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Anders Hedström

Publications and source records attributed to Anders Hedström.

2 recordsLinked to original sources

Remote sessions and frequency analysis for improved insight into cerebral function during pediatric and neonatal intensive care.

A project involving recording and analysing EEG together with cardiovascular signals and temperature has been initiated. The aim of this project is to establish difficulties and possibilities involved with implementing a system for remote sessions and analysing EEG in correlation with other physiological signals. One objective is to find indicators of cerebral function during postasphyxia neonatal intensive care and pediatric cardiopulmonary bypass surgery with hypothermia. Remote sessions for joint interpretation have been carried out between pediatricians and clinical neurophysiologists, and EEG has been analyzed using frequency analyzing tools. One result is the discovery of reversible spectral changes coinciding with blood pressure falls, which may indicate loss of autoregulation function. This finding is one outcome from initial use of a system, developed during the project to facilitate communication about, and analysis of the recorded signals. Thus, already from a limited number of remote sessions and the use of basic signal processing techniques, important results have been achieved and better insight has been gained of how cerebral function is affected by cardiopulmonary bypass surgery. In this paper, we present our experiences from introducing a system for remote consultations, and evaluate the use for such a system in the current applications.

Algorithms↗

Modification of the average reference montage: dynamic average reference.

The common average reference (CAR) is influenced strongly by high-amplitude artifacts at the recording electrodes. The authors suggest an algorithm for average reference modification that allows application of the average reference montage in the presence of high-amplitude artifacts at one or several EEG data channels. This dynamic average reference (DAR) method is based on analysis of kurtosis (DARkurt) or kurtosis and standard deviation (DARSD) of amplitude distribution at a single time point and elimination of outliers before calculating the average reference. This procedure can be performed on-line. The DAR improves visual EEG representation considerably in the presence of high-amplitude artifacts. The DAR also influences artifact-free EEG, increasing slightly the amplitude of high-amplitude waveforms. The modeling of the dipole source in the spherical conductor has shown that the DAR compared with the CAR can both decrease and increase the average reference bias depending on position and orientation of the source. In practice, the influence of the DAR with tested parameters on the artifact-free EEG was low and never exceeded 12% of the amplitude of the CAR-referenced signal. The DAR method can be useful for routine analysis of EEG contaminated by high-amplitude artifacts and for long-term EEG monitoring.

Algorithms↗