Patent Application
20050228300
Not Applicable
1. Field of the Invention
The present invention relates to a system that measures blood-pressure information.
2. Description of Related Art
Blood within a patient's body is characterized by a baseline pressure value, called the diastolic pressure. Diastolic pressure indicates the pressure in an artery when the blood it contains is static. A heartbeat forces a time-dependent volume of blood through the artery, causing the baseline pressure to increase in a pulse-like manner to a value called the systolic pressure. The systolic pressure indicates a maximum pressure in a portion of the artery that contains a flowing volume of blood. Pressure in the artery periodically increases from the diastolic pressure to the systolic pressure in a pulsatile manner, with each pulse corresponding to a single heartbeat. Blood pressure then returns to the diastolic pressure when the flowing pulse of blood passes through the artery.
Both invasive and non-invasive devices can measure a patient's systolic and diastolic blood pressure. A non-invasive medical device called a sphygmomanometer measures a patient's blood pressure using an inflatable cuff and a sensor (e.g., a stethoscope) that detects blood flow by listening for sounds called the Korotkoff sounds. During a measurement, a medical professional typically places the cuff around the patient's arm and inflates it to a pressure that exceeds the systolic blood pressure. The medical professional then incrementally reduces pressure in the cuff while listening for flowing blood with the stethoscope. The pressure value at which blood first begins to flow past the deflating cuff, indicated by a Korotkoff sound, is the systolic pressure. The stethoscope monitors this pressure by detecting periodic acoustic ‘beats’ or ‘taps’ indicating that the blood is flowing past the cuff (i.e., the systolic pressure barely exceeds the cuff pressure). The minimum pressure in the cuff that restricts blood flow is the diastolic pressure. The stethoscope monitors this pressure by detecting another Korotkoff sound, in this case a ‘leveling off’ or disappearance in the acoustic magnitude of the periodic beats, indicating that the cuff no longer restricts blood flow (i.e., the diastolic pressure barely exceeds the cuff pressure).
Low-cost, automated devices measure blood pressure using an inflatable cuff and an automated acoustic or pressure sensor that measures blood flow. These devices typically feature cuffs fitted to measure blood pressure in a patient's wrist, arm or finger. During a measurement, the cuff automatically inflates and then incrementally deflates while sensing electronics (located in the cuff or in an external device) measure changes in pressure and consequently blood flow. A microcontroller in the external device then processes this information to determine blood pressure. Cuff-based blood-pressure measurements such as these typically only determine the systolic and diastolic blood pressures; they do not measure dynamic, time-dependent blood pressure.
Time-dependent blood pressure can be measured with a device called a tonometer. The tonometer features a sensitive transducer positioned on the patient's skin above an underlying artery. The tonometer compresses the artery against a portion of bone, during which time the transducer measures blood pressure in the form of a time-dependent waveform. The waveform features a baseline that indicates the diastolic pressure, and time-dependent pulses, each corresponding to individual heartbeats. The maximum value of each pulse is the systolic pressure. The rising and falling edges of each pulse correspond to pressure values that lie between the systolic and diastolic pressures.
Data indicating blood pressure are most accurately measured during a patient's appointment with a medical professional, such as a doctor or a nurse. Once measured, the medical professional manually records these data in either a written or electronic file. Appointments typically take place a few times each year. Unfortunately, patients often experience ‘white coat syndrome’ where anxiety during the appointment affects the blood pressure that is measured. For example, white coat syndrome can elevate a patient's heart rate and blood pressure; this, in turn, can lead to an inaccurate diagnosis.
Pulse oximeters are devices that measure variations in a patient's arterial blood volume. These devices typically feature a light source that transmits optical radiation through the patient's finger to a photodetector. A processor in the pulse oximeter monitors time and wavelength-dependent variations in the transmitted radiation to determine heart rate and the degree of oxygen saturation in the patient's blood. Various methods have been disclosed for using pulse oximeters to obtain arterial blood pressure. One such method is disclosed in U.S. Pat. No. 5,140,990 to Jones et al., for a ‘Method Of Measuring Blood Pressure With a Photoplethysmograph’. The '990 patent discloses using a pulse oximeter with a calibrated auxiliary blood pressure to generate a constant that is specific to a patient's blood pressure. Another method for using a pulse oximeter to measure blood pressure is disclosed in U.S. Pat. No. 6,616,613 to Goodman for a ‘Physiological Signal Monitoring System’. The '613 patent discloses processing a pulse oximetry signal in combination with information from a calibrating device to determine a patient's blood pressure.
The present invention provides a cuffless, wrist-worn blood-pressure monitor that features a form factor similar to a conventional wristwatch. The blood pressure monitor makes a transdermal, optical measurement of blood pressure and wirelessly sends this information to a mobile device (e.g., a conventional cellular phone or PDA). The mobile device preferably features an embedded, short-range wireless transceiver and a software platform that displays, analyzes, and then transmits the information through a wireless network to an Internet-based system. With this system a medical professional can continuously monitor a patient's blood pressure during their day-to-day activities. Monitoring patients in this manner minimizes erroneous measurements due to ‘white coat syndrome’ and increases the accuracy of a blood-pressure measurement.
In one aspect, the invention provides a system for monitoring blood pressure that includes: 1) a blood-pressure monitor featuring a measuring component that generates blood-pressure information and a first short-range wireless component configured to wirelessly transmit the blood-pressure information; 2) a mobile device that includes i) an embedded second short-range wireless component configured to receive the blood-pressure information; and ii) a long-range wireless transceiver configured to transmit the blood-pressure information over a wireless network; and 3) a computer system configured to receive and display the blood-pressure information. For this system, ‘embedded’ means electronics for the short-range wireless component are integrated directly into the chipset, i.e. they are created during the microelectronic manufacturing of the chipset.
In another aspect, the invention provides a system for monitoring blood pressure that includes the above-mentioned system, with the embedded short-range wireless component replaced by a wireless component that connects to a serial port of a mobile device and features a second short-range wireless component configured to receive the blood-pressure information and send it to the mobile device.
The blood-pressure monitoring device typically features a short-range wireless transmitter operating on a wireless protocol that is matched to the wireless transceiver embedded in the mobile device. In typical embodiments the transceiver operates on a short-range wireless protocol such as Bluetooth™, 802.11a, 802.11b, 802.1g, or 802.15.4. A short-range wireless transmitter is defined as a transmitter capable of transmitting up to thirty meters. The mobile device also includes a long-range wireless transmitter that transmits information over a terrestrial wireless network, such as a network operating using a wireless protocol such as CDMA, GSM, GPRS, Mobitex, DataTac, iDEN, and analogs and derivatives thereof. A long-range wireless transmitter is defined as a transmitter capable of transmitting greater than thrity meters. Alternatively the network maybe based on a protocol such as 802.11a, 802.11b, 802.1g, or 802.15.4.
The invention has many advantages. In particular, it provides a system that continuously monitors a patient's blood pressure using a cuffless blood pressure monitor and an off-the-shelf mobile device. The mobile device can even be the patient's personal cellular phone. 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's blood pressure, such as a gradual increase or decrease, which may indicate a medical condition that requires treatment. The invention 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 monitor like that of the present invention. Measurements can be made completely unobtrusive to the patient.
The monitor can also characterize the patient'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's cardiac condition.
The monitor is small, 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.
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.
As shown in
The cuffless blood pressure monitor 10 preferably features an optical finger-mounted module 13 that attaches to a patient's finger, and a wrist-mounted module 11 that attaches to the patient's wrist where a watch is typically worn. A cable 12 provides an electrical connection between the finger-mounted 13 and wrist-mounted 11 modules. During operation, the finger-mounted module 13 measures an optical ‘waveform’ that the blood-pressure monitor 10 processes to determine real-time beat-to-beat diastolic and systolic blood pressure, heart rate, and pulse oximetry. Methods for processing the optical waveform to determine blood pressure are described in the following co-pending patent applications, the entire contents of which are incorporated by reference: 1) U.S. patent application Ser. No. 10/810,237, filed Mar. 26, 2004, for a CUFFLESS BLOOD PRESSURE MONITOR AND ACCOMPANYING WEB SERVICES INTERFACE; 2) U.S. patent application Ser. No. 10/709,015, filed Apr. 7, 2004, CUFFLESS BLOOD-PRESSURE MONITOR AND ACCOMPANYING WIRELESS, INTERNET-BASED SYSTEM; 3) U.S. patent application Ser. No. 10/752,198, filed Jan. 6, 2004, for a WIRELESS, INTERNET-BASED MEDICAL DIAGNOSTIC SYSTEM; and co-pending U.S. Patent Application, filed Oct. 18, 2004, for a BLOOD PRESSURE MONITORING DEVICE FEATURING A CALIBRATION-BASED ANALYSIS.
A preferred mobile device 15 is based on Qualcomm's CDMA technology and features a chipset that integrates both hardware and software for the Bluetooth™ wireless protocol. These mobile devices 15 operate with the above-described blood-pressure monitor with little or no modifications. Such chipsets, for example, include the MSM family of mobile processors (e.g., MSM6025, MSM6050, and the MSM6500) and are described and compared in detail in http://www.qualcomm.com. For example, the MSM6025 and MSM6050 chipsets operate on both CDMA cellular and CDMA PCS wireless networks, while the MSM6500 operates on these networks and GSM wireless networks. In addition to circuit-switched voice calls, the wireless transmitters used in these chipsets transmit data in the form of packets at speeds up to 307 kbps in mobile environments. Those skilled in the pertinent art will recognize that mobile devices 15 with other chipsets may be utilized with the system 5 without departing from the scope and spirit of the present invention.
Referring to
To generate an optical waveform and measure blood pressure, pulse oximetry, and heart rate, the monitor 10 includes a light source 30 and a photodetector 31 embedded within the finger-mounted module shown in
A wireless gateway 55 connects to the wireless network 54 and receives data from one or more mobile devices 15. The wireless gateway 55 additionally connects to a host computer system 57 that 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).
During typical operation, the patient continuously wears the blood-pressure monitor 10 for a period of time, ranging from a 1-2 days to weeks. For longer-term monitoring (e.g. several months), the patient may wear the blood pressure monitor 10 for shorter periods of time during the day. To view information sent from the blood-pressure monitor 10, the patient or medical professional accesses a user interface hosted on the web site 66 through the Internet 67 from the secondary computer system 69. The system 52 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.
In an alternate embodiment, the host computer system 57 includes a web services interface 70 that sends information using an XML-based web services link to a secondary, web-based computer application 71. This application 71, for example, could be a data-management system operating at a hospital.
Many of the mobile devices 15 described above can be used to determine the patient's location using embedded position-location technology (e.g., GPS or network-assisted GPS). In situations requiring immediate medical assistance, the patient's location, along with relevant medical data collected by the blood pressure monitoring system, can be relayed to emergency response personnel.
In other embodiments, the mobile device 15 described above is be replaced with a personal digital assistant (PDA) or laptop computer operating on a wireless network 14. In still other embodiments, the blood-pressure monitor 10 additionally includes a GPS module that receives GPS signals through an antenna from a constellation of GPS satellites and processes these signals to determine a location (e.g., latitude, longitude, and altitude) of the monitor 10 and, presumably, the patient. This location could be used to locate a patient during an emergency, e.g. to dispatch an ambulance. In still other embodiments, patient location information is obtained using position-location technology (e.g. network-assisted GPS) that is embedded in many mobile devices 15 that can be used for the blood-pressure monitoring system.
In other embodiments, the blood-pressure monitor 10 or the mobile device 15 use a ‘store and forward’ protocol wherein each device stores information when it is out of wireless coverage, and then transmits this information when it roams back into wireless coverage.
Still other embodiments are within the scope of the following claims.
This application is a continuation-in-part application of U.S. patent application Ser. No. 10/709,014, filed on Apr. 7, 2004.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 10709014 | Apr 2004 | US |
| Child | 10967511 | Oct 2004 | US |
