Patent Publication Number: US-2018042551-A1

Title: Device in the form of a garment for monitoring a physiological parameter of a user

Description:
FIELD OF THE INVENTION 
     The invention relates to a device for monitoring breathing, as a clothing item which may be worn by the user. 
     STATE OF THE ART 
     In order to continuously monitor the physiological condition of a user, it is known to fix sensors in textile structures intended to form a clothing item. Such sensors for example allow measurement of an electrocardiographic signal which is representative of the heart activity of a user who wears the clothing item. 
     However, such sensors may sometimes prove to be bulky, causing consequently a lack of comfort for the user. Further, the assembling of these sensors on the clothing item and their electric connection may prove to be complex. 
     Document EP 1 506 738 describes an elastic clothing item comprising textile sensors. The sensors include flexible textile electrodes applied against the skin used for collecting electric signals generated by the body for the elaboration of an electrocardiogram or an electromyogram on the one hand, and a mechanical deformation sensor used for measuring the respiratory movements of the user on the other hand. The electrodes are formed by weaving or knitting an elastic conductive yarn. The mechanical deformation sensor comprises a non-knitted elastic conductive yarn. The elastic conductive yarn is obtained by wrapping a non-extensible conductive yarn around a core consisting of non-conductive elastic yarn, i.e. the conductive yarn is helically wound around the non-conductive elastic yarn. When the elastic conductive yarn is stretched, the yarn elongates and the neighbouring turns of the winding move away from each other, causing a measurable change in electric resistance which depends on the elongation of the elastic conductive yarn. 
     Document US 2007/0171024 describes a clothing item in which is integrated a gauge giving the possibility of monitoring the breathing of the user who wears the clothing item. The clothing item comprises a textile base woven from non-conductive yarns. The gauge is formed by a conductive yarn gimped with a non-conductive yarn, and woven through the textile base, at the abdominal region or at the breast of the user. The conductive yarn consists of ultra-fine metal yarns twisted with textile fibres or textile fibres mixed with metal fibres. The respiratory movements of the user cause an elongation or a contraction of the conductive yarn. The change in the length of the conductive yarn causes a change in the electric properties of the yarn. 
     In such a clothing item, the connection of the conductive yarn to a measuring apparatus requires first stripping the conductive yarn, i.e. removing the non-conductive yarn which surrounds it, in order to be able to make an electric contact between the conductive yarn and a connecting cable. 
     Further, the wrapping of the conductive yarn with a non-conductive yarn increases the total diameter of the conductive yarn, which increases the costs for making the clothing item and may generate discomfort for the user who wears the clothing item. 
     SUMMARY OF THE INVENTION 
     An object of the invention is to propose a device for tracking the breathing of a user, which both has improved comfort and which minimizes the manufacturing steps required for making the device. 
     This object is attained within the scope of the present invention by means of a device for monitoring breathing of a user comprising:
         a textile support comprising a tubular portion formed by knitting an electrically insulating majority ground yarn, the tubular portion being able to cover the chest of the user,   at least one breathing sensor formed by knitting a detection yarn, the detection yarn forming a plurality of stiches, the detection yarn comprising at least one internal core in an electrically insulating material and an external sheath surrounding the internal core, the external sheath being formed in an electrically conducting material so as to generate electric contacts between the stitches of the detection yarn.       

     The breathing sensor forms a conductive band having a first end and a second end positioned at a distance from each other, the ends being able to be connected to an apparatus for measuring the electric resistance of the conductive band. 
     The conductive band is positioned relatively to the tubular portion so that when the chest of the user is covered with the textile support, the conductive band is stretched and shrunk alternately because of the breathing of the user, the stretching and the shrinking of the conductive band having the effect of modifying the electric contacts between the stitches of the detection yarn within the conductive band, causing modification of the electric resistance of the conductive band. 
     In such a device, the detection yarn is not insulated, which allows the use of a smaller yarn, less costly and more lightweight. In addition, the connecting of the detection yarn to the measuring apparatus does not require any preliminary stripping of the detection yarn. 
     Further, the successive stitches of the detection yarn form multiple contacts of the external sheath with itself. It is mainly the modification of these electric contacts during the stretching and the shrinking of the conductive band which generates a modification of the electric resistance, and not a stretching or contraction of the actual yarn. 
     The proposed device may further have the following features:
         the detection yarn comprises at least one core made of a polymer material, preferably of polyamide,   according to a first possibility, the sheath of the detection yarn is formed by wrapping the internal core with a yarn made of a conducting material, preferably of silver,   according to a second possibility, the sheath of the detection yarn is formed by coating the internal core with a layer made of a conductive material, preferably of silver,   the yarn may consist of several non-conductive filaments, each filament being coated with an external layer made of a conductive material, preferably of silver,   in this case, the coated filaments may be twisted together,   the tubular portion is formed by knitting the majority ground yarn and an elastic yarn,   the conductive band surrounds at least partly the chest of the user, preferably at the height of the sternum and/or the abdominal muscles, and extends over the belly and/or over the back of the user,   the conductive band may extend both over the belly and over the back of the user,   the tubular portion and the breathing sensor are formed by circular knitting in a single operation, the ground yarn and the detection yarn being alternately knitted,   during the knitting, the detection yarn is cut when the ground yarn is knitted,   the device further comprises an insulating layer positioned between the conductive band and the skin of the user when the user is covered with the textile support,   the device further comprises a sheath attached on the tubular portion and connecting cables located inside the sheath for connecting the ends of the conductive band to the apparatus for measuring electric resistance.       

    
    
     
       PRESENTATION OF THE DRAWINGS 
       Other features and advantages will further become apparent from the description which follows, which is purely illustrative and non-limiting and should be read with reference to the appended figures, wherein: 
         FIG. 1  schematically illustrates a front view of a device for monitoring breathing according to a possible embodiment of the invention, 
         FIG. 2  schematically illustrates a rear view of the device for monitoring breathing, 
         FIG. 3  is a detailed view of the device, 
         FIG. 4  schematically illustrates the device including a sheath and connecting cables, 
         FIGS. 5A and 5B  are schematic detailed views respectively of the face and of the back of the device, 
         FIGS. 6 and 7  schematically illustrate stitches forming a breathing sensor, when the sensor is in the rest condition and in the stretched condition respectively, 
         FIGS. 8 and 9  schematically illustrate a conductive yarn forming stitches, when the conductive yarn is in the rest condition and in the stretched condition respectively, 
         FIG. 10  schematically illustrates the structure of a non-conductive yarn used for forming the textile support, 
         FIG. 11  schematically illustrates the structure of a conductive yarn used for forming the sensor according to a first possibility, 
         FIG. 12  schematically illustrates the structure of a conductive yarn used for forming the sensor according to a second possibility, 
         FIG. 13  schematically illustrates the structure of a conductive yarn used for forming the sensor according to a third possibility, 
         FIG. 14  is an equivalent electric diagram of the breathing sensor and of an apparatus for measuring the electric resistance of the conductive band, 
         FIG. 15  schematically illustrates variations of electric resistance recorded from the breathing sensor. 
     
    
    
     DETAILED DESCRIPTION OF AN EMBODIMENT 
     In  FIGS. 1 to 4 , the device for monitoring breathing  1  illustrated comprises a textile support  2  and a plurality of sensors  3  and  4  integrated into the textile support  2  in order to monitor the breathing of a user. 
     The textile support  2  appears as a clothing item, such as a tee-shirt for example, able to cover the body of the user. 
     In the embodiment illustrated in  FIGS. 1 to 4 , the sensors include two breathing sensors  3  and  4 . 
     The breathing sensors  3  and  4  allow detection of the respiratory movement of the thorax cavity and/or of the abdomen of the user who wears the clothing item. 
     The textile support  2  comprises a tubular portion  21  able to surround the chest of the user. 
     The tubular portion  21  has a neck  24  for letting through the head, a front  25  (visible in  FIG. 1 ) able to cover a belly portion of the user and a back  26  (visible in  FIG. 2 ) capable of covering a portion of the back of the user. 
     The tubular portion  21  is formed by simultaneous knitting of an electrically insulating, majority ground yarn, and of an elastic yarn. 
     The majority ground yarn  16  is schematically illustrated in  FIG. 10 . The majority ground yarn  16  is a synthetic thread, made of a polymer material, such as a polyamide thread (PA) or a polyester thread (PES). 
     The elastic yarn (not shown) is a yarn made of a thermoplastic elastomer or in a polyurethane derivative, known under the brand of Lycra® (marketed by the company Invista). The elastic yarn may be wrapped (in French “guipé”) or double-wrapped (in French “double-guipé”). 
     The ground yarn  16  and the elastic yarn are knitted together so that the ground yarn exactly covers the elastic yarn. 
     Each breathing sensor  3  and  4  extends around the chest of the user in an area located between the top of the sternum and the bottom of the belly. 
     Each breathing sensor  3  and  4  is formed by knitting an electrically conductive detection yarn. 
     As illustrated in  FIGS. 11 to 13 , the detection yarn  17  comprises at least one internal core  171  made of an electrically insulating material and an external sheath  172  surrounding the internal core, the external sheath  172  being made of an electrically conducting material. The electrically insulating material of the core  171  may be a polymer, such as polyamide for example. 
     The conductive material of the external sheath  172  may be a metal, preferably a biocompatible metal, such as silver. 
     According to a first possibility (illustrated in  FIG. 11 ), the sheath  172  of the detection yarn  17  is formed by wrapping (in French “guipage”) the internal core  171  with a yarn  173  made of a conductive material. In other words, the yarn  173  made of a conductive material is helically wound around the internal core  171 . 
     According to a second possibility (illustrated in  FIG. 12 ), the sheath  172  of the detection yarn is formed by coating the internal core  171  with a layer  174  made of a conductive material. The coating may be achieved by a vacuum deposition technique; by cathode sputtering for example, of the conductive material. 
     According to a third possibility (illustrated in  FIG. 13 ), the detection yarn  17  consists of a bundle of conductive filaments  175  twisted together. Each conductive filament comprises a core  171  made of an insulating material covered with an external layer  172  made of a conductive material, preferably of silver. 
     As this is visible in  FIGS. 1 to 4 , the first breathing sensor  3  forms a first conductive band  31  extending around the chest of the user at the sternum, when the user wears the clothing item. The first conductive band  31  may comprise several branches extending parallel with each other around the chest of the user. 
     More specifically, in  FIGS. 1 to 4 , the first conductive band  31  comprises two longitudinal branches  311 ,  312  extending parallel with each other. 
     Each longitudinal branch  311 ,  312  extend along the knitting direction, i.e. parallel to the direction of a row. 
     Further, each longitudinal branch  311 ,  312  extends both on the front and on the rear of the clothing item. 
     The first band  31  also comprises junction portions  313 ,  314  extending transversely to the knitting direction, and electrically connecting the longitudinal branches  311 ,  312  with each other at their ends. 
     The first branch  311  is interrupted at a central axis X of the front of the clothing item (a virtual axis passing through the navel of the user). 
     The first band  31  forms an electric circuit having two ends  315 ,  316  located at a distance from each other, on either side of the central axis X. The ends  315  and  316  of the first band  31  are able to be electrically connected to an apparatus for measuring the electric resistance of the first conductive band  31 . 
     Each branch  311 ,  312  has a width comprised between 1 and 50 rows of stitches. 
     The second breathing sensor  4  forms a second conductive band  41  extending around the chest of the user at the abdominal muscles. 
     The second conductive band  41  is similar to the first conductive band  31 . The second conductive band  41  comprises two branches  411 ,  412  extending parallel with each other around the chest of the user and two junction portions  413 ,  414 . The first branch  411  is interrupted at a central axis X. The second conductive band  41  thus also has two ends  415  and  416  located at a distance from each other, on either side of the axis X, and able to be electrically connected to an apparatus for measuring the electric resistance of the second conductive band  41 . 
     The tubular portion  21  and the breathing sensors  3  and  4  are formed by circular knitting in a single operation. The insertion of the conductive yarns is said to be “by means of embroidery” (in French “par le biais de la broderie”). 
     Thus, the ground yarn  16  (with the elastic yarn) forming the main tubular portion  21  and the detection yarn  17  forming the sensors  3  and  4  are knitted alternately during the knitting operation. 
     In other words, during the knitting operation, the ground yarn  16  stops being knitted when the detection yarn  17  is knitted. Also, the detection yarn  17  stops being knitted when the ground yarn  16  is knitted. 
     Further, as illustrated in  FIGS. 5A and 5B , the detection yarn  17  is cut when the ground yarn  16  is knitted. In  FIG. 5A , the cut ends  176  of the detection yarn  17  appear on the back of the clothing item along the edges of the junction portions  313 ,  314  (also along the edges of the junction portions  413 ,  414 ) of the breathing sensors. 
     On the other hand, the ground yarn  16  is not cut so that non-knitted portions  166  of the ground yarn appear on the back of the clothing item behind the junction portions  313 ,  314  (also along the edges of the junction portions  413 ,  414 ) of the breathing sensors. 
     Moreover, the device  1  for monitoring breathing comprises one or several pockets attached on the textile support by crimping of a metal part of the type of press buttons, eyelets or rivets, by sewing, welding or thermally bonding. These additional pockets allow the insertion of electronic components into the clothing item, such as a battery or a measuring apparatus for example. In order to limit the displacement of the electronic components with respect to the textile support, the dimensions of each pocket are less than the dimensions of the component which it receives. The insertion of the component into the pocket is possible because of the elastic properties of the textile support. 
     In particular, the device  1  comprises a pocket  6  (visible in  FIGS. 1 to 4 ) and an apparatus for measuring resistance  61  (visible in  FIG. 3 ) accommodated in the pocket  6 . The pocket  6  is positioned on the textile support  2  so as to be located on a shoulder of the user when the user wears the clothing item. This position gives the possibility of minimizing the discomfort generated by the presence of the apparatus when the user is lying down. The apparatus for measuring the resistance  61  is able to measure and record the resistance variations of the conductive bands  31  and  41 , in order to track the breathing of the user. 
     The device  1  for monitoring breathing further comprises a central sheath  5  (visible in  FIG. 4 ) attached onto the tubular portion  21  along the central axis X and electric connecting cables  51  to  54  located inside the sheath  5  so as to connect to each of the sensors to the measuring apparatus  61 . The central sheath extends along the central axis X of the clothing item. The central sheath  5  is preferably attached on the back of the device. 
     The connection of the breathing sensors  3  and  4  is achieved in the following way. An exposed end of a connecting cable  51 ,  52 ,  53 ,  54  is sandwiched between an end  315 ,  316 ,  415 ,  416  to be connected and an added conductive textile part. The textile part is attached by adhesive bonding on the end  315 ,  316 ,  415 ,  416  by means of an adhesive. For example the adhesive used is an adhesive based on polyprocaprolactone (PCL). 
       FIGS. 6 and 7  schematically illustrate the structure of the conductive band  31  forming the breathing sensor  3 , in the rest condition and in the stretched condition respectively. 
     The ground yarn  16  is knitted so as to form a plurality of rows. 
     Also, the detection yarn  17  is knitted so as to form a plurality of rows. 
     The knitting technique used for the detection yarn  17  is weft-knitting (i.e. the stitches formed by a same continuous yarn are positioned in a same row), preferably with a Jersey base. The same knitting technique may be used for the ground yarn  16 . 
     Each row consists of a plurality of successive stitches. The stitches of a same row form loops alternatively curved in one direction and then in the other, so that the stitches of the row are alternatively interlaced with the stitches of the immediately lower row and with the stitches of the immediately upper row. 
     As illustrated in  FIG. 6 , when the conductive band  31  is in the rest condition, the stitches of a same row are in contact with each other in a plurality of contact points P. 
     As illustrated in  FIG. 7 , when the conductive band  31  is stretched in a direction Y parallel to the knitting direction (i.e. the direction of a row), the stitches of the detection yarn  17  move away from each other, which reduces the number of contact points P between the stitches. 
     The separation of the stitches thus causes a reconfiguration of the contact points P within the conductive band  31 , which has the effect of modifying the electric resistance of the conductive band  31 . 
     More specifically, as this is illustrated in  FIG. 8 , when the conductive band  31  is in the rest condition, an electric current may flow along the detection yarn  17  via the contact points P along the line in dotted lines. 
     On the other hand, as this is illustrated in  FIG. 9 , when the conductive band  31  is stretched, these contact points disappear which increases the effective electric resistance of the detection yarn  17 . 
     Thus, by measuring the variations in electric resistance of the conductive band  31 , it is possible to detect the respiratory movements of the user. 
     The same principle applies to the conductive band  41 . 
       FIG. 14  is a block diagram of an electric circuit of an apparatus  61  for measuring the electric resistance of the conductive band  31 . 
     The apparatus  61  comprises a voltage generator  611 , and a first resistor  612 . The voltage generator  611  generates a low input voltage U 1 , of the order of 10 millivolts. 
     The output voltage U 2  generated on the terminals of the conductive band is equal to: 
         U 2= U 1* R /( R+R 612) 
     wherein R is the resistance of the conductive band  31 , R 612  is the resistance value of the resistor  612  and U 1  is the input voltage generated by the generator  611 . 
     By measuring the voltage between the ends  315  and  316  of the conductive band  31 , it is possible to infer therefrom the resistance R of the conductive band  31 . 
       FIG. 15  is a diagram illustrating the variations of the resistance of the conductive band  31  measured over time when the device  1  is worn by a user who is breathing. 
     The resistance of the conductive band  31  directly depends on its extension. The measured variations of resistance may be processed in order to monitor breathing parameters, such as the breathing rate of the user or the amplitude of the breathing cycles. 
     The device  1  may further comprise one or several insulating layers (not shown), positioned between the conductive band(s)  31  and  41 , and the skin of the user when the user is covered with the textile support  2 . The insulating layer(s) may be formed with an extensible fabric or membrane. The insulating layer(s) give the possibility of electrically insulating the skin of the user from the conductive bands  31  and  41  in which the electric current flows.