Patent Application
20100185115
The present invention relates in general to electrode apparatus and methods for measuring bio-potentials in human individuals, and more particularly to apparatus including means for providing stimuli and methods of using the apparatus for measuring evoked bio-potentials in human individuals.
When multiple nerve cells or muscle cells depolarize simultaneously or sequentially, they generate a bio-potential that can be detected as an electrical signal by an externally positioned electrical circuit. External electrical circuits have long been used to measure such relatively small but measurable bio-potentials. The electrocardiogram (ECG or EKG), electromyogram (EMG), electroencephalogram (EEG), and Auditory Evoked Potentials, (AEP) are examples of systems and methods using such circuits to monitor, respectively, cardiac contractions, muscle contractions and brain cell activity.
Electrode apparatus for recording bio-potentials, for example for EEG biofeedback applications, include a minimum of one pair of electrodes, and a third electrode as the ground electrode. The pair of electrodes, including an “active” electrode and an “indifferent” electrode, record one channel of EEG signal. The active electrode is typically located on the head near a brain area being monitored, the indifferent electrode is located on the head, on an ear, or on the mastoid bone behind an ear, and the ground electrode is typically placed on the forehead or on an ear, but can be placed almost anywhere. Additional recording channels can be added as desired by adding additional electrodes.
Known electrodes and related apparatus for recording bio-potentials such as EEG's are disposable electrodes such as, but not limited to, disposable self-adhesive electrodes, ear clip electrodes, disc electrodes, needle electrodes and saline-based electrodes. With all types of electrodes, a key factor in obtaining accurate and relatively noiseless bio-potential recordings is maintaining adequate contact between the electrode and the skin, because bio-potentials are typically relatively small, i.e. less than about 20 mV, and the recordings are highly susceptible to noise and artifacts.
While the methods of ensuring proper electrical contact between the electrode and the skin vary somewhat with the type of electrode being used, the skin usually must be prepared by cleaning with alcohol and abrading with an electrode preparation gel. The steps of cleaning and abrading may be repeated several times for ideal surface preparation. Skin contact is established using an ear clip electrode with a metal clip that fastens to the outer ear, a self-adhesive disc electrode that adheres directly to an area of skin, or with a disc electrode having a cup that is filled with an electrode paste. These types of electrodes are unsuitable for use in areas with much hair, such as on the scalp, and generally provide electrical contact that is not very robust or long lasting, which affects the quality and duration of recordings that can be obtained.
Needle-type electrodes generally provide better and more long-lasting contact, and can be used on the scalp, but involves tedious, uncomfortable and costly procedure to secure contact. To utilize a needle-type electrode, the hair must be parted to reveal skin, a colloidin-treated gauze layer secured over the electrode, electrode gel injected with a hypodermic needle through a hole in an electrode cup, and finally the skin abraded with the blunt end of the needle. Headband-type and hat-style electrode connectors are known, in which electrodes, such as those described above, are coupled to a hat, or to a headband made of an elastomeric material that fits around the crown of the head, holding cup or disc-type electrodes in place across the forehead of the subject. Headband-type electrode connectors are typically used for recording signals from the frontal areas of the brain, and are less useful for recording from other areas of the brain because of the relatively poor signal quality that results. In addition, headband connectors still require careful skin preparation.
Saline-based electrodes are also known, in which salt water is used to maintain the electrical connection between electrode and skin, instead of electrode gel. An electrode connector such as a headband or clip is required for securing the electrodes to the head, and skin preparation is still required. Further, to maintain the proper electrical contact, the electrode placements must be carefully monitored to ensure that the mechanical contact is maximized and that the electrodes stay sufficiently wetted with the saline-based solution.
Each of the above-described electrodes and electrode apparatus may be utilized to monitor and record bio-potentials. The bio-potentials may be continuous, representative of normal brain activity, or may be evoked in response to an external stimuli. External stimuli may be provided to any of the sensory systems of a human body, and may include auditory stimuli, visual stimuli, olfactory stimuli, tactile stimuli, and gustatory stimuli, delivered by a suitable delivery mechanism. Conventionally, the delivery mechanism for the external stimuli is separate from the electrodes employed to measure the evoked response, requiring additional setup and handling.
Known electrode apparatus and connectors are therefore limited by being annoying or uncomfortable for the subject, especially when, placed on the head. With the additionally requirement of setting up a stimuli delivery system, the task can quickly become unduly complicated and time consuming. The discomfort or apprehension associated with the setup is a particular problem for children, infants, and uncooperative subjects. Interference by an uncooperative subject with the placement and contact of head electrodes can render recordings of evoked brain potentials impossible to obtain or useless because of minimal or inadequate contact.
A need therefore exists for an electrode apparatus configured adapted to deliver stimuli for measuring evoked potentials which is simply and comfortably positioned on the subject, which maintains adequate skin contact for obtaining measurable recordings, and which is readily and inexpensively adapted for use with small children and infants.
An apparatus of the present invention is provided for evoking and measuring bio-potentials in a human subject. In a preferred embodiment, the apparatus includes at least one flexible member having a first surface and a shape adapted to maximize a contact area between the first surface and a selected skin surface on the human subject. At least one electrode is disposed on the first surface and positioned to make contact with the skin surface of the subject when the flexible member is disposed on the skin surface. A stimulus delivery element is coupled to the flexible member. The apparatus is used for both evoking and measuring evoked bio-potentials in the human subject, or for measuring bio-potentials evoked using a separate stimulus delivery system.
In an alternate embodiment, an apparatus is provided for evoking and measuring bio-potentials in a human subject. The apparatus includes a flexible member having a first surface and a shape adapted to maximize a contact area between the first surface and a selected skin surface of the human subject. A detector is provided for detecting evoked bio-potentials disposed on the flexible member first surface and positioned to make contact with the skin surface of the subject when the flexible member is disposed on the skin surface. A means for delivering a sensory stimulus for evoking the bio-potentials is coupled to the flexible member. The detector consists of at least one electrode, which is, for example, a layer of conductive material. The means for delivering a sensory stimulus for evoking the bio-potentials is configured for delivering either an auditory stimulus, a tactile stimulus, a gustatory stimulus, a visual stimulus, or an olfactory stimulus.
In a second alternate embodiment, the apparatus of the present invention is configured for measuring bio-potentials in a human subject and includes a flexible ear cup. The flexible ear cup defines a central space for receiving an outer ear of the subject and includes at least one surface peripheral to the central space on which an electrode is disposed to make contact with a skin surface adjacent the outer ear of the subject when the ear cup is disposed on the ear of the subject.
In a third alternate embodiment, the invention is directed toward a method of evoking and recording bio-potentials in a human subject. A flexible member is adapted to maximize a contact area between a surface of the flexible member and a selected skin surface on a human subject. At least one electrode is disposed for detecting the bio-potentials on the flexible member first surface.
The foregoing and other objects, features, and advantages of the invention as well as presently preferred embodiments thereof will become more apparent from the reading of the following description in connection with the accompanying drawings.
In the accompanying drawings which form part of the specification:
Corresponding reference numerals indicate corresponding parts throughout the several Figures of the drawings.
The following detailed description illustrates the invention by way of example and not by way of limitation. The description clearly enables one skilled in the art to make and use the invention, describes several embodiments, adaptations, variations, alternatives, and uses of the invention, including what is presently believed to be the best mode of carrying out the invention.
Novel apparatus for evoking and measuring bio-potentials in a human subject and methods of use are described. In a preferred embodiment, an apparatus of the present invention includes at least one flexible member having a surface and a shape adapted to maximize a contact area between the surface and a selected skin surface on the human subject. At least one electrode is disposed on the surface and positioned to make contact with the skin surface of the subject when the flexible member is disposed on the skin surface. A stimulus delivery element is coupled to the flexible member to provide a stimulus to the human subject. The dimensions and shape of the flexible member are adapted to the specific use, i.e. type of bio-potential being measured.
More specifically, the dimensions and contours of the flexible member are adapted to conform to different surfaces on the subject's body depending on the type of bio-potential being recorded. For example, for recording auditory evoked potentials, the flexible member is adapted as a flexible ear cup that fits over the outer ear of the subject, or as an ear probe adapted for seating within the outer ear canal. For recording bio-potentials from orbital muscles attached to the eye, the flexible member is adapted as an eyecup or patch that contacts a periorbital skin surface.
A flexible member 18 including a central opening 20 which defines the central space 14.
For example, a flexible member having a semicircular, crescent shape or U-shape is also contemplated. Further, the overall dimensions of flexible member 18, the size of central opening 20, and thus also the extent of surface 16 is adaptable, to accommodate different head and ear sizes. More specifically, sizes of the elements are adapted so that the central opening receives the ear of the subject, and the flexible member fits around the outer ear of the subject so that electrode 12 on surface 16 makes contact at least with the skin over the mastoid bone of the human subject.
An ear cup 10 specifically adapted for use with infants and small children is formed in a relatively smaller size than one which would be used for adults. In particular, central space 14 and surface 16 are suitably proportioned to maintain ear cup 10 in a position that is sufficient to maintain contact of electrode 12 with an area of skin surrounding or merely adjacent to the outer ear of the subject. Thus, it will be clear that ear cups adapted for use with human infant subjects include a central space 14 and surface 16 that are suitably proportioned to maintain ear cup 10 in a position on the infant subject that is sufficient to maintain contact of electrode 12 with the area of skin surrounding or merely adjacent to the ear of the infant subject.
Flexible member 18 is fabricated from a material that can be flexibly adapted to maximize contact of electrode 12 on surface 16 with the selected area of skin, e.g. a skin surface adjacent to or surrounding the ear of the subject, such as any position along the mastoid or skull suitable for obtaining auditory evoked potentials. Any flexible material is suitable but especially suitable are resiliently compressible materials such as a closed-cell rubber material or a closed-cell synthetic foam material or the like. Other flexible materials such as rubberized materials, open-cell rubber, neoprene, stretch fabric impregnated with a rubberized material, or the like, can also be used. Also suitable are gel materials, such as a co-polymer gel or a silicone gel.
Electrode 12 is preferably formed as an annular layer of conductive material disposed on surface 16. The conductive layer defines a central opening for receiving an outer ear, wherein the central opening through the metal layer is aligned with central opening 20 through flexible member 18. Any conductive metal commonly used for surface electrodes can be used to fabricate electrode 12, and in one embodiment the conductive material is copper metal.
Alternatively, the conductive layer is a layer of conductive electrode gel or paste. The precise shape, and disposition of electrode 12 on flexible member 18 can be varied, subject only to the requirement that the conductive layer remains sufficiently pliable for the flexible member to conform to the skin surface of a human subject. More specifically, if the conductive layer is fabricated from a conductive metal such as copper metal, the metal layer must be sufficiently thin to be flexibly adjustable for maximizing the area of contact between the conductive layer and the area of skin around the outer ear of the subject. Alternatively, the relative size of electrode 12 with respect to flexible member 18 can be varied so that electrode 12 occupies only a fraction of surface 16, thus maintaining the flexibility of ear cup 10. In such a case, a relatively smaller electrode 12 is most suitably positioned on surface 16 so that in use, electrode 12 makes contact with an area of skin behind the ear, over the mastoid bone of the subject.
However, in the embodiment shown in
While the apparatus is adaptable for recording any bio-potentials, ear cup 10 as shown in
Optionally, the miniature speaker 28 may be disposed remotely from the ear cup 10, and operatively coupled thereto via a tube or other acoustic wave guide. This would permit a single miniature speaker 28 to be disposed remotely from the patient, and provide auditory stimuli to each ear of the patient simultaneously through an interconnecting tube or wave guide.
In alternative embodiments adapted for evoking and measuring other types of bio-potentials, other types of stimulus delivery elements are used in accordance with the type of bio-potential being measured. Visual stimulus may be provided using a light source such as an LED or multiple LED's. Tactile stimulus may be provided by a needle or textured surface. Olfactory stimulus may be provided by a nozzle or pipette configured to deliver a puff of gas or aerosolized scent, and gustatory stimulus may be provided by a mouthpiece, straw, or tube configured for delivering a sample of a liquid to be tasted.
In use for measuring bio-potentials, an electrode lead or leads 29 is secured to electrode 12 for example by a metal clip or solder, and the lead or leads are coupled to suitable data acquisition equipment as known, such as an amplifier and computer with software configured for real-time data acquisition. The ear cups are especially useful in combination with computerized auditory screening devices that use the ABR signal as a basis for determining hearing loss in infants, such as the AUDIOscreener™ commercially available from Everest Biomedical Instruments Company of Chesterfield, Mo.
An ear cup 10 is fitted over each ear of the subject and manually adjusted, taking advantage of the flexibility of ear cup 10 so that electrode 12 makes adequate contact with an area of skin surrounding, or adjacent to, the ear. A third, ground electrode such as a disc electrode, with a ground lead, is secured to the forehead of the subject and the lead coupled to the data acquisition set-up. Spontaneous brain activity can then be recorded. For evoked potentials, a stimulus or series of stimuli is introduced, and resulting bio-potentials are detected by the electrodes. As explained above, auditory stimuli for evoking auditory responses, such as a series of tones or tone bursts, are introduced through speaker 26 and the resulting auditory evoked potentials, including ABR are recorded.
In an alternate embodiment of the ear cup, a second opening through flexible member 18 is provided for receiving a miniature microphone for recording evoked otoacoustic emissions (OAF).
Auditory stimuli are introduced through speaker 26 and the resulting auditory evoked potentials, including ABR as well as OAE are recorded and analyzed to determine hearing loss.
The invention is further directed towards a headset with ear cups for recording bio-potentials in a human subject.
As shown in
In an exemplary embodiment, the flexible headband is fabricated from a resiliently flexible plastic material and is adjustable in size to adapt to different head sizes, particularly the dimensions of the head across the crown of the head top from ear to ear. Alternatively, headband 202 may be fabricated from any suitable resiliently flexible material including a vinyl, rubber or rubberized material, or any combination thereof. As used herein, the term “resiliently flexible” refers to the characteristic of a material that allows the material to be bent from a starting configuration without breaking, and then to return to the starting configuration. The size adjustment is achieved, for example by having two separate but slidably engaged elements that are manually positioned with respect to one another as is well known in the art of lightweight plastic headphones.
For example, each ear cup 10 may simply mounted on each end of headband 202 using an adhesive to bond the end of headband 202 to flexible layer 24. However, any number of attachment means might also be used to couple ear cup 10 to headband 200. For example, using releasable attachments for each ear cup 10 permits either the ear cups 10 or the headband 202 to be removed for replacement or discarding. Optionally, the ear cups 10 may be secured to the patient using a releasable medical adhesive, eliminating the need for a headband 202.
A ground electrode 212 is disposed on a central support member 214 that extends from the flexible headband 202. Central support member 214 is configured to maintain contact between ground electrode 212 and an area of skin on the forehead of the subject. While multiple configurations will satisfy this last requirement, an exemplary embodiment includes central support member 214 extending anteriorly with respect to the subject's head, and in a downward curve that brings electrode 212 into contact with an area of skin on the subject's forehead. Electrode 212 is secured, for example, with adhesive, or with a detachable connector, to the undersurface of central support member 214, and positioned to make contact with an area of skin on the subject's forehead.
In an alternative embodiment, as shown in
Headset 200 further includes a lead or cable 220 for electronically coupling first ear cup electrode 208, second ear cup electrode 210 and ground electrode 212 to biofeedback monitoring apparatus. In accordance with the ear cup shown in
In the alternative embodiment of headset 200, as shown in
In an additional embodiment of the present invention, shown in
Bio-potentials generated by the human subject in response to the auditory stimuli are received by an electrode 316 preferably formed as an annular layer of conductive material disposed on the hemispherical shaped head 308. The conductive layer Any conductive metal commonly used for surface electrodes can be used to fabricate electrode 316, and in one embodiment the conductive material is copper metal. Electrode 316 is disposed on the hemispherical shaped head 308 such that when the ear probe 300 is seated within the ear canal of a human subject, the electrode 316 is in operative contact with skin surfaces to receive and detect bio-potentials generated in response to the auditory stimuli. Signals from the electrode 316 are routed through detachable contacts 318 between the hemispherical shaped head 308 and the elongated neck portion 304 of the ear plug 300, and conveyed via internal an internal lead 320 to the data acquisition equipment for subsequent processing. Those of ordinary skill in the art will recognize that the hemispherical shaped head 308, and associated electrode 316 are configured to be removed from the elongated neck portion 304, for disposal and replacement.
In an alternate configuration, shown in
As a method of providing electrodes for measuring bio-potentials in a human subject, at least a first electrode is disposed on a first flexible ear cup. The first ear cup is positioned on a human subject to receive a first outer ear of the human subject and to maintain a position on the outer ear sufficient to maintain contact of the first electrode with a skin surface adjacent to the first outer ear. Depending on the age and cooperativeness of the subject and type of bio-potential being measured, a second electrode is also provided disposed on a second flexible ear cup. The second ear cup disposed to receive a second outer ear of the subject and to maintain a position of the second ear cup on the second outer ear sufficient to maintain contact of the second electrode with a skin surface adjacent to the second outer ear. Alternatively, the second electrode and ground electrode are disposed as conventional surface electrodes on the skin of the human subject, and are not disposed on a second ear cup.
Alternatively, the first ear cup and second ear cup are provided disposed on a flexible headband as described above, and the headband is fitted over the head of a human subject such that the first ear cup receives a first outer ear of the human subject and the second ear cup receives a second outer ear of the human subject. A ground electrode is provided on a central support member as described above, and brought into contact with the human subject's forehead skin. Alternatively, a ground electrode separate and apart from the headband is secured in a conventional manner to skin on the forehead.
During use, each ear cup 10 is fitted over an outer ear of the human subject so that contact is maintained between the electrode and the skin surface. The flexibility of the ear cup flexible member is used advantageously to adjust the ear cup to conform to the subject's surrounding bone structure. A stimulus, such as an audible tone or pulse, is provided to the human subject, through first speaker disposed on the first ear cup and a second speaker disposed on the second ear cup. Bio-potential responses from the human subject are detected through the electrodes. Alternatively, oto-acoustic emissions evoked in response to the stimulus may be recorded via first and second microphones disposed in the first and second ear cups.
In view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results are obtained. As various changes could be made in the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 10545221 | Apr 2006 | US |
| Child | 12710603 | US |
