Supplementary Material for: Coupling between regional oxygen saturation of the brain and vital signs during immediate transition after birth

Introduction. The primary aim was to analyze any coupling of heart rate (HR)/arterial oxygen saturation (SpO2) and cerebral regional oxygen saturation (rScO2) and tissue oxygen extraction (cFTOE) during immediate transition after birth in term and preterm neonates to gain more insight into interactions.

Methods. The present study is a post-hoc analysis of data from 106 neonates, obtained from a prospective, observational study. Measurements of HR, SpO2, rScO2 and cFTOE were performed during the first 15 minutes after birth. The linear and nonlinear correlation was computed between these parameters in a sliding window. The resulting coupling curves were clustered. After clustering demographic data of the clusters were de-blinded and compared.

Results. Due to missing data, 58 out of 106 eligible patients were excluded. Two clusters were obtained: cluster 1 (N=39) and cluster 2 (N=9). SpO2 had linear and nonlinear correlations with rScO2 and cFTOE, whereby the correlations with rScO2 were more pronounced in cluster 2. HR-rScO2 and HR-cFTOE demonstrated a nonlinear correlation in both clusters, again being more pronounced in cluster 2, whereby linear correlations were mainly absent. After de-blinding, the demographic data revealed that the neonates in cluster 2 had significantly lower gestational age (mainly preterm) compared to cluster 1 (mainly term).

Discussion. Besides SpO2 also HR demonstrated a nonlinear correlation with rScO2 and cFTOE in term and preterm neonates during immediate transition after birth. In addition, the coupling of SpO2 and HR with cerebral oxygenation was more pronounced in neonates with a lower gestational age.