The evaluation of heart rate variability (HRV) is often ušed for examination of regulation/dysregulation of heart functions and detection of pathological changes of autonomous nervous systém. In neonatal period, authors háve to regard specific conditions in examination and evaluation of obtained records. The heart rate variability is mařkedly influenced by age of the patient. The clinical application of this method is dependent on establishment of physiological values for certain age group. The breathing pattern affects markedly the high frequency band (HF). High breathing rate of newborns (40-60 per minuté) reflects above the HF wave-length specified for adults. So, it is necessary to elect different type of evaluation and shift the upper limit of HF band to 1 Hz (the neonatal version). The position during examination is important input affecting the activity of regulation systems and variability of cardiovascular parameters of children and aďults. Authors prefere supine position for examination in neonatology. HRV changes in dependence of sleep stage or alertness. Theese changes are relative to physiological parasympathetic prevalence and type of respiration during sleep. Neonatology is a big challenge for clinical application of HRV examination. They háve to accept different conditions of examination, postnatal adjustment of cardiovascular systém to extrauterine life and continuing development of autonomous nervous systém. The knowledge of physiological changes of HRV may contribute to application of this method in specific pathological conditions.

        Key words: heart rate variability, newborns, respiratory sinus arhytmia, autonomie nervous systém