Abstract:
A telemetry system is disclosed herein. The telemetry system includes a transmitter configured to provide tracking data, and a receiver adapted to define a coverage area. The receiver is configured to receive the tracking data from the transmitter only when the transmitter is within the coverage area. The telemetry system also includes a processor configured to receive the tracking data from the receiver. The processor is configured to estimate the location of the transmitter when the transmitter is outside the coverage area based on the tracking data.

Description:
FIELD OF THE INVENTION 
     This disclosure relates generally to a telemetry system and method. 
     BACKGROUND OF THE INVENTION 
     Telemetry systems can be implemented to acquire and transmit data from a remote source. The telemetry system may incorporate a wireless technology such as wireless fidelity (WiFi); infrared (IR); or ultrasound in order to facilitate finding an object and/or data transmission. As an exemplary implementation, a medical telemetry system can be implemented to remotely monitor the cardiac electrical activity of a plurality of ambulatory patients while they remain within a predefined coverage area. The medical telemetry system may also be implemented locate and track patients within the coverage area. 
     The coverage area is often relatively small due to financial considerations associated with the requisite infrastructure. Accordingly, the coverage area typically does not cover the entire hospital interior, and does not extend outside the hospital. One problem with conventional medical telemetry systems is that patients cannot be monitored or located after they leave the coverage area. 
     BRIEF DESCRIPTION OF THE INVENTION 
     The above-mentioned shortcomings, disadvantages and problems are addressed herein which will be understood by reading and understanding the following specification. 
     In an embodiment, a telemetry system includes a transmitter configured to provide tracking data, and a receiver adapted to define a coverage area. The receiver is configured to receive the tracking data from the transmitter only when the transmitter is within the coverage area. The telemetry system also includes a processor configured to receive the tracking data from the receiver. The processor is configured to estimate the location of the transmitter when the transmitter is outside the coverage area based on the tracking data. 
     In another embodiment, a telemetry system includes a portable transmitter configured to provide tracking data, and a receiver network adapted to define a coverage area. The receiver network is configured to receive the tracking data from the portable transmitter only when the portable transmitter is within the coverage area. The telemetry system also includes a processor configured to estimate the speed of the portable transmitter based on the tracking data, estimate the trajectory of the portable transmitter based on the tracking data, and measure the elapsed time after the portable transmitter leaves the coverage area. The processor is also configured to estimate the location of the transmitter when the transmitter is outside the coverage area based on the speed of the portable transmitter, the trajectory of the portable transmitter, and the elapsed time after the portable transmitter leaves the coverage area. 
     In another embodiment, a method includes providing a telemetry system comprising a portable transmitter configured to provide tracking data, and a receiver network defining a coverage area. The receiver network is configured to receive the tracking data from the portable transmitter only when the portable transmitter is within the coverage area. The method also includes estimating the speed of the portable transmitter within the coverage area, estimating the trajectory of the portable transmitter within the coverage area; and measuring the elapsed time after the portable transmitter leaves the coverage area. The method also includes estimating the location of the portable transmitter based on the speed of the portable transmitter, the trajectory of the portable transmitter, and the elapsed time after the portable transmitter leaves the coverage area. 
     Various other features, objects, and advantages of the invention will be made apparent to those skilled in the art from the accompanying drawings and detailed description thereof. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic representation of a telemetry system in accordance with an embodiment; 
         FIG. 2  is a schematic representation of a hospital map in accordance with an embodiment; and 
         FIG. 3  is a flow chart illustrating a method in accordance with an embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In the following detailed description, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration specific embodiments that may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the embodiments, and it is to be understood that other embodiments may be utilized and that logical, mechanical, electrical and other changes may be made without departing from the scope of the embodiments. The following detailed description is, therefore, not to be taken as limiting the scope of the invention. 
     Referring to  FIG. 1 , a telemetry system  10  is shown in accordance with an embodiment. The telemetry system  10  includes one or more transmitter/monitors  12 ; one or more receivers  14 ; and a central server  16  comprising a processor  18 . The telemetry system  10  may also optionally include a display  20 ; and an alarm  22 . Those skilled in the art will appreciate that the telemetry system  10  is configured to track the relative location of the transmitter/monitors  12 , and that a transmitter/monitor  12  can be assigned to a specific patient in order to track and/or monitor that patient. For illustrative purposes assume that three patients  30 - 34  are being tracked and monitored by the telemetry system  10 . It should, however, be appreciated that the telemetry system  10  may be implemented to track and/or monitor a much larger number of patients. 
     The transmitter/monitors  12  will be described in accordance with an embodiment as a portable device comprising an electrocardiograph and a plurality of electrograph sensors  36  configured to monitor cardiac electrical activity. For purposes of this disclosure, a portable device should be defined to include any device that is sufficiently compact and lightweight such that a typical patient can conveniently carry the device wherever they go. A separate transmitter/monitor  12  is assigned to each of the patients  30 - 34 , and thereafter the assigned transmitter/monitor  12  generates patient monitoring data and/or patient tracking data. The patient monitoring data and/or patient tracking data from the transmitter/monitors  12  is transferred to the receivers  14  via the wireless connections  38  represented by a dashed line. 
     The receiver  14  will be described in accordance with an embodiment as comprising a network of receivers  14  that are uniformly distributed throughout a region of interest in order to define a coverage area. The region of interest may include a relatively small area with a high-patient density such as a patient ward. The region of interest generally does not include areas such as the cafeteria; areas with low-risk patients; areas designated exclusively for hospital staff; areas immediately outside the hospital; etc., due to economic considerations associated with the requisite infrastructure. The network of receivers  14  transfers the patient monitoring data and/or patient tracking data to the central server  16  via connection  40 . 
     The central server  16  comprises the processor  18  configured to process the patient monitoring data and/or patient tracking data in a known manner. For example, the processor  18  may convert raw patient monitoring data acquired by the sensors  36  into more conveniently readable electrocardiogram (ECG) data comprising a P-wave, a QRS complex and a T-wave. The processor  18  may also be implemented to predict the location of a patient (or a transmitter/monitor  12  associated therewith) that has recently left a coverage area as will be described in detail hereinafter. 
     The display  20  may optionally be implemented to graphically convey patient monitoring data and/or patient tracking data from the central server  16  in a conveniently readable manner. As one example, the patient monitoring data may be graphically conveyed as a conventional ECG plot comprising a sequence of P-waves, a QRS complexes and a T-waves. As another example, the patient tracking data may be graphically conveyed as an icon superimposed onto a map to indicate the patient&#39;s relative location. 
     The alarm  22  may optionally be implemented to alert hospital personnel when a patient has exited or is about to exit a given coverage area. The alarm  22  may comprise an audible device (e.g., a loudspeaker) and/or a visual device (e.g., a flashing light). As one example, patient position may be tracked and the alarm  22  may be sounded when the patient approaches the periphery of a given coverage area. As another example, the alarm  22  may be sounded based on the patient&#39;s trajectory such that a patient walking in a direction that is generally perpendicular to the peripheral edge of a coverage area would generate an alarm while a patient walking in a direction that is generally parallel to the peripheral edge of the coverage area would not generate an alarm. As yet another example, the alarm  22  may be sounded based on the strength of a patient tracking signal from a transmitter/monitor  12  as an indication that the patient is approaching the limits of a given coverage area. As yet another example, the alarm  22  may be sounded only when the patient actually leaves a given coverage area. 
     Having described the components of the telemetry system  10  in detail, a method  100  (shown in  FIG. 3 ) for predicting the location of a patient (or a transmitter/monitor  12  associated therewith) outside a coverage area will now be described with respect to  FIGS. 2 and 3 . 
     Referring to  FIG. 2 , a schematic representation of a hospital map  50  is shown in accordance with an embodiment. The region circumscribed by the dashed line  52  represents a coverage area  53  that may be defined by the receiver network  14  (shown in  FIG. 1 ). As previously described, any patient having a transmitter/monitor  12  (shown in  FIG. 1 ) can be tracked and monitored as long as they remain within the coverage area  53 . As soon as a patient exits the coverage area  53 , the signal from their transmitter/monitor  12  is lost and they can no longer be monitored or tracked in a conventional manner. 
     A solid line represents the path  54  of the patient  30  walking from a known position within the coverage area  53  to an unknown position outside the coverage area  53 . Positions  56 - 62  are known positions along the patient&#39;s path  54  and within the coverage area  53 . The cross-hatched region  64  of the map  50  represents a first region outside the coverage area  53 , and the stippled region  66  of the map  50  represents a second region outside the coverage area  53 . Reference numbers  70 - 76  identify specific hallways of the map  50 . 
     Referring to  FIG. 3 , the method  100  for predicting the location of a patient (or a transmitter/monitor  12  associated therewith) that is disposed outside a coverage area will now be described in accordance with an embodiment. The method  100  comprises a plurality of steps  102 - 110 . One or more of the steps  102 - 110  may be performed by the processor  18  (shown in  FIG. 1 ). Referring now to both  FIGS. 2 and 3 , the method  100  will be described as it applies to the exemplary embodiment of  FIG. 2  in order to more clearly illustrate the steps  102 - 110 . 
     At step  102  the method  100  identifies two or more patient positions within the coverage area  53 . For illustrative purposes, the two or more patient positions will be described as including the positions  56 - 62 . According to one embodiment, the positions  56 - 62  are established by the processor  18  (shown in  FIG. 1 ) based on patient tracking data acquired from the specific transmitter/monitor  12  (shown in  FIG. 1 ) assigned to patient  30 . 
     At step  104  the method  100  estimates patient speed based on the patient positions acquired at step  102 . Patient speed may be estimated by the processor  18  (shown in  FIG. 1 ) by calculating the patient&#39;s change in position divided by the change in time. 
     At step  106  the method  100  estimates patient trajectory based on the patient positions acquired at step  102 . Patient trajectory may be estimated by the processor  18  (shown in  FIG. 1 ) by generating a line or curve based on two or more of the positions acquired at step  102 . According to one embodiment, patient trajectory may be defined by a straight line passing through both of the two most recent patient positions acquired just prior to the patient  30  leaving the coverage area  53 . According to another embodiment, patient trajectory may be defined by a best-fit curve passing through three or more patient positions acquired at step  102 . 
     At step  108  the method  100  measures the time elapsed after the patient  30  leaves the coverage area  53 . At step  110  the method  100  estimates the current patient position outside the coverage area  53  based on patient speed (acquired at step  104 ); patient trajectory (acquired at step  106 ); and elapsed time (acquired at step  108 ). 
     To further illustrate step  10 , assume first that only a relatively short time has passed after the patient  30  left the coverage area  53 . Based on this assumption and the patient&#39;s speed (acquired at step  104 ), it can be estimated that the patient  30  is somewhere in the cross-hatched area  64 . Additionally, based on the patient&#39;s trajectory in combination with the relatively short elapsed time, it can be estimated that the patient  30  is most likely in hallway  70 . 
     If a relatively longer time has passed after the patient  30  left the coverage area  53 , it can be estimated based on the patients speed (acquired at step  104 ) that the patient  30  is somewhere in the stippled area  66 . Additionally, based on the patient&#39;s trajectory in combination with the relatively longer elapsed time, it can be estimated that the patient  30  is most likely in hallway  74 . 
     This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims.