Abstract:
A system is provided that furnishes physiological or biomechanical parameters from sensors placed upon or within a subject. The system comprises radio frequency energized biosensor (RFEB) devices that are powered by and communicate with an external receiver and monitoring apparatus. One embodiment of the system provides for infant monitoring in a crib utilizing RFEB devices incorporated into a dermal patch. Said patch communicates with a receiver suspended above the crib and alerts of early warning signs of sudden infant death syndrome (SIDS) or other physiologic abnormalities. Another embodiment comprises implantable RFEB devices that relay information related to the condition of an internal tissue, organ, or cavity to an external receiver, monitor, and recorder. Other embodiments include wearable sensors for detecting a subject attempting to get out of bed, dislodge medical equipment, or stray from a given location.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to wireless medical telemetry systems (WMTS), specifically telemetry systems used to gather and relay physiologic parameters through interrogation of radio frequency energized biosensors (RFEB). 
       BACKGROUND ART 
       [0002]    Wireless medical telemetry is generally used to monitor patient physiological parameters over a distance via radio frequency (RF) communications between a transmitter worn by the patient and a central monitoring station. These devices have the advantage of allowing patient movement without tethering the patient to a bedside monitor with a hard-wired connection. 
         [0003]    Traditional WMTS consist of at least one battery powered module worn by the patient for collection and transmission of physiologic parameters. U.S. Pat. No. 6,215,403 discloses a battery powered wireless sensor for monitoring blood oxygen content, and temperature. U.S. Patent Application No. 20020097155 discloses an infant monitor for prevention of sudden infant death syndrome (SIDS); the battery powered sensor straps around the infant&#39;s chest, and uses traditional RF communication. The battery powered modules are expensive to produce, susceptible to battery failure, of substantial weight, and produce toxicity hazards. In addition, the traditional patient module consists of a sending unit into which remotely placed physiologic sensor(s) are coupled through hard-wires. This hard-wire coupling creates uncomfortable and potentially hazardous conditions for the patient. Patients become entwined in the web of wires emanating from the sending unit. Furthermore the cost of the patient modules requires that they be reusable. Therefore time consuming decontamination is requisite and adds to patient cost. Sub par cleaning of the modules can lead to transmission of infectious agents. Thus, prior art patient modules are expensive, heavy, cumbersome, and potentially hazardous. 
         [0004]    There exists a need for WMTS which collect physiologic/biomechanical data through small, wearable, inexpensive, and disposable transmitters with integrated sensor(s) that are powered by radio frequency energy. 
       SUMMARY OF THE INVENTION 
       [0005]    An advantage of the present invention is a wireless medical telemetry system which utilizes radio-frequency transmissions to energize and collect physiologic and/or biomechanical data from at least one sensor(s) placed in contact with, or coupled to a subject tissue, organ, appendage, or body of a patient. Sensing modalities include optical sensors, electrical sensors, chemical sensors, mechanical sensors, MEMS sensors, nano sensors, biochemical sensors, acoustic sensors, immunologic sensors, fluidic sensors, ‘lab-on-a-chip’ type sensors, or other types of sensors. Such sensors can be used to detect general health, blood oxygen saturation, blood glucose levels, electrical activity, pulse presence, pulse rate and character, respiratory motion, respiratory rate, temperature, pH, chemical composition, or body motion including acceleration and mechanical shock. The sensors may alternatively be powered by a pre-charged or rechargeable battery, or other power storage device. 
         [0006]    Another aspect of the present invention is a system for monitoring a living tissue of a patient&#39;s body, comprising a sensor implantable in the patient&#39;s body for generating/recording a signal indicative of one or more properties of the tissue; a controller for receiving the signal outside the patient&#39;s body; and a communications interface for communicating the signal from the sensor to the controller. A representative application of this system is in the monitoring/recording of a condition at an operative site, or of the condition of a transplanted organ. Other potential applications include but are not limited to the monitoring/recording of intra-cranial, intra-thecal, intra-ocular, intra-otic, intra-nasal, intra-sinusoidal, intra-pharyngeal, intra-laryngeal, intra-esophageal, intra-tracheal, intra-thoracic, intra-bronchial, intra-pericardial, intra-cardiac, intra-vascular, intra-abdominal, intra-gastric, intra-cholecystic, intra-enteric, intra-colonic, intra-rectal, intra-cystic, intra-ureteral, intra-uterine, intra-vaginal, intra-scrotal; intra-cerebral, intra-pulmonic, intra-hepatic, intra-pancreatic, intra-renal, intra-adrenal, intra-lienal, intra-ovarian, intra-testicular, intra-penal, intra-muscular, intra-osseous, and intra-dermal physiologic/biomechanical parameters. 
         [0007]    An additional advantage of the present invention is the ability to monitor/record the physiologic/biomechanical parameters of an infant or child. One application is the detection and prevention of SIDS. In this application the RF energized wireless sensors can be affixed to the infant, while the receiver unit can be integrated into a piece of furniture, a bedding material, a toy, a mobile or other accessory. Another application is in the quantification of motion, acceleration, and/or shock for, but not limited to, the following: the detection, and prevention of infant or child abuse, the detection of an injury or fall, and the prevention of travel, or abduction out of preset boundaries. 
         [0008]    Another advantage of the present invention is the detection, monitoring, and recording of abnormal physiologic or biomechanical parameters of an infant, child, or adult. Abnormal parameters relate to febrile or convulsive activity, respiratory perturbations, cardiac arrhythmia, and hemodynamic instability. 
         [0009]    There is a trend to incorporate RFID tags into hospital supplies for inventory management. An RFID tag reader incorporated into on a patient&#39;s wrist band would allow an alarm or other notification to sound if the reader comes in close proximity to sensitive medical equipment that is equipped with an RFID tag. Therefore, a further advantage of the present invention is the detection and resultant prevention of a patient&#39;s motion to climb out of bed, and/or dislodge indwelling of external medical equipment including but not limited to endotracheal tubes, IV catheters, thorocostomy tubes, urinary catheters, drainage catheters, naso-/oro-gastric tubes, and percutaneous feeding tubes. 
         [0010]    Another aspect of the described invention is the ability to monitor/record a subjects physiology/biomechanical parameters during exercise. 
         [0011]    A still further advantage of the present invention is the ability to monitor/record the physiologic/biomechanical parameters of the independent elderly, assisted living/nursing home residents, home care or hospital based patients. 
         [0012]    An additional advantage of the present invention is the ability to monitor/record the physiologic/biomechanical parameters of a patient at home for confirmation or quantification of a medical condition. One representative example is the ability to detect and quantify sleep apnea. Another example is the ability to non-invasively measure blood glucose levels in a diabetic patient. 
         [0013]    A still further advantage of the present invention is the ability of a superior or medic to assess and monitor the physiologic/biomechanical parameters of a deployed/injured soldier in the battlefield. 
         [0014]    Additional advantages of the present invention will become readily apparent to those skilled in this art from the following detailed description, wherein only selected embodiments of the present invention are shown and described, simply by way of illustration of the best mode contemplated for carrying out the present invention. As will be realized, the present invention is capable of other and different embodiments, and its several details are capable of modifications in various obvious respects, all without departing from the invention. Accordingly, the drawings and description are to be regarded as illustrative in nature, and not as restrictive. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]    Reference is made to the attached drawings, wherein elements having the same reference numeral designations represent like elements throughout, and wherein: 
           [0016]      FIG. 1  shows a pediatric monitoring system according to an embodiment of the present invention. 
           [0017]      FIG. 2  shows an adult monitoring system according to an embodiment of the present invention. 
           [0018]      FIG. 3  is a block diagram of a generic wireless medical telemetry system according to an embodiment of the present invention. 
           [0019]      FIG. 4  shows an implantable medical telemetry sensor according to an embodiment of the present invention. 
           [0020]      FIG. 5  shows an array of sensing elements according to an embodiment of the present invention. 
           [0021]      FIG. 6  shows an RF energized biosensor patch according to an embodiment of the present invention. 
           [0022]      FIG. 7  shows a block diagram of an oxygenation sensor according to an embodiment of the present invention. 
           [0023]      FIG. 8  is a block diagram for an RF energized oxygenation sensor according to an embodiment of the present invention. 
           [0024]      FIG. 9   a  is a graph showing the relationship between light absorption and incident wavelength for varying tissue oxygen saturation. 
           [0025]      FIG. 9   b  is a graph showing an example of light absorption in tissue during de-oxygenation and re-oxygenation. 
           [0026]      FIG. 10  is a timing diagram for an RF energized oxygenation sensor according to an embodiment of the present invention. 
           [0027]      FIG. 11  is a block diagram of the operation of RF energized oxygenation sensor&#39;s operation according to an embodiment of the present invention. 
           [0028]      FIG. 12  shows an array of sensing dermal patches for monitoring electrical activity according to an embodiment of the present invention. 
           [0029]      FIG. 13  shows a wearable physiological and/or biomechanical sensing patch or armband that communicates with a wearable monitor according to an embodiment of the present invention. 
           [0030]      FIG. 14  shows a wearable monitor that detects the proximity of passive RFID tags coupled to medical equipment, beds, cribs, or other devices, and can alert to changes according to an embodiment of the present invention. 
           [0031]      FIG. 15  shows a proximity sensing system according to an embodiment of the present invention. 
       
    
    
     DESCRIPTION OF THE INVENTION 
       [0032]      FIG. 1  shows a pediatric monitoring system. One embodiment of the monitoring system is for early detection and prevention of sudden infant death syndrome (SIDS). The infant  101  is in crib  103 . Attached to infant  101  is a sensor  105 . The sensor  105  can be used to sense one or more physiologic/biomechanical parameters including, but not limited to, general health, systemic blood oxygenation, local tissue oxygenation, pulse (rate, presence, and character), respiration (rate, presence, and character), temperature, electrical activity, moisture, motion, acceleration, and skin stretching or strain. In one embodiment, the sensor  105  is included in a flexible, disposable patch or other pad that is placed on the skin surface and contains no internal power source. In this embodiment, the sensor  105  is powered by techniques known to those skilled in the art of passive/semi-passive radio frequency identification (RFID) by radio frequency (RF) signal  107 . RF signal  107  can be emitted by the base antenna  109  or from another external source. Power can be stored in a capacitor, battery, or other storage components. The RF signal energizes the electronics in the sensor  105 , which senses the parameter or parameters and then transmits the sensor data over the RF signal  107  to the base antenna  109 . In one embodiment, the base antenna and controller  109  is enclosed in a child&#39;s toy such as a mobile that is suspended  113  over the crib  103 . In other embodiments, base  109  can be a standalone device, integrated directly into a crib, a bed, a bedding material, a stroller, a child&#39;s toy such as a stuffed animal, or into a pillow. The base antenna and controller  109  can be communicatively coupled with a base station, baby monitor, or other external device either in the same location or remote location by wires or wireless methods. The connected monitor may be a standard baby monitor with additional feedback, a connection to a nurses&#39; station or monitoring facility, or it may be incorporated into a device such as a pager, pendant, wrist band, mobile phone, portable computer/PDA, telephone dialer, or computer. Monitor information may be transmitted to remote locations through wireless technology including wireless internet, cellular, or other networks, through an internet connection, or through another network. 
         [0033]      FIG. 2  shows a monitoring system for the elderly, assisted living residents, home care patients, or hospital patients. The functionality is similar to that described in the previous paragraph for  FIG. 1 . A patient  201  lies on a bed  203 . A sensor unit  205  communicates with and is energized by an RF signal  207 . A base antenna and controller  209  may be built into the bed, an attachment to the bed, a stand alone device, or a portable, wearable device. The base antenna is communicatively coupled through  213  to an external monitor, controller, phone dialer, alert system, or other external device including those described in the previous paragraph. 
         [0034]      FIG. 3  shows the layout of a generic wireless medical telemetry system with radio-frequency energized sensor. A sensor unit  301  may be embedded into a wearable, self-adhesive, disposable dermal patch/pad. Enclosed in the sensor unit  301  are an antenna  307 , a power storage and power regulator system  309 , a processor  311 , and one or more sensing elements  313 . The telemetry sensor device communicates with and is energized by an RF signal  315 , which may be emitted from and is received by a communications interface  317 . This interface is communicatively coupled via  321  to a controller  325  such as a standard personal computer, stand alone monitoring device, an integrated single unit, or one of the devices described previously. In one embodiment, optical oxygenation and/or pulse sensors are placed on disposable patches that are passively powered and placed on the surface of a patient&#39;s skin. Embodiments of these patches can be used in applications including, but not limited to, oxygenation sensing, pulse sensing, temperature sensing, ECG, EMG, chemical sensing including electrolytes or blood sugar with or without a ‘lab-on-a-chip’ type device, motion, acceleration, or mechanical shock monitoring, injury monitoring and assisted triage, exercise and stress test monitoring, infant SIDS monitoring, infant/child abuse surveillance, and elderly, home care, and hospital patient monitoring. The sensors  301  can also be used to detect the proximity of the subject to the communication interface  317 . 
         [0035]      FIG. 4  shows an implantable embodiment of the above described telemetry sensor. A sensor unit  401  is placed on a tissue or organ  403 , within an organ, or within a bodily cavity inside of a body  405 . On the sensor unit is an antenna  409  and a power storage and regulator unit, a processor, and at least one sensing element  411 . The sensor communicates with and may be energized by an RF signal  415 , which is emitted from and received by an antenna and communications interface  417 . The interface  417  is communicatively coupled by  421  to a controller  425  as described earlier. In one embodiment, the sensor unit  401  is placed on, or about bowel tissue  403  after performing a surgical procedure to monitor the operative site for adequate perfusion, or surgical complication such as anastomotic leak. In another embodiment the sensor can be used to detect the viability of a transplanted organ or tissue. A further embodiment would allow for the sensor to be placed in the intra-pericardial sac after cardiac procedure to detect pericardial tamponade. In another embodiment, the sensing element  401  is made in whole, or in part, of bioabsorbable/biodegradable materials including the antenna and substrate. 
         [0036]      FIG. 5  shows a grid of sensing elements  507  on a sensing patch/pad/mesh  501  as described earlier. One or more sensor(s) sense one or more properties of tissue  503 . Communication is wireless via RF connection  511  and the sensors are passively energized as described earlier. In one embodiment, a grid or array of one or more sensor(s) monitors perfusion in a transplanted organ or tissue. 
         [0037]      FIG. 6  shows a close up of a radio-frequency energized biosensor unit. The sensor unit is integrated into a patch or pad  601 . The patch may be self adhesive, disposable, and flexible. The antenna  605  may be constructed of a conductive, biocompatible, and potentially bioabsorbable material. In one embodiment, antenna  605  may also be constructed of a bioabsorbable or biologically inert conductive ink on a bioabsorbable substrate. In another embodiment, the antenna may be constructed of conductive biocompatible gel or fluid contained in bioabsorbable tubular structures or other guides. The antenna  605  receives RF energy and uses them to generate power which is stored and regulated by controller  607 . Controller  607  is coupled to antenna  605 , and contains an RFID or similar transponder chip, a power regulator, and a power storage device such as a capacitor or battery. Sensing element  613  is powered by the power supply of  607 . The sensing element may contain a processor, analog and digital input and outputs, a signal processor, filters, light emitters and receivers, amplifiers, temperature sensors, strain gauges, accelerometers, tilt sensors, electrodes, or other elements that would allow for sensing a physiological/biomechanical property and transmitting the data back via antenna  605 . The sensing element  613  and the controller  607  may be one single integrated unit or made up of a plethora of coupled subcomponents. 
         [0038]      FIG. 7  shows one embodiment of the sensor for measuring oxygenation and or pulse via optical sensors. Sensing patch or pad  701  is placed on skin or other tissue  703 . Antenna  707  receives power which is stored and regulated. The processor  709  commands light source  713  to transmit light. Light source  715  may be of one, two, or more wavelengths. In one embodiment, infrared and red light are transmitted sequentially as known to those skilled in the art of pulse oximetry. Light  715  is transmitted through or reflected off of tissue  703 , and is detected by light sensor  717 . Light sensor  717  communicates information about the respective light intensities for each wavelength to processor  709  for computation. Processor  709  transmits data via antenna  707  using techniques know to those skilled in the art of RFID. Transmissions  721  to and from antenna  707  are received by and transmitted from the communications interface  723  respectively. The communications interface  723  is coupled  725  to a controller  727  which may be a computer, stand-alone monitor, or integrated into the same device as described earlier. 
         [0039]      FIG. 8  shows a flowchart of one embodiment of the system described in the previous paragraph. Computer  801  is communicatively coupled via  803  to antenna device  805 . Antenna  805  transmits RF signals  807  to transponder/sensor  811 . In the transponder unit is a microprocessor or microcontroller  813  which is programmed either via a wired connection or wirelessly  815 . Also contained in the transponder is a power storage and regulator unit  819 . A processor  813  controls light emitters  821  which are powered by the energized storage unit  819 . A light source  823  emits a plethora of wavelengths of light that travel through or reflect off of tissue  825  before being received by a light sensor  827  which relays data back to the processor  813 . In one embodiment, the light source  823  emits red and infrared light for oximetry based measurement techniques as know by those skilled in the art. The processor  813  relays data to the transponder which is transmitted over RF signal  807  to antenna  805  which is relayed back to the computer or controller  801 . 
         [0040]      FIG. 9   a  illustrates the fundaments of oximetry based sensing, which are known to those skilled in the art. Light absorption  901  varies as a function of wavelength  902  and blood oxygen saturation  903 . At a minimum, red light  920  at around 660 nm and infrared light  928  at around 880 nm are emitted into the tissue. Light at the isobestic wavelength  924  of about 780 nm may be used as well to increase the robustness of measurements. Further wavelengths of light may be used to increase robustness and accuracy. 
         [0000]      FIG. 9   b  shows an experiment that verifies the increased attenuation of red light  954  and decreased attenuation of infrared light  952  as blood oxygen saturation is decreased starting at time  958  and restored at time  960 . To sense relative changes in a patient&#39;s blood oxygen saturation, in some embodiments it is only necessary to monitor trends in this change in attenuation and not correlation to standard SpO2 values as in  FIG. 9   a.    
         [0041]      FIG. 10  shows a timing diagram for one embodiment for a simple RF energized oxygenation sensor. Representative emitted light intensity  1001  and received light intensity  1003  are plotted with respect to time. During interval  1003 , the RF signal is energizing the power storage unit, and there is no light emission from the sensor. After charging is complete, light is emitted and received sequentially during time period  1011 . In one embodiment, the light emissions  1013 ,  1015 , and  1017  correspond to red light, no emitted light, and infrared light, respectively. The corresponding received light intensities are  1021 ,  1023 , and  1025 , respectively. In this embodiment, two wavelengths are transmitted; in general, one or more wavelengths can be emitted and received. If optical filters, frequency modulation, or other techniques know to those in the art are used, multiple wavelengths of light may be used simultaneously. If pulse, and not oxygenation, is being detected, it may be possible to use ambient light transmitted through tissue in place of emitted light. 
         [0042]      FIG. 11  shows a flow chart for the oxygenation sensor described above. After starting the system by querying the sensor, the sensor is energized by the RF signal. After the stored electrical charge is sufficient to power the sensor, red light is emitted and the signal is sensed. The same is done for the baseline of no light transmission and infrared light as described above. The baseline is subtracted out and any tissue-dependent normalization is taken into account. Oxygenation and/or pulse related information is calculated and transmitted from the sensor and the cycle repeats. Similar workflows can be implemented in other embodiments using other sensing modalities as described earlier. 
         [0043]      FIG. 12  shows a further embodiment of a sensing patch. The sensors are designed to monitor electrical activity and can be used for ECG monitoring. Two, three, five, or other numbers of sensing pads or patches with electrodes  1201  are placed on the skin of the chest  1203 . The pads may be communicatively coupled to each other by  1207  which may be a wired or wireless connection, and may contain one or more RF telemetry devices. At least one device is energized by and communicates using the RF signal  1209 . The main RF transmitter/receiver  1213  may be an external device. In one embodiment, it is a portable, wearable device. The RF transmitter/receiver  1213  may be communicatively coupled via  1215  with a base station, monitor, or other device  1219  including those described earlier. In another embodiment, similar sensors may be used to monitor EMG or other electrical activity in the body. In one embodiment, two ECG or similar electrodes are placed on opposing sides of a single dermal patch that can be worn by the patient. 
         [0044]      FIG. 13  shows a further embodiment comprising a wearable sensor  1301  that may take the form of dermal patch, armband, a watch, a fashion accessory, a article of clothing, or other wearable device  1301  where the sensor contains an accelerometer, tilt sensor, or other motion sensor. The sensor  1301  is placed on an extremity  1303  or on the main body  1305  itself to detect significant patient motion. The sensors are energized by and communicate with RF signal  1309 . In one embodiment, the main RF transmitter/receiver  1313  is a portable, wearable device. The RF transmitter/receiver  1313  is communicatively coupled via  1315  to a base station, monitor, or other device  1319  including those described earlier. The sensor can be used for detecting motion; this can be applied to detecting a patient&#39;s attempts to get out of bed, make large motions, or remove restraints. It can also be used to alert when convulsive activity is present and to ensure that respiratory and/or cardiac motion present. A further use is for monitoring an infant for abusive or dangerous treatment. 
         [0045]    In another embodiment, sensor  1301  represents an oxygenation and/or pulse sensor. The sensor  1301  is energized by and transmits data via RF signal  1309  to a portable monitor  1313 . In this embodiment, the sensor  1301  can be used as an exercise monitor and portable monitor  1313  can be used to record and display pulse and other information to the user in real time. In one embodiment, portable monitor  1313  is integrated into or part of an add-on module to standard portable electronics including, but not limited to, mobile phones, pagers, portable computers, portable music players, or belts, clothing, jewelry, or watches. A coupling  1315  may be used to download data to a base unit, central monitoring station, or computer  1319 . Coupling  1315  may be through a wired connection, through a short range wireless connection, through standard wireless internet or cellular connection, or through another network. A similar embodiment uses an independent monitor  1313  for monitoring pulse rate and other physiologic parameters. One application of such an embodiment is in military or other health care situations where a soldier or patient wears a sensing dermal patch, and a medic or healthcare professional carries a portable monitor. Alternatively the medic or healthcare provider is located at a central monitoring station, thus allowing the medical personnel or supervisors to remotely monitor the subject. 
         [0046]      FIG. 14  shows one embodiment of a sensor  1401  incorporated into a watch, a pendant, an article of clothing, a fashion accessory, a dermal patch, an armband, or other device placed on extremity  1403  and communicates via RF signal  1405 . Endotracheal tubes, IV catheters, thorocostomy tubes, urinary catheters, drainage catheters, naso-/oro-gastric tubes, percutaneous feeding tubes, electrodes, wires, and other devices  1409  have embedded RFID or similar tags  1411 . When the tag  1411  comes within a specified distance of the sensor  1401 , a signal is sent via  1415  to a controller, monitor, or other device  1417 . An alert or other action will take place if the sensor becomes too close to the tag in the tube or other device to warn when a patient may be attempting to dislodge the device. 
         [0047]      FIG. 15  illustrates an embodiment in which guardian  1501  wears or carries RFID reader or similar  1503 . RFID reader or similar  1503  can be integrated into a watch, an armband, a pendant, a portable computer, a mobile phone, a portable music player, a pager, a portable gaming system, an article of clothing, a fashion accessory or other wearable accessory or portable electronic device. Child/infant or other subject  1507  wears RFID tag  1509 . RFID tag  1509  can be integrated into an armband, dermal patch, piece of jewelry, article of clothing, a watch, a pendant, a portable computer, a mobile phone, a portable music player, a pager, a portable gaming system, an article of clothing, a fashion accessory, or other accessory. In another embodiment the RFID tag  1509  can be ingested, implanted or injected into the subject&#39;s body. RFID reader  1503  is communicatively coupled to RFID tag  1509  through RF signal  1511 . In this embodiment RFID reader  1503  would generate a signal to alert the guardian that the infant/child has moved outside of a preset proximity. In another embodiment  1509  can be a RFEB monitoring physiologic/biomechanical properties of subject  1507 . In a further embodiment the RFID reader  1503  communicates through  1517  to a communications interface  1519 . This would allow for external monitoring/recording. In an alternative embodiment RFID reader  1503  is incorporated into the bed, crib, or other location. This embodiment can be used to determine if an infant tries to get out of his/her crib, if an elderly or hospital care patient tries to get out of bed, or other application where it is important to determine if the subject is within or outside of a specific range.