title: Heart period variability of intubated very-low-birth-weight infants during incubator care and maternal holding.
abstract: BACKGROUND
  Heart rate has been used to measure infants' physiological stability during skin-to-skin holding. Variability in heart period (interbeat interval), a more sensitive measure of autonomic nervous system tone, has not.
  
  
  OBJECTIVE
  To describe heart period variability in intubated very-low-birth-weight infants during incubator care and during maternal skin-to-skin holding.
  
  
  METHODS
  An experimental, interrupted time series, crossover design was used; infants served as their own controls. Infants were randomly assigned to treatment order: 2 hours of intermittent skin-to-skin holding for 2 consecutive days followed by 2 days of incubator care or vice versa. The analog signal representing heart period was sampled and quantized at 5 Hz via a dedicated computer system in multiple 300-second epochs each day.
  
  
  RESULTS
  Fourteen infants with similar characteristics completed the protocol. The mean interbeat interval was 332 ms during skin-to-skin care and 368 ms during incubator care. Power within the low- and high-frequency regions of heart period was not significantly different between skin-to-skin holding and incubator care. Mean low-frequency power was 124.6 ms2 during skin-to-skin holding and ranged from 51.9 ms2 to 71.4 ms2 during all periods of incubator care. Mean high-frequency power was similar during skin-to-skin holding and incubator care (8.8 ms2 and 6.1 ms2). Infants of 32 to 34 weeks' corrected gestational age had increased power in the low- and high-frequency regions.
  
  
  CONCLUSIONS
  Heart period variability did not improve during skin-to-skin holding. Gestationally older infants had increased power in the low- and high-frequency regions, suggesting a maturing autonomic nervous system.
authors.affiliation: University of Utah College of Nursing, Salt Lake City, Utah, USA.
authors.forename: Sandra Lee
authors.initials: SL
authors.lastname: Smith
mesh_terms: D000704:Analysis of Variance; D001341:Autonomic Nervous System / Q000254:growth & development / Q000502:physiology*; D018592:Cross-Over Studies; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D007185:Incubators; D007224:Infant Care / Q000379:methods*; D007231:Infant, Newborn; D019102:Infant, Very Low Birth Weight / Q000502:physiology*; D007442:Intubation, Intratracheal