Abstract:
A patient monitoring system comprising a central station for analyzing and displaying patient data; a system receiver connected to the central station; and an antenna array connected to the system receiver and including a plurality of antennae, each having connected thereto a respective transmitter.

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to patient monitoring systems and particularly to patient monitoring systems that allow the patient to ambulate through the care unit of a clinical facility. 
     Most patient monitoring systems that allow a patient to ambulate through a care unit in a clinical facility use telemetry-based communication schemes. In its most common form, a patient wears a telemetry transmitter attached to the patient using common ECG electrodes. The telemetry transmitter acquires an ECG signal, conducts a nominal amount of filtering on the ECG signal, and transmits the ECG signal to an antenna array, typically located in the ceiling of the care unit. The ECG signal is conducted through the antenna array to a telemetry receiver, which in turn, is connected to a central station that analyzes and displays the ECG information for viewing and evaluation by the clinicians staffing the care units. 
     However, it is frequently desirable to be able to quickly locate the patient in a care unit if circumstances indicate that there is a problem with the patient. In other cases, it is desirable to be able to send data back from the central station to the telemetry transmitter. 
     SUMMARY OF THE INVENTION 
     Accordingly, the invention provides a telemetry-based patient monitoring system that allows the clinician to determine the location of the telemetry transmitter, and that allows the clinician to send data from the central station to the telemetry transmitter. More specifically, the invention includes a portable telemetry transmitter. The telemetry transmitter is connected to the patient to receive physiological signals from the patient and transmit those signals to the antenna array. The telemetry transmitter includes an RF receiver. 
     The invention also provides a patient monitoring system including a central station for analyzing and displaying the physiological signals. The patient monitoring system further includes a receiver subsystem connected to the central station and an antenna array connected to the receiver subsystem. The antenna array includes a plurality of antennae each connected to an RF amplifier and supporting circuitry. Each antenna also has connected thereto a respective transmitter. In one form of the invention, each antenna includes a printed circuit board and the transmitter is mounted on the printed circuit board with the antenna circuitry, i.e., the RF amplifier and supporting circuitry. In another form of the invention, the transmitter is a discrete component that can be connected to the antenna after the system has already been installed in the care facility in order to “retro-fit” the patient monitoring system. 
     Each antenna is given a discrete address, the location of which is programmed into the central station. The antenna uses the antenna transmitter to transmit the address as a low power beacon. When the beacon is received by the telemetry transmitter, the telemetry transmitter combines the physiological data with the address and transmits the combined data signal to the receiver subsystem via the antenna array. From the receiver subsystem, the data is sent to the central station to be processed and displayed as required by the clinicians. 
     The receiver subsystem also allows communication from the central station to the transmitter associated with each antenna. Most commonly, the data will be in the form of voice communications, and will be transmitted to the telemetry transmitter and output from the transmitter on a speaker so that the communication is audible to the patient or to the clinician caring for the patient. 
     In still another form of the invention, each telemetry transmitter includes a microphone for receiving voice data and transmitting the voice data back to the central station. 
     A principal advantage of the invention is to provide a telemetry-based patient monitoring system that allows for complete two-way communication of both voice and physiological data, and that allows the clinician to accurately detect the location of the telemetry transmitter. 
     It is another advantage of the invention to provide a way of retro-fitting existing telemetry-based patient monitoring systems with a transmitter at each antenna in the antenna array to thereby allow for complete two-way communication of voice and physiological data, and allow the clinician to accurately determine the location of the telemetry transmitter. 
     Other features and advantages of the invention are set forth in the following detailed description, claims and drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram of the patient monitoring system embodying the invention. 
         FIG. 2  is a schematic of the antenna transmitter subsystem. 
         FIG. 3  is a schematic illustration of the portable telemetry unit receiver subsystem. 
     
    
    
     Before one embodiment of the invention is explained in detail, it is to be understood that the invention is not limited in its application to the details of the construction and the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Shown in  FIG. 1  of the drawings is a block diagram of a telemetry-based patient monitoring system  10  embodying the invention. As is commonly known in the art, the patient monitoring system  10  includes a central station  14 . The central station  14  typically has a CPU or central processing unit  18 , which, in its most common form is a computer. The central station  14  also includes a display or display units  22  connected to the CPU  18 . The display  22  typically shows patient waveforms and other patient data. 
     The central station  14  also includes various means for the clinician to interact with the CPU  18 . As shown in the drawing, these means include a keyboard  26  for entering information relating to the patient, a mouse  30  for controlling CPU operations, a speaker  34  for generating audible alarms, data or other audible information, and a microphone  38  for receiving audio information and transmitting that information in electronic form to the CPU  18 . 
     The central station  14  is connected to a receiver subsystem  42 . The receiver subsystem  42  includes a single input/output (I/O) port  46  connected to the central station  14 , and a series of I/O ports  50  connected to a plurality of antennae  54  spaced about the care unit to form an antenna array connected to the receiver subsystem  42 . While the number of antennae  54  may vary in any particular situation, the antennae  54  are all identical and accordingly only the single antenna  54  shown in  FIG. 1  will be described. 
     The antenna  54  includes a control circuit  58  coupled with a radio frequency (RF) amplifier. A common RF antenna  62  is connected to the control circuit and RF amplifier  58  so that incoming radio frequency signals are picked up by the RF antenna  62 , and are transmitted to the control circuit and RF amplifier  58  where they are filtered, amplified and sent to the receiver subsystem  42 . 
     The antenna  54  also includes an antenna transmitter circuit  66  connected to the control circuit and RF amplifier  58 . The antenna transmitter circuit  66  generates a low power RF carrier signal  70  (represented as a phantom line in FIG.  1 ).  FIG. 2  illustrates a schematic diagram of the antenna transmitter circuit  66 . As shown in  FIG. 2 , the antenna transmitter circuit includes an EPROM-based 8-bit CMOS microcontroller  68  (Microchip Technology, Inc. Part No. PIC16C62X) connected to an RF antenna  72  through an inverting buffer  78  and a transmitter  82 . While any appropriate transmitter can be used, the transmitter  82  prototyped for the preferred embodiment is a 303.825 megahertz hybrid transmitter (Model No. HX1006 produced by RF Monolithics, Inc.) As shown in  FIG. 2 , the antenna transmitter circuit  66  also includes an oscillator  86 , and various support circuitry, as well as power connections  90  and common connections  94  as those of skill in the art understand are required for operating the antenna transmitter circuit  66 . 
     Referring again to  FIG. 1 , the telemetry-based patient monitoring system  10  also includes a portable telemetry monitor  98 . In use, the portable telemetry monitor  98  is connected to the patient (not shown) via ECG leads (also not shown) or through a patient connection suitable for measuring other patient parameters. Once connected to the patient, the patient is free to ambulate throughout the care unit as desired or able. As is commonly known in the art, the portable telemetry monitor  98  includes a transmitter sub-circuit  102  connected to a transmitting antenna  106 . The transmitter sub-circuit  102  generates a RF carrier signal  110  (represented as a phantom line in  FIG. 1 ) for transmitting patient and other data to the antenna array. 
     The portable telemetry monitor  98  also includes a receiver sub-circuit  114  connected to a receiving antenna  118 , a speaker  122 , and a microphone  126 .  FIG. 3  illustrates in greater detail a schematic illustration of the receiver sub-circuit  114 . As shown in  FIG. 3 , the receiver sub-circuit  114  includes an RF receiver  130  connected to antenna  118 . While any appropriate RF receiver can be used, the RF receiver  130  prototyped in the preferred embodiment is a 303.825 megahertz amplifier-sequenced hybrid receiver (Model No. RX1120, manufactured by RF Monolithics, Inc.). The receiver sub-circuit  114  also includes support circuitry, power inputs  134  and common connections  138  as those of skill in the art understand are required for operating the receiver sub-circuit  114 . The receiver sub-circuit  114  also includes an microprocessor input  142  connected to the microprocessor (not shown) of the portable telemetry unit. The microprocessor is responsible for receiving all physiological data and other incoming signals and routing them to the transmitter sub-circuit  102 . Inverting buffer  144  is connected between microprocessor input  142  and RF receiver  130 . 
     In operation, the antenna transmitter circuit  66  generally functions in a default or beacon mode. In this mode, the antenna transmitter circuit  66  generates an 8-bit address and transmits (via the low power RF carrier  70 ) the 8-bit address. In the lower power beacon mode, the carrier  70  is capable of being received by the portable telemetry monitor  98  at a range of approximately ten to twenty feet from the RF antenna  62 . While the range of the low power beacon mode may vary, it is important that the range be sufficiently limited so as not to overlap with the low power beacon mode transmission of another antenna transmitter. The location of the RF antenna  62  is programmed into the central station  14  at the time of installation using the 8-bit address. In the preferred embodiment, the 8-bit address is re-transmitted every 500 milliseconds and represents approximately five percent of the total available broadcast time of the antenna transmitter. The remaining 95 percent of the antenna transmitter broadcast time is kept available to be used for data communication. 
     The receiver sub-circuit  114  in the portable telemetry monitor  98  picks up the 8-bit sequence and combines the 8-bit sequence with the physiological patient data acquired by the portable telemetry monitor  98 . The transmitter sub-circuit  102  in the portable telemetry monitor  98  then broadcasts the combined 8-bit address and physiological data signal back to the antenna array via the RF carrier signal  110 . The signals at the various antennae  54  are then transmitted to the receiver subsystem  42  and from there, to the central station  14  for processing and subsequent display. 
     In the event that data communication is desired, i.e., that the clinician wishes to send information from the central station  14  to the portable telemetry monitor  98 , the antenna transmitter circuit  66  switches into a communication mode. In this operational mode, a digital signal is encoded by the central station  14  and routed to all of the antennae  54  in the antenna array, where it is transmitted via the antenna transmitter  66  to the receiver sub-circuit  114  in the portable telemetry monitor  98 . The information contained in this data can be either digital voice communication or system command data. The data is sent with a header address that is unique to each individual portable telemetry monitor  98 . In this way, only the portable telemetry monitor  98  that is intended to receive the information will process and respond to the information. 
     Various features and advantages of the invention are set forth in the following claims.