Abstract:
A system for unobtrusively measuring bioelectric signals developed by an individual includes multiple sensors, one or more of which constitutes a capacitive sensor attached to a holding device. The holding device serves as a mounting structure that holds sensors in place within a wearable garment. The holding device and sensors are horizontally and vertically adjustable relative to the garment, while the sensors are pressed against the individual and prevented from undesirable shifting upon movement of the individual.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     The present invention claims the benefit of U.S. Provisional Patent Application Ser. No. 60/578,349 filed Jun. 10, 2004 entitled “Garment Incorporating Embedded Physiological Sensors.” 
     
    
     BACKGROUND OF INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention pertains to the art of measuring and monitoring bioelectric signals using sensor systems incorporating at least one capacitive-type electric sensor and, more particularly, to an adjustable garment incorporating embedded psychological sensors.  
         [0004]     2. Discussion of the Prior Art  
         [0005]     It is widely known that electric potentials and fields are developed in free space from many different sources. For example, organs in the human body, including the heart and brain, produce electric fields throughout the body and in the space outside the body. For a variety of reasons, it is often desirable to measure these electric fields, such as in performing an electrocardiogram (ECG). Indeed, the measurement of bioelectric signals can provide critical information about the physiological status and health of an individual, and is widely used in monitoring, evaluating, diagnosing and caring for patients. Prior methods of measuring electric potentials associated with human or animal subjects employ securing gel-coated electrodes directly to the skin or scalp, or inserting electrodes into the body.  
         [0006]     More specifically, electrodes that make a resistive (i.e. Ohmic) electrical contact have been predominantly employed in connection with measuring electric potentials produced by animals and human beings. The disadvantages of such resistive electrodes have been described previously and include discomfort for the patient, the requirement for conducting gels and/or adhesives, difficulty in establishing good electrical contact because of differing physical attributes of the subject (hair, skin properties, etc.), and the degradation in resistive coupling quality over time, among others. These limitations have created a significant barrier to the use of resistive electrodes over extended periods of time and/or when convenience of use is paramount.  
         [0007]     Another type of sensor that has been proposed in measuring biopotentials is a capacitive sensor. Early capacitive sensors required a high mutual capacitance to the body, thereby requiring the sensor to also touch the skin of the patient. The electrodes associated with these types of sensors are strongly affected by lift-off from the skin, particularly since the capacitive sensors were not used with conducting gels. As a result, early capacitive sensors were not found to provide any meaningful benefits and were not generally adopted over resistive sensors. However, advances in electronic amplifiers and new circuit techniques have made possible a new class of capacitive sensor that can measure electrical potentials when coupling to a source on the order of 1 pF or less. This capability makes possible the measurement of bioelectric signals with electrodes that do not need a high capacitance to the subject, thereby enabling the electrodes to be used without being in intimate electrical and/or physical contact with the subject. Such capacitive-type sensors and sensing systems have been previously disclosed.  
         [0008]     To enhance the measurement of bioelectric signals, there still exists a need for a system that can unobtrusively measure the signals with minimal set-up or preparation time. In addition, there exists a need for a bioelectric signal measuring system that is convenient to use, both for the patient and an operator, such as a nurse, doctor or technician. Furthermore, there exists a need for an effective bioelectric signal measuring system that is adaptable for use by many different sized patients. Specifically, a truly unobtrusive measurement system, which does not require significant preparation or modification for use by different patients, is needed.  
       SUMMARY OF THE INVENTION  
       [0009]     The present invention is directed to a system for unobtrusively measuring bioelectric signals developed by an individual, inclusive of a human or animal. The measurement system enables bioelectric signals to be collected through multiple sensors, one or more of which constitutes a capacitive-type sensor carried by a holding device incorporated into a garment worn by the individual.  
         [0010]     In accordance with one embodiment of the invention, the sensors are attached to an elastic band which is held within a shirt, however other garment arrangements can be employed, e.g., belts, hats, headbands and the like. In any case, the band is both horizontally and vertically adjustable within the shirt through the use devices, such as snaps, Velcro, patches, and elastic cord and toggle systems. With this arrangement, an individual, regardless of his or her size, only needs to put on the garment and adjust the position of the band with the simple adjustment devices. The sensors may be attached to the band through sensor carriers, which include a layer of high-traction or anti-slip material for contacting the skin of an individual such that the sensor remains undisturbed by movement of the individual or by adjustment of the holding device. In the alternative, the sensors themselves may carry one or more anti-slip elements. Furthermore, the band may include a foam or inflatable material for pressing the sensors firmly against the individual.  
         [0011]     Regardless of the particular implementation, the sensor system of the invention is integrated into a holding device that is incorporated into a garment to be worn by an individual to enable bioelectric signals to be continuously measured in an extremely convenient, unobtrusive and effective way with little or no intervention needed on the part of the individual.  
         [0012]     Additional objects, features and advantages of the present invention will become more readily apparent from the following detailed description of preferred embodiments when taken in conjunction with the drawings wherein like reference numerals refer to corresponding parts in the several views. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]      FIG. 1  is a schematic view illustrating a garment incorporating the sensor system of the invention provided on an individual and attached to a control unit;  
         [0014]      FIG. 2  is a front view illustrating the garment of  FIG. 1 ;  
         [0015]      FIG. 3  is a back view illustrating the garment of  FIGS. 1 and 2 ;  
         [0016]      FIG. 4  is a side view illustrating the garment of  FIGS. 1-3 ;  
         [0017]      FIG. 5  is a front view illustrating the garment and sensor system of the invention with vertical adjustment attachment structures;  
         [0018]      FIG. 6  is an enlarged view of the attachment structures of  FIG. 5 ;  
         [0019]      FIG. 7  is a front view illustrating the garment and sensor system of the invention incorporating sensor carriers;  
         [0020]      FIG. 8A  is an enlarged view of the sensor carrier of  FIG. 7 ;  
         [0021]      FIG. 8B  is a still larger, yet exploded view of the sensor carrier of  FIG. 8A ;  
         [0022]      FIGS. 9A  is a top view illustrating a foam insert for use with the sensor system of the invention;  
         [0023]      FIG. 9B  is another top view illustrating the foam insert of  FIG. 9A ;  
         [0024]      FIG. 10A  is a top view illustrating inflatable inserts for use with the sensor system of the invention;  
         [0025]      FIG. 10B  is another top view illustrating the inflatable inserts of  FIG. 10A ; and  
         [0026]      FIG. 11  is a view illustrating the sensor system of the invention incorporating the foam insert of  FIGS. 9A and 9B  against a torso of an individual.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0027]     With initial reference to  FIG. 1 , a sensor system constructed in accordance with the present invention is generally indicated at  2 . In general, sensor system  2  functions to measure biopotentials of an individual  5 , such as a medical patient, animal, test subject or the like. As shown, individual  5  includes a head  7  and a torso  8  having a chest  9  and back  11 , with torso  8  being surrounded by a holding device which forms part of sensor system  2 . In the embodiment shown, the holding device constitutes a band  14 . More specifically, sensor system  2  includes band  14  having embedded or otherwise integrated therein at least first and second sensors  17  and  18 . In accordance with the invention, at least first sensor  17  constitutes a capacitive-type sensor and, in the most preferred embodiment of the invention, both first and second sensors  17  and  18  constitute capacitive-type sensors.  
         [0028]     As shown, each of first and second sensors  17  and  18  is preferably hardwired to a connector  21  and linked through a cable  23  to a remote control unit  25  of sensor system  2 . In the embodiment shown, controlling unit  25  constitutes a laptop computer having a display panel  28  and a keyboard  30 . The use of sensor system  2  enables individual  5  to wear band  14  whereby a bioelectric field produced by individual  5  can be sensed by first and second sensors  17  and  18 , with bioelectric signals being transmitted to control unit  25  for analysis and display purposes. That is, individual  5  will inherently produced time-varying potentials which will be sensed through first and second sensors  17  and  18 . As first and second sensors  17  and  18  preferably constitute capacitive-type sensors, no electrically conducting path to the individual  5  is needed. In other words, no flow of real current (electrons) occur between individual  5  and first and second sensors  17  and  18  such that first and second sensors  17  and  18  need not be in physical contact with individual  5 . Therefore, the use of capacitive-type sensors enables first and second sensors  17  and  18  to be embedded or otherwise integrated into a holding device worn by individual  5 . In this manner, an extremely unobtrusive and convenient sensing system  2  is established which requires very little setup or intervention.  
         [0029]     Reference will now be made to  FIGS. 1-5  which depict a particular embodiment of the invention. In accordance with this embodiment, sensor system  2  is incorporated into band  14  which is attached to a garment  35 . In the embodiment shown, garment  35  constitutes a shirt. However, other types of garments including belts, hats, headbands and other articles worn by an individual, could also be employed. Attached to band  14  are sensors  17  and  18 . Although only sensors  17  and  18  are shown, additional sensors may be used. In any case, each sensor  17 ,  18  constitutes a capacitive-type sensor and includes a capacitive-type electrode having an associated mounting strip (not shown). Each electrode is linked through one or more conductors to connector  21  adapted to be interconnected to control unit  25 . Additional information regarding the connection of sensors to the control unit is disclosed co-pending application Ser. No. 10/919,461 entitled “Unobtrusive Measurement System for Bioelectric Signals” and hereby incorporated by reference.  
         [0030]     As illustrated by  FIGS. 2 and 3 , garment  35  may be a sleeveless shirt having a front  43  and a back  44 . A zipper  47  extends up front  43  of garment  35  such that individual  5  may easily put on or take off garment  35 . As best shown in  FIGS. 3 and 5 , band  14  is held in position on an inside  50  of garment  35  by a plurality of strips or loops, one of which is indicated at  55 , that define respective slots (not labeled) which alternate with a plurality of gaps, one of which is indicated at  57 . Preferably, sensors  17  and  18  are positioned on band  14  at one of the plurality of gaps  57 , exposing sensors  17  an  18  to individual  5 . Band  14  is actually fed through the plurality of slot or sleeve defining strips  55  to limit shifting of band  14  within garment  35 . Sensor  17  may be connected to other sensors (not separately labeled) and communicate with control unit  25 , such as through cable or cord  23 . However, it should be noted that a wireless connection could also be employed. Garment  35  may include a pocket (not shown) for holding a smaller control unit or wireless transmitter (not shown).  
         [0031]     In accordance with an aspect of the invention, band  14  is horizontally adjustable or capable of being cinched or otherwise adjusted in combination with garment  35  to accommodate individuals  5  of varying shapes and sizes. To this end, a cord  60  having free ends, two of which are shown at  63  and  64  in  FIGS. 2 and 3 , is coupled to band  14 . Free ends  63  and  64  can be drawn in opposite directions through grommets  67  and  68  and held by a toggle (not shown) to bring band  14  from a first larger circumference to a second smaller circumference, thereby drawing band  14  and sensors  17  and  18  closer to torso  8  of individual  5 . Alternatively, other horizontal adjustment or cinching devices may be used to change the circumference of band  14 . Some additional adjustment devices include, but are not limited to, Velcro patches, snaps, hook and eyelet fasteners, and plastic loop fasteners. Alternatively, the sensor  17 ,  18  may have a Velcro patch (not shown) attached thereto such that the sensor  17 ,  18  may be independently adjustable along band  14 .  
         [0032]     In accordance with another aspect of the invention as best illustrated in  FIGS. 5-7 , band  14  is also vertically adjustable to accommodate individuals  5  of varying heights or to simply vertically reposition sensors  17  and/or  18 . In accordance with a preferred embodiment, vertically spaced apart attachment structures, such as snaps  71 - 74 , are integrated into garment  35  to allow band  14  to be easily moved between different vertical positions. More specifically, in the embodiment shown, band  14  includes snaps  77  and  78  which may be coupled to either snaps  71  and  72 , snaps  72  and  73 , or snaps  73  and  74 , each of which would place band  14  at a different vertical position. Each of  FIGS. 5-7  shows belt snaps  77  and  78  fastened to snaps  72  and  73 , thereby placing band  14  in an intermediate vertical position. In order to allow individual  5  or other personnel to easily adjust the vertical position of band  14 , snaps  71 - 74  are preferably positioned adjacent to zipper  47  of garment  35 . Although band  14  is vertically adjustable through the use of snaps  71 - 74  in the embodiment shown, other adjustment devices, such as Velcro patches, snaps, hook and eyelet fasteners, plastic loop fasteners or any other attachment or adjustment device, may be used. As described above, sensor  17 ,  18  may include separate fasteners (not shown) to allow sensor  17 ,  18  to be independently moved horizontally or vertically on band  14 .  
         [0033]     Horizontal expansion or contraction of band  14  may cause pulling or dragging of sensor  17 ,  18  with a lateral force which could cause moving of sensor  17 ,  18  with respect to torso  8  of individual  5 . Movement of sensor  17 ,  18  generates electrostatic charges, which induces noise artifacts. Noise artifacts are generated by either triboelectric effects between the surface of the electrode (not separately labeled) of sensor  17 ,  18  and the skin or clothing of individual  5  or by sensor  17 ,  18  loosing communication with individual  5 , such as by tilting, and thus becoming sensitive to free space electric fields.  
         [0034]     In order to substantially eliminate noise artifacts generated by movement of sensor  17 ,  18 , a sensor carrier  85  may be used in connection with the sensor system  2  of the invention, as illustrated with reference to sensor  18  in  FIGS. 7, 8A  and  8 B. Sensor carrier  85  includes a first surface  87  to be positioned adjacent individual  5 , a second surface (not shown) for facing away from individual  5 , and a slot  89  formed therebetween for band  14  to slide through. This arrangement enables sensor carrier  85  to shift along band  14  as needed. That is, garment  35  and band  14  can shift when individual  5  twists, turns, bends or otherwise moves, while sensor carrier  85  can remain substantially stationary. Formed within first surface  87  is a cut-out or recessed portion  90  into which sensor  18  is adapted to fit. Preferably, sensor  18  is frictionally, adhesively or otherwise fixedly secured in cut-out portion  90 . Lateral pressure between sensor  18  and the cut-out portion  90  holds sensor  18  in place. Therefore, sensor  18  may be installed or removed from sensor carrier  85  without the use of fasteners or external hardware. First surface  87  is preferably formed from a high-traction material, such as rubber as depicted in  FIG. 8B , which has an increased coefficient of friction with the skin or clothing of individual  5 . Interior walls (not shown) of sensor carrier  85  are coated with or formed from a material that minimizes the frictional forces between sensor carrier  85  and band  14  and allows relative movement between sensor carrier  85  and band  14 . Therefore, the force of sensor carrier  85  and corresponding sensor  17 ,  18  against individual  5  remains substantially constant and undisturbed by horizontal adjustments of band  14  or through breathing or movement by individual  5 . In addition, various types of anti-slide coatings or devices may be applied directly to band  14 . The high-traction material could also be provided directly on sensor  17  and/or  18 . For instance, this high-traction material can take the form of a ring, pegs of rubber or other structure which will effectively reduce the amount of relative motion between sensor  17 ,  18  and the skin of individual  5 , or an optionally interposed fabric layer. The use of the high-traction material in connection with enhancing the ability of band  14  to move and slide relative to sensor  17 ,  18  and sensor carrier  85  has been found to advantageously prevent translational motion and frictional forces from being transferred to sensor carrier  85  based on movement of band  14  and enables each sensor  17 ,  18  to remain essentially fixed relative to the skin of individual  6  in order to minimize any artifact noises in the measurements taken.  
         [0035]      FIGS. 9A-11  illustrate another aspect of the invention that ensures suitable pressure between sensor  18  and individual  5 . Since torso  8  of individual  5  is contoured in a non-uniform manner, band  14  may not create uniform pressure against torso  8 . This may cause sensor  18  to move relative to torso  8  in an undesired manner. As shown in  FIGS. 9A, 9B  and  11 , an insert  101  may be used to distribute pressure uniformly behind one or more sensors  18 .  FIG. 9A  illustrates insert  101  in a first position prior to being worn by individual  5 .  FIGS. 9B and 11  illustrate band  14  and insert  101  as worn by individual  5 . Alternatively, multiple inserts  105 - 107  may be used to distribute pressure behind a respective sensor  18 .  FIGS. 10A and 10B  illustrate band  14  with inserts  105 - 107  before and during use, respectively. Inserts  101  and  105 - 107  may be formed from passive foam, dynamic foam, compressible “memory” foam, inflatable air bladders or any other material capable of filling concave voids based on body type and applying positive, substantially perpendicular pressure of the sensor  17 ,  18  to the individual  5 .  
         [0036]     Although described with reference to preferred embodiments of the invention, it should be readily understood that various changes and/or modifications can be made to the invention without departing from the spirit thereof. Regardless of the particular implementation, the sensor system of the invention is integrated with a holding device, such as a band or spring member, and a garment, e.g., shirt, belt, hat, headband and the like, to be worn by an individual in a manner which provides a force to hold the sensor to the body of the individual while not transferring translational motions of the individual to the sensor through the holding device in order to enable bioelectric signals to be continuously measured for various applications, including EEG, ECG, EOG and EMG, in an extremely convenient, unobtrusive and efficient manner, with little or no intervention needed on the part of the individual producing the bioelectric field to be measured and with minimal artifact noises. The holding device and garment allow the sensors to be easily adjusted both horizontally and vertically to accommodate individuals of different shapes and sizes. Although only a single band  14  has been described, multiple band segments could be employed, preferably ranging from about 4 inches (approximately 10 cm) to 8 inches (approximately 20 cm) apart. Circumference variations can be readily provided in accordance with the invention. Finally, height adjustments can be a fraction of an inch to six or more inches, e.g., 0.25 inches (approximately 0.6 cm) to 6.5 inches (approximately 16.5 cm). In the overall system, the bioelectric signals can be pre-processed either prior to or by the control unit. For instance, the difference between the outputs of one or more sensors can be taken before transmitting the data or simply prior to further analyzing the data. In any event, the invention is only intended to limited by the scope of the following claims.