Forecasting epilepsy from the heart rate signal.

Information contained in the R-R interval series, specific to the pre-ictal period, was sought by applying an unsupervised fuzzy clustering algorithm to the N-dimensional phase space of N consecutive interval durations or the absolute value of duration differences. Data sources were individual, complex partial seizures of temporal-lobe epileptics and generalised seizures of rats rendered epileptic with hyperbaric oxygen. Forecasting success was 86% and 82% (zero false positives in resistant rats), respectively, at times ranging from 10 min to 30 s prior to seizure onset Although certain forecasting clusters predominated in the patient group and different ones predominated in the animal group, forecasting on the whole was seizure-specific. The high prediction sensitivity of this method, which matches that of EEG-based methods, seems promising. It is believed that an on-line version of the algorithm, trained on each patient's peri-ictal ECG, could serve as a basis for a simple seizure alarm system.

Forecasting generalized epileptic seizures from the EEG signal by wavelet analysis and dynamic unsupervised fuzzy clustering.

Dynamic state recognition and event-prediction are fundamental tasks in biomedical signal processing. We present a new, electroencephalogram (EEG)-based, brain-state identification method which could form the basis for forecasting a generalized epileptic seizure. The method relies on the existence in the EEG of a preseizure state, with extractable unique features, a priori undefined. We exposed 25 rats to hyperbaric oxygen until the appearance of a generalized EEG seizure. EEG segments from the preexposure, early exposure, and the period up to and including the seizure were processed by the fast wavelet transform. Features extracted from the wavelet coefficients were imputed to the unsupervised optimal fuzzy clustering (UOFC) algorithm. The UOFC is useful for classifying similar discontinuous temporal patterns in the semistationary EEG to a set of clusters which may represent brain-states. The unsupervised selection of the number of cluster overcomes the a priori unknown and variable number of states. The usually vague brain state transitions are naturally treated by assigning each temporal pattern to one or more fuzzy clusters. The classification succeeded in identifying several, behavior-backed, EEG states such as sleep, resting, alert and active wakefulness, as well as the seizure. In 16 instances a preseizure state, lasting between 0.7 and 4 min was defined. Considerable individual variability in the number and characteristics of the clusters may postpone the realization of an early universal epilepsy warning. University may not be crucial if using a dynamic version of the UOFC which has been taught the individual's normal vocabulary of EEG states and can be expected to detect unspecified new states.

Respiration maintained by externally applied vibration and tracheal insufflation in the cat.

It was reported recently that adequate gas exchange could be maintained in patients and experimental animals by applying very high-frequency (15 Hz), low-volume oscillations at the upper airways. This report deals with a new mode of high-frequency ventilation, in which gas exchange is achieved in paralyzed cats by externally vibrating the chest wall. These vibrations, which alone caused very small-volume (less than 0.5 ml) oscillations at the tracheal opening, maintained gas exchange at normal PaCO2 for hours when coupled with tracheal air insufflation. PaCO2 values as low as 15 torr could be achieved by increasing the insufflation rate. Vibration frequencies in the range of 20-45 Hz were equally effective. The method required little or no continuous positive airway pressure, caused little elevation of mean tracheal pressure, and no consistent changes in arterial and central venous pressures during ventilation. In addition to the potential merits of this method of ventilation, the described vibrations seem to considerably reduce the anatomic dead space and as such may assist conventional methods of artificial ventilation or even spontaneous breathing when rapid and shallow.