Monitoring system for monitoring of a physiological parameter of a recipient
The present invention relates to a monitoring system for monitoring physiological parameters of a recipient, comprising at least one electrode having a working surface to be brought into contact with the recipient's skin.
Monitoring systems for monitoring physiological parameters of a recipient are known. However, most of these systems, e.g. electroencephalographic (EEG) systems, electrocardiographic (ECG ) or electromyographic (EMG) systems, are adapted for clinical use only. Monitoring systems for home use are not widely established, since they are complicated to use and/or do not show a comparable measurement quality.
It is an object of the invention to provide a user-friendly monitoring system having an improved measurement quality and suitable for home use.
This object is achieved according to the invention by a monitoring system for monitoring a physiological parameter of a recipient, comprising at least one dry electrode having a working surface that is to be brought into contact with the recipient' s skin, the system being characterized in that the at least one electrode comprises a flexible conductive shell that is to be integrated into a fabric or a garment and an electronic circuit embedded in said shell.
A core idea of the invention is to use dry electrodes with flexible, elastic shells made from a conductive material. These electrodes are directly applied to the recipient's skin without any use of a conductive jelly or the like. The easy handling of such electrodes clearly enhances the user comfort thereof compared with the wet electrodes mainly used in clinical applications. The flexible shell provides a good mechanical contact with the skin. A part of the shell is adapted to serve as the working surface. Since the shell is adapted for integration into textiles or garments, the comfort of handling is high and the inventive monitoring system is suitable for long-term continuous monitoring of electrophysiological signals and other parameters. Since the electrodes suggested by the present invention are very robust, the monitoring system is more durable and reliable than prior art systems. Another core idea of the invention is to integrate an electronic circuit into the electrode. In contrast to the prior art, where electrical signals are usually transmitted from the monitoring electrode to a backstage electronic circuit by a cable connection with a typical length of 0.1 to 1 m, which cable is shielded because of the weak monitoring signals, the present invention allows the use of unshielded cables, since the influence of capacitive couplings is diminished. The fact that no shielded cables are necessary reduces the manufacturing cost. Furthermore, a reduction in motion artifacts caused by cable movements leads to an improved measurement quality.
The present invention provides a user-friendly monitoring system with improved measurement quality. The invention is preferably used in the field of personal health care for continuous monitoring of electro-physiological parameters outside hospitals with a maximum of comfort.
These and other aspects of the invention will be further elaborated on the basis of the following embodiments, which are defined in the dependent claims. In a preferred embodiment of the invention, the shell is made from conductive rubber. This material is flexible enough to ensure a good skin contact. Furthermore, rubber is easy to handle during manufacture of the electrode. Other materials that may be used are conductive foams or conductive polymers, a mixture of conductive graphite with a silicon gel, or any other material which permits long-term use without skin irritation. In a preferred embodiment of the invention, the electrode is adapted to be integrated into a fabric by vulcanization (pressing and heating) e.g. of rubber material. In other words, the design and material of the electrode are chosen such that the electrode is attached to a textile by means of a molding operation. For example, the electrode is integrated into an undergarment or the like. Such an arrangement is not only very user- friendly, but also contributes to the comfort of the user.
In another preferred embodiment of the invention, the rubber shell comprises a border area adapted to be sewn to a garment, e.g. to a cotton fabric. This electrode design provides a very easy and reliable way of attaching the electrode. Electrode and textile can be produced and assembled separately. The inclusion of the electrode does not limit the textile design. The electrode can be fixed to any position of the textile. The reduced number of production steps and the reduced production cost compared with other attachment methods render these electrodes suitable for mass production.
Instead of a molding operation or sewing, other methods of attaching the electrode to the recipient's garment or the like are possible, e.g. gluing, knitting, embroidering, etc.
According to still another embodiment of the invention, the electronic circuit comprises an operational amplifier in order to enhance the signal quality. The measured data are amplified directly on location. Only amplified signals are transmitted to an external monitoring device, e.g. using a wireless transmission technique or a cable connection.
According to another preferred embodiment of the invention, the electronic circuit comprises a buffer circuit adapted for impedance conversion. The placement of a buffer circuit close to the high-impedance body signal sources will strongly increase signal-to-noise ratios, especially for ECG or EEG measurements. Furthermore, this measure leads to a better matching of source and amplifier impedances, which can lead to an increase of the system's up-time. Additionally, the time needed before a sufficient signal-to-noise ratio is reached (warm-up time) will become shorter.
According to yet another embodiment of the invention, the electrode further comprises a number of sensors embedded in the rubber shell, the sensors being adapted to provide additional non-invasive data. Different kind of sensors may be used, e.g. temperature sensors, pressure sensors, acoustic wave sensors, sensors for measuring the chemical composition, etc. If additional sensors are integrated into the electrode, the number of accessible vital parameters is increased without any additional discomfort besides the electrode that is placed against the recipient's skin anyway. In other words, the electrode is used as a multi- sensor platform for the monitoring system. Such electrodes diminish the complexity of the monitoring system and increase the reliability and functionality of the system. This monitoring system can be used for a large number of further application areas with a minimum number of electrodes and a maximum level of comfort of the recipient. i These and other aspects of the invention will be described in detail hereinafter, by way of example, with reference to the following embodiments and the accompanying drawings; in which:
Fig.l is a plan view of an electrode as used in a monitoring system according to the invention,
Fig. 2 is a lateral cross- sectional view of the electrode of Fig. 1, and Fig. 3 shows a simplified wiring scheme of an electronic circuit contained in an electrode as used in a monitoring system according to the invention.
Figs. 1 and 2 show a dry electrode 1 according to the present invention. The electrode 1 is adapted for use in an ECG monitoring system (not shown). The electrode 1 comprises a flexible shell 2 made from conductive rubber. The shell 2 comprises a central container 3 and a flat border area 4 along the periphery of the container 3. The raised upper side of the container 3 serves as a plane working surface 5. As shown in Fig. 2, the border area 4 can be sewn to a cotton fabric 6 with a number of stitches 7. The electrode 1 is thus positioned in an opening 8 of the fabric 6 such that the working surface 5 is accessible. The border 9 of the fabric 6 is placed on top of the flat border area 4 of the electrode 1. The fabric 6 is seamed along the border 9 to prevent the fabric from fraying. The height 10 of the container 3, i.e. the spacing between the upper side 11 of the border area 4 and the working surface 5, is chosen in relation to the thickness of the fabric 6 such that a permanent contact between the working area 5 and the skin is guaranteed. In another embodiment of the invention, the border area 4 of the rubber shell 2 is enlarged by a piece of cotton fabric 12 embedded into the flat border area 4 and extending along the periphery of the border area 4. This fabric 12 is shown in Fig.l as a dotted line and can also be used for sewing.
The central container 3 contains an integrated electronic circuit 13 in the form of a printed circuit board. A connecting cable 14 is connected to the electrode 1. Instead of the connecting cable 14, a radio frequency transmitter device may be used for wireless data transmission to an external monitoring device (not shown). The electronic circuit 13 and the cable 14 are embedded into the rubber material, e.g. by thermal molding. To obtain additional data for use in analyzing the user' s heart activity, the container 3 further contains a temperature sensor 15 for measuring the user's body temperature. The close contact between the working surface 5 and the skin renders it possible to obtain a very precise and reliable measure of the skin's temperature. After the electrode 1 has been placed on the recipient' s skin, the electrical properties of the skin-electrode contact changes from purely capacitive to a mixture of resistive and capacitive. In the illustrated embodiment of the invention, the electrical circuit 13 used is adapted to decrease the warm-up time, i.e. to decrease the time after which a sufficient signal-to-noise ratio has been reached. This renders it possible to measure ECG signals in a more capacitive region. This is realized by a buffer circuit that transforms the ECG signal from the high-impedance voltage source (heart) to a low-impedance source. This circuit, integrated in the electrode, is positioned very close to the user' s body.
Fig.3 illustrates a buffer circuit 15 used in an electrode 1 according to the invention. The circuit 15 comprises an operational amplifier 16 for enhancing the signal quality. The input 17 of the amplifier 16 is connected to the working surface 5 of the electrode 1. The output 18 of the amplifier is then connected to a central processing unit, which includes a typical amplifier and additional storage and processing capabilities (not shown). An RC filter 20 is provided for noise suppression. At least two such electrodes and one reference electrode are required for ECG-measurements. It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrative embodiments and that the present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. It will furthermore be evident that the word "comprising" does not exclude other elements or steps, that the words "a" and "an" do not exclude a plurality, and that a single element, such as a computer system or some other unit, may fulfil the functions of several means recited in the claims. Any reference signs in the claims shall not be construed as limiting the claim concerned.
REFERENCE LIST
1 electrode
2 shell
3 container
4 border area
5 working surface
6 fabric
7 stitch
8 opening
9 border
10 height
11 upper side
12 fabric
13 electrical circuit
14 cable
15 buffer circuit
16 amplifier
17 input
18 output
19 free
20 RC filter