Abstract:
A garment accessory includes a member having first and second ends, with the length of the member between the first and second ends being less than the circumference of a subject that the member is configured for and a pair of fastener mechanisms disposed in proximity to the first and second ends of the member, the fastener mechanisms configured to attach the member to an article of clothing worn by a subject. The garment accessory also includes at least a pair of sensors supported by the member with the sensors being at least one of ECG sensors, motion sensors, body temperature sensors and impedance plethysmography sensors.

Description:
BACKGROUND 
       [0001]    The present invention relates to electrocardiogram (EGG) monitoring, and in particular to a wearable device with integrated ECG sensors for ambulatory ECG monitoring. 
         [0002]    Heart disease is a leading cause of death in the United States. Some patients would benefit from long-term ECG monitoring outside of a clinical setting. For example, atrial fibrillation and myocardial ischemia may occur episodically. Some episodes may occur without patient symptoms. Myocardial ischemia, if persistent and serious, can lead to myocardial infarction (heart attack). During a myocardial infarction, electrophysiological changes are usually seen on the ECG. For accurate diagnosis and effective treatment of many episodic heart conditions, it is useful to know the frequency and duration of such episodes, in a timely manner. 
         [0003]    In conventional long-term ECG monitoring, such as with continuous Holter monitors or event monitors, the skin is prepared by a technician. Chest hair may be shaved or clipped from men. The skin is abraded to remove dead skin cells, and cleaned. Abrading often leaves the skin irritated. A technician trained in electrode placement applies the electrodes to the skin with an adhesive. The monitor can be worn for up to a month. 
         [0004]    Each electrode of such conventional monitors is attached to an insulated wire that is routed to an amplifier to amplify the ECG signal. The patient has to take care not to pull on the wires connected to the electrode, because the electrode could be pulled off the skin. Removing the electrode with its strong adhesive may be painful. Many electrodes also use a gel next to the skin to improve conductivity of connection of the metal electrode to the skin. Prolonged exposure to the gel can irritate the skin. 
       SUMMARY 
       [0005]    Aspects of the present invention include a garment accessory including a member having first and second ends, with the length of the member between the first and second ends being less than the circumference of a subject that the member is configured for, a pair of fastener mechanisms disposed in proximity to the first and second ends of the member, the fastener mechanisms configured to attach the member to an article worn by a subject and at least a pair of sensors supported by the member. 
         [0006]    The following are embodiments within the scope of the invention. 
         [0007]    The member further has a fastener mechanism disposed at the center of the member. The fastener mechanisms at the first and second ends of the member and the central portion of the member are configured to couple the member to a brassiere. The pair of sensors are removable from the member. The garment accessory further includes a circuit arrangement electrically coupled to the pair of sensors, the circuit arrangement carried by the member. The fastener mechanism is at least one of hooks, clips, elastic band, hook and loop fasteners and snaps. The fastener mechanism includes a hook mechanism which hooks over a portion of an article of clothing. The fastener mechanism includes a set of clips disposed on the bottom outside edge of the garment accessory, configured such that when the garment accessory is underneath an article of clothing that encircles the torso of a subject, the clips attach to the bottom edge of the article of clothing. 
         [0008]    The circuit arrangement includes a wireless transmitter. The sensors are at least one of ECG sensors, motion sensors, body temperature sensors and impedance plethysmography sensors. The garment accessory is configured to attach to a brassiere. At least part of the garment accessory is held in place underneath the lower portion of the front and sides of a brassiere. The part of the assembly is held in place by a pouch or loop portion of a bra. The garment accessory is configured to be secured on side straps of a brassiere. Each of the sensors include a sensor membrane in electrical contact with the mating snap, the sensor membrane comprised of an electrically conductive, flexible material. The sensor membrane is comprised of conductive rubber or conductive silicone. The sensor membrane has a major surface thereof that is exposed to make contact with the skin of a subject, the major surface being curved. The sensor membrane has a major surface thereof that is exposed to make contact with the skin of a subject, the major surface being flat. The sensor membrane has the major surface covered with a conductive gel film. The garment accessory further includes a snap comprised of an electrically conductive material disposed in intimate contact with the backside of the sensing membrane to provide an electrical path for a signal from the sensing membrane, the snap engaging a mating snap supported by the strap member. The sensor further includes a sensor frame comprised of a firm, flexible material supporting the sensor membrane. The sensor membrane includes a water resistant material to induce sweat. The garment accessory further includes a layer of sweat-absorbing material disposed adjacent to the sensor membrane. 
         [0009]    Additional aspects of the present invention include a brassiere including at least one accommodation disposed on a portion of the brassiere for holding at least a pair of sensors and a pair of detachable sensors carried by the at least one accommodation. 
         [0010]    Additional aspects of the present invention include a brassiere-based heart monitor device including a fastener mechanism that attaches the brassiere-based heart monitor device to a brassiere worn by a subject, the brassiere-based heart monitor device including a pair of physiological sensors and an electrical circuit arrangement electrically coupled to the pair of sensors. 
         [0011]    One or more aspects of the present invention may provide one or more of the following advantages. 
         [0012]    Some embodiments of the device attach to a variety of off-the-shelf bra styles and models. Whereas, other embodiments of the device attach to bras having accommodations for the device, such as pouches to hold part or all of the device, loops to hold part of the device, or slits for part of device to pass through and be held in place with the assistance of the bra. Bras can be worn with or without the device attached. 
         [0013]    The heart monitor device is unobtrusive under clothes and comfortable enough to be worn all day for continuous ECG monitoring. The device includes at least two ECG sensors made of comfortable materials and held in place between the bra and the user&#39;s skin. Generally the sensors are located in the area of the bra&#39;s chest band. The sensors are wired to an electronics module that includes one or more ECG amplifiers and a transmitter for wireless transmission of the ECG, heart rate, or other derived data to a nearby computing device. The heart monitor device includes a battery to power the electronics. In most embodiments the housing material is flexible to be comfortable against the body and thin to provide a low profile under or next to the bra. The device could be a flexible assembly or could have sensors attached by wires to an electronics module. 
         [0014]    The device and bra cooperate as a system to provide ECG, with the bra providing tension to hold sensors reliably close to the skin, while providing access to those locations on the body known for high-quality ECG signal characteristics. Tension from the bra helps to keep the sensors from sliding across the surface of the skin. The device may be held in place solely by the tension of the bra or the device may include mechanisms for attachment to the bra, including, for example, a high friction material against the bra and/or the skin, hooks to hang onto the bra, or clips to attach to the bra. 
         [0015]    The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims. 
     
    
     
       DESCRIPTION OF DRAWINGS 
         [0016]      FIG. 1  is a front view of a bra on a female torso with an attachable monitor. 
           [0017]      FIG. 2  is the back view of the bra of  FIG. 1 . 
           [0018]      FIG. 3  is a block diagram of a typical circuit arrangement. 
           [0019]      FIG. 4  is a perspective view of the bra with attachable monitor. 
           [0020]      FIG. 5  is a perspective view of a bra with an alternative attachable monitor. 
           [0021]      FIG. 6  is a perspective view of a bra with another attachable monitor. 
           [0022]      FIG. 7  is a perspective view of an attachment mechanism. 
           [0023]      FIG. 8  is a perspective view of a bra with clip-on sensors. 
           [0024]      FIGS. 9-12  are cross-sectional views of removable sensors. 
           [0025]      FIGS. 13A-13D  are cross-sectional views showing possible surface preparation for sensor membranes. 
           [0026]      FIGS. 14A and 14B  are plan and cross-sectional views of an alternative sensor. 
           [0027]      FIG. 15  is view depicting lead configurations. 
       
    
    
     DETAILED DESCRIPTION 
       [0028]    Referring to  FIGS. 1 and 2 , a bra  10  with a removably attached monitor device  60  carrying physiological sensors is shown. The bra  10  is shown being worn on a female subject, but the bra  10  could be worn by a male with cups appropriately dimensioned. 
         [0029]    The bra  10  includes a front portion  14  comprising bra cups from which a pair of shoulder strap portions  12   a ,  12   b  emanate that rest over shoulders of the subject and terminate at a back portion  18  of the bra  10 . The strap portions  12   a ,  12   b  extend over the shoulders and meet at the hack portion  18  that rests against the back of the subject, as shown in  FIG. 2 . 
         [0030]    The bra  10  supports a plurality of sensors carried by the monitoring device  60  ( FIG. 4 ). The monitor device  60  can also have an electronics module  50  ( FIG. 3 ) that can wirelessly transmit signals from the sensors to a nearby computer, PDA or wireless phone. A PDA  43 , as shown in  FIG. 4 , may be carried by the person wearing the bra  10 . Although the sensors described herein will be principally ECG sensors, it is to be understood that the sensors can be any type of physiological type sensor such as motion sensors, body temperature sensors and impedance plethysmography sensors, and so forth. 
         [0031]    Referring to  FIG. 3 , the electronics module  50  typically includes input connectors  51  that are connected to signal amplifiers  52 - 53 . Each amplifier is connected to two sensors to create one ECG lead. Thus in the configuration of  FIGS. 3 ,  4  individual sensors could be connected to the 4 inputs, or 3 sensors could be used, with one sensor connected to the input of 2 different amplifiers. For a system with two sensors, only one ECG amplifier  52  and A/D converter  56  is needed. The amplifiers receive signals from sensors, via an integrated wiring system. The signals from the sensors are amplified, and the amplified signals from these amplifiers are fed into pre-processing circuitry  54  that prepares the signals for transmission and subsequent processing. 
         [0032]    The pre-processing circuitry  54  can include A/D converters  56  to digitize the signals from the amplifiers, and may optionally include filters to filter the signals or perform signal processing and identification of physiological conditions. The pre-processing circuitry  54  includes a memory  57  and a processor  58  to implement filtering and processing functions to provide intermediate results and to store information before transmission. Other circuitry is not shown; for instance, timing, storage, interface circuitry and so forth. 
         [0033]    The pre-processing circuitry  54  couples the pre-processed signals to a transmitter  60  and antenna  59  that transmits the signal to a base station  43  ( FIG. 4 ). The signal may be transmitted using, for example, Zigbee or Bluetooth protocols, to a base station that can be a computer, PDA (as in  FIG. 4 ) or wireless phone and so forth. 
         [0034]    An example of an electronic module is the Alive heart monitor by Alive Technologies Pty. Ltd., (International publication No. WO2005/048830). The Alive heart monitor receives an ECG signal from 2 sensors, amplifies the signal, digitizes the signal, and transmits the signal via the Bluetooth protocol. 
         [0035]    Typically, the electronics module  50  is an integral part of the device  60 . An alternative is to enclose the electronics module  50  in a case that can be removed from the device  60 , and reattached using connectors  51 . The electronics module is powered by a battery, which is typically removable from the electronics module  50  for replacement, but alternatively can be permanently sealed in the electronics module  50 . 
         [0036]    In some configurations, the sensors are coupled to an analog multiplexer and the output of the multiplexer can be coupled to an amplifier. In that configuration a circuit (not shown) selects which sensor to couple through the analog multiplexer. 
         [0037]    There are several scenarios for how the monitor device might be used, including, for example, chat signals might be analyzed by the PDA/phone and transmitted to a monitoring center for analysis by a physician. 
         [0038]    The monitoring device  60  attaches to any suitable garment that tightly encircles the torso or other parts of the body, for example, certain types of clothing for instance, a bra, or a chest strap, a tight chest harness (e.g. sports or military accessory), and so forth. 
         [0039]    Many types of commercial and military chest harness, have characteristics to suitably hold the monitoring device  60  tightly against the skin and hold sensors in useful positions for ECG or other physiological monitoring functions, for example, mountain climbing chest harness, cave exploration chest harness, medical monitoring harness (e.g. breathing monitor), chest harness for camera, military chest harness, radio chest harness, rescue harness. 
         [0040]    Referring to  FIG. 4 , a monitor device  60 , i.e., a garment accessory, which is attachable to an article of clothing such as a conventional bra  20 , is shown. The monitor device  60  is configured to attach to a variety of off-the-shelf articles of clothing such as a chest strap or a bra. Attached to a bra  20  of the basic type shown in  FIG. 4 , the bra  20  does not need any modifications to work with the device  60 . Other embodiments that work with modified bras  20  are discussed below. 
         [0041]    The monitor device  60  is comprised of a thin, firm, flexible band  61  of material that may be similar to, for example, flexible printed circuit material, such as that used for circuit cables in computers. In this particular embodiment, the monitor device  60  is in a shape that conforms to the front bottom portion of the bra  20 , at the lower portion of the bra cups (not numbered), allowing the band  61  of thin material of the monitor device  60  to comfortably slip underneath the front bottom portion of the bra  20 . 
         [0042]    The monitor device  60  includes a fastener mechanism, e.g., a tab  62   a  on the user&#39;s right side that is folded over to form a hook portion  63  that bends away from the user&#39;s body. The tab  62   a  is comprised of a relatively stiff material to maintain the hook shape of the folded tab. The folded tab  62   a  hooks over the bra  20  on the bra&#39;s right side strap  22   a . Similarly, the device&#39;s left tab  62   b  hooks over the bra&#39;s left side strap  22   b . The monitoring device  60  also has a center tab  62   c  configured to hook over a central portion  22   c  of the bra  20  (e.g., in the area of the bra between the two bra cups). 
         [0043]    The monitoring device  60  includes sensors  30   a  and  30   b  on the side of the device facing the user (the “skin side”). ECG sensor  30   a  is on the skin side of tab  62   a  and ECG sensor  30   b  is on the skin side of tab  62   b . The sensors  30   a ,  30   b  are connected by wires (not shown) to an electronics module  50  which includes an amplifier and wireless transmitter, as discussed above. The electronics module  50  is preferably located at the center tab  62   c . The wires are integrated into monitoring device  60  to run through the body of the device  61 , preferably using flexible circuit material. Alternative arrangements for sensors and electronics module  50  are possible. For instance, sensors could be located anywhere on the skin side of the band  61  of monitoring device  60 . 
         [0044]    The heart monitor device  60  uses the module  50  to transmit data  42  to a nearby computer, PDA  43  or wireless phone carried by the person wearing the device  20 . 
         [0045]    Referring now to  FIG. 5 , an alternative monitoring device  80 , a variation of monitoring device  60  in  FIG. 4  is shown. The monitoring device  80  is arranged to be worn outside of the bra  20 . Again other types of clothing could be used instead of the bra. Depending on the underlying bra type, this embodiment may be more easily attachable to certain bras or may be more comfortable than monitoring device  60 . When the user is already wearing the bra, it may be easier to attach monitoring device  80  than to attach monitoring device  60  which is slid underneath the bra cups. 
         [0046]    The monitor device  80  is comprised of a thin, firm, flexible band  81  of material that may be similar to, for example, flexible printed circuit material, as mentioned above. In this particular embodiment, the monitor device  80  includes a fastener mechanism, e.g., a tab  82   a  on the user&#39;s right side that folds over inwards toward the user&#39;s body to form a hook portion  83  bending inwards (opposite to that of  FIG. 4 ). As with the monitoring device  60 , the tab  82   a  is comprised of a relatively stiff material to maintain the hook shape of the folded tab. The folded tab  82   a  hooks over the bra  20  on the bra&#39;s right side strap  22   a  and a similar arrangement of a left tab  82   b  hooks is provided for the bra&#39;s left side scrap  22   b . The monitoring device  80  also has a center tab  82   c  configured to hook over a central portion  22   c  of the bra  20  (e.g., in the area of the bra between the two bra cups). 
         [0047]    In addition, the monitoring device  80  includes sensors  30   a  and  30   b  on the side of the device facing the user (the “skin side”). ECG sensor  30   a  is on the skin side of tab  82   a  and BCG sensor  30   b  is on the skin side of tab  82   b . The sensors  30   a ,  30   b  are connected by wires (not shown) to an electronics module, as discussed above. 
         [0048]    Referring to  FIG. 6 , another variation  100  of a monitoring device that attaches to a bra is shown. In this variation, a clip mechanism is used to attach the monitoring device  100  to the bra  20 , rather than use hooked tabs and gravity, as above. The monitoring device  100  is similar to those discussed in  FIG. 4  in that the monitoring device  100  is shaped to conform to the front bottom portion of the bra  20 , at the lower portion of the bra cups, and is comprised of a thin flexible, e.g., circuit board material, allowing monitoring device  100  to comfortably slip underneath the front bottom portion of the bra  20 . 
         [0049]    The device  100  has one end  102   a  that is held between the bra&#39;s right side strap  22   a  and the user&#39;s skin. At the right end  102   a , a sensor  30   a  is integrated into the device. The other end of the device  202   b  is held under the bra&#39;s left side strap  22   b  and has a sensor  30   b . The device  100  also has a central portion  102   c  that is secured under the bra&#39;s center  22   c  (the area of the bra between the two bra cups). The electronics module  50  is shown in this central portion  102   c , although the sensors and electronics module could be at any location in the device  100 . 
         [0050]    The monitoring device has attachment mechanisms  104   a - 104   c  on the outside of the device  100  (e.g., clips or anchors) that attach to the bra. 
         [0051]    Referring now to  FIG. 7 , a detail of one embodiment of the attachment mechanism  104   a - 104   c  is shown. The mechanism  104   a  has a side  105  that attaches to the outside of the device  100 . It is comprised of a plastic material that generally holds its shape but is flexible. The mechanism  104   a  is shaped to form a trough  106  that is large enough to accept the bottom seam of a bra. Inside the trough  106  are teeth  103  that are attached to the outer portion  110  of the mechanism. To attach the device  100  to the bra  20 , the bra  20  is pulled into the trough  106 . The trough  106  expands somewhat when the bra  20  is being inserted, because of the flexible nature of the mechanism  104   a . A bra seam (not shown) of the bra  20  is pulled past the teeth  108  to hold the bra within the trough  106 . 
         [0052]    Referring to  FIG. 8 , an alternative design  120  for the heart monitor is shown attached to a bra  20 . The device  120  has an electronics module  50  that attaches to the central portion  22   c  of the bra  20  (between the two bra cups). The electronics module  50  is attached to two sensor assemblies  122   a  and  122   b  via wires  140   a  and  140   b  respectively. The wires can be shielded for electromagnetic interference. The shielding can extend to the sensor assembly. Sensor assembly  122   a  is shown worn on the user&#39;s back in a position for ischemia detection. On the skin side of the sensor assemblies is a wearable sensor: sensor assembly  122   b  having wearable sensor  30   b.    
         [0053]    The wires  140   a  and  140   b  could be permanently attached to the electronics module  50  and sensor assemblies or could have connectors such as a clip to attach to the sensor. For example, a removable connector on the sensor assemblies could accommodate different sensor assemblies for different activities. The electronics module could be attached to different locations than the one shown, for example, to the back of the bra or to the waistband of pants. 
         [0054]    The sensor assemblies  122   a  and  122   b  could be attached to the bra straps  22   a ,  22   b  by a number of mechanisms, including a snap hinge that applies pressure to the bra strap and prevents the sensor from slipping off the bra strap; or the sensor assembly could be provided with teeth next to the bra strap to hold it in place. In addition, an elastic strap around the bra strap which attaches back to the assembly, Velcro straps, clips or other mechanisms could be used to hold the assembly in place on the bra strap. 
         [0055]    A number of different sensor configurations are possible. For example, a sensor could be on the skin side of the electronics module  50 . This sensor could take the place of the sensor on the user&#39;s right bra strap or could be used as an additional sensor. Sensors could be placed at different places on the bra  20 . 
         [0056]    The wires can be loosely coupled to the bra or wire guides can be provided in the bottom of the bra to hold the wires comfortably in place. The wire guides could be slots to hold the wires in place. Additionally, the bra could have clips to affix the wires to the bra. A bra could be provided with other accommodations for a removably attachable heart monitor device, as will be discussed below in  FIG. 10 . 
         [0057]    The devices  60  ( FIG. 4 ),  80  ( FIG. 5 ), and  100  ( FIG. 6 ) are shown as single unitary solid devices, with the sensors, electronics module and wiring being part of one solid assembly. Each aspect (sensors, electronics, wiring) could be a permanent part of the assembly  60 ,  80 ,  100 . Similarly for device  120  ( FIG. 8 ), the two sensors and the electronics module could each be unitary solid devices (as shown), permanently attached by the insulated wires to each other. Another option is to have some portion of the device  60 ,  80 ,  100 ,  120  removable and/or disposable, such as the electronics module, battery, or sensors. For example, having removable sensors would allow different types of sensors to be used for different activities. Exercise generates a lot of sweat, and desk work does not, so different sensor designs could be used depending on the anticipated level of perspiration. 
         [0058]    Referring to  FIG. 9 , a removable sensor  150  for sensing voltages from the skin to provide a signal for EGG monitoring is shown disposed in a portion of a monitor device  60  ( FIG. 4 ), a monitor device  80  ( FIG. 5 ), a monitor device  100  ( FIG. 6 ) or a monitor device  120  ( FIG. 8 ). 
         [0059]    The removable sensor  150  has a snap  152 . The snap  152  is attached to a sensor frame or housing  154  that is comprised of a firm but flexible material (e.g., rubber). The housing  154  is used to support a more flimsy, e.g. compliant low Young&#39;s modulus material that provides a sensor membrane  156 . The sensing membrane  156  is comprised of an electrically conductive and flexible material, e.g., a conductive rubber or conductive silicone and is disposed inside the housing  154  and has a major surface thereof that is exposed so that the sensing membrane  156  can make contact with the skin. The sensing membrane  156  can be a flat or curved surface, as shown, to ensure secure and adequate contact with the skin. 
         [0060]    The sensing membrane  156  may be temporarily covered with a conductive gel or a hydrogel film  158 . A thin hydrogen film could be cut to size, and would provide excellent skin conduction to a wearable sensor material such as conductive silicone. Hydrogel, however, is not very durable and so the hydrogel might be used for, e.g., a day and then discarded and replaced. 
         [0061]    The snap  152  is comprised of an electrically conductive material, e.g., a metal, conductive plastic, or hard conductive rubber and is disposed in intimate contact with the backside of the sensing membrane  156  to provide an electrical path for a signal from the sensing membrane  156  to a mating snap  160  on the device  60 ,  80 ,  100 , or  120 . This contact can be provided either by having the membrane  156  in intimate contact with a conductive back portion  154   a  of housing  154  or through an aperture (not shown) in the back portion  154   a  of the housing  154  that allows the snap  152  to be directly and electrically connected to the membrane  156 . 
         [0062]    The device  60 ,  80 ,  100 , or  120  in this example would have an accommodation for the sensor  150 . Here the accommodation is a mating snap  160 . The removable sensor  150  thus attaches to the device by mating the snap  152  on the sensor  150  with the corresponding mating snap  160  on the device. In this configuration a wire  140  would be coupled to the mating snap  160  to carry the electrical signal to the electrical circuitry ( FIG. 3 ). The snap  160  attaches to the device  60 ,  80 ,  100 , or  120  by being disposed through an aperture in the material and crimped to surrounding material of the or device to hold the snap  160  in place. 
         [0063]    The conductive snap arrangement just described could also be used to attach an aspect of a removable electronics module  50  to a device  60 ,  80 ,  100 , or  120 . Other attachment mechanisms can be used for those aspects that require electrical connectivity, for example, conductive Velcro or other hook and loop type fastener mechanisms could be used instead of a conductive snap. 
         [0064]    Thus, sensors could be permanently attached to the heart monitor device, or could be removable. Parts or all of a removable sensor could be disposable (e.g. the hydrogel membrane). 
         [0065]    A bra  10 ,  20  could be provided with accommodations for a removably attachable heart monitor device, including pockets, loops of material, slits and accommodations briefly mentioned above, which would help attach the heart monitor  60 ,  80 ,  100 ,  120  to the bra  10 ,  20 , holding the heart monitor securely in place. Accommodations such as pockets, loops of material, slits and clips would allow the bra to be comfortably worn with or without the attachable heart monitor. The bra&#39;s accommodations could accommodate any aspect of the heart monitor  60 ,  80 ,  100 ,  120 , that is, any portion could thread through the loop of material to be securely held in place, for example. The portion of the device that fits in the accommodation may be a section of the device assembly that includes the electronics module, wiring or sensors. As an example, referring back to  FIG. 6 , the bra  20  could be fashioned with pockets for the device  100 , to hold the ends  102   a  and  102   b , as an alternative to or an additional attachment mechanism to the clips  104   a - 104   c . As another example, a bra accommodation such as a pocket in a bra  10 ,  20  may be especially useful to place and hold a sensor assembly in locations on the body that are known for quality ECG sensing. The face of the sensor can make contact with the skin of the user or alternatively capacitive-coupled sensors could be used. 
         [0066]    Referring to  FIG. 10 , an example of a bra  20  accommodation is shown. The bra  20  includes a pocket  18  (or a pouch or opening) to accommodate a sensor assembly  150  which is shaped to fit in the pocket. The pocket  18  is located in the side strap of the bra. Other locations in the bra or garment are possible. The pocket  18  is provided in the garment that is comprised of two layers of material. The sensor assembly  150  is shaped so that the bottom of the sensor assembly  162  fits in the pocket  18 . The sensor assembly  150  may fit snuggly in the pocket  18 , in which case the bra would provide the function of holding the sensor in place. Alternatively, the sensor assembly  150  could fit loosely in the pocket  18 , with the bottom of the sensor assembly  150  preferably being coated with a low-friction material like Teflon, allowing the bra to move and stretch. The face of the sensor  150  would preferably be a high friction material to hold the sensor against the skin. 
         [0067]    Referring to  FIG. 11 , an example of an arrangement with a sensor  150 ′ that does not need direct skin contact, such as a capacitively coupled sensor for measuring ECG is shown. These types of sensors  150 ′ could slip into a pocket  54  on the outside of the bra  20  and would not need to be in direct contact with the skin of the subject. 
         [0068]    The heart monitor device is designed to place ECG sensors at physiologically interesting and useful places. The device can also hold other types of sensors, some of which can be of use in interpreting or processing the ECG signal. The device could incorporate motion sensors: detected motion can be used, for example, to invalidate portions of time in the ECG signal from a nearby ECG sensor when a large amount of motion is detected. ECG sensors can be used in conjunction with impedance plethysmography sensors to measure cardiac output. Sensors to measure surface skin temperature may add to the overall measure of user health. 
         [0069]    The ECG sensors can be provided with a sensing material comprised of metal such as a conventional silver/silver chloride compound. While this metal material could be used, the metal material is somewhat inflexible, does not naturally stick to the skin, and can become slippery in the presence of perspiration. Other materials can be used such as conductive silicone, a wearable material commonly used for shock therapy electrodes, or conductive rubber provided by adding conductive, skin-friendly materials such as silver, gold or carbon to liquid rubber and molding the composition into the desired shape of a sensor. Other conductive materials such as conductive fabric provided by weaving fine threads of silver together with conventional fabric threads; or coating fabric threads with metal can be used. 
         [0070]    Hydrogels can be used as a thin layer between any of these wearable sensor materials and the skin, as previously mentioned. These materials are suitable for sensing ECG signals from the skin without any skin preparation. The shape of the sensor can help maintain contact with the skin. 
         [0071]      FIGS. 3 and 10  depict a smooth rounded sensor that would gently push against the skin to make contact with the skin of a subject. 
         [0072]    Referring to  FIG. 12 , a variation of the heart monitor device has sensors  190  configured with the structure of buttons, such that the button sensors can be slipped through slits  28  (like buttonholes) in some portion of the bra  10 , for example, the chest band portion of a bra  10  such as that pictured in  FIG. 1 . The slit  28  allows a button sensor  190  to touch the skin, and also holds the sensor in place. For a suitable bra, adding these buttonholes is a very simple modification. The sensor  190  has a post  192  attached to the bottom of the sensor, which fits through the slit  28  in the bra  10  chest band. The post  192  is connected to the heart monitor device, e.g.  60  and the button hole in the chest band slips over the sensor and post. 
         [0073]      FIGS. 13A-13D  shows cross sections of sensor faces showing different textures. In  FIG. 13A , the sensor  150  has a sensor face  156   a  with nubs or bumps  166  shaped like gumdrops on the surface of the sensor that touches the skin. This configuration of the surface would be suitable for working around body hair, as the nubs would have a good chance of pressing in between the hairs to reach the skin. Excessive sweat could also be channeled between the nubs  166 . 
         [0074]      FIG. 13B  shows a sensor face  156   b  having sharp ridges  168  which may be more suitable for reaching the skin through hair, than the nubs  166  of  FIG. 13A . Sweat could also be channeled through the grooves in between the ridges  166 . 
         [0075]      FIG. 13C  shows another variation with grooves cut into the sensor face  156   c  forming softer ridges  170 . In  FIG. 13D  conductive threads  156   d  are provided in the sensor face and help maintain contact with the skin even when the sensor is sliding across the surface of the skin. 
         [0076]    Referring to  FIG. 14 , to prevent the sensor  150  from sliding, a ring of sticky or high-friction material  159   a  such as rubber or soft silicone could foe placed around the sensing material  156 . The friction ring  159   a  may be made of waterproof material (silicone, for example), which may also induce sweat. 
         [0077]    Sweat is a good conductor for ECG sensors, and inducing a little sweat can help maintain skin contact and conductivity. However, if there is too much sweat, the sensor may slide against the skin, inducing noise in the signal, and the excess sweat may be uncomfortable. For this reason it may be beneficial to have a sweat absorbing ring  159   b  that surrounds the rest of the sensor. The sweat-absorbing material  155   b  can be made of cotton, for example. 
         [0078]    The sensing material may be in the shape of a flat disk, as shown in  FIG. 14A , and made of a conductive fabric which can absorb some sweat. These conductive fabrics tend to dry out when the user is not perspiring, which may drastically reduce the sensor&#39;s conductivity. One solution is to apply a waterproof or water resistant backing  159   a  to the sensing material  156 , to help keep the sensing material  156  damp by sweat. The material  159   a  extends beyond the edges of the sensing material  156  to make contact with the skin and provide the high-friction function, while also providing a water resistant barrier around the sensing material  156  to induce sweat. For applications where large amounts of sweat are anticipated, the sweat disk  159   a  could be constructed of water resistant material that allows some evaporation. The sweat-absorbing ring  159   b  is shown in  FIG. 15B  does not overlap any other part of the sensor, but is a separate ring to ensure direct shin contact and prevent sweat from dripping down from the sensor. 
         [0079]    The sensing material  156 , friction ring  159   a  and sweat-absorbing ring  159   b  are shown as circular shapes. However, these elements could be rectangular or any other shape or provided in alternating strips, and still provide the same functions. 
         [0080]    The ideal physiological sensor would be able to induce enough sweat for good conduction, but wick away excess sweat. In the absence of the ideal, users may desire to have different sensors for different activities, different amounts of sweat, and differences in comfort. Users may differ in how dry their skin is, how much body hair they have, or how much they sweat, requiring different sensors. To work in the presence of sweat or hair, an uneven surface will allow parts of the sensor to reach the skin and make good contact. 
         [0081]    The devices  60 ,  80 ,  100 , or  120  carry comfortable sensors that need not use adhesive against the skin and can stay in place against the skin. The mechanisms that hold the sensors against the skin include a tensile force that is imparted to the sensors by the bra  20 . Also, in some embodiments, the sensors will tend to stay in place against the body by providing the sensor faces with a relatively high-friction surface to minimize slippage against the skin. The bra  20  allows sensors to be placed at physiologically useful places on the body. In some embodiments, the sensors may also have slightly sticky or tacky surface to help to hold the sensors in place against the skin. 
         [0082]    Referring now to  FIG. 15 , there are several possible ECG lead configurations with the attachable heart monitor  60 ,  80 ,  100 , or  120 . Using ECG sensors at the position of V 6  and V 6 R, a lead from V 6  to V 6 R will provide ECG with good amplitude. V 6  to V 2  would also be good, and adding a ground sensor at V 6 R would help signal stability. Additional leads could use sensors at V 3 , V 4  and V 5 , which are very close to the heart and provide good amplitude. A sensor on the back chest band of the bra may provide information about ST changes in the ECG over time, which can be an indication of myocardial ischemia. 
         [0083]    A number of embodiments of the invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention.