Heart rate and respiration relationships as a diagnostic tool for late onset sepsis in sick preterm infants

The objective of the study was to test the heart rate variability (HRV) and the association between RR interval and the spontaneous respiration in a selected population of sick premature infants. Approximated Entropy (ApEn) and Regularity index were computed for RR series while four numerical indexes able to quantify association between signals were compared: (quadratic spectral coherence, linear correlation index, non linear association functions, and synchronization index). From a methodological point of view, both linear and non linear indexes were able to enhance the relationships between the signals. From a clinical point of view, lower relationships values were strongly associated with Sepsis Group while the Non Sepsis Group was characterized by a stronger relationship between RR series and the respiration. These results suggest that the exploration of RR and respiration relationships may help revealing systemic infection in premature newborns.