Surgery – Diagnostic testing – Detecting brain electric signal
Reexamination Certificate
2001-01-17
2003-05-06
Gilbert, Samuel G. (Department: 3736)
Surgery
Diagnostic testing
Detecting brain electric signal
Reexamination Certificate
active
06560479
ABSTRACT:
FIELD OF THE INVENTION
The present invention pertains generally to medical monitoring methods and devices for analyzing and displaying electrophysiologic signals, and more particularly to systems and methods for connecting and disconnecting electrophysiologic signals detected at electrodes placed on a subject to and from detection amplifiers employed in such a medical monitoring device.
BACKGROUND OF THE INVENTION
Medical monitoring involves monitoring the body of a subject to determine the state of health of the subject and to detect, identify, and diagnosis changes or abnormalities in the state of the body which may be indicative of problems, or for treatment evaluation. Medical monitoring may involve, for example, the motion of a subject's body, temperature or chemical changes of the subject's body, and/or audible or electrical signals reflected or generated by the subject's body. For example, electroencephalography (EEG) is a form of medical monitoring wherein the electrical potentials of the subject's brain are monitored by attaching electrodes to the subject's scalp. In electromyography (EMG), electrical activity generated in the subject's muscles is monitored using surface and/or needle recording electrodes. Medical monitoring may take place when a subject is at rest, in motion, or during the performance of a medical procedure. In some cases, medical monitoring involves monitoring the response of a subject to a stimulus. For example, evoked potential (EP) monitoring may be used to detect the electrical response of a subject's nervous system to audible, visual, or electrical stimuli. Medical monitoring involving stimulus and response detection may be used in combination with EMG and various other medical monitoring methods as well.
Monitoring of the various physiologic signals generated by a subject's body is typically performed using dedicated devices and/or systems. For example, EEG monitoring may be performed using a dedicated EEG monitoring system, by attaching electrodes to a subject to detect the electrical potential of the subject's brain, amplifying and filtering the signals received from the electrodes for the desired frequency range of interest for EEG analysis, and providing the amplified and filtered signals to an EEG analysis system including software for further manipulating the EEG signals for analysis and display on an EEG system monitor. Similarly, EMG monitoring may be performed using a dedicated EMG monitoring system, by placing electrodes on the subject to detect electrical activity generated in the subject's muscles, amplifying and filtering the signals detected by the electrodes for the desired frequency range of interest for EMG signals, and providing the amplified and filtered signals to an EMG analysis system including software for further manipulating the EMG signals for analysis and display on an EMG system monitor. Other signals of interest, e.g., vital signs, may be monitored in a similar manner, with a separate dedicated system provided for each type or modality of monitored signal of interest. Each such dedicated monitoring system may include or be connected to a system for providing stimulus to a subject, and for analyzing the particular detected signal of interest in response to the stimulus provided.
U.S. patent application Ser. No. 09/295,167, entitled “Medical Signal Monitoring and Display”, by Wim Van Drongelen, and assigned to the assignee of the present application, describes a medical signal monitoring system and method providing the capability for an operator of the system to display and analyze physiologic signals of various types, frequencies, and modalities. Such a system may be provided with data from various physiologic signal acquisition systems, including systems for acquiring electrophysiologic signals from electrodes positioned on the subject. The system may further be connected to auditory, visual, and/or electrical stimulator systems, for controlling the providing of stimulation to a subject, while analyzing the physiologic signals received in response to the stimulus provided. Such a system includes an operator-friendly user interface which allows an operator of the system to designate and control, display, and analyze the physiologic signals received by the system and stimulus provided thereby. Such an integrated system provides a full range of diagnostic capability in a single device for use in a doctor's office, operating room, intensive care unit, or emergency department.
In a typical application of a medical signal monitoring system, a plurality of electrodes may be attached to the body of a subject. Electrophysiologic signals, picked up by the electrodes, are carried by leads to a signal amplifier which may be part of or separate from the medical monitoring system. Typically, the signal provided on each such lead is amplified by a separate amplifier. The amplified signals may, for example, be filtered, digitized, and provided to the medical monitoring system for analysis and display. In this manner, several electrophysiologic signals, e.g., EEG and EMG signals, produced by a subject may be monitored continuously or periodically.
At times, it may be desirable to determine a subject's response to an electrical signal applied to the subject (e.g., transcranial electric stimulation). A strong (high voltage) electrical signal applied to a subject's body will be picked up by electrodes placed on the subject for detecting electrophysiologic signals. The stimulation signal will typically be much larger than any electrophysiologic signal produced by the subject's body, especially in the area near where the electrical stimulation is provided. Thus, the electrical stimulation will tend to saturate the amplifiers which are connected by leads to electrodes placed on the subject near the point of electrical stimulation. Such over-saturation prevents recording of the response to the stimulation and may damage the amplifiers. Thus, to protect the amplifiers from damage, electrodes attached to a subject's body near the point of electrical stimulation (and which are not used for monitoring the subject's response to the stimulation) are typically physically removed from the subject before the electrical stimulation is provided to the subject. This situation is typical for a multi-modality monitoring device. By disconnecting selected electrodes from a subject, responses occurring at other electrodes can be recorded and potential damage to the amplifier is prevented. After the electrical stimulation is provided, these electrodes must be reattached to the subject if monitoring of the desired electrophysiologic signals is to continue. Thus, in a situation where it is desired to continually monitor certain physiologic signals, while periodically performing tests involving the application of electrical signals to a subject, it may be necessary to repeatedly physically remove electrodes from a subject (or remove the amplifier inputs), before electrical stimulation, and reattach the electrodes to the subject (or reattach the amplifier inputs), after stimulation is completed. This process is obviously time-consuming, and prone to error, as each time an electrode is removed from a subject there is the possibility that the electrode will not be placed back in the proper position on the subject (or reattached to the correct amplifier input).
What is desired, therefore, is a system and method for easily and quickly disconnecting electrophysiologic signals provided from electrodes attached to a subject from the amplifiers to which such signals are provided, when desired, such as before applying an electrical stimulation signal to the subject, and for easily and quickly reconnecting the electrophysiologic signals to the amplifiers after electrical stimulation is complete. Preferably, such a system and method provides for disconnecting electrophysiologic signals from the amplifiers without physically removing the electrodes from a subject or physically removing electr
Foley & Lardner
Gilbert Samuel G.
Viasys Healthcare Inc.
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