Patent Publication Number: US-2021169391-A1

Title: Electrode configuration to record ear electroencephalogram (eeg) during sleep and wakefulness

Description:
CROSS-REFERENCE TO PRIOR APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 62/945,507, filed on 9 Dec. 2019. This application is hereby incorporated by reference herein. 
    
    
     BACKGROUND 
     1. Field 
     The present disclosure pertains to apparatuses and methods that generate and record ear electroencephalogram (EEG) signals from the ear of a patient. 
     2. Description of the Related Art 
     Measurement of sleep and wake EEG patterns enables several applications in the consumer context to facilitate falling asleep and staying asleep, sleep staging and coaching, and monitoring wakefulness to predict sleep architecture and sleep quality. Current methods of EEG monitoring include placing electrodes at various locations of the scalp, or within both ears with a galvanic connection between the in ear electrodes. EEG monitoring with these types of existing devices does not facilitate effective real-time frequent measurement of EEG signals while a patient is asleep. Thus, accuracy and volume of useful data will be improved by unobtrusive devices that improve patient comfort during sleep. 
     SUMMARY 
     Accordingly, one or more embodiments provide an apparatus configured to generate an EEG signal from an ear of a patient in a minimally obtrusive manner, based on a signal at the concha of the ear referenced to a signal from within the same ear canal. The apparatus comprises a housing, a first electrode provided on a first portion of the housing, a second electrode provided on a second portion of the housing, and electronic circuitry provided within the housing. The first electrode is structured to be received within an ear canal of an ear of the patient, and to be disposed against a first surface of the ear canal when the first portion of the housing is received within the ear for generating a first ear canal signal. The second electrode is structured to be received within a concha of the ear when the first portion is received within the ear canal, and to be disposed against a surface of concha when the second portion is received within the concha for generating a concha signal. The electronic circuitry is structured and configured to receive the first ear canal signal and the concha signal, and to generate a first in ear signal based on the first ear canal signal and the concha signal. 
     It is yet another aspect of one or more embodiments to provide a method of generating an EEG signal from an ear of a patient. The method comprises generating, by a first electrode disposed against a first surface of an ear canal of the patient, a first ear canal signal; generating, by a second electrode disposed against a surface of a concha of the patient, a concha signal; receiving, with electronic circuitry, the first ear canal signal and the concha signal; generating, with the electronic circuitry, a first in ear signal by referencing the concha signal to the first ear canal signal; and generating, with the electronic circuitry, the ear EEG signal based on at least the first in ear signal. 
     These and other aspects, features, and characteristics of the present disclosure, as well as the methods of operation and functions of the related elements of structure and the combination of parts and economies of manufacture, will become more apparent upon consideration of the following description and the appended claims with reference to the accompanying drawings, all of which form a part of this specification, wherein like reference numerals designate corresponding parts in the various figures. It is to be expressly understood, however, that the drawings are for the purpose of illustration and description only and are not intended as a definition of any limits. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an isometric view of left and right ear pieces configured to generate an EEG signal from a patient according to an exemplary embodiment of the disclosed concept; 
         FIGS. 2A-2B and 3A-3B  illustrate exploded views of the left and right ear pieces illustrated in  FIG. 1 ; and 
         FIG. 4  is a schematic diagram of electronic circuitry for processing raw ear signals measured by the ear pieces in  FIGS. 1-3  to produce an EEG signal and transmit the signal to, for example, a receiver for further processing according to an exemplary embodiment of the disclosed concept. 
     
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     As used herein, the singular form of “a”, “an”, and “the” include plural references unless the context clearly dictates otherwise. As used herein, the statement that two or more parts or components are “coupled” shall mean that the parts are joined or operate together either directly or indirectly, i.e., through one or more intermediate parts or components, so long as a link occurs. As used herein, “directly coupled” means that two elements are directly in contact with each other. 
     As used herein, the word “unitary” means a component is created as a single piece or unit. That is, a component that includes pieces that are created separately and then coupled together as a unit is not a “unitary” component or body. As employed herein, the statement that two or more parts or components “engage” one another shall mean that the parts exert a force against one another either directly or through one or more intermediate parts or components. As employed herein, the term “number” shall mean one or an integer greater than one (i.e., a plurality). 
     Directional phrases used herein, such as, for example and without limitation, top, bottom, left, right, upper, lower, front, back, and derivatives thereof, relate to the orientation of the elements shown in the drawings and are not limiting upon the claims unless expressly recited therein. 
       FIG. 1  illustrates a pair of ear pieces  1 , left ear piece  2  and right ear piece  3 , each of which is configured to generate an EEG signal from an ear of a patient. Left ear piece  2  and right ear piece  3  contain identical components, but are shaped appropriately to fit securely within a left ear and a right ear, respectively. In some implementations, ear piece  1  is a unitary body while in other implementations, ear piece  1  is composed of separate components that can be combined securely to form one composite body. In one exemplary embodiment, ear piece  1  is composed of a cover  4  and an electronics casing  5 , such that cover  4  and electronics casing  5  are separate components that snap together securely to form one composite body.  FIG. 1  further illustrates a concha electrode  6 , a superior canal electrode  7 , and an inferior canal electrode  8  coupled to cover  4 . In some implementations, electrodes  6 ,  7 ,  8  may be integrated into removable flexible coverings that can be affixed to and removed from concha piece  9  and canal piece  10 , each forming respective parts of cover  4 . In all implementations, cover  4  has concha electrode  6  affixed to it, and additionally has either one or both of superior canal electrode  7  and inferior canal electrode  8  affixed to it. Concha piece  9  is structured to fit securely within the concha of the ear of the patient and canal piece  10  is structured to fit securely within the ear canal of the patient, such that electrodes  6 ,  7 ,  8  are in sufficient contact with the concha, superior portion of the ear canal, and inferior portion of the ear canal, respectively, in order to measure an electrical signal at each of those portions of the ear with efficacy. A secure fit of concha piece  9  and canal piece  10  is crucial to ensure that ear piece  1  will remain in the ear while a patient is sleeping. Electronics casing  5  contains electronic circuitry (described in detail herein) which receives the raw signals measured by electrodes  6 ,  7 ,  8  coupled to cover  4 . 
       FIGS. 2A-2B  show exploded views of left ear piece  2  where cover  4  and electronics casing  5  thereof are not coupled together, and  FIGS. 3A-3B  similarly show exploded views of right ear piece  3  where cover  4  and electronics casing  5  thereof are not coupled together. In the particular embodiments shown in  FIGS. 2A-2B and 3A-3B , cover  4  and electronics casing  5  are structured to snap together; however, it will be appreciated that cover  4  and electronics casing  5  may be structured to be coupled to one another in a manner other than snapping together without departing from the scope of the disclosed concept. In  FIGS. 2A-2B and 3A-3B , male component  11  is received within female component  12  when cover  4  and electronics casing  5  are snapped together. In one exemplary embodiment, producing cover  4  and electronics casing  5  separately allows a single electronics casing  5  to be snapped together with any of a number of different covers  4  having a concha piece  9  of varying sizes and a canal piece  10  of varying sizes, in order to produce a better fit within a patient&#39;s ear. In this exemplary embodiment, a standardized size electronics casing  5 , male component  11 , and female component  12  can be produced to streamline manufacturing processes, while only concha piece  9  and canal piece  10  would be produced with size variations. 
       FIG. 4  illustrates an exemplary embodiment of electronic circuitry  100  for processing electrical signals measured by electrodes  6 ,  7 ,  8  to generate ear EEG signals from the ear of a patient. In one exemplary embodiment, electronic circuitry  100  may be implemented within one or more processing devices (e.g., an integrated processor, a digital processor, an analog processor, a digital circuit designed to process information, an analog circuit designed to process information, and/or other mechanisms for electronically processing information) contained within the electronics casing  5 . Furthermore, electronic circuitry  100  is structured and configured to implement a method of processing electrical signals measured by electrodes  6 ,  7 ,  8  to generate the ear EEG signals as described in detail herein. Thus, the one or more processing devices electronic circuitry  100  may include one or more devices executing some or all of the operations of the method in response to instructions stored electronically on an electronic storage medium. The one or more processing devices may include one or more devices configured through hardware, firmware, and/or software to be specifically designed for execution of one or more of the operations of the described method. 
     The electronic circuitry  100  contained within electronics casing  5  is electrically connected to concha electrode  6 , superior canal electrode  7 , and inferior canal electrode  8  as shown schematically in  FIG. 4 .  FIG. 4  also shows a concha signal  111  generated by concha electrode  6 , a superior ear canal signal  112  generated by superior canal electrode  7 , and an inferior ear canal signal  113  generated by inferior canal electrode  8 . Signals  111 ,  112 ,  113  represent the raw electrical signals measured by electrodes  6 ,  7 ,  8  respectively. In a step performed by portion  110  of electronic circuitry  100 , concha signal  111  is received both by a non-inverting input terminal of a first differential operational amplifier  114  and by a non-inverting input terminal of a second differential operational amplifier  115 . Also in the step performed by portion  110  of electronic circuitry  100 , superior ear canal signal  112  is received by an inverting input terminal of first differential operational amplifier  114 , and inferior ear canal signal  113  is received by an inverting input terminal of second differential operational amplifier  115 . Ear canal signals are known to be flat, electrically neutral signals. As such, ear canal signals  112 ,  113  are received at the inverting input terminals of differential operational amplifiers  114 ,  115  in order to act as reference signals for concha signal  111 . At a step performed by portion  120  of electronic circuitry  100 , the output signals of differential operational amplifiers  114 ,  115  are received as input signals to high pass filter and gain adjustment units  116 ,  117 , respectively. At a step performed by portion  130  of electronic circuitry  100 , the output signals of high pass filter and gain adjustment units  116 ,  117  are received as input signals to low pass filters  118 ,  119 , respectively. It will be appreciated that high pass filtering, gain adjustment, and low pass filtering are used to eliminate unwanted noise from the output signals of differential operational amplifiers  114 ,  115 , and that other modes or circuitry for eliminating signal noise may be employed without departing from the scope of the disclosed concept. 
     At a step performed by portion  140  of electronic circuitry  100 , the output signals of low pass filters  118 ,  119  are digitized by analog to digital converters (ADC)  120 ,  121 , respectively. ADC  120  outputs a digital first in ear EEG signal and ADC  121  outputs a digital second in ear EEG signal as shown in  FIG. 4 . It will be appreciated that digital signals may be preferable in certain contexts while analog signals may be preferable in other contexts, and that the method may be performed without step  140  without departing from the scope of the disclosed concept. In addition, while in the exemplary embodiment, the method performs the steps consecutively in the sequence described above, it will also be appreciated that, in an alternative exemplary embodiment, the step employing differential amplifiers  114  and  115  may be omitted without departing from the scope of the disclosed concept. In such an alternative embodiment, electronic circuitry  100  of electronics casing  5  would first high pass filter signals  111 ,  112 , and  113  with high pass filter units  116 ,  117 . Electronic circuitry  100  would next low pass filter signals  111 ,  112 , and  113  with low pass filter units  118 ,  119 . Electronic circuitry would then digitize the filtered signals  111 ,  112 , and  113  with ADCs  120 ,  121 . The first digitized in ear signal would be produced by subtracting digitized superior ear canal signal  112  from digitized concha signal  111 , and the second digitized in ear signal would be produced by subtracting digitized inferior ear canal signal  113  from digitized concha signal  111 . 
     Moreover, according to an aspect of the disclosed concept, the first and second in ear EEG signals are analyzed with a quality switching algorithm  150  implemented in electronic circuitry  100 . Quality switching algorithm  150  determines which of the first in ear EEG signal and second in ear EEG signal is of better quality for outputting by electronic circuitry  100  (and thus the left ear piece  2  or the right ear piece  3 , as the case may be) to another component, such as a separate EEG signal analysis processor. In the exemplary embodiment, the selected (i.e., better quality) in ear EEG signal is transmitted from left ear piece  2  or the right ear piece  3 , as the case may be, by wireless transmission circuitry  160  forming a part of electronic circuitry  100 . Wireless transmission circuitry  160  may be, for example and without limitation, a Bluetooth or WiFi module. It will be appreciated that other means of transmitting the selected EEG signal to the EEG signal analysis processor may be employed without departing from the scope of the disclosed concept. 
     In the exemplary embodiment, quality switching algorithm  150  estimates the root mean square (RMS) voltage of both digitized in ear EEG signals and then compares the RMS voltage of both digitized in ear EEG signals to a minimum voltage threshold and a maximum voltage threshold. For an in ear EEG signal to be of acceptable quality, it must have a RMS voltage above the minimum voltage threshold and below the maximum voltage threshold. For example and without limitation, a minimum voltage threshold of 60 μV and a maximum threshold of 150 μV may be implemented so that only in ear EEG signals with RMS voltage greater than or equal to 60 μV and less than or equal to 150 μV sustained over a six-second interval would be considered to be of acceptable quality. If only one of the digitized in ear EEG signals has a RMS voltage above the minimum voltage threshold and below the maximum voltage threshold, that in ear EEG signal will be transmitted as the EEG signal of electronics  100 . If both digitized in ear EEG signals are of acceptable quality with a RMS voltage between the minimum voltage threshold and the maximum voltage threshold, only one of the digitized in ear EEG signals will be transmitted as the EEG signal to electronic circuitry  100 . In the exemplary embodiment, it is intended that concha and ear canal electrical signals  111 ,  112 ,  113  would be continuously measured by electrodes  6 ,  7 ,  8 . Accordingly, the quality switching algorithm continuously compares the digitized in ear signals that result from processing signals  111 ,  112 ,  113  with the method implemented by electronic circuitry  100 . In the exemplary embodiment, the digitized in ear signal that was most recently transmitted by electronic circuitry  100  will continue to be transmitted by electronic circuitry  100  for as long as it remains of acceptable quality, even if the other in ear signal is of acceptable quality, in order to avoid discontinuity. It will be appreciated that, when both digitized in ear signals are of acceptable quality, either of the two signals may be transmitted by electronic circuitry  100  without departing from the scope of the disclosed concept. It will also be appreciated that the quality switching algorithm  150  could be implemented by a processor outside of ear piece  1  such that all of the digitized in ear signals resulting from the method described herein would be transmitted to such processor outside of ear piece  1 , and the quality switching algorithm  150  would thereafter be performed, without departing from the scope of the disclosed concept. 
     In one exemplary embodiment, a patient would don both left ear piece  2  and right ear piece  3  simultaneously. It will be appreciated, therefore, that in this exemplary embodiment, two in ear signals would be produced from each ear simultaneously. In addition, in this exemplary embodiment, the quality switching algorithm  150  would be implemented separately from both left ear piece  2  and right ear piece  3 , and would receive and compare four signals, i.e. the two digitized in ear signals from left ear piece  2  and the two digitized in ear signals from right ear piece  3 , to determine which is of the highest quality for use by an EEG signal analysis processor. 
     In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. The word “comprising” or “including” does not exclude the presence of elements or steps other than those listed in a claim. In a device claim enumerating several means, several of these means may be embodied by one and the same item of hardware. The word “a” or “an” preceding an element does not exclude the presence of a plurality of such elements. In any device claim enumerating several means, several of these means may be embodied by one and the same item of hardware. The mere fact that certain elements are recited in mutually different dependent claims does not indicate that these elements cannot be used in combination. 
     Although this description includes details for the purpose of illustration based on what is currently considered to be the most practical and preferred embodiments, it is to be understood that such detail is solely for that purpose and that the disclosure is not limited to the disclosed embodiments, but, on the contrary, is intended to cover modifications and equivalent arrangements that are within the spirit and scope of the appended claims. For example, it is to be understood that, to the extent possible, one or more features of any embodiment are contemplated to be combined with one or more features of any other embodiment.