Bob Kemp

Bob Kemp

PhD

About

92
Publications
16,772
Reads
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3,552
Citations
Introduction
Recent R&D activities: - SIS: patient organizer and database for my sleep centre. - EDF at edfplus.info: standard files for Sleep and EEG. - Modeling and analysis of the sleeping brain. - Sensors and electronics for ambulatory recording of respiration, ambient light and sound. - Polyman software for sleep stage scoring.
Additional affiliations
January 1992 - August 2014
Haaglanden Medisch Centrum
Position
  • Medical Professional
Description
  • Development of sensors and software for diagnosis of sleep disorders.
March 1977 - February 2014
Leiden University Medical Centre
Position
  • Medical Professional
Description
  • Development of equipment and software for diagnosis of neurological, sleep, and movement disorders.

Publications

Publications (92)
Article
This work presents a method for the derivation of two new features characterizing the occurrence of both, saccadic and slow eye movements (SEM), in electrooculographic (EOG) sleep recordings. Analysis of EOG activity is of fundamental importance for the clinical interpretation of a subject’s sleep pattern. The features here presented are derived fr...
Article
Full-text available
Human sleep depth was traditionally assessed by scoring electro-encephalographic slow-wave amplitudes at the globally standardized C4-M1 electrode derivation. Since 2007, the American Association of Sleep Medicine (AASM) has accepted three additional derivations for the same purpose. These might well differ in slow wave amplitudes which would bias...
Article
Sleep and EEG recordings in European Data Format (EDF or EDF+) are often accompanied by Video recordings. In contrast to EDF(+) files, Video files usually do not know their own start date and time. Therefore, time-synchronization of the two files requires additional measures. This article proposes a simple standard measure by coding the start date...
Article
Full-text available
The International Pharmaco-EEG Society (IPEG) presents guidelines summarising the requirements for the recording and computerised evaluation of pharmaco-sleep data in man. Over the past years, technical and data-processing methods have advanced steadily, thus enhancing data quality and expanding the palette of sleep assessment tools that can be use...
Article
Snoring, circadian actors, lights-off time and sleep disturbers such as the bed partner, dawn or ambient sounds can now reliably be quantified in ambulatory PSG.
Article
Rapid eye movement (REM) and non-REM sleep processes affect the electrical signals from brain, eyes and muscles. Recording these signals during sleep imposes special demands on electrodes, technicians and equipment. Both human and computerized signal analysis can then be applied to quantify the sleep processes. The most practical and state-of-the-a...
Article
Traditional electroencephalogram (EEG) recorders reject low frequencies and DC and therefore cannot handle fullband EEG. Dedicated fullband recorders use non-standard file formats, because the standard format (EDF) cannot handle large DC electrode offset voltages. Both facts limit the development and use of fullband EEG. We developed a modification...
Article
The Sleep Information System (SIS) was developed by engineers working in the Sleep centre who collaborated intensively with medical and paramedical staff. SIS automates the workflow and data handling of all equipment and investigations in the centre: intakes, questionnaires, actigraphy, apnea screening, PSG, and so on.
Article
Question of the studyOne of the aims of the SIESTA project was to establish a normative database of sleep parameters for healthy and sleep-disturbed patients. Reference data for sleep parameters in non-sleep-disturbed subjects are scarce and usually refer to means and standard deviations. However, since most of the parameters do not follow a Gaussi...
Article
To date, the only standard for the classification of sleep-EEG recordings that has found worldwide acceptance are the rules published in 1968 by Rechtschaffen and Kales. Even though several attempts have been made to automate the classification process, so far no method has been published that has proven its validity in a study including a sufficie...
Article
Both SignalML and EDF+ offer a solution for the incompatibility between different data storage formats in biomedicine. This article discusses the SignalML approach from an EDF+ point of view.
Article
To specify a simple conversion of neurophysiological signals contained in sleep recordings into standard audio files and to illustrate how our cerebral audio processor can then detect specific signal characteristics. A software package (freely accessible from the Internet) has been developed that converts signals from standard EDF (or EDF+) format...
Article
The prevalence of restless legs syndrome (RLS) in various regions in the world has been estimated between 2.5 and 29%. For The Netherlands these figures are not known. Our observational and cross-sectional study was performed to estimate the prevalence of RLS in The Netherlands. A cross-sectional survey by postal questionnaire was carried out throu...
Article
Interrater variability of sleep stage scorings is a well-known phenomenon. The SIESTA project offered the opportunity to analyse interrater reliability (IRR) between experienced scorers from eight European sleep laboratories within a large sample of patients with different (sleep) disorders: depression, general anxiety disorder with and without non...
Article
The European data format (EDF) is a widely accepted standard for exchange of electroencephalogram and polysomnogram data between different equipment and labs. But it hardly accommodates other investigations. EDF+ is a more flexible but still simple format which is compatible to EDF except that an EDF+ file may contain interrupted recordings. Also,...
Article
The whole-head MEG sleep records for each of three subjects were separated into segments of 5.12 seconds and then grouped according to sleep phase ranging from drowsiness-sleep onset to deep slow-wave sleep. Spectral decomposition was employed to find "collective modes," defined as narrow frequency ranges at which all or nearly all of the MEG detec...
Article
The SIESTA project had two major goals: developing new tools for analyzing computer-based sleep recordings and creating a reference database for sleep-related features. Basically, both goals have been reached, although validation and fine tuning of the sleep analyzer is still on-going. Investigations on the Web interface will be finished soon and a...
Article
Full-text available
Aspects to consider when building a database are presented. The work is based on experiences from the SIESTA project which identified sleep disorders
Article
Full-text available
This article presents some requirements imposed on data format specifications derived from different biosignal recording environments. This is followed by a review of four particularly interesting data formats and some notes about other specifications. Finally, the merits of different formats are discussed and some views about future developments a...
Article
A hypnogram shows how sleep travels through its various stages in the course of a night. The sleep stage changes can be quantified to study sedative drug effects. Hypnograms from 21 patients with primary insomnia were collected during a randomized, placebo-controlled crossover study of 20 mg temazepam. A separate daytime session was performed to de...
Article
SUMMAR Y Interrater variability of sleep stage scorings is a well-known phenomenon. The SIESTA project offered the opportunity to analyse interrater reliability (IRR) between experienced scorers from eight European sleep laboratories within a large sample of patients with different (sleep) disorders: depression, general anxiety disorder with and wi...
Article
Sixteen polysomnographic recordings from 8 European sleep laboratories were analyzed. The histogram analysis was used to introduce quality control of all-night EEG recordings. It was found that the header information does not always provide the real saturation values of the recording equipment. The entropy measure was used for the quantitative anal...
Article
The study and diagnosis of movement disorders can be improved by monitoring body position simultaneously with the EMG. We developed a monitor of the 3-dimensional (3D) orientation of body parts that can be applied in long-term ambulatory recordings in the daily life of a patient. The 3D sensor combines miniature sensors for earth's gravity and magn...
Article
The Sleep Disorders Questionnaire (SDQ) is a 176-item questionnaire designed to diagnose the presence of common sleep disorders. This study set out to assess the validity of a Dutch translation of the SDQ. Scores on 145 questionnaires were analyzed. A cluster analysis of these scores revealed the following clusters: healthy, depression, insomnia, n...
Article
Description of driving behaviour of patients with excessive daytime sleepiness (EDS) and the influence on their driving of diagnosis, therapy, legal guidelines and advices. Inventory based on questionnaires. Centre for Sleep and Wake Disorders, The Hague, the Netherlands. All patients with EDS who were in a stable condition for at least 6 months af...
Article
Full-text available
Figures for the prevalence of sleep apnoea syndrome range from 0.3% to 8.5%. These widely ranged estimates are probably due to differences in the definitions used, study designs, and study populations. A study was undertaken to determine the lower limit of the prevalence of clinically significant sleep apnoea syndrome. A cross sectional survey by p...
Article
This paper describes a simple method of event encoding as an extension to a previously defined standard format, the European Data Format (EDF). The specification ensures full backward compatibility with the existing definition. By using this extension, the format can be used to store both continuous recordings and selected epochs of recordings. The...
Article
STANDARD EDF CAN STORE FLOATING-POINT ANALYSIS RESULTS WITH A RESOLUTION OF ABOUT 0.5%.
Article
Background and objectivequantitative electroencephalographic parameters and saccadic eye movements are frequently used as pharmacodynamic measures of benzodiazepine effect. We investigated the relationship between these measures and the hypnotic effect.Methods The correlation between the pharmacodynamic measures and sleep quality was determined in...
Article
Temazepam improved sleep quality but decreased slow-wave time. Still, we found a positive correlation between the two effects. Apparently improved sleep quality correlates to less decrease of slow-wave time. This can be explained by assuming that the detected co-variation (correlation coefficient 0.52, p<0.02) between the spindle and slow-wave gene...
Article
Low-frequency EEG was analyzed quantitatively during 2 nights in 40 females and 34 males aged 26 to 101 years. Analyses were based on Rechtschaffen and Kales NREM sleep stages, on absolute low-frequency amplitude (i.e. power in the range of 0.2–2.0 Hz) and on low-frequency continuity. The latter parameter describes how much (0–100%) of the current...
Article
Although various investigators have suggested algorithms for the automatic detection of eye movements during sleep, objective comparisons of the proposed methods have previously been difficult due to different recording arrangements of different investigators. In this study the results of five eye movement detection algorithms applied to the same d...
Article
The task group on Signal Analysis within the EC Concerted Action 'Methodology for the analysis of the sleep-wakefulness continuum' has proposed general guidelines for a computer-based sleep analyser that would not suffer from the most conspicuous limitations of manual standard scoring. The proposal specifies a standard format for digitized polygrap...
Article
A simple digital format supporting the technical aspects of exchange and storage of polygraphic signals has been specified. Implementation of the format is simple and independent of hard- or software environments. It allows for any local montages, transducers, prefiltering, sampling frequencies, etc. At present, 7 laboratories in various countries...
Article
The study was designed to investigate sleep-wake patterns in healthy elderly men and women (greater than 88 years) using ambulatory recording techniques. Cross-sectional observations on 2 consecutive days. Two consecutive 24-hour recordings were made. Each 30-second period of the recording was scored as characteristic of wakefulness, REM, and non-R...
Article
Processing of complex information by the brain desynchronizes neuronal cells and therefore increases the unpredictability of the EEG, rather than its amplitude or power. A model of this mechanism describes the EEG as being composed of both an unpredictable fraction and a fraction that can be predicted from the past EEG. The model realistically simu...
Article
We report here the first sleep deprivation study done on a group of 5 healthy students (1 female, 4 males, 23-24 years of age) while playing a game (Triviant). In 2 persons an EEG was recorded for 6 consecutive 24 h periods with an ambulatory monitor from the baseline night until 72 h after deprivation. The baseline night showed normal hypnograms....
Article
Full-text available
Evaluations were made of the diurnal variations of tremor power at rest, after fatigue and after mass loading, and plasma norepinephrine in patients with familial essential tremor and normal subjects. Diurnal tremor power rhythms for both essential and physiological tremor pursued identical temporal profiles. Plasma norepinephrine levels followed a...
Article
Les auteurs ont enregistré pendant 40 jours ľélectroencéphalogramme de façon continue, pendant la veille et pendant le sommeil, au moyen de 4 électrodes posées sur le scalp. Les électrodes n'ont entraîné aucune lésion, aucun inconfort ni artéfactbien qu'elles aient été utilisées en partie sous des conditions arctiques. Les caractéristiques du somme...
Article
Sleep-wakefulness (S-W) patterns were recorded continuously for 40 consecutive 24 h using subcutaneous chronic electrodes and an ambulatory cassette recorder in a healthy 57-year-old volunteer. Variability of sleep patterns was assessed in steady-state conditions and in the course of a scientific journey encompassing flights in both west/east and s...
Article
A model of sleep phasic events such as vertex waves, K complexes, delta waves and sleep spindles is proposed. It consists of feedback loops that are driven by white noise (simulating tonic delta and sigma activity) and by isolated random impulses, simulating vertex waves or K complexes, depending on the background tonic activity. A model-based meth...
Article
Episodic nocturnal phenomena represent a separate cluster of disturbances within the classification of sleep disorders. The reported case history covers paroxysmal signs occurring secondary to a REM-dependent mixed sleep apnoea syndrome. The pathophysiology of similar episodes in elderly (non)epileptic patients is discussed. Ambulatory monitoring i...
Article
K-complexes play an important role in sleep research. However, their analysis is hampered by an unknown physiological basis, functional meaning, and lack of a morphological definition. During slow-wave sleep they can, if present, hardly be distinguished from spontaneous delta-wave activity. Kcomplexes often occur without any apparent provocation bu...
Article
Neurophysiological signals (such as the EEG and the EMG) are usually recorded in order to obtain relevant information about the state (be it physiological, psychologi-calor pathological) of the underlying systems. However, in general, this information is hidden in noise. Besides, these neurophysiological signals are recorded at a rate of several ki...
Chapter
Methods for analyzing sleep should preserve the relevant information about the physiological sleep mechanism while removing the “noise”. Several probabilistic models of sleep and sleep-related signals (such as EEG, EOG, and EMG) differentiate the part of recorded signals that is noise from the part that reflects the relevant state (physiological, d...
Article
The purpose of this study is to investigate whether the international standard electrode placement (C4-A1) can be replaced by an alternative placement (Fpz-Cz/Pz-Oz) in an automatic sleep monitoring system without losing Rechtschaffen and Kales (R-K) balances. Single night-sleep polygraphic recordings of 10 patients, screened in a clinical sleep di...
Article
The effect of a single dose (30 mg) of Org 3770 (metirzapine) on human sleep was assessed in a double blind, placebo controlled, cross over study in 6 young, healthy male volunteers. The sleep stage classification was based on visual scoring of 24 h electroencephalographic recordings according to the criteria of Rechtschaffen and Kales. Org 3770 30...
Article
It was hypothesized that the daily intake of a geriatric preparation containing vitamins, minerals, trace elements and ginseng, would strengthen the sleep‐wake rhythm and thus have a positive influence upon characteristics of sleep. A total of 32 subjects (age 61 ‐92, mean 78 yr, 23 females) was recruited from a local elderly home. In a double‐blin...
Article
Problems associated with the determination of signal spectra in real time with the aid of computers due to time expenditures are considered. A simpler solution is suggested which requires only the determination of spectral changes. A circuit is described which can be used for determining and measuring such changes.
Article
A muscle fatigue indicating parameter is proposed, which can be computed from the surface EMG in real time by a simple analogue device. It is compared with the well known offline algorithms that are currently in use. It is fairly robust and a relatively good indicator.
Thesis
Full-text available
Probabilistic models of sleep and of the sleep-related activity of brain, eyes and muscles have been proposed. These models describe how the corresponding overnight recordings of electroencephalogram (EEG), electrooculogram (EOG) and electromyogram (EMG) signals are influenced both by chance and by the various sleep stages. On the basis of these mo...
Article
Stochastic models are proposed for sleep and for the sleep related electroencephalogram (EEG), electrooculogram (EOG), and electromyogram (EMG). The evolution of sleep through its various stages is described as a Markov chain. The EEG is modelled using Wiener processes. The EOG and EMG are modelled as combinations of Poisson point processes and Gau...
Article
Probabilistic models of sleep and of the sleep-related activity of brain, eyes and muscles have been proposed. These models describe how the corresponding overnight recordings of electroencephalogram (EEG), electrooculogram (EOG) and electromyogram (EMG) signals are influenced both by chance and by the various sleep stages. On the basis of these mo...
Article
A Markov chain model has been proposed as a mechanism that generates human sleep stages. A method for estimating the parameters of the model, i.e., the transition probabilities (rates) between sleep stages, has been introduced and applied to 95 hypnograms taken from 23 subjects. The rates characterize interindividual differences and nightly variati...
Article
A model has been proposed for the stochastic occurrence of bursts of rapid eye movements (REMs) during sleep. REM-burst are simulated by a Poisson counting process with a rate that depends on a binary Markov "sleep state". The corresponding maximum likelihood detector, that continuously monitors the current sleep state based on the observed REM-bur...
Article
In 143 normal subjects latencies of H-reflexes of the flexor carpi radialis muscle were well correlated with arm lengths. In 32 patients with injury to cervical roots C5 to C8 it was shown that latencies were only abnormal in lesions of roots C6 or C7. It is suggested that in most instances root C6 or C7 and, probably both roots in some cases are i...
Article
A model has been proposed for a Markov-jumping sleep depth that modulates a white-noise driven structure generating the sigma rhythm in the electroencephalogram. The corresponding maximum likelihood monitor, that continuously detects the current sleep stage from the observed electroencephalogram, has been derived and implemented. Simulations show h...
Article
An accurate method for measuring flash evoked alpha attenuation has been derived, based on a model of the alpha generator. The method has been applied to 10 healthy volunteers in order to determine their alpha attenuation latencies (AALs). For the 9 subjects which showed at least some alpha rhythm, the AAL group mean is 95 msec. The AAL inaccuracy...
Article
A device for quantification of involuntary body movements is described. Patients are situated within the low-intensity radiation beam of a Doppler radar motion transducer. This device converts all body movements into one electrical signal which contains information on the size and trajectory of the moving parts of the body. This signal is processed...
Article
A simple and effective method is described to quantify involuntary movements. The method is based on the Doppler radar principle. Reproducibility of the method is demonstrated in a group of patients with Huntington's chorea and Tardive Dyskinesia. It is shown that the method correlates with clinical assessments, but is preferable because of its obj...
Article
In 40 controls and 19 patients with neoplastic lesions of the eighth cervical and first thoracic nerve roots confirmed by myelography, ulnar F-wave conduction velocity (FWCV) was estimated using the shortest F-wave latency (FWL). F-waves were recorded from needle electrodes inserted in the abductor digiti minimi manus muscle after stimulation of th...
Article
Twenty-two patients with Huntington's chorea were investigated in a double-blind controlled cross-over trial. The effect was measured by counting the number of involuntary movements from video-recordings and by a Doppler-radar device. Besides these methods, subjective assessments were made on analogue scales by patients, family, nurses and attendan...
Article
The effect was measured by a Doppler-radar device and by counting the number of involuntary movements from video-recordings. Besides these methods, subjective assessments were made on analogue scales by family, nurses and attendant doctors. The subjective evaluation appeared to be useless because of many inconsistent answers. The quantitative metho...
Article
A model of the EEG with waxing, waning and blocking alpha rhythm is described. One parameter is time dependent and simulates the ‘physiological alpha state’ of the EEG generating network.A theoretically optimal detector of this state appears to be described by the model and the statistics of the alpha state parameter. It minimizes the expected fals...
Article
Five patients with unilateral posterior fossa tumors were investigated with Auditory Brainstem Evoked Responses (B.E.R.). The B.E.R., recorded from the ear ipsilateral to the tumor, were consistent with a lesion of the acoustic nerve or the cochlear nuclei in all patients. The contralaterally evoked responses in four patients with large tumors and...
Article
When linear relationships between bio-electrical signals have to be established, it is important to consider the possible influence of noise added to these signals during recording and processing. Using a model for the signal generation (Fig. 1A) and one for the signal processing (Fig. 1B), the influence of uncorrelated noise in parallel signal pro...

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