Biomedical subjects

E Poiseau

Publications and source records attributed to E Poiseau.

10 recordsLinked to original sources

PubMed2002

[Magnetocardiography: principles and potential uses in cardiology].

Magnetocardiography (MCG) is a non-invasive technique of studying cardiac electrophysiology activity. It appears that electric and magnetic measurements are not only complementary but provide independent information. Described over 25 years ago, recent technical progress in the field of supraconductivity has provided MCG with real clinical applications. It is still mostly used in research, but its clinical applications are beginning to develop. The most interesting clinical application of the MCG is certainly its capacity to provide a non-invasive anatomical localisation of the arrhythmogenic substrate or of accessory pathways. Nowadays, however, the accuracy of these localisations needs to be improved. When this has been accomplished, MCG could play a significant role in non-invasive cardiological investigation with well-defined clinical applications.

Arrhythmias, Cardiac↗

PubMed2000

Role of the mode of sensory stimulation in presurgical brain mapping in which functional magnetic resonance imaging is used.

OBJECT: The aim of this study was to evaluate different types of sensory stimulation used to distinguish between microvasculature and venous drainage on functional magnetic resonance (fMR) images with blood oxygen level-dependent (BOLD) contrast. METHODS: Seven volunteers received three sensory stimulations. One consisted of small discontinuous automated pokes to the ventral aspect of the right thumbtip. The other two were delivered by the investigator, who vigorously brushed the ventral aspect of the right thumbtip either alone or in combination with the thenar region. Seven contiguous axial slices of the head were acquired using echoplanar fMR imaging during each mode of stimulation. Boxcar analysis and Student's t-test were performed. Cluster analysis was used to determine significant differences between rest and activation phases. The major findings were 1) that a discontinuous sensory stimulation involving a small skin area was able to evoke a limited activated area in the postcentral gyrus with a low activation index (AI [2%]); 2) that this limited activated area was included in the activated area elicited by the continuous sensory stimulations; and 3) that this also evoked multiple activated areas exhibiting AIs of either approximately 2% or greater than 5%. This indicated that the limited discontinuous tactile stimulation evoked a BOLD-contrast fMR image essentially of microvasculature, whereas the more extensive continuous stimulations evoked a BOLD-contrast fMR image in both microvasculature and venous drainage. CONCLUSIONS: Different sensory stimulations are necessary to differentiate primary sensory cortex from venous drainage for presurgical brain mapping.

Adult↗

PubMed1996

In vivo assessment of neurotransmitter system in cardiovascular diseases. Clinical issues.

Cardiac neurotransmitter systems, especially the adrenergic receptor pathway, are impaired in heart diseases. In patients with heart failure, these abnormalities contribute to arrhythmogenesis and to progression of cardiac dysfunction. The use of MIBG with single photon imaging has provided useful information on the mechanisms of ventricular arrhythmias, and on the causes of death in patients with heart failure or hypertrophic cardiomyopathy. It has been suggested as a prognostic indicator in patients with heart failure. Positron Emission Tomography (PET) now allows us to obtain noninvasively the quantitative determination of regional receptor density and affinity in humans as well as innervation integrity and functioning. These measurements are based upon the synthesis of a radioligand, usually either a selective receptor antagonist or a false neurotransmitter labeled with a positron-emitting radioisotope. Mathematical compartmental models are fitted to activity-versus-time curves obtained during saturation or displacement experiments in order to calculate the rate constants and the receptor density in the myocardium. PET has only recently begun to be applied to the study of cardiac physiology and disease. PET and SPECT cardiac neuroimaging techniques are able to demonstrate the physiological regulation of receptors, and to provide the possibility of studying regional abnormalities of cardiac neurotransmission, especially in arrhythmogenic cardiomyopathy. Furthermore these non invasive techniques could be useful in exploring the alteration of neurotransmission in the early stage of heart disease and could allow repeated scintigraphic examinations in order to evaluate the effects of cardiac medications.

Animals↗

PubMed1995

ECG activity in the sleep of insomniac patients under the influence of lormetazepam and zopiclone.

The influence of the benzodiazepine hypnotic lormetazepam (1 mg) and the cyclopyrrolone hypnotic zopiclone (7.5 mg) on heart rate activity was studied in 16 elderly insomniacs in a placebo-controlled, randomised, 3-fold crossover trial. After digital preprocessing of the ECG, QRS complexes were automatically recognised by a detection technique based on adaptative thresholds. Both R-R periodicity and heart rate variability were analysed as a function of sleep stages and time of night. Under placebo, heart rate decreased significantly from the first to the second half of the night. The relationship between sleep stages and heart rate remained constant under both hypnotics. Although the two substances significantly modified the distribution of sleep stages, no relevant changes in ECG activity were observed when the proportion of the different sleep stages was taken into consideration.

Aged↗

PubMed1994

Automatic analysis of sleep using two parameters based on principal component analysis of electroencephalography spectral data.

A computer program for the analysis of a sleep electroencephalogram (EEG) is presented. The method relies on two steps. First, a spectral analysis is performed for signals recorded from one or more electrode locations. Then, two EEG parameters are obtained by storing the spectral activity in a multidimensional space, whose dimension is reduced using principal component analysis (PCA) techniques. The main advantage of these parameters is in describing the process of sleep on a continuous scale as a function of time. Validation of the method was performed with the data collected from 16 subjects (8 young volunteers and 8 elderly insomniacs). Results showed that the parameters correlate highly with the hypnograms established by conventional visual scoring. This signal parametrisation, however, offers more information regarding the time course of sleep, since small variations within individual sleep stages as well as smooth transitions between stages are assessed. Finally, the concurrent use of both parameters provides an original way of considering sleep as a dynamic process evolving cyclically in a single plane.

Adult↗

PubMed1994

Wavelets-a new tool in sleep biosignal analysis.

The wavelet transform is a relatively new approach to data processing which has been applied in different areas such as signal, speech and image processing. In the last decade, many papers have been published on wavelet theory and its applications. The wavelet transform provides an elegant alternative to the classical Fourier or Gabor transforms unifying numerous signal processing techniques in a common framework. The purpose of the present paper is to provide an overview of the applicability of the wavelet transform to EEG signal analysis. In the first part of the paper the mathematical background is summarized. In the second part, applications to the sleep EEG field are presented and discussed. The results of these illustrations demonstrate the usefulness of the wavelet transform to solve various problems including signal parametrization, pattern recognition and biosignal representation.

Journal Article↗

PubMed1992

Pattern recognition by matched filtering: an analysis of sleep spindle and K-complex density under the influence of lormetazepam and zopiclone.

The evaluation of sleep EEG patterns is mostly accomplished by visual analysis. With modern personal computers however, it is possible to perform signal detection within a reasonable length of time automatically. This paper presents a method for signal processing based on matched filtering. This allows the detection of sleep spindles and K-complexes in a sleep EEG recording with a high degree of accuracy. First the technique is described, and the results of a validation study based on the comparison of visual evaluations and computer analysis are presented. Thereafter, results of an application study are presented. Sleep spindle and K-complex density under the influence of lormetazepam and zopiclone were examined. Under both medications sleep spindle density increased while K-complex density decreased. Computation of Pearson's correlation coefficients demonstrated that the interindividual sleep spindle and K-complex variations under both treatments are highly correlated. The data suggest that lormetazepam and zopiclone, although chemically different, have a similar mode of action and display comparable effects on the sleep EEG.

Adult↗

PubMed1992

Topographical analysis of sleep spindle activity.

There is evidence for two types of sleep spindle activity, one with a frequency of about 12 cycles/s (cps) and the other of about 14 cps. Visual examination indicates that both spindle types occur independently, whereby the 12-cps spindles are more pronounced in the frontal and the 14-cps spindles in the parietal region. The purpose of this paper is to provide more information about the exact topography of these patterns. First the occurrence of distinct signals in anterior and posterior brain regions was verified using pattern recognition techniques based on matched filtering. Thus the existence of two distinct sources of activity located in the frontal and parietal region of the brain, respectively, was demonstrated using EEG frequency mapping. Evaluation of sleep recordings showed high stability both in the frequency and location of the presumed spindle generators across sleep. Pharmacological effects of lormetazepam and zopiclone on both spindle types were investigated. Both substances enhanced the sleep spindle activity recorded from the frontal and parietal electrodes, but this increase was more pronounced in the parietal brain region.

Adult↗

PubMed1991

[Pattern recognition techniques in sleep polygraphy].

The evaluation of EEG-patterns is usually accomplished by visual analysis. Nowadays however, even personal computers are fast enough for an efficient pattern recognition of EEG signals. Using sleep spindles and K-complexes as examples, our aim was to demonstrate how patterns can be detected in an EEG signal with a high degree of accuracy. Furthermore, recognition of K-complexes has been improved by applying an additional "adaptive algorithm" allowing individual adjustments to the signal's form and amplitude.

Algorithms↗

PubMedDate not supplied

Respiration and heart rate variation in normal infants during quiet sleep in the first year of life.

Forty-three all-night sleep recordings have been performed on 19 control infants of the ages 6 weeks, 6 months and 1 year. During eight hour periods 22 physiological parameters were sampled by a personal computer based monitoring system and stored on an optical disk. This paper reports on spectral analysis of breathing and heart rate patterns during the first and last episode of quiet sleep at three different age groups. The results demonstrate that the respiratory rate during quiet sleep decreases (6 weeks: 37.2 +/- 5.4; 6 months: 30.1 +/- 4.9; 1 year: 24.1 +/- 1.8; adults (mean age 25.1 +/- 2.8 years; n = 10): 14.8 +/- 1.8; values are means +/- one standard deviation in breaths/min) and the respiratory coefficient Pm/Ps (higher values of Pm/Ps indicate lower respiratory variability) increases with age (6 weeks: 2.3 +/- 0.7; 6 months: 3.2 +/- 1.1; 1 year: 3.4 +/- 1.0; adults: 4.5 +/- 1.0). The calculation of the heart rate in beats per minute (bpm) and heart rate variability (%) revealed the following results: 6 weeks: 127.4 +/- 11.5 bpm, 3.8 +/- 1.5%; 6 months: 119.4 +/- 17.3 bpm, 4.2 +/- 1.7%; 1 year: 110.3 +/- 21.5 bpm, 5.8 +/- 2.3%; adults: 59.2 +/- 8.5 bpm, 4.3 +/- 2.2%. A comparison of the cardiorespiratory data from the first and last quiet sleep period showed no significant differences within either age group.

Cerebral Cortex↗