title: Influence of hypoxia and hypercapnia on sleep state-dependent heart rate variability behavior in newborn lambs.
abstract: OBJECTIVE
  Although hypercapnia and/or hypoxia are frequently present during chronic lung disease of infancy and have also been implicated in sudden infant death syndrome (SIDS), their effect on cardiac autonomic regulation remains unclear. The authors' goal is to test that hypercapnia and hypoxia alter sleep-wake cycle-dependent heart rate variability (HRV) in the neonatal period.
  
  
  METHODS
  Experimental study measuring HRV during sleep states in lambs randomly exposed to hypercapnia, hypoxia, or air.
  
  
  METHODS
  University center for perinatal research in ovines (Sherbrooke, Canada). INSERM-university research unit for signal processing (Rennes, France).
  
  
  METHODS
  Six nonsedated, full-term lambs.
  
  
  METHODS
  Each lamb underwent polysomnographic recordings while in a chamber flowed with either air or 21% O(2) + 5% CO(2) (hypercapnia) or 10% O(2) + 0% CO(2) (hypoxia) on day 3, 4, and 5 of postnatal age.
  
  
  RESULTS
  Hypercapnia increased the time spent in wakefulness and hypoxia the time spent in quiet sleep (QS). The state of alertness was the major determinant of HRV characterized with linear or nonlinear methods. Compared with QS, active sleep (AS) was associated with an overall increase in HRV magnitude and short-term self-similarity and a decrease in entropy of cardiac cycle length in air. This AS-related HRV pattern persisted in hypercapnia and was even more pronounced in hypoxia.
  
  
  CONCLUSIONS
  Enhancement of AS-related sympathovagal coactivation in hypoxia, together with increased heart rate regularity, may be evidence that AS + hypoxia represent a particularly vulnerable state in early life. This should be kept in mind when deciding the optimal arterial oxygenation target in newborns and when investigating the potential involvement of hypoxia in SIDS pathogenesis.
authors.affiliation: INSERM, U1099, Rennes, F-35000, France. alain.beuchee@chu-rennes.fr
authors.forename: Alain
authors.initials: A
authors.lastname: Beuchée
authors.forename: Alfredo I
authors.initials: AI
authors.lastname: Hernández
authors.forename: Charles
authors.initials: C
authors.lastname: Duvareille
authors.forename: David
authors.initials: D
authors.lastname: Daniel
authors.forename: Nathalie
authors.initials: N
authors.lastname: Samson
authors.forename: Patrick
authors.initials: P
authors.lastname: Pladys
authors.forename: Jean-Paul
authors.initials: JP
authors.lastname: Praud
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D006339:Heart Rate; D006935:Hypercapnia / Q000503:physiopathology*; D000860:Hypoxia / Q000503:physiopathology*; D017286:Polysomnography / Q000379:methods; D012756:Sheep; D012890:Sleep; D014851:Wakefulness
keywords: Entropy; REM sleep; frequency domain analysis; quiet sleep; scale-invariance; sympathovagal coactivation