Heart rate variability in healthy term newborns: the contribution of respiratory sinus arrhythmia.

Cardiorespiratory interactions in healthy full term newborns were investigated. Spectral analysis was used on heart rate and breathing data from 22 neonates 2-5 days old to reveal coincident frequencies in the breathing and heart rate variability (HRV) spectra, thus identifying respiratory sinus arrhythmia (RSA). The spectral description of HRV in healthy term newborns revealed a consistent and distinct RSA feature, with a mean contribution of over 30%. The contribution of RSA to HRV was dependent on breathing frequency and absolute RSA power. The mechanisms that produce this cardiorespiratory interaction are considered to be functionally active in the healthy term neonate.