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W. Guggenbühl

Bio: W. Guggenbühl is an academic researcher from École Polytechnique Fédérale de Lausanne. The author has contributed to research in topics: Ultrasonic sensor & Image processing. The author has an hindex of 6, co-authored 16 publications receiving 228 citations.

Papers
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Journal ArticleDOI
TL;DR: The correlation dimension was high in episodes of rapid eye movement (REM) sleep, declined progressively within each non-REM sleep episode, and reached a low level at times when EEG slow waves were dominant, which does not support the hypothesis that the sleep EEG is generated by a chaotic attractor.

78 citations

Journal ArticleDOI
TL;DR: The correlation dimension was high in episodes of rapid eye movement (REM) sleep, declined progressively within each non‐REM sleep episode, and reached a low level at times when EEG slow waves were dominant, whereas slow‐wave activity showed its typical progressive decline from non‐REMIREM sleep cycle 1 to 4, no such trend was present for the correlation dimension.
Abstract: The complexity of the electroencephalogram (EEG) during human sleep can be estimated by calculating the correlation dimension. Due to the large number of calculations required by this approach, only selected short (4-164 s) segments of the sleep EEG have been analysed previously. By using a new type of personal supercomputer, we were able to calculate the correlation dimension of overlapping 1 min EEG segments for the entire sleep episode (480 min) of 11 subjects and thereby delineate the time course of the changes. The correlation dimension was high in episodes of rapid eye movement (REM) sleep, declined progressively within each non-REM sleep episode, and reached a low level at times when EEG slow waves (0.75-4.5 Hz) were dominant. However, whereas slow-wave activity showed its typical progressive decline from non-REM/REM sleep cycle 1 to 4, no such trend was present for the correlation dimension. By providing an estimate of the complexity of a signal and being independent of amplitude and frequency measures, the correlation dimension represents a novel approach to exploring the dynamics of sleep and the processes underlying its regulation.

49 citations

Patent
06 Sep 1994
TL;DR: In this article, an apparatus for measuring the parameters of respiratory gases comprising a respiratory tube, ultrasonic sensors and pre-amplifier electronic circuitry arranged in a separate housing was described.
Abstract: The invention relates to an apparatus for measuring the parameters of respiratory gases comprising a respiratory tube, ultrasonic sensors and pre-amplifier electronic circuitry arranged in a separate housing. In order to prevent dangerous cross infections between patients following repeated utilization of the such measuring apparatus the ultrasonic sensors are permanently integrated in the respiratory tube so that they constitute a single part therewith and in that at least the respiratory tube together with the integrated ultrasonic sensors is designed in the form of an interchangeable part for use once only.

36 citations

Journal ArticleDOI
TL;DR: This respiratory air flowmeter is extremely fast and accurate, with low noise (below 9ml/s), with a wide flow range (bidirectional from 0 to 9 l/s and with a linear frequency response up to 70 Hz).
Abstract: The construction and specific function of a new ultrasonic flowmeter are described. The mean velocity of the respiratory air flow is calculated by measuring the transit times of short ultrasonic pulse-trains simultaneously transmitted upstream and downstream at a 650 Hz rate. The flowmeter system consists of a control unit and a separate flowhead. The former includes the power supplies, a controlling microprocessor, most of the signal processing circuitry, and three analog outputs for flow, volume, and temperature, respectively. The flowhead contains the respiratory tube with a constant circular cross section (length 90 mm, diameter 20 mm, dead space 35 cm3), a fast temperature sensor, two electronic circuits for processing of flow and temperature data, and a sound transmission channel with two capacitive ultrasonic wide-band transducers. This respiratory air flowmeter is extremely fast (response time 1-2 ms) and accurate, with low noise (below 9ml/s), with a wide flow range (bidirectional from 0 to 9 l/s) and with a linear frequency response up to 70 Hz.

32 citations

Patent
11 Jul 1994
TL;DR: In this paper, a Vorrichtung zur Messung von Atemgasparametern with einem Atemrohr, Ultraschallsensoren and einer in einem separaten Gehause angeordneten Vorverstarkerelektonik is described.
Abstract: Die Erfindung betrifft eine Vorrichtung zur Messung von Atemgasparametern mit einem Atemrohr, Ultraschallsensoren und einer in einem separaten Gehause angeordneten Vorverstarkerelektonik. Um gefahrliche Kreuzinfektionen zwischen den Patienten bei Mehrfachverwendung der Mesvorrichtung zu verhindern, sind die Ultraschallsensoren in dem Atemrohr fest integriert, so das sie mit diesem ein einstuckiges Teil bilden, wobei zumindest das Atemrohr mit den integrierten Ultraschallsensoren als austauschbares Teil zur einmaligen Verwendung ausgebildet ist.

7 citations


Cited by
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Journal ArticleDOI
TL;DR: Dynamical properties of brain electrical activity from different recording regions and from different physiological and pathological brain states are compared and strongest indications of nonlinear deterministic dynamics were found for seizure activity.
Abstract: We compare dynamical properties of brain electrical activity from different recording regions and from different physiological and pathological brain states Using the nonlinear prediction error and an estimate of an effective correlation dimension in combination with the method of iterative amplitude adjusted surrogate data, we analyze sets of electroencephalographic (EEG) time series: surface EEG recordings from healthy volunteers with eyes closed and eyes open, and intracranial EEG recordings from epilepsy patients during the seizure free interval from within and from outside the seizure generating area as well as intracranial EEG recordings of epileptic seizures As a preanalysis step an inclusion criterion of weak stationarity was applied Surface EEG recordings with eyes open were compatible with the surrogates' null hypothesis of a Gaussian linear stochastic process Strongest indications of nonlinear deterministic dynamics were found for seizure activity Results of the other sets were found to be inbetween these two extremes

2,387 citations

Journal ArticleDOI
TL;DR: Interpretation of results in terms of 'functional sources' and 'functional networks' allows the identification of three basic patterns of brain dynamics: normal, ongoing dynamics during a no-task, resting state in healthy subjects, and hypersynchronous, highly nonlinear dynamics of epileptic seizures and degenerative encephalopathies.

1,226 citations

Patent
25 Sep 2000
TL;DR: In this article, a personal digital assistant (PDA) stores data from physiological monitors (12) so that the data can be used in various software applications, such as medical applications.
Abstract: A personal digital assistant (PDA) (10) stores data from physiological monitors (12) so that the data can be used in various software applications. In different embodiments the physiological monitor (12) can include data storage or have memory modules that are accepted by accessory slots (48 and 50).

899 citations

Proceedings ArticleDOI
09 Oct 1994
TL;DR: This paper compares the performance of several classifier algorithms on a standard database of handwritten digits by considering not only raw accuracy, but also training time, recognition time, and memory requirements.
Abstract: This paper compares the performance of several classifier algorithms on a standard database of handwritten digits. We consider not only raw accuracy, but also training time, recognition time, and memory requirements. When available, we report measurements of the fraction of patterns that must be rejected so that the remaining patterns have misclassification rates less than a given threshold.

647 citations

Patent
10 Oct 2000
TL;DR: In this article, an improved health management system for a person is disclosed, in which the person's resting metabolic rate (RMR) is determined at intervals using an indirect calorimeter.
Abstract: An improved health management system for a person is disclosed, in which the person's resting metabolic rate (RMR) is determined at intervals using an indirect calorimeter. RMR values are used in setting and revising goals in, for example, a weight control program. The effects of a weight control program on RMR can hence be compensated for, which enables an improved weight control program to be developed. In one embodiment, the person is provided with a portable electronic device, for use as a caloric intake calculator, caloric expenditure calculator, and caloric balance calculator.

591 citations