Patent Publication Number: US-11660034-B2

Title: Wearable electrode

Description:
TECHNICAL FIELD 
     The present invention relates to a wearable electrode to be used to acquire a bioelectric signal such as an electrocardiographic waveform on a daily basis. 
     BACKGROUND ART 
     Recently, the importance of daily self-care of health is pointed out. One method of personal healthcare like this is to record and analyze bioelectric signals such as electrocardiographic waveforms for long time periods. This method is known to be able to find disturbances of autonomic nerves and symptoms of heart diseases in early stages, and effective in preventive medicine. A garment to which a biological electrode is attached (a wearable electrode) in order to acquire bioelectric signals for long periods of time is attracting attention (see non-patent literature 1). 
     RELATED ART LITERATURE 
     Non-Patent Literature 
     
         
         Non-Patent Literature 1: David M. D. Riberio, et al., “A Real time, Wearable ECG and Continuous Blood Pressure Monitoring System for First Responders”, 33rd Annual International Conference of the IEEE EMBS, pp. 6894-6898, 2011 
       
    
     DISCLOSURE OF INVENTION 
     Problem to be Solved by the Invention 
       FIGS.  7 A to  7 C  are schematic views showing the way a conventional wearable electrode is put on a human body.  FIG.  7 A  is a human body front view,  FIG.  7 B  is a human body side view, and  FIG.  7 C  is a human body rear view. In the conventional wearable electrode as shown in  FIGS.  7 A to  7 C , biological electrodes  101  and  102  are often installed in two, left and right portions of the chest at the height of the heart muscle of a heart  100  of a wearer  110  (this height is near the central line of the left ventricle, which is near the lower line of the nipple in the case of a male). 
     Such a conventional wearable electrode, however, has the following problems. That is, the biological electrodes  101  and  102  are sometimes detached from the body of the wearer when the wearer bends forward, so that measurement of bioelectric signals cannot be measured, or, the wearer feel unpleasant when the biological electrodes  101  and  102  are fastened on the body of the wearer by a flexible material so that the biological electrodes  101  and  102  do not leave the body. 
     It is an object of the present invention to provide a wearable electrode capable of reducing the unpleasant feeling of a wearer, and acquiring bioelectric signals even when the wearer takes various postures. 
     Means of Solution to the Problem 
     According to the present invention, a wearable electrode for detecting a bioelectric signal of a wearer of a garment is characterized by including one or more first electrodes fixed to the garment such that the first electrodes can simultaneously come in contact with skin of respective parts from a ventral side to a dorsal side of an upper left part of a body of the wearer, and one or more second electrodes fixed to the garment such that the second electrodes can simultaneously come in contact with skin of respective parts from a ventral side to a dorsal side of an upper right part of the body of the wearer, wherein the first electrodes and the second electrodes are installed such that attaching positions gradually descend from the ventral side to the dorsal side with the wearer standing upright, or the attaching positions gradually ascend from the ventral side to the dorsal side with the wearer standing upright. 
     Effect of the Invention 
     The present invention includes the first electrodes fixed to the garment such that the first electrodes can simultaneously come in contact with the skin of respective parts from the ventral side to the dorsal side of the upper left part of the body of the wearer, and the second electrodes fixed to the garment such that the second electrodes can simultaneously come in contact with the skin of respective parts from the ventral side to the dorsal side of the upper right part of the body of the wearer. Even when the wearer bends forward, therefore, the bioelectric signal of the wearer can be acquired because at least a part of each of the first and second electrodes come in contact with the body of the wearer. Also, the present invention can reduce the unpleasant feeling of the wearer because it is unnecessary to tighten the body of the wearer by the first and second electrodes. Furthermore, in the present invention, the first and second electrodes are installed such that the attaching positions gradually descend from the ventral side to the dorsal side with the wearer standing upright, or the attaching positions gradually ascend from the ventral side to the dorsal side with the wearer standing upright. Accordingly, it is possible to reduce an impediment to expansion and compression of the garment around the waist of the wearer caused by the first and second electrodes, and further reduce the unpleasant feeling of the wearer. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIGS.  1 A to  1 C  are schematic views showing the way a wearable electrode according to the first embodiment of the present invention is put on a human body; 
         FIG.  2    is a graph showing the tension per unit width of the chest, which is necessary to measure the heartbeat, when using the wearable electrode according to the first embodiment of the present invention and a conventional wearable electrode; 
         FIG.  3    is a view for explaining an example of a method of putting the wearable electrode according to the first embodiment of the present invention on a human body; 
         FIG.  4    is a graph showing the tension per unit width of the chest, which is necessary to measure the heartbeat, when using the wearable electrode according to the first embodiment of the present invention and a wearable electrode in which electrodes are horizontally arranged; 
         FIG.  5    is a view for explaining the wearable electrode in which the electrodes are horizontally arranged; 
         FIGS.  6 A to  6 C  are schematic views showing the way a wearable electrode according to the second embodiment of the present invention is put on a human body; and 
         FIGS.  7 A to  7 C  are schematic views showing the way a conventional wearable electrode is put on a human body. 
     
    
    
     BEST MODE FOR CARRYING OUT THE INVENTION 
     The present invention will be explained below by referring to preferred embodiments, but the present invention is not limited to these embodiments. 
     First Embodiment 
       FIGS.  1 A to  1 C  are schematic views showing the way a wearable electrode according to the first embodiment of the present invention is put on a human body.  FIG.  1 A  is a front view of a human body,  FIG.  1 B  is a side view of the human body, and  FIG.  1 C  is a rear view of the human body. As shown in  FIGS.  1 A to  1 C , the wearable electrode of this embodiment includes a garment  21 , one or more belt-like electrodes  203 , and one or more belt-like electrodes  204 . The electrodes  203  are fixed to the inside of the garment  21  (the side in contact with the skin of a wearer  20  (a living body) of the garment  21 ), so that the electrodes  203  simultaneously come in contact with the skin of a left breast  210  of the wearer  20  of the garment  21 , the skin of at least one ( 211  in  FIG.  1 A ) of the left side chest, the left hypochondriac region, and the left armpit of the wearer  20 , and the skin of at least one ( 212  in  FIG.  1 C ) of the dorsal side of the left side chest, the dorsal side of the left hypochondriac region, and the lower portion of the left scapular region of the wearer  20 , and the attaching positions gradually descend from the ventral side to the dorsal side with the wearer  20  standing upright. The electrodes  204  are fixed to the inside of the garment  21 , so that the electrodes  204  simultaneously come in contact with the skin of a right breast  213  of the wearer  20  of the garment  21 , the skin of at least one ( 214  in  FIG.  1 A ) of the right side chest, the right hypochondriac region, and the right armpit of the wearer  20 , and the skin of at least one ( 215  in  FIG.  1 C ) of the dorsal side of the right side chest, the dorsal side of the right hypochondriac region, and the lower portion of the right scapular region of the wearer  20 , and the attaching positions gradually descend from the ventral side to the dorsal side with the wearer  20  standing upright.  FIGS.  1 A to  1 C  also depict a heart  200  of the wearer  20 . 
     Note that the armpit means a so-called underarm region, the side chest means a region below the armpit, and the hypochondriac region means a region below the side chest. Note also that the lower portion of the scapular region means a region below the scapular region having the scapula. The names of the individual parts of the human body are disclosed in, e.g., reference literature ‘Shoji Hashimoto, “Introduction to Nursing 1 Mechanism and Work of Human Body”, pp. 3-8, 2013’. 
     The electrodes  203  and  204  are respectively connected to a biological signal acquisition apparatus  233  by interconnections  231  and  232 . Of the one or more electrodes  203  and the one or more electrodes  204 , some of them are positive electrodes, and the rest are negative electrodes. 
     A material of the electrodes  203  and  204  is not particularly limited, and it is possible to unlimitedly use a carbon filler mixed resin, Ag cloth, conductive polymer impregnated fabric, and fabric impregnated with an electrolyte. The conductive polymer impregnated fabric is favorable because stimulation to the skin in a tight contact state is low and the durability is high. Also, the size of the electrodes  203  and  204  is not particularly limited as long as the installation conditions explained with reference to  FIGS.  1 A to  1 C  are met. 
     Note that a reference potential often used when receiving a bioelectric signal may also be obtained by installing an additional reference electrode on the garment  21  so that the reference electrode does not come in contact with the abovementioned positive and negative electrodes, and connecting the reference electrode to the biological signal acquisition apparatus  233  via an interconnection. In this case, of the one or more electrodes  203  separated from each other and the one or more electrodes  204  separated from each other, some are positive electrodes, and some are negative electrodes, and the electrode  203  or the electrode  204  other than the electrodes that function as the positive electrodes and the negative electrodes is the reference electrode. 
     Furthermore, the reference potential may also be an intermediate potential obtained from signals received by the positive electrode and the negative electrode, or the GND potential of the circuit of the biological signal acquisition apparatus  233 . 
     The garment  21  is not particularly limited as long as the electrodes  203  and  204  can be installed, and it is possible to take forms such as a stomach band, a belt, and a corset, in addition to a shirt shown in  FIGS.  1 A to  1 C . 
     When the garment  21  is a shirt as shown in  FIGS.  1 A to  1 C , the body including a part below the neck and the scapular regions is wrapped up, so the electrodes  203  and  204  are arranged and maintained in more appropriate positions. 
     The electrodes  203  and  204  are arranged on the inside of a front body  22  of the garment  21 . The electrodes  203  and  204  extend from the ventral side to the dorsal side so as to go round nearly the half of the body surface of the wearer  20 . Accordingly, a part from the armpit to the abdomen of the front body  22  is extended toward the dorsal side from a center  26  of the armhole of the garment  21  so as to accommodate the dorsal-side distal ends of the electrodes  203  and  204 . In accordance with this extension of the front body  22 , therefore, a part from the armpit to the abdomen of a back body  23  of the garment  21  to be sewed up to the front body  22  is restricted in the direction of the posterior median line of the wearer  20  from the center  26  of the armhole, so a width W 2  of this part is smaller than a body width W 1 . Consequently, sewing lines  24  and  25  of the front body  22  and the back body  23  are arranged nearer the dorsal side than the body-side barycentric line of the wearer  20 . 
     As the material of the garment  21 , it is possible to unlimitedly use natural fiber materials such as cotton and wool and synthetic fiber materials such as polyester and nylon used in ordinary clothes. However, the present invention is not limited to the shapes and materials of the garment  21  as described above. 
     Examples of the method of fixing the electrodes  203  and  204  to the garment  21  are a method of sewing the electrodes  203  and  204  to the garment  21 , a method of adhering the electrodes  203  and  204  to the garment  21 , and a method of impregnating the garment  21  with the electrodes  203  and  204 . Of these methods, the adhesion method is particularly easy. It is also possible to bond the electrodes  203  and  204  to the front body  22  or the back body  23  of the garment  21  by thermocompression bonding by using an iron or a hot press machine before sewing the garment  21 , and sew the front body  22  and the back body  23  after that. 
     As the interconnections  231  and  232 , although well-known wiring materials can unlimitedly be used, it is more desirable to use a flexible wiring material (e.g., conductive rubber), or a material having a flexible structure or layout such as a spring, since the interconnections  231  and  232  are installed on the garment  21  which deforms in accordance with the motion of the wearer  20 . 
     Also, the interconnections  231  and  232  are desirably covered with an insulator so as not to acquire signals from, e.g., the human body other than the electrode installation portions. Like the electrodes  203  and  204 , the interconnections  231  and  232  are fixed to the front body  22  of the garment  21  such that the attaching positions gradually descend from the end portions on the side of the biological signal acquisition apparatus  233  to the end portions on the side of the electrodes  203  and  204 , with the wearer  20  standing upright. Examples of the method of fixing the interconnections  231  and  232  to the garment  21  are a method of sewing the interconnections  231  and  232  to the garment  21 , and a method of adhering the interconnections  231  and  232  to the garment  21 . 
     In this embodiment, the electrodes  203  and  204  do not cross the sewing lines  24  and  25  because the electrodes  203  and  204  and the interconnections  231  and  232  are fixed to the front body  22  of the garment  21 . As a consequence, the garment  21  fits the three-dimensional body structure, and the electrodes  203  and  204  hardly get out of positions. In addition, the electrodes  203  and  204  and the interconnections  231  and  232  can be installed on the front body  22  before sewing the garment  21 , and this facilitates the sewing step. 
     The biological signal acquisition apparatus  233  acquires and processes a bioelectric signal (in this embodiment, an electrocardiographic waveform) detected by the electrodes  203  and  204 . As the biological signal acquisition apparatus  233 , it is possible to unlimitedly use a well-known apparatus that acquires an electrocardiographic waveform and detects an R wave. The biological signal acquisition apparatus  233  has a function of detecting the heartbeat from the electrocardiographic waveform, various display functions, and a function of wirelessly transmitting the acquired bioelectric signal and heartbeat information to the outside. Also, the biological signal acquisition apparatus  233  can be fixed on either the inside or the outside (the side opposite to the side in contact with the skin of the wearer  20 ) of the garment  21 . 
     In this embodiment as described previously, however, the positions of the end portions of the interconnections  231  and  232  on the side of the electrodes  203  and  204  must be obliquely below the positions of the end portions of the interconnections  231  and  232  on the side of the biological signal acquisition apparatus  233 , with the wearer  20  standing upright. Therefore, the position of the biological signal acquisition apparatus  233  must be determined so as to implement the layout of the interconnections  231  and  232  like this. 
       FIG.  2    shows the results of measurement of the tension of the chest necessary to measure the heartbeat, when the same wearer wore the conventional wearable electrode ( FIG.  7   ) in which electrodes were installed in two, left and right portions of the chest at the height of the heart of the wearer and the wearable electrode of this embodiment in turn, and walked at 4 km per hour. In  FIG.  2   , the lowest value of the tension per unit width (1 cm) around the waist when normal heartbeat measurement was successful is taken as the measurement result. Also, as shown in  FIG.  3   , the electrodes  203  and  204  of the wearable electrode of this embodiment made an angle θ of 30° with a horizontal plane  27  when the wearer  20  was standing upright. 
     Referring to  FIG.  2   , tension  300  was necessary to measure the heartbeat when using the conventional wearable electrode, and tension  301  was necessary to measure the heartbeat when using the wearable electrode of this embodiment. As shown in  FIG.  2   , compared to the conventional wearable electrode, this embodiment reduces the tension of the chest necessary to measure the heartbeat, and hence can reduce the unpleasant feeling of the wearer. 
       FIG.  4    shows the results of measurement of the tension of the chest when the same wearer wore the wearable electrode in which the electrodes  203  and  204  were horizontally arranged on the garment  21  and the wearable electrode of this embodiment in turn. In  FIG.  4   , the tension per unit width (1 cm) around the waist when the around-the-waist dimension of the chest on which the electrodes  203  and  204  were arranged was extended by 20% is taken as the measurement result. As shown in  FIG.  3   , the electrodes  203  and  204  of the wearable electrode of this embodiment made an angle θ of 30° with the horizontal line  27  when the wearer  20  was standing upright. As shown in  FIG.  5   , the wearable electrode in which the electrodes  203  and  204  are horizontally arranged is an electrode in which the horizontal plane  27  and the extending direction of the electrodes  203  and  204  are parallel (θ is 0°) when the wearer  20  was standing upright. 
     Referring to  FIG.  4   , tension  400  was obtained when using the wearable electrode in which the electrodes  203  and  204  were horizontally arranged, and tension  401  was obtained when using the wearable electrode of this embodiment. 
       FIG.  4    shows that this embodiment can reduce the tension of the chest and the unpleasant feeling of the wearer by obliquely installing the electrodes  203  and  204 , compared to the wearable electrode in which the electrodes  203  and  204  are horizontally installed. 
     In this embodiment as described above, the electrode  203  is so installed as to simultaneously come in contact with the skin in respective parts from the ventral side to the dorsal side of the upper left part of the body of the wearer, and the electrode  204  is so installed as to simultaneously come in contact with the skin in respective parts from the ventral side to the dorsal side of the upper right part of the body of the wearer. Even when the wearer is bending forward, therefore, at least a part of each of the electrodes  203  and  204  comes in contact with the body of the wearer, so the bioelectrical signal of the wearer can be acquired. Also, this embodiment does not adopt a structure that tightens the body of the wearer by the electrodes  203  and  204 , and hence can reduce the unpleasant feeling of the wearer. Furthermore, the electrodes  203  and  204  and the interconnections  231  and  232  are installed obliquely to the horizontal plane with the wearer standing upright. Therefore, even when materials having flexibility lower than that of the material of the garment  21  are used as the electrodes  203  and  204  and the interconnections  231  and  232 , it is possible to reduce an impediment to expansion and contraction of the garment  21  around the waist caused by the electrodes  203  and  204  and the interconnections  231  and  232 , and reduce the unpleasant feeling of the wearer. 
     Second Embodiment 
     Next, the second embodiment of the present invention will be explained.  FIGS.  6 A to  6 C  are schematic views showing the way a wearable electrode according to the second embodiment of the present invention is put on a human body.  FIG.  6 A  is a human body front view,  FIG.  6 B  is a human body side view, and  FIG.  6 C  is a human body rear view. As shown in  FIGS.  6 A to  6 C , the wearable electrode of this embodiment includes a garment  21   a , one or more belt-like electrodes  203   a , and one or more belt-like electrodes  204   a . The electrodes  203   a  are fixed to the inside of the garment  21   a , so that the electrodes  203  simultaneously come in contact with the skin of at least one of the ventral side of the left side chest and the ventral side of the left hypochondriac region of a wearer  20  of the garment  21   a , the skin of at least one ( 211  in  FIG.  6 A ) of the left side chest, the left hypochondriac region, and the left armpit of the wearer  20 , and the skin of at least one ( 216  in  FIG.  6 C ) of the dorsal side of the left side chest and the left scapular region of the wearer  20 , and the attaching positions gradually ascend from the ventral side to the dorsal side with the wearer  20  standing upright. The electrodes  204   a  are fixed to the inside of the garment  21   a , so that the electrodes  204   a  simultaneously come in contact with the skin of at least one of the ventral side of the right side chest and the ventral side of the right hypochondriac region of the wearer  20  of the garment  21   a , the skin of at least one ( 214  in  FIG.  6 A ) of the right side chest, the right hypochondriac region, and the right armpit of the wearer  20 , and the skin of at least one ( 217  in  FIG.  6 C ) of the dorsal side of the right side chest and the right scapular region of the wearer  20 , and the attaching positions gradually ascend from the ventral side to the dorsal side with the wearer  20  standing upright. 
     The electrodes  203   a  and  204   a  are respectively connected to a biological signal acquisition apparatus  233  by interconnections  231   a  and  232   a . When using a reference electrode, the electrode  203   a  or  204   a  other than the electrodes  203   a  and  204   a  that function as positive electrodes and negative electrodes can be used as the reference electrode, as in the first embodiment. 
     The electrodes  203   a  and  204   a  are made of the same material as the electrodes  203  and  204  of the first embodiment, but are arranged on the inside of a back body  23   a  of the garment  21   a . In this embodiment, the electrodes  203   a  and  204   a  extend from the dorsal side to the ventral side so as to go round nearly the half of the body surface of the wearer  20 . Accordingly, a part from the armpit to the abdomen of the back body  23   a  is extended toward the ventral side from a center  26  of the armhole of the garment  21   a  so as to accommodate the ventral-side distal ends of the electrodes  203   a  and  204   a . In accordance with this extension of the back body  23   a , therefore, a part from the armpit to the abdomen of a front body  22   a  of the garment  21   a  to be sewed up to the back body  23   a  is restricted in the direction of the anterior median line of the wearer  20  from the center  26  of the armhole, so a width W 3  of this part is smaller than a body width W 1 . Consequently, sewing lines  24   a  and  25   a  of the front body  22   a  and the back body  23   a  are arranged nearer the ventral side than the body-side barycentric line of the wearer  20 . 
     Like the electrodes  203   a  and  204   a , the interconnections  231   a  and  232   a  are fixed to the back body  23   a  of the garment  21   a  such that the attaching positions gradually descend from the end portions on the side of the biological signal acquisition apparatus  233  to the end portions on the side of the electrodes  203   a  and  204   a , with the wearer  20  standing upright. 
     In this embodiment, the electrodes  203   a  and  204   a  do not cross the sewing lines  24   a  and  25   a  because the electrodes  203   a  and  204   a  and the interconnections  231   a  and  232   a  are fixed to the back body  23   a  of the garment  21   a . As a consequence, the garment  21   a  fits the three-dimensional body structure, and the electrodes  203   a  and  204   a  hardly get out of positions. In addition, the electrodes  203   a  and  204   a  and the interconnections  231   a  and  232   a  can be installed on the back body  23   a  before sewing the garment  21   a , and this facilitates the sewing step. Furthermore, in this embodiment, the interconnections  231  and  232  and the biological signal acquisition apparatus  233  need not be installed on the ventral side. Accordingly, the garment  21   a  can be front-open garment, and this can facilitate dressing and undressing. 
     In the first embodiment and this embodiment, the method of fixing the electrodes  203 ,  203   a ,  204 , and  204   a  and the interconnections  231 ,  231   a ,  232 , and  232   a  to the front body  22  or the back body  23   a  is not particularly limited, and an arbitrary method can be used. Especially when performing fixation by thermocompression bonding, if the electrodes  203 ,  203   a ,  204 , and  204   a  and the interconnections  231 ,  231   a ,  232 , and  232   a  do not cross the sewed portions as in the first embodiment and this embodiment, the compression-bonding surface is flat, so the front body or back body before sewing in which members to be compression-bonded are arranged can be placed on the plate of a hot press machine normally used in thermocompression bonding. This not only facilitates forming the garment  21  and  21   a , but also improves the durability of adhesion because the electrodes  203 ,  203   a ,  204 , and  204   a  and the interconnections  231 ,  231   a ,  232 , and  232   a  can evenly be adhered on the entire surface. 
     The function of the biological signal acquisition apparatus  233  is the same as explained in the first embodiment. In this embodiment, however, the positions of the end portions of the interconnections  231   a  and  232   a  on the side of the electrodes  203   a  and  204   a  must be obliquely below the positions of the end portions of the interconnections  231   a  and  232   a  on the side of the biological signal acquisition apparatus  233 , with the wearer  20  standing upright. Therefore, the position of the biological signal acquisition apparatus  233  must be so determined as to be able to implement the layout of the interconnections  231   a  and  232   a  as described above. 
     The rest of the arrangement is the same as explained in the first embodiment. Thus, this embodiment can achieve the same effect as that of the first embodiment. 
     Note that in the first and second embodiments, the electrode shape is an almost rectangular shape in planar view when the electrode is not fixed to a garment but stretched flat. However, the present invention is not limited to this, and it is also possible to adopt an electrode shape that is an almost elliptical shape when the electrode is stretched flat. 
     Note also that the biological signal acquisition apparatus  233  may also have a structure that can detachably be attached to the garment  21  and  21   a . In this case, the biological signal acquisition apparatus  233  and the interconnections  231 ,  231   a ,  232 , and  232   a  are electrically connected via connectors. 
     INDUSTRIAL APPLICABILITY 
     The present invention is applicable to a technique of acquiring a bioelectric signal. 
     EXPLANATION OF THE REFERENCE NUMERALS AND SIGNS 
       20  . . . wearer,  21 ,  21   a  . . . garment,  22 ,  22   a  . . . front body of a garment,  23 ,  23   a  . . . back body of garment,  24 ,  24   a ,  25 ,  25   a  . . . sewing line of front or back body,  26  . . . center of armhole,  200  . . . heart,  203 ,  203   a ,  204 ,  204   a  . . . electrode,  210  . . . left breast,  211  . . . at least one of left side chest, left hypochondriac region, and left armpit,  212  . . . at least one of dorsal side of left side chest, dorsal side of left hypochondriac region, and lower portion of left scapular region,  213  . . . right breast,  214  . . . at least one of right side chest, right hypochondriac region, and right armpit,  215  . . . at least one of dorsal side of right side chest, dorsal side of right hypochondriac region, and lower portion of right scapular region,  216  . . . at least one of dorsal side of left side chest and left scapular region,  217  . . . at least one of dorsal side of right side chest and right scapular region,  231 ,  231   a ,  232 ,  232   a  . . . interconnection,  233  . . . biological signal acquisition apparatus