Characteristics of the cardiointervalogram in newborns during sleep

Abstract

One hundred and seven healthy full-term newborns were examined in this study. The cardiointer-valogram (CIG) was continuously recorded on the fifth to seventh day of life. An electropolygram (EPG) was recorded in 14 newborns along with the CIG and included the electroencephalogram, electrooculogram, electrocardiogram, and pneumogram. The functional state of the infants was continuously monitored, and calm or active wakefulness and active or calm sleep were distinguished using common criteria. Quantitative analysis of the sleep EPG was used to differentiate sleep phases by a standard method. The CIG was analyzed during orthodox (OS) and paradoxical (PS) sleep, and three different CIG types were distinguished by visual assessment and differential criteria established previously. The three types of CIG considerably differed in the structure and power spectrum of slow oscillations of R-R intervals, especially in the range from 0.04 to 0.15 Hz. The type I CIG was recorded during OS. At the end of this phase, the variability range increased while the amplitude of the mode and the tension index were reduced, indicating the type II CIG, with a duration of 3–4 min. All three CIG types were observed during PS; the type III CIG dominated, accounting for 58.3 ± 4.6% of the phase duration. A relationship was found between the CIG types and the cyclic organization of sleep, pointing to a difference in mechanisms regulating the heart rate in different functional states of the central nervous system in newborns.