Abstract:
Apparatuses, systems, and methods for monitoring a pressure exerted on a tissue site are provided. In one embodiment, an apparatus includes a pressure switch adapted for placement adjacent the tissue site. The pressure switch includes an antenna operable to receive a first signal, a diode disposed adjacent the antenna, and a membrane covering the antenna and the diode. The membrane is movable from an unpressed position to a pressed position when a force is exerted on the membrane to cause electrical communication between the antenna and the diode. The antenna is operable to send a second signal when the membrane is in the pressed position. The apparatus may also include a transmitter operable to emit the first signal to the antenna. The transmitter may output an alert when the transmitter receives the second signal.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 61/036,433 filed Mar. 13, 2008, which is hereby incorporated by reference. 
    
    
     BACKGROUND 
     The illustrative embodiments relate generally to medical treatment systems and, more particularly, to pressure switches, transmitters, systems, and methods for monitoring a pressure at a tissue site. 
     Tissue sites on a patient&#39;s body often experience varying levels of pressure due to the position or behavior of the patient. A patient or caretaker may desire to know whether the pressure exerted on a particular tissue site is excessive. By way of example, the foot ulcers experienced by a diabetic patient may undergo varying levels of pressure due to certain behaviors, such as walking. Off-loading shoes or boots may be used to alleviate pressure on the foot ulcer, but do not always effectively reduce the pressure on the foot ulcers. In addition, more than 82 percent of diabetic patients may also lack the protective sensation to determine whether excessive amounts of pressure are being exerted on the ulcer. This lack of protective sensation may be caused by peripheral neuropathy, which often afflicts diabetic patients having ulcers. 
     SUMMARY 
     According to an illustrative embodiment, an apparatus for monitoring a pressure exerted on a tissue site includes a pressure switch adapted for placement adjacent the tissue site. The pressure switch includes an antenna operable to receive a first signal, a diode disposed adjacent the antenna, and a membrane covering the antenna and the diode. The membrane is movable from an unpressed position to a pressed position when a force is exerted on the membrane to cause electrical communication between the antenna and the diode. The antenna is operable to send a second signal when the membrane is in the pressed position. The apparatus may also include a transmitter operable to emit the first signal to the antenna. The transmitter may output an alert when the transmitter receives the second signal. 
     In another embodiment, a method for monitoring a pressure exerted on a tissue site includes receiving a first signal from a transmitter, detecting a force at the tissue site, and sending a second signal to the transmitter in response to detecting the force. 
     In another embodiment, a method for monitoring a pressure exerted on a tissue site includes sending a first signal from a transmitter, and outputting an alert in response to receiving a second signal from a pressure switch adjacent the tissue site. 
     Other objects, features, and advantages of the illustrative embodiments will become apparent with reference to the drawings and detailed description that follow. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  illustrates a front view of a system for indicating a pressure exerted on a tissue site according to an illustrative embodiment; 
         FIG. 1B  illustrates a bottom view of the foot shown in  FIG. 1A ; 
         FIG. 2  illustrates a top view of a pressure switch of the system of  FIGS. 1A and 1B  according to an illustrative embodiment; 
         FIG. 3A  illustrates a cross-sectional side view of the pressure switch of  FIG. 2  taken along line  3 A- 3 A; 
         FIG. 3B  illustrates a cross-sectional side view of the pressure switch of  FIG. 3A , the pressure switch being shown in a pressed position; and 
         FIG. 4  illustrates a perspective view of a transmitter of the system of  FIG. 1A  according to an illustrative embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     In the following detailed description of the illustrative embodiments, reference is made to the accompanying drawings that form a part hereof. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, and it is understood that other embodiments may be utilized and that logical structural, mechanical, electrical, and chemical changes may be made without departing from the spirit or scope of the invention. To avoid detail not necessary to enable those skilled in the art to practice the embodiments described herein, the description may omit certain information known to those skilled in the art. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the illustrative embodiments are defined only by the appended claims. 
     Referring to  FIGS. 1A and 1B , a system  100  for indicating a pressure exerted on a tissue site according to an illustrative embodiment includes a transmitter  106  and at least one pressure switch  110 . In the embodiment illustrated in  FIGS. 1A and 1B , two tissue sites  102 ,  104  are located on a foot of a patient  107 . Pressure switch  110  is positioned at the tissue site  102 , and a second pressure switch  112  is positioned at the tissue site  104 . In system  100 , the transmitter  106  is worn by the patient  107  and emits a first signal  108 . The pressure switches  110 ,  112  receive the first signal  108  from the transmitter  106 . Each of the pressure switches  110 ,  112  is capable of detecting the pressure exerted on the tissue sites  102 ,  104 . The pressure switch  110  may emit a second signal  114  when the pressure exerted on the tissue site  102  exceeds an amount that changes the state of the pressure switch  110 . Similarly, the pressure switch  112  may emit a second signal  116  when the pressure exerted the tissue site  104  exceeds a amount that changes the state of the pressure switch  112 . Upon receiving either or both of the second signals  114 ,  116 , the transmitter  106  may alert the patient  107  in a variety of ways, such as by vibrating or emitting an audio or visual alert. The first and second signals  108 ,  114 ,  116  may be any wireless signal, including, without limitation, electromagnetic, radio, or Bluetooth signals. 
     The tissue sites  102  and  104 , in the example of  FIGS. 1A and 1B , are foot ulcers  103 ,  105 . The alert emitted by transmitter  106  in response to pressure at the foot ulcers  103 ,  105  may alert the patient  107  when there is excessive pressure on the foot ulcers  103 ,  105 . Such an alert may be used when the patient  107  may be otherwise unable to properly determine the pressure being exerted on the foot ulcers  103 ,  105 , such as when the patient  107  suffers from peripheral neuropathy. By alerting the patient  107  when excessive pressure is being applied to the foot ulcers  103 ,  105 , the patient  107  may take measures to alleviate the pressure on the foot ulcers  103 ,  105 , such as by altering the patient&#39;s position, weight distribution, or movement. Thus, aggravation or worsening of the foot ulcers  103 ,  105  may be prevented. 
     While the pressure switches  110 ,  112  have been described as being used with foot ulcers  103 ,  105 , the pressure switches  110 ,  112  may instead be placed on or adjacent to any part of the patient&#39;s  107  body, including those parts where ulcers or other wounds may be subjected to prolonged pressure. For example, the pressure switches  110 ,  112  may be placed on or adjacent the patient&#39;s  107  heel, shoulder blades, or buttocks. 
     In addition, any number of pressure switches  110 ,  112  may be placed on the patient&#39;s  107  body, depending upon the number of tissue sites to be monitored by the system  100 . In one embodiment, when more than one pressure switch is placed on the patient&#39;s  107  body, the transmitter  106  may output a different alert depending on the pressure switch from which the second signal is received. For example, the transmitter may output a different audio alert depending on whether the transmitter  106  receives the second signal  114  from the pressure switch  110  or the second signal  116  from the pressure switch  112 . 
     The pressure switches  110 ,  112  may be placed adjacent the tissues sites  102  and  104  by adhering the pressure switches  110 ,  112  to locations other than the tissue sites  102 ,  104  themselves. The pressure switches  110 ,  112  may be adhered, or otherwise placed, on an article of clothes worn by the patient  107 , including, without limitation, a shoe, off-loading boot/shoe, shirt, or sock, such that the pressure switches  110 ,  112  are adjacent the tissue sites  102 ,  104  when the article is worn. For example, the pressure switches  110 ,  112  may be adhered to an insole, or inner surface, of an off-loading boot intended to alleviate pressure from the foot ulcers  103 ,  105  such that the pressure switches  110 ,  112  are adjacent the foot ulcers  103 ,  105  when the boot is worn by the patient  107 . 
     In one embodiment, the transmitter  106  is secured to the patient&#39;s leg  118  by a strap  120 . In other embodiments, the transmitter  106  may be secured to any part of the patient&#39;s  107  body, an article being worn by the patient  107 , or coupled to one or more of the pressure switches  110 ,  112 . Also, in lieu of or addition to the strap  120 , the transmitter  106  may use any attachment mechanism to directly or indirectly attach to the patient&#39;s  107  body, such as a buckle, velcro, a magnet, a hook, a harness, or any other attachment device. In another embodiment, the transmitter  106  may not be secured to the patient&#39;s  107  body, but instead held or placed in an article worn by the patient  107 , such as a pocket or purse. The location and attachment mechanism used by the transmitter  106  may depend on the output that is emitted by the transmitter  106  when the second signals  114 ,  116  are received. For example, if the transmitter  106  emits an audio, visual, or vibrational output, the transmitter  106  may be located where the transmitter  106  may be heard, seen, or felt by the patient  107 , respectively. 
     In another embodiment, a tactile feedback device (not shown) may be coupled to, adjacent, or inside one or both of the pressure switches  110 ,  112 . In one example, the pressure switches  110 ,  112  and one or more tactile feedback devices may be located inside of an article of footwear, such as an off-loading boot. When either or both of the pressure switches  110 ,  112  detect a force, the tactile feedback device may output a tactile alert to the patient  107 . The tactile alert may include vibration, including one or more taps, or electrical stimulation. 
     Referring to  FIGS. 2 ,  3 A, and  3 B, the pressure switch  110  includes an antenna  122  and a diode  124  that is separated from the antenna  122  by a gap  126 . The pressure switch  110  also includes a membrane  128  that is movable between an unpressed position  130  and a pressed position  132  based on a force  134  exerted on the membrane  128 . When the force  134 , which may be a pressure, is exerted on the membrane  128 , the membrane  128  moves from the unpressed position  130  to the pressed position  132  to cause electrical communication between the antenna  122  and the diode  124 . The electrical communication between the antenna  122  and the diode  124  causes the antenna  122  to emit the second signal  114 , which may be received by the transmitter  106  and cause the transmitter  106  to output an alert. Thus, a patient may be alerted when the pressure or force on a tissue site collapses the membrane  128  into the pressed position. 
     The antenna  122  may be formed from a conducting conduit  136 . The conducting conduit  136  may be made from any conducting material, such as metal. In one embodiment, the metal used to form the conducting conduit  136  may be stainless steel or any resilient material that is capable of returning to an original shape after the force  134  is removed. The conducting conduit  136  may also form a spiral, such as that shown in  FIG. 2 . An inner portion  137  of the spiral may terminate at about the center  138  of the pressure switch  110 , and an outer portion  139  of the spiral may terminate at a periphery  140  of the pressure switch  110 . In one embodiment, the outer portion  139  may terminate just before reaching the diode  124  to form the gap  126 . 
     The pressure switch  110  may be a passive device that does not require an independent power source, such as a battery. In one embodiment, the first signal  108  from the transmitter  106  may cause the diode  124  to agitate or have a current. In the pressed position  132 , the membrane  128  may directly or indirectly touch both the antenna  122  and the diode  124  to electrically bridge the gap  126 , or close the circuit, between the antenna  122  and the diode  124 . In this manner, any agitation or current from the diode  124  is communicated to the antenna  122 , thereby causing the antenna  122  to emit the second signal  114 . 
     The material from which the membrane  128  is formed may facilitate electrical communication between the antenna  122  and the diode  124  when the membrane  128  touches both the antenna  122  and the diode  124 . In one embodiment, the membrane  128  may be formed from a conducting material, such as metal. In another embodiment, an inner surface  142  of the membrane  128  may be coated, or otherwise include, a conducting material. In yet another embodiment, only a portion  144  of the inner surface  142  of the membrane  128  may be coated, or otherwise include, a conducting material. 
     Although the membrane  128  is shown to form a dome shape, the membrane  128  may have any shape that allows the membrane  128  to have unpressed and pressed positions. For example, the membrane  128  may be a button that, when pressed, causes electrical communication between the antenna  122  and the diode  124  by electrically bridging the gap  126 . The pressure switch  110  also has a low-profile, which may allow the pressure switch  110  to be unobtrusively placed adjacent a tissue site or hide the pressure switch  110  when located under an article of clothes worn by a patient. For example, the low-profile of the pressure switch  110  facilitates the placement of the pressure switch  110  on a patient&#39;s foot while the patient wears a shoe or off-loading boot, and may help to reduce discomfort experienced by the patient. 
     In addition, although the perimeter  146  of the pressure switch  110  has an approximately square shape, the perimeter  146  may have any shape, such as a circular, elliptical, rectangular, polygonal, or customized shape. In the embodiment in which the perimeter  146  of the pressure switch  110  is a customized shape, a user may cut, or otherwise shape, the pressure switch  110  to adapt to the tissue site or other object adjacent to which the pressure switch  110  will be applied. 
     The amount of force  134  required to move the membrane  128  from the unpressed position  130  to the pressed position  132  may depend on a variety of factors. Such factors may include, without limitation, the shape of the membrane  128 , the thickness of the membrane  128 , the material from which the membrane  128  is formed, the curvature of the membrane  128 , and the conductivity of the membrane  128 . One may desire to adjust the amount of force  134  that is required to move the membrane  128  from the unpressed position  130  to the pressed position  132  for a variety of reasons. For example, the force  134  may be varied based on the location of the tissue site adjacent to which the pressure switch  110  is to be placed to take account of the varying amounts of pressure normally experienced by different parts of the body. 
     When all or a portion of the force  134  is removed from the membrane  128 , the membrane  128  may move from the pressed position  132  to the unpressed position  130 , including any position intermediate between the pressed position  132  and the unpressed position  130 . In the unpressed position  130 , the membrane  128  does not electrically bridge the gap  126  between the antenna  122  and the diode  124 . Little or no electrical communication may occur across the gap  126  when the membrane  128  is in the unpressed position  130 . 
     Referring now specifically to  FIGS. 3A and 3B , the pressure switch  110  may include a padding layer  148 . The antenna  122  and the diode  124  are disposed between the padding layer  148  and at least a portion of the membrane  128 . The pressure switch  110  may also include an adhesive layer  150  that is adapted to adhere the pressure switch  110  adjacent or onto a tissue site. The adhesive layer  150  is located on a contacting side  152  of the pressure switch  110 , which may adhere, or otherwise contact, a tissue site or an object adjacent or near the tissue site. Also, the padding layer  148 , the antenna  122 , or the diode  124  may be disposed between the adhesive layer  150  and at least a portion of the membrane  128 . 
     The padding layer  148  may buffer, or otherwise provide separation, between the antenna  122 , diode  124 , or membrane  128 , and the surface onto which the pressure switch  110  is adhered. By way of example, the padding layer  148  may prevent the antenna  122  and the diode  124 , which may be formed from metal, from irritating or touching a tissue site to which the pressure switch  110  may be adhered. The padding layer  148  may be composed of any cushioning or shock-absorbing material, such as a gel. In one embodiment, the padding layer  148  may have adhesive characteristics such that the padding layer  148  may incorporate the function of the adhesive layer  150 , dispensing with the need to include a separate adhesive layer  150 . 
     The force  134  that causes the membrane  128  to move from the unpressed position  130  to the pressed position  132  may be from any source, such as those described with respect to  FIGS. 1A and 1B . In the example in which the contacting side  152  of membrane  128  contacts a tissue site, the force  134  may be from contact with an object that is pressed against the tissue site as a result of the position or movement of the patient. For example, a floor or shoe may press against the membrane  128  as a result of walking when the pressure switch  110  is adhered to a plantar region of the patient&#39;s foot. In the example in which the contacting side  152  of the membrane  128  contacts an object, such as an article of clothes, adjacent the tissue site, the force  134  may originate from contact with the tissue site itself. For example, if the pressure switch  110  is adhered to the insole of a shoe, the plantar portion of a patient&#39;s foot may directly or indirectly press against the membrane  128  as the patient walks. 
     In one embodiment, while the pressure switch  110  is receiving a first signal, such as the first signal  108  in  FIGS. 1A and 1B , from a transmitter, the membrane  128  may collapse into the pressed position  132  due to the force  134  on the membrane  128 , and cause electrical communication between the antenna  122  and the diode  124 . The antenna  122  may emit the second signal  114  in response to this electrical communication between the antenna  122  and the diode  124 . The second signal  114  may be received by the transmitter. 
     Referring to  FIG. 4 , the transmitter  106  is shown according to an illustrative embodiment. The transmitter  106  outputs an alert to a patient upon receiving a second signal from a pressure switch, such as the second signals  114 ,  116  in  FIGS. 1 and 3B , thereby alerting a patient that pressure is being exerted on the tissue site adjacent the pressure switch. The first signal  108  emitted by the transmitter  106  may serve as the power source that powers the pressure switches, which may be passive. The power derived from the first signal  108  may allow the pressure switches to transmit signals back to the transmitter  106 . In addition, the transmitter  106  may continuously or intermittently emit the first signal  108 . 
     The transmitter  106  may include one or more output devices that allow the transmitter  106  to output an alert when a signal is received from a pressure switch. For example, the transmitter  106  may include a vibrational device (not shown) located inside the transmitter  106  that causes the transmitter  106  to vibrate. Thus, a patient feeling the vibration of the transmitter  106  may be alerted to the presence of excess pressure at a tissue site. The transmitter  106  may also include a light emitting device  156  that emits light to visually alert a patient when a signal is received from a pressure switch. The transmitter  106  may also include a speaker  158  that emits a sound to audibly alert a patient when a signal is received from a pressure switch. The transmitter  106  may also have an electrical output device (not shown) that electrically stimulates a patient when a signal is received from a pressure switch. Other types of output devices may also be included with the transmitter  106 . 
     The transmitter  106  may also have any shape or size. For example, one or more surfaces of the transmitter  106  may be curved to contour a patient&#39;s body, such as when the transmitter  106  is worn on the body of the patient. In another example, the transmitter  106  may be small in size to permit convenient and unobtrusive carrying of the transmitter  106  by the patient. 
     In an alternate embodiment, the transmitter  106  may output an alert only when the transmitter  106  receives a signal from a pressure switch for a predetermined period of time, such as one second, five seconds, or ten seconds. In this embodiment, the patient would not be alerted by the transmitter  106  when the pressure exerted on the pressure switch is only insignificant, momentary, or for a very short period of time. 
     Although the illustrative embodiments described herein have been disclosed in the context of certain illustrative, non-limiting embodiments, it should be understood that various changes, substitutions, permutations, and alterations can be made without departing from the scope of the invention as defined by the appended claims. It will be appreciated that any feature that is described in a connection to any one embodiment may also be applicable to any other embodiment.