Short and Long-Term Heart-Rate Parameters in Newborns with Different Post-menstrual Ages and Sleep Position

The paper aims at quantifying, through heart rate variability (HRV) analysis, cardiorespiratory control mechanisms in newborns and one-month old infants, as a function of sleep position and Post-Menstrual Age (PMA). Position and age both affect Autonomic Nervous System (ANS) functioning whose mechanisms control HRV. Position and age have been also related to the occurrence of Sudden Infant Death Syndrome (SIDS). Term and premature (PMA ≤ 37 weeks) infants have been analyzed when sleeping in supine and prone position. The dataset includes 308 subjects (mean PMA 38.8 ± 1.49 weeks). RR-intervals series 180 s long have been obtained by detecting R peaks in the ElectroCardioGram (ECG). Ectopic beats were removed before processing. HRV parameters included standard variability parameters in the time domain: standard deviation NN intervals, distance between normal beats, (SDNN), HRV triangular index (HRVTI) and mean NN. In addition, parameters from fetal HRV analysis have been considered: Short-Term Variability (STV) and Long-Term Irregularity (LTI). The autoregressive spectral estimation provided frequency domain parameters by estimating Power Spectral density (PSD). Parameters show differences in sleep position comparison. SDNN, mean NN, STV and LTI always reported higher values when infants are supine. Moreover, STV and LTI succeeded in comparing one-month old and newborn groups. PSD components in High-Frequency range (HF) were significant for both comparisons. These results quantitatively show that maturation of the parasympathetic nervous system one month after birth is still in progress, later with respect to the sympathetic one. Understanding this complex control is a key point in the deeper investigation of the cardiovascular control in newborns.