EMDLAB: A toolbox for analysis of single-trial EEG dynamics using empirical mode decomposition.

BACKGROUND: Empirical mode decomposition (EMD) is an empirical data decomposition technique. Recently there is growing interest in applying EMD in the biomedical field. NEW METHOD: EMDLAB is an extensible plug-in for the EEGLAB toolbox, which is an open software environment for electrophysiological data analysis. RESULTS: EMDLAB can be used to perform, easily and effectively, four common types of EMD: plain EMD, ensemble EMD (EEMD), weighted sliding EMD (wSEMD) and multivariate EMD (MEMD) on EEG data. In addition, EMDLAB is a user-friendly toolbox and closely implemented in the EEGLAB toolbox. COMPARISON WITH EXISTING METHODS: EMDLAB gains an advantage over other open-source toolboxes by exploiting the advantageous visualization capabilities of EEGLAB for extracted intrinsic mode functions (IMFs) and Event-Related Modes (ERMs) of the signal. CONCLUSIONS: EMDLAB is a reliable, efficient, and automated solution for extracting and visualizing the extracted IMFs and ERMs by EMD algorithms in EEG study.

Dynamic correlation between tissue PO2 and near infrared spectroscopy.

Multimodal O2 monitoring including tissue pO2 measurements and near infrared spectroscopy (NIRS) are techniques increasingly employed for monitoring patients on neurosurgical intensive care units. NIRS measures a mixed venous arterial oxygen saturation, whereas tissue pO2 evaluates the oxygen pressure in the white matter. In contrast to the tissue pO2 measurements, the NIRS at the moment has not been completely established in clinical practice. We wanted to evaluate whether both techniques are monitoring different dynamic changes. Thirteen patients were included (SAH n = 3, TBI n = 10), 12 patients were male and 1 was female. Mean age was 34 years with a range from 16-76 years. Tissue pO2 probes (Licox, GMS, Germany) were implanted in the frontal lobe showing most pathological changes on the initial CT scan. A near infrared spectroscopy sensor (Invos, Somanetics, USA) was placed simultaneously at the patient's forehead. Due to the drift of the tissue pO2 probe, only data sets were taken into further account in which a tissue pO2 value above 15 mmHg was measured. 66 data sets were analyzed by calculating the spectral coherence with multi taper methods. The coherence of two independent white noise signals were defined as an observation by chance. The significance level for correlated frequencies was 90%. In the spectral long time regime (frequency > or = 0.02), more than 80% of the data sets showed a higher percentage of correlated frequencies as compared to the observation by chance. The assumption that tissue pO2 and near infrared spectroscopy probes are measuring different dynamic changes in neurosurgical intensive care patients could not be supported by our data.