Abstract:
The invention provides system for measuring vital signs from multiple patients, typically in an in-hospital setting. The system features a body-worn vital sign monitor that includes: i) a sensor configured as a patch that measures electrical and optical signals from a patient; ii) a controller featuring a microprocessor that receives and processes the electrical and optical signals to determine the patient&#39;s vital sign information, including blood pressure; and iii) a first short-range wireless component that wirelessly transmits a packet comprising the vital sign information to an external receiver. A portable, wireless computer (e.g., a PDA, cellular telephone, or a laptop computer) communicates with the body-worn module. The wireless computer includes: i) a second short-range wireless component that receives the vital sign information and displays it; and ii) a long-range wireless transmitter that transmits the vital sign information over a wireless network. The system also includes an Internet-based system that receives the vital sign information from the wireless network, and avails this to medical professionals through an in-hospital information system.

Description:
CROSS REFERENCES TO RELATED APPLICATION  
       [0001]     This application is a continuation of U.S. patent application Ser. No. 11/162,719, filed Sep. 20, 2005. 
     
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT  
       [0002]     Not Applicable  
       BACKGROUND OF THE INVENTION  
       [0003]     1. Field of the Invention  
         [0004]     The present invention relates to a device, method, and system for measuring vital signs, particularly blood pressure.  
         [0005]     2. Description of Related Art  
         [0006]     Personal digital assistants (‘PDAs’) are currently used in hospitals and medical clinics to, e.g., record notes, collect patient information, and generate prescriptions. Some PDAs, such as Palm&#39;s Treo 650 and Audiovox&#39;s PPC 6600/6601, include long-range wireless transmitters (e.g., a CDMA modem) that allow them to wirelessly transmit and receive information and ultimately and communicate wirelessly with in-hospital information systems. For example, the above-mentioned PDAs can run software programs that wirelessly connect through the Internet to the hospital&#39;s information system to access medical and patient records. Examples of these software programs, sometimes called ‘rounding tools’, have been developed by companies such as MercuryMD (www.mercurymd.com/), Patient Keeper (www.patientkeeper.com/), VISICU (www.visicu.com/index_flash.asp), and Global Care Quest (www.gcq.ucla.edu/index pc.html).  
       BRIEF SUMMARY OF THE INVENTION  
       [0007]     In one aspect, the invention provides system for measuring vital signs from multiple patients, typically in an in-hospital setting. The system features a small-scale, body-worn vital sign monitor that includes: i) a sensor configured as a patch that measures electrical and optical signals from a patient; ii) a controller featuring a microprocessor that receives and processes the electrical and optical signals to determine the patient&#39;s vital sign information, including blood pressure; and iii) a first short-range wireless component that wirelessly transmits a packet containing the vital sign information to an external receiver. A portable, wireless computer (e.g., a PDA, cellular telephone, or a laptop computer) communicates with the body-worn module. This component includes: i) a second short-range wireless component that receives the vital sign information and displays it; and ii) a long-range wireless transmitter that transmits the vital sign information over a wireless network. The system also includes an Internet-based system that receives the vital sign information from the wireless network, and avails this to medical professionals through an in-hospital information system.  
         [0008]     In embodiments, the portable, wireless computer features a software program that processes the packet to determine the body-worn vital sign monitor from which it originated, and a patient associated with the monitor. Typically the packet includes an identifying code, such as a serial number, and the software program includes a database that associates a patient&#39;s name with an identifying code. In this case, the Internet-based system can periodically wirelessly transmit contents of the database to the portable, wireless computer.  
         [0009]     In a preferred embodiment the patch includes: i) a first adhesive component featuring a first electrode that measures a first electrical signal from the patient; ii) a second adhesive component featuring a second electrode that measures a second electrical signal from the patient; and iii) a third adhesive component, in electrical communication with the first and second adhesive components, featuring an optical system that measures the optical signal from the patient.  
         [0010]     In embodiments, the optical system features a light-emitting diode and an optical detector disposed on a same side of a substrate (e.g., a circuit board) to operate in a ‘reflection mode’ geometry. Alternatively, these components can be disposed opposite each other to operate in a ‘transmission mode’ geometry.  
         [0011]     The controller typically operates an algorithm (e.g., compiled computer code) configured to process the first and second electrical signals to generate an electrical waveform, and the optical signals to generate an optical waveform. The algorithm then processes the electrical and optical waveforms to calculate a blood pressure value. For example, the controller can determine blood pressure by processing: 1) a first time-dependent feature of the optical waveform; 2) a second time-dependent feature of the electrical waveform; and 3) a calibration parameter determined by another means (e.g., a conventional blood pressure cuff or tonometer).  
         [0012]     In embodiments, the third adhesive component further includes a connector configured to connect to a detachable cable that connects to the first and second electrodes. An additional cable can connect the adhesive components to the controller. Alternatively, the third adhesive component can include a first wireless component, and the controller further includes a second wireless component configured to communicate with first wireless component. In yet another embodiment the controller is attached directly to the third adhesive component.  
         [0013]     The optical system typically includes a first light-emitting diode that emits radiation (e.g. red radiation) that generates a first optical signal, and a second light-emitting diode that emits radiation (e.g., infrared radiation) that generates a second optical signal. In this case the controller additionally includes an algorithm that processes the first and second optical signals to generate pulse oximetry and heart rate values. In other embodiments the controller features an algorithm that processes the first and second electrical signals to generate an ECG waveform.  
         [0014]     In other embodiments the third adhesive component includes a third electrode that measures a third electrical signal from the patient. In this case, the controller includes an algorithm that processes the first, second, and third electrical signals to generate an ECG waveform along with the other vital signs described above.  
         [0015]     The invention has many advantages. In particular, it provides a single, low-profile, disposable system that measures a variety of vital signs, including blood pressure, without using a cuff. This and other information can be easily transferred from a patient to a central monitor through a wired or wireless connection. For example, with the system a medical professional can continuously monitor a patient&#39;s blood pressure and other vital signs during their day-to-day activities, or while the patient is admitted to a hospital. Monitoring patients in this manner minimizes erroneous measurements due to ‘white coat syndrome’ and increases the accuracy of a blood-pressure measurement. In particular, as described below, one aspect of the invention provides a system that continuously monitors a patient&#39;s blood pressure using a cuffless blood pressure monitor and an off-the-shelf mobile communication device. Information describing the blood pressure can be viewed using an Internet-based website, using a personal computer, or simply by viewing a display on the mobile device. Blood-pressure information measured continuously throughout the day provides a relatively comprehensive data set compared to that measured during isolated medical appointments. This approach identifies trends in a patient&#39;s blood pressure, such as a gradual increase or decrease, which may indicate a medical condition that requires treatment. The system also minimizes effects of ‘white coat syndrome’ since the monitor automatically and continuously makes measurements away from a medical office with basically no discomfort to the patient. Real-time, automatic blood pressure measurements, followed by wireless transmission of the data, are only practical with a non-invasive, cuffless system like that of the present invention. Measurements can be made completely unobtrusive to the patient.  
         [0016]     The system can also characterize the patient&#39;s heart rate and blood oxygen saturation using the same optical system for the blood-pressure measurement. This information can be wirelessly transmitted along with blood-pressure information and used to further diagnose the patient&#39;s cardiac condition.  
         [0017]     The monitor is easily worn by the patient during periods of exercise or day-to-day activities, and makes a non-invasive blood-pressure measurement in a matter of seconds. The resulting information has many uses for patients, medical professional, insurance companies, pharmaceutical agencies conducting clinical trials, and organizations for home-health monitoring.  
         [0018]     Having briefly described the present invention, the above and further objects, features and advantages thereof will be recognized by those skilled in the pertinent art from the following detailed description of the invention when taken in conjunction with the accompanying drawings. 
     
    
     BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS  
       [0019]      FIG. 1A  shows a semi-schematic view of a vital sign-monitoring system according to the invention featuring a disposable patch sensor connected to a body-worn monitor that, in turn, communicates with an external wireless PDA;  
         [0020]      FIG. 1B  shows a top view of the disposable patch sensor of  FIG. 1A ;  
         [0021]      FIG. 2  shows a semi-schematic view of the wireless PDA of  FIG. 1A  connected to multiple body-worn monitors in, e.g., a hospital setting;  
         [0022]      FIG. 3  shows a graph of time-dependent optical and electrical waveforms collected by the body-worn module of  FIG. 1A ;  
         [0023]      FIG. 4  shows a screen shot of a user interface deployed on the wireless PDA of  FIG. 1A ; and  
         [0024]      FIG. 5  shows an Internet-based system used to route information from the PDA to an in-hospital information system. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0025]      FIGS. 1A and 1B  show, respectively, a body-worn vital sign monitor  22  that connects through a cable  27  to a disposable patch sensor  28  attached to a patient  30 . The patch sensor  28  measures optical and electrical waveforms, described in detail below with reference to  FIG. 3 , that the body-worn monitor  22  receives and processes to calculate the patient&#39;s blood pressure and other vital signs. Once this information is calculated, the body-worn monitor  22  sends it to an external, wireless PDA  20  through a wireless link (e.g., a Bluetooth connection). The PDA  20  can process and display the information and then transmit it wirelessly over a nation-wide network (e.g. a CDMA network) to an Internet-accessible website or hospital information system, as described in more detail below with reference to  FIG. 5 .  
         [0026]     Preferably the patch sensor  28  attaches to a region near the patient&#39;s neck, chest, ear, or to any other location that is near the patient&#39;s head and proximal to an underling artery. Typically the patient&#39;s head undergoes relatively little motion compared to other parts of the body (e.g., the hands), and thus attaching the patch sensor  28  to these regions reduces the negative affects of motion-related artifacts.  
         [0027]      FIG. 1B  shows the disposable patch sensor  28  that features primary  11  and reference  12  electrodes and an optical system  10  operating in concert as described below to measure vital signs from a patient  30 . The electrodes  11 ,  12  and optical system  10  each attach to the patient&#39;s skin using a separate adhesive pad  16 ,  17 ,  18 , and connect to each other using a Y-shaped cable  14 . During operation, the primary  11  and reference  12  electrodes detect electrical impulses, similar to those used to generate a conventional ECG, from the patient&#39;s skin. Each heartbeat generates a unique set of electrical impulses. Concurrently, the optical system  10  measures an optical waveform by detecting a time-dependent volumetric change in an underlying artery caused by blood flow following each heartbeat. The optical waveform is similar to an optical plethysmograph measured by a pulse oximeter. During operation, the body-worn monitor  22  receives the electrical impulses and converts these to an electrical waveform (e.g., an ECG), and is described in more detail in U.S. patent application Ser. No. 10/906,314, filed Feb. 14, 2005 and entitled PATCH SENSOR FOR MEASURING BLOOD PRESSURE WITHOUT A CUFF, the contents of which are incorporated herein by reference. The body-worn monitor includes a microprocessor that runs an algorithm to process the electrical and optical waveforms to measure vital signs, such as pulse oximetry, heart rate, ECG, and blood pressure.  
         [0028]     For the purposes of measuring blood pressure as described herein, the primary  11  and reference  12  electrodes only need to collect electrical signals required to generate an electrical waveform found in a 2-lead ECG. These electrodes can therefore be placed on the patient at positions that differ from those used during a standard multi-lead ECG (e.g., positions used in ‘Einthoven&#39;s Triangle’).  
         [0029]      FIG. 2  shows how a single wireless PDA  20  operates in a hospital environment to collect vital sign information from a set of body-worn monitors  22   a - g , each associated with a separate patch sensor  28   a - g  attached to a unique patient  30   a - g . For example, each patient  30   a - g  wearing a body-worn monitor  22   a - g  and patch sensor  28   a - g  can be located within a unique hospital room. A medical professional making ‘rounds’ sequentially enters each room and downloads the patient&#39;s most recent vital sign information from each body-worn monitor  22   a - g  through a short-range wireless connection (using, e.g., a pair of matched Bluetooth™ transceivers). In this case, each body-worn monitor  22   a - g  sends information in a packet that includes a header describing a serial number of the monitor, and a payload describing the vital sign information. The PDA  20 , in turn, includes a database that is typically downloaded wirelessly from a central server. The database associates the serial number and the vital sign information with the patient&#39;s name. Once the vital sign information is collected from each patient  22   a - g , the PDA  20  formats it accordingly and sends it using an antenna  26  through a nation-wide wireless network  31  to a computer system on the Internet  32 . The computer system then sends the information through the Internet  32  to an in-hospital network  34  (using, e.g., a frame-relay circuit or VPN). From there, the information is associated with a patient&#39;s medical records, and can be accessed at a later time by a medical professional.  
         [0030]      FIG. 3  shows a graph  40  that plots both the optical  38  and electrical  39  waveforms generated by, respectively, the electrodes and optical system in the disposable patch sensor. Both waveforms include multiple ‘pulses’ each corresponding to an individual heartbeat. Following the heartbeat, electrical impulses travel essentially instantaneously from the patient&#39;s heart to the electrodes, which detect it to generate a pulse in the electrical waveform  39 . At a later time, a pressure wave induced by the same heartbeat propagates through the patient&#39;s arteries, which are elastic and increase in volume due to the pressure wave. Ultimately the pressure wave arrives at a portion of the artery underneath the optical system, where light-emitting diodes and a photodetector detect it by measuring a time-dependent change in optical absorption to generate the optical waveform  38 . The propagation time of the electrical impulse is independent of blood pressure, whereas the propagation time of the pressure wave depends strongly on pressure, as well as mechanical properties of the patient&#39;s arteries (e.g., arterial size, stiffness). The microprocessor runs an algorithm that analyzes the time difference ΔT between the arrivals of these signals, i.e. the relative occurrence of pulses in the optical  38  and electrical  39  waveforms as measured by the patch sensor. Calibrating the measurement (e.g., with a conventional blood pressure cuff or tonometer) accounts for patient-to-patient variations in arterial properties, and correlates ΔT and other properties of the waveforms to both systolic and diastolic blood pressure. This results in a calibration table. During an actual measurement, the calibration source is removed, and the microprocessor analyzes ΔT along with other properties of the optical and electrical waveforms and the calibration table to calculate the patient&#39;s real-time blood pressure.  
         [0031]     In one embodiment, for example, the microprocessor ‘fits’ the optical waveform using a mathematical function that accurately describes the waveform&#39;s features, and an algorithm (e.g., the Marquardt-Levenberg algorithm) that iteratively varies the parameters of the fitting function until it best matches the time-dependent features of the waveform. In this way, blood pressure-dependent properties of the waveform, such as its width, rise time, fall time, and area, can be calibrated as described above. After the calibration source is removed, the patch sensor measures these properties along with ΔT to determine the patient&#39;s blood pressure. Alternatively, the waveforms can be filtered using mathematical techniques, e.g. to remove high or low frequency components that do not correlate to blood pressure. In this case the waveforms can be filtered using well-known Fourier Transform techniques or simple smoothing algorithms to remove unwanted frequency components, and then processed as described above.  
         [0032]     Methods for processing the optical and electrical waveform to determine blood pressure are described in the following co-pending patent applications, the entire contents of which are incorporated by reference: 1) CUFFLESS BLOOD-PRESSURE MONITOR AND ACCOMPANYING WIRELESS, INTERNET-BASED SYSTEM (U.S. Ser. No. 10/709,015; filed Apr. 7, 2004); 2) CUFFLESS SYSTEM FOR MEASURING BLOOD PRESSURE (U.S. Ser. No. 10/709,014; filed Apr. 7, 2004); 3) CUFFLESS BLOOD PRESSURE MONITOR AND ACCOMPANYING WEB SERVICES INTERFACE (U.S. Ser. No. 10/810,237; filed Mar. 26, 2004); 4) VITAL-SIGN MONITOR FOR ATHLETIC APPLICATIONS (U.S. Ser. No.; filed Sep. 13, 2004); 5) CUFFLESS BLOOD PRESSURE MONITOR AND ACCOMPANYING WIRELESS MOBILE DEVICE (U.S. Ser. No. 10/967,511; filed Oct. 18, 2004); and 6) BLOOD PRESSURE MONITORING DEVICE FEΔTURING A CALIBRATION-BASED ANALYSIS (U.S. Ser. No. 10/967,610; filed Oct. 18, 2004); 7) PERSONAL COMPUTER-BASED VITAL SIGN MONITOR (U.S. Ser. No. 10/906,342; filed Feb. 15, 2005); and 8) PATCH SENSOR FOR MEASURING BLOOD PRESSURE WITHOUT A CUFF (U.S. Ser. No. 10/906,315; filed Feb. 14, 2005).  
         [0033]      FIG. 4  shows a screen shot of a graphical user interface (GUI)  41 , rendered on the wireless PDA, which displays patient information  45  and vital sign information  42 . For example, a medical professional (e.g. a nurse) can turn on the PDA before making rounds at a hospital; this process loads the GUI  41 . When the nurse enters a hospital room, the PDA detects a short-range wireless signal indicating the presence of a patient wearing a body-worn vital sign monitor, described above. The PDA displays a serial number associated with the monitor, along with the patient&#39;s name, in the patient information  45 . The nurse then depresses a ‘Get Vital Signs’ button  44  on the GUI  41 . This initiates a wireless serial link with the body-worn monitor, and then downloads a set of vital signs collected recently by the patch sensor. As shown in the figure, this information includes:  
         [0034]     1) Systolic blood pressure  
         [0035]     2) Diastolic blood pressure  
         [0036]     3) Pulse blood pressure  
         [0037]     4) Heart rate  
         [0038]     5) Pulse oximetry  
         [0039]     6) Temperature  
         [0040]     7) Weight  
         [0041]     8) ECG ‘rhythm strip’ (e.g., the electrical waveform shown in  FIG. 3 )  
         [0042]     Note that for the above-mentioned information, temperature is measured with a conventional temperature sensor embedded in the patch sensor. Weight is measured at an earlier time when the patient steps on a scale that includes a short-range wireless transceiver that connects to a matched transceiver within the body-worn unit. Such a system, for example, is described in the pending patent application entitled ‘SMALL-SCALE, VITAL-SIGNS MONITORING DEVICE, SYSTEM AND METHOD’, U.S. Ser. No. 10/907,440, filed Mar. 31, 2005, the contents of which are incorporated herein by reference.  
         [0043]     In addition to collecting the patient&#39;s most recent vital sign information  42 , the nurse can depress a ‘History’ button  43  to collect historical values of a particular vital sign. Once collected, these values can be plotted in a variety of graphical formats, such as a time-dependent or histogram format. Similarly, the GUI  41  includes a ‘Rhythm Strip’ button  47  that, once depressed, renders and analyzes a graphical ECG rhythm strip, similar to the electrical waveform shown in  FIG. 3 .  
         [0044]     Once the nurse collects the patient&#39;s most recent or historical vital sign information, a ‘Transmit Vital Signs’ button  46  is depressed to transmit this information over a wireless network, such as a nation-wide (e.g., a CDMA network) or in-hospital wireless network (e.g.. an 802.11-based network), to the hospital&#39;s information system. This information can then be accessed at a later time by any relevant medical personnel associated with the patient or hospital.  
         [0045]     The GUI  41  also includes other tools for managing information, such as a link  49  to a web page on the Internet, a link  50  to a email program, a button  48  that connects the nurse to a home page of the GUI that includes links to other data-processing functions, and an icon  51  that describes the strength of the wireless signal.  
         [0046]      FIG. 5  shows a preferred embodiment of an Internet-based system  52  that operates in concert with the body-worn unit  22  to send information from a patient  30  to an in-hospital information system  71 . Using a wireless PDA  20  operating a GUI such as that shown in  FIG. 4 , a medical professional  31  collects vital sign information from the patient&#39;s body-worn unit  22  through a short-range wireless connection. The wireless PDA  20  then sends the information through a wireless network  54  to a web site  66  hosted on an Internet-based host computer system  57 . The wireless network can be a nationwide wireless network or a local wireless network. A secondary computer system  69  accesses the website  66  through the Internet  67 . A wireless gateway  55  connects to the wireless network  54  and receives data from one or more wireless PDAs  20 , as discussed below. The host computer system  57  includes a database  63  and a data-processing component  68  for, respectively, storing and analyzing the data. The host computer system  57 , for example, may include multiple computers, software pieces, and other signal-processing and switching equipment, such as routers and digital signal processors. The wireless gateway  55  preferably connects to the wireless network  54  using a TCP/IP-based connection, or with a dedicated, digital leased line (e.g., a frame-relay circuit or a digital line running an X.25 or other protocols). The host computer system  57  also hosts the web site  66  using conventional computer hardware (e.g. computer servers for both a database and the web site) and software (e.g., web server and database software). To connect to the in-hospital information system  71 , the host computer system  57  typically includes a web services interface  70  that sends information using an XML-based web services link to a computer associated with the in-hospital information system  71 . Alternatively, the wireless network  54  may be an in-hospital wireless network (e.g., a network operating Bluetooth™, 802.11a, 802.11b, 802.11g, 802.15.4, or ‘mesh network’ wireless protocols) that connects directly to the in-hospital information system  71 . In this embodiment, a nurse working at a central nursing station can quickly view the vital signs of the patient using a simple computer interface.  
         [0047]     To view information remotely, the patient or medical professional can access a user interface hosted on the web site  66  through the Internet  67  from a secondary computer system  69 , such as a Internet-accessible home computer. The system  53  may also include a call center, typically staffed with medical professionals such as doctors, nurses, or nurse practioners, whom access a care-provider interface hosted on the same website  66 .  
         [0048]     During typical operation, the patient continuously wears the body-worn monitor  22  and its associated patch sensor system during their hospital stay, which is typically a period of time ranging from a few hours to weeks.  
         [0049]     The body-worn can optionally be used to determine the patient&#39;s location using embedded position-location technology (e.g., GPS, network-assisted GPS, or Bluetooth™, 802.11-based location system). In situations requiring immediate medical assistance, the patient&#39;s location, along with relevant vital sign information, can be relayed to emergency response personnel.  
         [0050]     In a related embodiment, the wireless PDA may use a ‘store and forward’ protocol wherein one of these devices stores information when the wireless device is out of wireless coverage, and then sends this information to the wireless device when it roams back into wireless coverage.  
         [0051]     In still other embodiments, electronics associated with the body-worn monitor (e.g., the microprocessor) are disposed directly on the patch sensor, e.g. on a circuit board that supports the optical system. In this configuration, the circuit board may also include a display to render the patient&#39;s vital signs. In another embodiment, a short-range radio (e.g., a Bluetooth™, 802.15.4, or part-15 radio) is mounted on the circuit board and wirelessly sends information (e.g., optical and electrical waveforms; calculated vital signs such as blood pressure, heart rate, pulse oximetry, ECG, and associated waveforms) to an external controller with a matched radio, or to a conventional cellular telephone or wireless personal digital assistant. Or the short-range radio may send information to a central computer system (e.g., a computer at a nursing station), or though an internal wireless network (e.g. an 802.11-based in-hospital network). In yet another embodiment, the circuit board can support a computer memory that stores multiple readings, each corresponding to a unique time/date stamp. In this case, the readings can be accessed using a wireless or wired system described above.  
         [0052]     In still other embodiments, the patch sensor can include sensors in addition to those described above, e.g. sensors that measure motion (e.g. an accelerometer) or other properties.  
         [0053]     Still other embodiments are within the scope of the following claims.