Ventilator-associated sinus arrhythmia in a preterm neonate--an indicator for a mature autonomic nervous system?

According to control theory, the interactions between respiration and heart rate (i.e. respiratory sinus arrhythmia, RSA, and breath amplitude sinus arrhythmia, BASA) reflect the inner workings of the physiological control systems of respiration and circulation. This paper reports on a preterm neonate (28.5 weeks old, 940 g) who showed the presence of ventilation-associated sinus arrhythmia (VASA) under moderate artificial ventilation. His heart rate variability was entrained to the ventilatory stimulus. VASA and entrainment suggest that the parasympathetic part of the autonomic nervous system might be more mature than expected in some preterm neonates.