title: Regional respiratory time constants during lung recruitment in high-frequency oscillatory ventilated preterm infants.
abstract: OBJECTIVE
  To assess the regional respiratory time constants of lung volume changes during stepwise lung recruitment before and after surfactant treatment in high-frequency oscillatory ventilated preterm infants.
  
  
  METHODS
  A stepwise oxygenation-guided recruitment procedure was performed before and after surfactant treatment in high-frequency oscillatory ventilated preterm infants. Electrical impedance tomography was used to continuously record changes in lung volume during the recruitment maneuver. Time constants were determined for all incremental and decremental pressure steps, using one-phase exponential decay curve fitting. Data were analyzed for the whole cross section of the chest and the ventral and dorsal lung regions separately.
  
  
  RESULTS
  Before surfactant treatment, the time constants of the incremental pressure steps were significantly longer (median 27.3 s) than those in the decremental steps (16.1 s). Regional analysis showed only small differences between the ventral and dorsal lung regions. Following surfactant treatment, the time constants during decremental pressure steps almost tripled to 44.3 s. Furthermore, the time constants became significantly (p < 0.01) longer in the dorsal (61.2 s) than into the ventral (40.3 s) lung region.
  
  
  CONCLUSIONS
  Lung volume stabilization during stepwise oxygenation-guided lung recruitment in high-frequency oscillatory ventilated preterm infants with respiratory distress syndrome is usually completed within 5 min and is dependent on the position of ventilation on the pressure volume curve, the surfactant status, and the region of interest of the lung.
authors: Department of Neonatology, Emma Children's Hospital, Academic Medical Center, P.O. Box 22660, Amsterdam 1100 DD, The Netherlands. m.miedema@amc.uva.nl
authors: Martijn
authors: M
authors: Miedema
authors: Frans H
authors: FH
authors: de Jongh
authors: Inez
authors: I
authors: Frerichs
authors: Mariëtte B
authors: MB
authors: van Veenendaal
authors: Anton H
authors: AH
authors: van Kaam
mesh_terms: D006612:High-Frequency Ventilation; D006801:Humans; D007231:Infant, Newborn; D007234:Infant, Premature; D008168:Lung / Q000502:physiology*; D012129:Respiratory Function Tests