RESUMO
AIMS: To determine the reproducibility and minimum detectable change (MDC) of heart rate variability (HRV) measures during two sequential 24-h periods, at week 32 of gestation, in preterm infants born between 28 and 32â¯weeks, hospitalized in the neonatal intensive care unit (NICU). The second aim is to assess postnatal changes in HRV measures between 32 and 35â¯weeks. STUDY DESIGN: 32 preterm infants born between 28 and 32â¯weeks of gestation were recruited. For each infant 48â¯h of recordings of RR interval were performed at week 32 and week 35. HRV parameters included time and frequency parameters. RESULTS: At week 32, the intra-class correlation coefficient (ICC) of all HRV values was statistically significant with high correlation coefficients (ICCâ¯=â¯0.83-0.97). At week 35, a significant increase was noted in the HRV parameters, characterize mainly the sympathetic tone, with over half the infants showing an increase greater than the MDC for these parameters. CONCLUSIONS: Using 24-h recording at week 32 of gestation during NICU routine is reliable, feasible, not costly and may have important implications for an early identification of premature in a state of stress such as sepsis, or as a follow-up measure.