Development of features of the autonomic circulatory regulation in late premature and full term infants

Objective: In this work, the development of the features of an autonomic system of blood circulatory regulation from the period of late prematurity to full-term infants is investigated using the example of signals of the photoplethysmogram of blood vessels, electrocardiogram, and respiration. The previous works of foreign and domestic authors show that interdependency between physiological rhythms emerges early in development. Much attention was paid to the study of cardiorespiratory coupling and his development in newborns, nevertheless, there are still many questions in this area. In this study, in addition to studying the standard low-frequency cardiorespiratory effect, we studied the relationships between the low-frequency components of the autonomic regulation of heart rate (using an electrocardiogram) and the tone of the arterial vessels (using photoplethysmogram of blood vessels). Approach: The goal of the work is to estimate the dynamics of the development of the coupling of the autonomic regulatory circuits of the cardiovascular system and respiratory system. In this paper, special attention is paid to the study of phase synchronization of these processes, as well as to the interaction of frequency components. We studied the coherence between heart rate variability, photoplethysmograms of blood vessels, and respiration signals of newborns with a gestational age of 30 weeks to 40 weeks. Main results: No significant changes in the measure of the estimation of phase synchronization with increases in the gestational age of the infant were found. The reason may be a notable change in the degree of connectedness of the studied systems after birth. There was also an assumption about the presence of changes in the direction of connectedness, but not in its strength. Significance: This study carries a fundamental interest - an understanding of the higher risk for negative results at the end of a premature population. Moreover, the continuation of work in this direction may allow creating a tool for the development of early markers of impaired autonomic regulation of the functions of the cardiovascular system and respiration in young children.