxygen saturation (SpO2) targeting in the preterm infant may be improved with a better understanding of the SpO2 responses to changes in inspired oxygen (FiO2).
  
  
  OBJECTIVE
  We investigated the first-order FiO2-SpO2 relationship, aiming to quantify the parameters governing that relationship, the influences on these parameters and their variability.
  
  
  METHODS
  In recordings of FiO2 and SpO2 from preterm infants on continuous positive airway pressure and supplemental oxygen, we identified unique FiO2 adjustments and mapped the subsequent SpO2 responses. For responses identified as first-order, the delay, time constant and gain parameters were determined. Clinical and physiological predictors of these parameters were sought in regression analysis, and intra- and inter-subject variability was evaluated.
  
  
  RESULTS
  In 3,788 h of available data from 47 infants at 31 (28-33) post-menstrual weeks [median (interquartile range)], we identified 993 unique FiO2 adjustments followed by a first-order SpO2 response. All response parameters differed between FiO2 increments and decrements, with increments having a shorter delay, longer time constant and higher gain [2.9 (1.7-4.8) vs. 1.3 (0.58-2.6), p < 0.05]. Gain was also higher in less mature infants and in the setting of recent SpO2 instability, and was diminished with increasing severity of lung dysfunction. Intra-subject variability in all parameters was prominent.
  
  
  CONCLUSIONS
  First-order SpO2 responses show variable gain, influenced by the direction of FiO2 adjustment and the severity of lung disease, as well as substantial intra-subject parameter variability. These findings should be taken into account in adjustment of FiO2 for SpO2 targeting in preterm infants.
authors.affiliation: School of Engineering and ICT, University of Tasmania, Hobart, Tas., Australia.
authors.forename: Omid
authors.initials: O
authors.lastname: Sadeghi Fathabadi
authors.forename: Timothy J
authors.initials: TJ
authors.lastname: Gale
authors.forename: Kathleen
authors.initials: K
authors.lastname: Lim
authors.forename: Brian P
authors.initials: BP
authors.lastname: Salmon
authors.forename: Jennifer A
authors.initials: JA
authors.lastname: Dawson
authors.forename: Kevin I
authors.initials: KI
authors.lastname: Wheeler
authors.forename: Jan C
authors.initials: JC
authors.lastname: Olivier
authors.forename: Peter A
authors.initials: PA
authors.lastname: Dargaville
mesh_terms: D045422:Continuous Positive Airway Pressure / Q000379:methods*; D006801:Humans; D007231:Infant, Newborn; D007234:Infant, Premature; D010092:Oximetry / Q000379:methods*; D010100:Oxygen / Q000032:analysis*; D010102:Oxygen Inhalation Therapy / Q000379:methods*
chemical_list: D010100:Oxygen