Surgery – Diagnostic testing – Detecting brain electric signal
Reexamination Certificate
1999-05-20
2001-08-07
Nasser, Robert L. (Department: 3736)
Surgery
Diagnostic testing
Detecting brain electric signal
Reexamination Certificate
active
06272378
ABSTRACT:
The invention relates to a device and a method for the determination of sleep profiles.
In the current state of research and therapy, diagnosis of chronic and severe disturbances of sleep are secured by carrying out polygraphic tracings during the night by means of EEG-amplifiers, in laboratories which are specially equipped for this purpose. Trained and experienced personnel are required for operating such laboratories, including mainly polygraph assistants and sleep stage scorers. The latter carry out a visual sleep stage classification according to the rules of Rechtschaffen and Kales on the basis of at least one central EEC-lead, one EMG-lead and one EOC-lead.
Now, a sleep analyzer based on one single EEG-channel with a classic central lead position is introduced in U.S. Pat. No. 5,154,180. In connection with this method, the user himself has to preset by experimentation a threshold that substantially influences the number of resulting classifications and thus the number of resulting sleep stages.
A further significant drawback of this solution is that the method introduced in U.S. Pat. No. 5,154,180 corresponds with a cluster method, which by nature is not capable of realizing nonlinear associations of EEG-epochs with sleep stages because no sleep profile usable for diagnostic purposes can be generated solely from similar characteristics. Therefore, it is not possible on the basis of said solution proposed in U.S. Pat. No. 5,154,180 to generate a sleep profile that is comparable with a sleep profile developed by sleep experts.
Now, another method for the automatic classification of sleep stages is introduced in U.S. Pat. No. 5,299,118 that is not afflicted with said drawbacks. Every effort is made in connection with said method to offer all potentially available information and to create a system that satisfies the highest requirements. With respect to extraction of characteristics, said system contains everything that corresponds with the international state of system analysis of the year 1991. The method itself is based on 64 analog channels and operates with very high expenditure in terms of storage and computer capacities. The realization of said solution is consequently connected with relatively high costs and therefore preferably reserved for stationary application in sleep laboratories.
Furthermore, the employment of this system requires an acclimatization phase on part of the patient as well, who has to get used to both the changed environmental conditions of the sleep laboratory and the multitude of electrodes attached to the skull and face.
However, since sleep laboratories are available only in a very low number and tests in a sleep laboratory are, furthermore, very cost-intensive, it is necessary to make a tentative diagnosis before a patient is referred to a costly sleep laboratory.
In the current state of the art, no ambulatory equipment is available to the privately practicing physician for objectively evaluating the quality of sleep, and the physician is therefore dependent upon the subjective statements of his patients.
For example, the present state of tentative diagnosis consists in answering the questions of a questionnaire relating to subjective data on the medical history (sleep anamnesis) particularly concerning which type of sleep disorder is involved. In other cases, the tentative diagnosis is made with an ambulatory actometer. This instrument registers the movements of the arm and in this way supplies information about activity and rest phases during the sleep. Such methods, however, cannot supply any objective evaluation of the quality of sleep. Exact diagnosis and therapy derived therefrom, for example with medications require an objective evaluation. Patients currently much too often take sleep-inducing medications without having available to them an objective correlate with respect to their subjectively perceived complaints. Sleep profiles, as time series of sleep stages, supply this objective “copy” of the quality of sleep if interpreted in a suitable manner, and give clear indications of pathological processes.
Therefore, there is currently a worldwide demand for generating sleep profiles automatically with negligible discomfort to the sleeper caused by additional technical equipment in his or her ordinary environment in order to make available objective quality measures for the quality of sleep and to permit ambulatory diagnosis. Furthermore, the costs for ambulatory diagnoses are to be kept as low as possible. This can be accomplished especially when no trained medical technicians are needed for mounting the electrodes and for operating the equipment for data acquisition and data evaluation.
Furthermore, it has to be noted that in the state of the art, data on night sleep are exclusively collected by physiological methods, whereas data on the wake state are exclusively gathered with psychological parameters of behavior and the condition of being.
The falling-asleep behavior during the day and the performance became evaluable only with the very costly multiple sleep latency test (MSLT).
Therefore, the invention is based on the problem of developing a device and a method for the determination of sleep profiles, which automatically generate a sleep stage classification with a grading of about 85% (measured according to the crosscorrelation function between automatically and manually generated sleep profiles) with negligible discomfort to the sleeper caused by additional technical equipment in his or her normal environment, permitting in this way ambulatory diagnoses, whereby the newly development arrangement, furthermore, is characterized by minimal manufacturing expenditure as well as practical equipment technology with high operational safety and reliability that can be easily handled by each patient on his or her own, and which, moreover, is capable of registering even a 24-hour continuum in a physiologically objective manner by a simple method at favorable cost.
According to the invention, said problem is solved by an arrangement for the determination of sleep profiles. Said arrangement operates on the basis of one single frontal EEG-channel and consists of an electrode strip with a preamplifier (active electrode). Said electrode strip is placed on the forehead and is connected to an autonomously working measuring and analysis unit controlled by a microprocessor. Said unit, which is supplied with energy via a storage battery (accumulator), consists of analog filters, a final amplifier, an analog-to-digital converter, a microcontroller with internal system software, a memory, a display and an operating keyboard, and is connected for the further data analysis via a serial interface by means of a light conductor cable (potential separation) to a commercially available PC with special software for adaptive classification by means of populations of neural networks for visualizing the electric potentials of the brain as well as the sleep and awake profiles.
Said electric potentials of the brain are processed in real time by the measuring, storing and analysis unit controlled by the microprocessor. According to the invention, said device operates in two modes: the so-called off-line mode and the on-line mode. Said terms relate to the fact that it is possible to couple the unit with a computer, preferably with a laptop. Off-line mode means that the unit operates autonomously, whereby it detects the electric potentials of the brain, extracts and stores characteristics relevant to the classification, as well as classifies sleep stages, if need be in real time (provided they amount to 30 seconds), and stores such sleep stages as a function or time.
The highest stage of content-related data compression is reached through such generation of sleep profiles in real time. The off-line mode is the primary operating mode. Temporarily connecting the computer at the end of a night serves the purpose of generating the sleep profiles and their graphic display. The on-line mode requires continuous coupling with a separate unit for storing the original electri
2RCW GmbH
Collard & Roe, PC.
Nasser Robert L.
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