GB2425180A - Wearable physiological monitor with wireless transmitter - Google Patents

Abstract

A physiological monitoring device worn by a user comprises a plurality of physiological sensors 10-14 (e.g. ECG, temperature, blood pressure, heart rate etc.), a processor 18 and a transceiver 17. The processor 18 analyses the measured physiological data and generates a health status indication of at least two levels (e.g. normal and abnormal). The health status indication is then wirelessly transmitted to a remote monitoring station. If necessary some or all of the actual physiological measurements can be transmitted in addition to the health status summary. For example if the health status indication is normal no additional data may be required, whereas if the indication was abnormal further data may be required. Thus the data transmission is selective depending upon the welfare of the user.

Description

MONITORING SYSTEM

Background to the invention

The invention relates to a device for monitoring the health and welfare of an ambulatory subject by the collection of a pluralily of physiological signals, the real-time analysis of these signals, and the transmission of the analysis and optionally the signals to a monitoring station which may be local or remote to the subject.

The monitoring station may use this data to assist in the determination of well-being of the user and to assist in determining the need for appropriate interventions (eg: despatching of medical expertise to the user).

The types of physiological signals to be collected, analysed and transmitted may include, for example, ECG, Respiration Effort, Respiration Rate, Body Temperature, Blood pressure, Blood oxygen level, pulsatile pressure waveform, Heart Rate, Heart Rate Variability, Body Orientation, Body Motion, and Electro-ocular activity. The system also provides for combinatorial assessment of the signals.

Devices which extract, process and transmit one or more of the above signals are known in the art, but are generally intended for the monitoring of patients with known or suspected ailments, such as heart disease. The operation of the devices is under the control of a doctor or other medical worker, who controls the operation of the device. Analysis of the data is undertaken usually after collection. A drawback of these devices when used to continuously monitor a subject is that they require large volumes of physiological data To be sent to the monitoring station which makes their use in remote communications systems which have limited bandwidth problematic. They are also not ideal for simultaneous monitoring of a group of individuals where it may be impractical to closely review each individual's physiological signals continuously. In addition the requirements placed on the system by the monitoring personnel will vary depending on the perceived overall welfare status of the user.

For example, once a person is known to be injured then monitoring of vital signs waveforms and data is of benefit by those skilled in the interpretation of such data in determining the action to be taken. If the person is healthy only a small amount of data is needed however.

An object of this invention is to provide a body worn device suitable for the collection of data and analysis of the physiological data, and based on an appropriate algorithm produce an overall score of predicted welfare, thus removing the need to send the physiological signals from the sensor to a remote unit for analysis and review. This welfare score must have a minimum of two levels (normal and abnormal) but may be extended to have any number of interim values to provided higher granularity to the monitoring point.

If the device determines that the physiological signals are abnormal in some way, perhaps indicating that the subject is over-exerting himself or herself, or that they have been injured or incapacitated in some way, then the device signals this to the monitoring point and can either automatically or on request from the monitoring point transmit additional physiological data and signals itself, for further analysis possibly with the assistance of a further processing system at the monitoring station.

The ability of the invention to determine whether to transmit the physiological data or not has three advantages. First it reduces the bandwidth, under normal conditions, that is needed to transmit the information. Secondly, because, under normal conditions, it does not have to transmit very much information, the transmitter needs to be turned on only for a short time, at infrequent intervals. This reduces the power consumption of the device and accordingly increases the battery life. Lastly, it aides the rapid identification of users who may need more detailed observation particularly when prioritising care amongst a group of users.

Important Features Accordingly, this invention provides a body-worn part or parts capable of collecting a pluralily of physiological signals, collecting and analysing those signals, and selectively transmitting the signals or the analysis of them over a communications link, which may be radio or wire, and which may be constrained to be low bandwidth.

The user wears a sensor, which captures physiological signals off the body, processes them as necessary and then transmits either a periodic signal that summarises the user's health status, and summary measurements or, if the signals are abnormal in some way, in addition transmits the physiological signals themselves.

In order to achieve a reasonable battery life and system transmission load for the sensor, it uses a multilevel control on the way data is transferred.

Abbreviated Disclosure is intended to be the normal mode of operation for the sensor when attached to a healthy user. In the abbreviated disclosure system data need only be transferred in short bursts (say every thirty seconds or so). The data that could be transferred in this message is likely to contain: * Welfare Status Indicator * Heart and Respiration Rate * Temperature * Motion / Activily Level * Body Orientation * Unit/User Identification Information * Unit self check diagnostics (lead off signal, battery status etc) This data would be in the order of a few bytes and presents a very low transmission load on the system. The use of abbreviated disclosure therefore results in a substantial reduction of both transmission bandwidth and of power consumption.

Full Disclosure is entered into on detection of a change in certain parameters measured by the sensor, which may indicate a need for medical attention. These could be (by way of

example):

* A certain percentage increase or decrease in heart or respiration rate over a time window * Exceeding a certain threshold of heart rate or respiration rate (including failure to detect a rate) * Failure to detect motion for a certain time period * Detection of orientation (user prone) * A repetitive time interval has passed * The value of an overall scored index derived from a combination of parameters exceeds a threshold.

* Full disclosure may also be triggered manually via a protected button, which could be operated by a distressed user, or by a medic * Remote request from the monitoring device Once switched to full disclosure the system could remain in that mode, or go back to abbreviated disclosure after a time period or the cessation of the triggering event.

The signals provided in full disclosure may vary depending on system preferences and may also be controlled by the remote monitoring station.

Preferably, the body worn device is able to communicate, by wired or wireless means, to a radio communication device such as a GSM mobile phone, satellite communication or public safely communication device leg: TETRA radio) in order to allow data transfer from a user over a wide area back to the monitoring point.

Additionally it should also provide the ability for the user to be monitored from close proximity by communication with a remote hand held communications device leg a Pocket PC) with an appropriate function to view the data.

Introduction to the Drawings

With reference to the drawings: FIGURE 1 shows a block diagram of one embodiment of the welfare monitoring system.

FIGURE 2 shows a block diagram of the body worn unit.

Preferred Embodiment In a preferred embodiment, with reference to FIGURE 1, the user wears a monitoring unit which records multiple signals from the user and processes them in order to determine a welfare status.

With reference to FIGURE 2, the monitoring unit comprises two or more electrode sensors [10] which connect to the user's skin. Sensors suitable for the purpose are well known and may be made from conductive patches connecting to the skin via a conductive gel (eg: Medico), or from conductive fabrics such as silver loaded thread or semi conductive rubbers (eg: Santoprene).

The electrodes [10] present an electrical signal which is then processed and filtered using appropriate electronic means, digitised and passed to a microcontroller [18] for analysis. The microcontroller may extract from the received data, the users ECG waveform and by suitable calculation use this signal to derive the users Heart Rate, Heart Rate Variability, Respiratory Sinus Arrhythmia and ECG derived respiration effort rate. Those skilled in the art will be aware of established mathematical formula and techniques for deriving this information.

A respiration effort sensor [11] provides a direct means of measuring respiratory effort by measurement of the chest/abdominal expansion and contraction. This signal is amplified and filtered [15] , digitised and processed in [18] which can use the data to compute a respiration rate based on the periodicity of the signal and also to detect the absence of respiration effort over a period of time (for example 20 seconds).

An embedded Sp02 sensor [12], such as the Nonin OEM Ill pulse oximeter module, provides a measure of blood oxygen content along with a waveform indicating the pulsatile blood flow and communicates with the microcontroller [18] via a simple serial data link.

An accelerometer, such as the ADXL2O2E, can be organised to provide 2 or 3 axis measurement of g forces applied to the body which can be computed by [18] to a determine activily level over a period of time, for example, none, low, moderate and high.

Body position may also be derived from the relative levels of g recorded by the accelerometers.

In addition a mechanical activity switch may also provide a measure of user activity by the measurement of switch activations over a time window.

A skin temperature sensor [14] is used to derive an electrical signal, digitised by [18] from which an accurate (<0.25C) temperature value can be computed. Those skilled in the art will be aware that the sensor may be achieved by the use of temperature sensitive resistive devices (ie: thermistor) housed in appropriate holder to contact the skin or by the use of an infra red sensor detecting device.

The sensor is powered by either primary battery cells (egg: Alkaline LRO3 cells) or by a rechargeable battery device (egg: Li Ion 553048 cell) The microcontroller [18] connects to a radio transceiver module which may be for example a Bluetooth radio transceiver.

The microcontroller [18] will derive the welfare score by measuring a combination of the above signals depending on an appropriate algorithm periodically (for example, every 30 seconds) A user alerting device [19] may be provided to indicate to the user to take a certain pre- determined action, such as make voice contact with the remote monitoring station. The alerting device may be a silent vibrating alert as found commonly on handheld communications devices.

A user input button [20] allows for the user to signal an event has occurred to the remote monitoring station.

It will be clear to those skilled in the art that other methods of deriving the physiological parameters would be possible, and that other parameters could also be measured using well-known techniques.

Referring to FIGURE 1, the user monitoring unit communicates to a mobile radio terminal via a communication link [3] in order to send and receive data over the mobile radio terminal device which in turn communicates [4] to an infrastructure to which the remote monitoring station [7] is connected. The communications system could be, for example, a land based mobile communications system such as a GSM mobile cellular network. Those skilled in the art will be aware that alternate network both terrestrial and satellite based may be used to transport the data to the remote user [7] and that the remote user may also be not in direct connection with the mobile communications network.

In addition a local monitoring station [8] may also be used to communicate with the monitoring unit directly either by wire or wireless. In a preferred embodiment, this unit may be a hand held computer such as a Pocket PC.

Claims (9)

1. We Claim: 1. A monitoring device worn by a user comprising: a plurality of sensors to record physiological information from the user in real time.

   a processing element which: processes the physiological information to derive additional secondary physiological information such a rates and periodicity; processes two or more of the physiological or secondary physiological information items in real time in order to derive welfare indication of a least two levels (abnormal/normal); a transceiver device capable of communicating the welfare indication wirelessly to a mobile communications device periodically which can then forward this information to a remote (to the user) monitoring station for review and assement.
2. 2. A device according to Claim 1, where the welfare indication comprises of three states red, amber and green.
3. 3. A device according to Claim 1, where some or all of the physiological signals waveforms may also be transferred on request from the monitoring station.
4. 4. A device according to Claim 1, where some or all of the physiological signals waveforms may also be transferred automatically on processing of a welfare indication of type abnormal or by wearers request.
5. 5. A device according to Claim 1, where interim values of the welfare assement are derived to provide a indicator of increasing importance between the normal and abnormal conditions.
6. 6. A device according to Claim 1, where the assessment of the users welfare is optimised by the sending of user personalisation information to the sensor.
7. 7. A device according to Claim 1, where the communication to the mobile communications device is achieved via a wired connection.
8. 8. A measuring device substantially as herein before described with reference to or as shown in accompanying drawings.
9. 9. A measuring system substantially as herein before described with reference to or as shown in accompanying drawings.