Abstract
The immature autonomic nervous system (ANS) in premature infants regulates heart rate (HR) and respiration different during quiet sleep (QS) and active sleep (AS). Little information is available about ANS regulation in these subjects. The aim of this study was to investigate changes in autonomic regulation and cardiorespiratory coupling during AS and QS in five very preterm neonates with gestational age (GA) 26–31 weeks, applying univariate and bivariate linear and non-linear dynamics methods to the recorded cardiorespiratory signals. During QS univariate linear indices revealed lower standard deviations and entropies, indicating decreased heart rate (HR) variability. More balanced sympatho-vagal behavior of the ANS was revealed by decreased low frequency (LF), increased high frequency (HF), and a trend toward lower ratio LF/HF in QS. Applied non-linear indices (probabilities, entropies, and fractal measures) quantifying the complexity and scaling behavior of HR regulation processes were significantly altered in QS in comparison to AS. This reflects a lower short-term variability, less complexity, and a loss of fractal-like correlation properties of HR dynamics in QS. One major finding is that cardiorespiratory coupling is not yet completely developed in very preterm neonates with 26–31 weeks GA. Significantly different regulation patterns in bivariate oscillations of HR and respiration during AS and QS could be recognized. These patterns were characterized on the one hand by predominant monotonous regulating sequences originating from respiration independently from HR time series in AS, and to a minor degree in QS, and on the other hand by some prominent HR regulation sequences in QS independent of respiratory regulation. We speculate that these findings might be suitable for monitoring preterm neonates and for detecting disorders in the developing cardiorespiratory system.
Highlights
The first postnatal period for preterm infants is characterized by periods of active sleep (AS) and quiet sleep (QS) states, with intermediate undetermined sleep phases
As a trend the frequency domain index low frequency (LF)/high frequency (HF) was decreased in newborns within QS compared to AS (6.4 ± 2.7 vs. 13.3 ± 12.2 a.u.)
The HR variability (HRV) regulation patterns in QS are independent from respiratory regulation and probably representing an increasing vagal modulation
Summary
The first postnatal period for preterm infants is characterized by periods of active sleep (AS) and quiet sleep (QS) states, with intermediate undetermined sleep phases. Multivariate autoregressive analysis has revealed higher coherence values in the ultra HF band (0.7– 1.5 Hz) in late preterm infants. This suggests significantly stronger coupling in the frequency range associated with regular breathing, indicating a mild, but present, respiratory sinus arrhythmia (RSA) (Indic et al, 2008). It has been shown that sleep states and HR regulation have a predominant influence on respiratory variability in non-healthy preterm infants, such that the ventilatory frequency and its variability are greater in AS (Elder et al, 2010, 2011) than in QS. Cardiorespiratory coupling is less complex in QS in the HF (0.2–2 Hz) band only and shows different, probably sympathetically mediated, oscillations influencing the HR and respiration regulation
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call