Comparison of Cerebral and Peripheral Tissue Oxygenation Index (TOI) Measured with Spatial Resolved NIRS Pichler Gerhard, MD Automatic Detection of “Delta-Brush” and Induced Heart Rate Changes in Preterm Infants

Statement of problem: Spatial-resolved near-infrared spectroscopy enables non-invasive continuous measurement of " tissue oxygenation index " (TOI), which correlates to mixed venous oxygenation (SvO2). The aim of the present study was to compare cerebral TOI and peripheral TOI. Statement of methods: Repeated simultaneous measurements on right forehead and calf, were performed in 10 neonates with gestational age (GA) >32 weeks within the first two days after birth by reapplying the NIRS optodes five times. All patients were stable without respiratory or cardio-circulatory support. After each reapplying procedure TOI values of five 15-seconds periods were analysed. On calf in addition SvO2 was calculated with NIRS and the venous occlusion method. TOI values of calf were included for further analysis, when differences of obtained TOI and SvO2 (%) values were <3. Heart rate, peripheral arterial oxygen saturation, central and peripheral temperatures were measured continuously. Arterial blood pressure was measured before and after measurement procedures. Summary Results: The ten neonates had a mean gestational age of 35.9±4.4 weeks, a mean birth weight of 2350±780 and mean postnatal age of 18.2 ±18.8 hours. All cerebral TOI measurements and 4±2 measurements/neonate of peripheral TOI were included for further analysis. Implications: Cerebral TOI is significantly higher than peripheral TOI in neonates with gestational age > 32 weeks. Objective: The aim of this work was to study the relationship between delta-brush and induced heart rate (HR) changes in preterm infants. Delta brush is a high frequency (8-20Hz) spindle-like activity superimposed on 1-3Hz delta waves (Eyre 1988). During quiet sleep in preterm infants induced HR changes in form of an acceleration (lasting about 6 seconds) are closely linked with the occurrence of slow-wave EEG bursts (Pfurtscheller et al. Brain Dev. 2005). Methods: A group of 10 preterm infants with conceptional age (CA) of 36.55 ± 1.25 (mean ± SD) weeks was studied. From long-term EEG and ECG recordings, periods of about 15 min with low HR variability and slow-wave bursts were selected. From the raw EEG (0.5-100Hz) two data sets were generated, one by high-pass filtering (5Hz) and the other by low-pass filtering (4Hz). All 3 data sets (original, 0.5-4Hz and 5-100Hz) were subject of an automatic burst detection method with the goal to search for slow-waves and delta brush, respectively. In addition to automatic EEG burst detection also induced HR changes were analysed synchronously to EEG bursts. Results: Delta brush is accompanied by a HR acceleration in …