WO2004078038A1

WO2004078038A1 - Detector patch for biosignals

Info

Publication number: WO2004078038A1
Application number: PCT/NO2004/000061
Authority: WO
Inventors: Birger Orten
Original assignee: Meditron Asa
Priority date: 2003-03-05
Filing date: 2004-03-04
Publication date: 2004-09-16
Also published as: NO20031022D0; NO317810B1

Abstract

A novel detector patch (4) for picking up biosignals from a skin surface on the body of a patient (1) comprises an electrode (9) for picking up electrical signals, for instance from the patient’s heart. The electrode (9) is connected directly to an electrical pole in a sound transducer (8) in the detector patch (4).

Description

DETECTOR PATCH FOR BIOSIGNALS

The present invention relates to picking up biosignals from the body of a patient. The term biosignals is intended to mean electrical signals created in connection with muscular activity, nerve activity and brain activity in a living body, as well as acoustical signals in connection with movements internally in a body. Hence, for instance heart activity will cause both electrical signals, traditionally sensed by means of ECG equipment, and clearly audible sound signals, traditionally picked up by a stethoscope. Thus, the invention deals with both signal types.

Some literature can be found regarding picking up and possibly synchronizing detection of acoustical and electrical signals, for instance from heart activity in a human body. For instance, it is previously known from German Offenlegungsschrift DE 3804616 and from Japanese patent application, publication No. 10127626, per se traditional stethoscopes where electrodes are built into the stethoscope housing that is brought to engagement with the patient's body. In this manner it is possible to pick up electrical signals as well as sound signals at the same time. Also US patent No. 4,428,380 discloses such a combination, however with an electronic recording device instead of the traditional stethoscope bell. But also in this case, the recording device ("The chest piece") comprises separate electrodes and a separate microphone. Moreover, US 4,129,125 discloses a monitoring device for e.g. heart activity, which device comprises one or several microphones and electrodes for picking up electrical activity, as separate units.

Common to these previously known devices, is the complexity of systems with many different detail units built into complicated and compound devices.

The present invention has as its goal to provide a simplified device for detecting biosignals. Hence, in accordance with a first aspect of the present invention, there is provided a detector patch for picking up biosignals from a skin surface on a patient's body, comprising at least one electrode for picking up electrical signals, for instance from the patient's heart. The detector patch in accordance with this first aspect, is characterized in that each electrode is connected directly to at least one of a number of electrical poles in a sound transducer in the detector patch.

In a preferred embodiment of the first aspect of the invention, the sound transducer is an acoustoelectric transducer having at least two electrical poles. Preferably, the transducer comprises at least one piezoelectric foil as transducer element, each foil having two electrical poles. The transducer may be mounted in a housing that can be attached to the skin of a patient. The housing may have a skin-friendly attachment tape along its circumference for adhesive attachment to the skin, or it may have a nipple for applying vacuum for suction attachment to the skin.

In accordance with a second aspect of the present invention, there is provided a detector unit for simultaneous pickup of both electrical and acoustical signals from a delimited skin area on a patient's body, and the detector unit comprises at least one electrode and one sound transducer. The detector unit in accordance with the second aspect of the present invention, is characterized in that it is mounted in a patch of a per se known type, and in that each electrode is connected directly to at least one of a number of poles on the sound transducer.

In accordance with the preferred embodiment of the second aspect of the invention, the sound transducer is constituted by an acoustoelectric transducer with at least two electrical poles. At least one of a number of signal conductors from the transducer may be adapted and connected for transmission of a voltage signal picked up from the patient's body, for instance from heart activity.

In the following, the invention shall be discussed in further detail by going through exemplary embodiments, and with reference to the appended drawings, of which

Fig. 1 shows a patient subjected to a traditional ECG investigation,

Fig. 2 shows a commonly known ECG patch (adhesive patch),

Fig. 3 shows an example of a detector patch in accordance with an embodiment of the present invention, in a perspective view and with a cover sheet,

Fig. 4 shows in an exploded perspective view from above, partly cut in the middle, the same detector patch as in Fig. 3, without a cover sheet,

Fig. 5 shows, in an exploded perspective view from above, the same detector patch as in Figs. 3 and 4, without a cover sheet,

Fig. 6 shows an example of the internal construction of a detector patch with combined acoustoelectric sensor and ECG electrode, in accordance with a somewhat different embodiment of the present invention,

Fig. 7 shows the same type of detector patch as in Fig. 6, with a cable connected, in an outside view, and

Fig. 8 shows how several such detector patches as in Figs. 6 and 7 can be connected in cascade. In Fig. 1 appears a basically traditional investigation situation with regard to picking up an electrocardiogram for a person 1 by means of electronic equipment 2. attachment/adhesive patches 4 are attached on chosen locations on the patient's body, and the metal electrodes in the adhesive patches are connected, via cables 3, back to the apparatus 2. A doctor may then pay attention to the electrical activity 5 on a screen or a printer unit. As regards the adhesive patches 4 with metal electrode, these patches are most often of the type shown uppermost in Fig. 1 , i.e. a circular adhesive patch with a centrally arranged electrode. (Possibly, for instance three separate electrode points can be arranged in one and the same patch.)

Fig. 2 shows such an adhesive patch electrode in a closer view, reference numeral 3 shows the cable, 7 shows a housing that envelopes the centrally arranged electrode, and reference numeral 6 designates the adhesive tape. In the present invention, in principle a device of similar type as shown in Fig. 2 is used, but cable 3 will comprise at least two separate conductors, often even more, and the housing 7 will contain something more than only a metal electrode. Hence, inside the housing 7 there will be a sound transducer, and at least one of the electric poles of the sound transducer is connected electrically directly to an electrode that engages the patient's skin and works in a similar manner as in the system shown in Fig. 1. Furthermore, the attachment manner is not limited to relying on an adhesive tape, but other attachment means can be used also.

Fig. 3 shows an interesting embodiment of a detector patch in accordance with the present invention. This patch is equipped with a flat sound transducer inside, and it has a disc-shaped shell/housing 7 of soft material, further a multi-pole connector 13 for connecting a signal cable, and an area with adhesive in a circle on the underside of the patch. A cover paper 14 can be peeled away in order to uncover the adhesive area and the electrode(s) on the underside, for obtaining direct engagement to the skin of a patient.

The same construction is shown in better detail in Fig. 4, which is an exploded view where some elements have been cut in the middle to obtain better clarity. Uppermost appears the multi-pole connector 13, which may have plural lead connections arranged centrally downward and out various electrical poles on the sound sensor/transducer 8, which transducer may for instance be of a type as disclosed in Norwegian Patent No. 312 792 that belongs to the proprietor of the present invention. Such a flat sensor design is favourable regarding geometry. This sensor/transducer may be equipped with several areas having piezoelectric foils 14 that, when sound is picked up, vibrate and thereby produce electrical signals on electrodes on opposite surfaces of each foil, and further out to separate conductors from respective electrodes or poles. It is also possible to interconnect several foils 14 electrically in order to provide a common signal. A construction with only one vibrating foil, or several or more separate foils 1 than the six foils shown in this figure, is of course possible also. Nor is the invention restricted to such a special sensor/transducer 8 as shown here, but the transducer to be used, must exhibit at least two electric poles for supplying a sound-representative electric signal.

In the figure, signal conductors are shown only in a schematically manner and with broken lines from the foil poles of the sensor. Even though two separate conductors are suggested from each foil 14 in this figure, it is an evident rationalization to interconnect one pole from each foil, so that all foils thereby have one common pole with one common signal conductor going out, that is a "ground" or "common" type pole/conductor. Thereby, with six foils there will be one common conductor for "ground" and six "active" signal conductors leading up toward the connector 13, that is seven signal conductors.

The transducer 8 has a centre body 15 also, which centre body may have a conductive area connected to the "ground/common" pole, and centrally a conducting connection to the front pad 9 arranged lowermost, which front pad is made of a material that is highly conductive, i.e. a metal or an electrically highly conducting plastic material. Hence, the front pad also lies on the "ground/common" potential for sound transducer 8. But the front pad 9 also has a function regarding picking up electrical signals from a patient's body, i.e. from a skin surface, and hence has a function as an ECG electrode when the patch is brought to engagement with the skin.

In other words, the front electrode 9 picks up a variable electrical signal from the patient's body, and this varying signal thus constitutes a "basis potential" for sound sensor 8, i.e. the other voltages on the six "active" poles/conductors in the sensor are measured relative to such a varying basis potential for the ECG front pad 9. In the same manner as suggested in Fig. 1 , the electπcal signals are conducted through a cable to an electronic equipment 2 that detects and processes the signals.

The ECG front pad 9 is attached centrally to a lower part 7b of housing 7, which has an upper part 7a also. The lower part is made of a soft material, and has an adhesive area 6 provided substantially circumferentially to obtain attachment to the patient's skin. Centrally there is a passage for electrical connection between the front pad 9 and the transducer 8 such as mentioned above. Furthermore, the lower part 7b of housing 7 has acoustical characteristics adapted to body tissue/skin, in order to ensure good acoustical coupling from the skin and up to the sound sensor 8.

Fig. 5 shows the same elements as Fig. 4, in the same manner but from above. Electπcal signal conductors from "active" poles on the piezofoils 14 are shown, schematically, as leading to connector 13 that has a corresponding number of poles. (The conductor assembly suggested in the figure means merely a physical collection of conductors, the conductors are run separately all the way up to the connector.) Also a common conductor (ground) from the ECG front pad 9 via "ground" on transducer 8 runs further to connector 13.

In a variant embodiment of the above mentioned detector patch, several, for instance three, front pad electrodes 9 are included, and each one of these electrodes are interconnected to one and the same electrical pole in the sound transducer 8. In another variant, each respective one of the several front pad electrodes is connected to respective separate poles in the sound transducer.

An attachment means in the form of an adhesive area 6 is effective, but not obligatory for the invention, the detector patch can also be attached by means of a vacuum, such as discussed below, or by means of a strap or clamps.

In Fig. 6 appears, in an exemplary embodiment, one possible layout of the insides in a housing 7 made e.g. of plastic mateπal. A sound transducer or acoustical sensor 8 is arranged centrally in the housing and has a front pad 9 for engagement toward the patient's skin. The front pad 9 is made of electrically conductive material, and is connected directly to one of the electrical poles of the transducer. The transducer may e.g. work in accordance with a principle with a piezoelectric foil/diaphragm, where the foil has electrodes i.e. poles on respective sides thereof. Also, the transducer may comprise several separate foils, such as appearing from the drawing, and hence a higher number of separate electrodes or poles. Thus, the front pad 9 that is made of metal or some other electrically conductive material, is connected directly to one of the electrical poles of the transducer.

Transducer 8 is mounted on a circuit board 10 which further may comprise electronic circuitry 11 for processing acoustical signals picked up by the sensor/transducer 8. The electronic circuitry 11 may for instance perform digitising, so that the conductors in cable 3 conduct signals that are immune to influence from noise. It should be noted, however, that the simplest and cheapest embodiment of patch 4 does not need to contain anything else than a sound transducer with poles connected to output conductors, and in such a manner that one of the poles at the same time is connected to external equipment 2 for recording electrical potential relative to corresponding poles in other patches that have been attached at the same time in other positions on the patient's body. Such simple and cheap devices will advantageously have an adhesive tape as an attachment means, and be usable and disposable in a similar manner as ordinary ECG adhesive patch electrodes.

The more advanced embodiment shown in Fig. 6, with a built-in signal processor 11, exhibits another possible attachment means. The nipple 12 on top can be used for attachment by means of an elastic strap, a vest or similar. Possibly, an air suction (vacuum) may be connected to the nipple in order to cause the whole patch 4 clings to the patient's skin by suction. This requires that attachment patch 4 is air tight in the area limited between nipple 12 and the contact zone against the skin, and there must be an air passage from the nipple, through the interior of housing 7 and out centrally in the front part, possibly a special (not shown) through tube from the nipple to a front opening.

For the rest, the sound transducer 8 (possibly including signal processor equipment 11) should be supported in the housing 7 by means of a vibration dampening coupling, in order to limit transfer to the transducer of noise caused by touching/rubbing on the housing.

In Fig. 7, the same detector patch 4 as in Fig. 6 appears, in a view from the outside and in perspective, and with signal cable 3 connected.

In an embodiment such as appearing in Fig. 6, the electronic circuitry (the processor) 1 on circuit board 10 may, in addition to digitising the sound signal from the adjoining acoustical sensor 8, also digitise the picked-up instantaneous potential difference between its own sensor front pad 9 and a similar front pad in another, "serially connected" patch. See Fig. 8, in which figure it appears how a number of patches with sensors can be connected in cascade.

In a chain consisting of patch/sensor elements A, B, C, D, E etc., a potential difference between two neighbours; A-B, B-C, C-D etc. can thereby be measured in element B, C, D etc. respectively. If each difference is transmitted digitally through the signal cable, any combination of potential difference can be deduced. For example, potential difference A-C can be expressed mathematically as:

(A - B) + (B - C) = (A - C)

As shown in Fig. 6, the element contains an electronics circuit board 10. This circuitry will, in general, have functionality like analogue amplification and digital signal processing. Digital signal processing is here intended to mean filtering, active noise removal, event-controlled processes etc. One imagines that electrical energy for powering these units, is supplied through the cable. In a chain of several elements, one may envisage a Master-Slave situation, in which an element is Master for the element to which its cable is connected. The last element must finally be connected to a digital unit that is able to communicate with the chain. Here one may envisage a wireless unit or a unit with cable connection to for instance a PC, Palm etc. This unit may also send a signal into the chain to request data from only selected elements, and to request that the elements "identify themselves". Due to limitations in the system bandwidth, the number of elements in such a chain will be limited to a maximum number of elements.

The sound sensor in the attachment patch can be selected among a large choice of electro-acoustic sensors, but in a preferred embodiment, a sensor of the type appearing from the proprietor's on Norwegian patent No. 312 792, "mechano-electric sensor", will be used, as previously mentioned. Such a sensor is based on a piezoelectric foil, it can be built with a rather flat design, and hence is well suited to be mounted in an attachment patch.

Claims

1. A detector patch (4) for picking up biosignals from a skin surface on the body of a patient (1), comprising at least one electrode (9) for picking up electrical signals, for instance from the patient's (1) heart, characterized in that each electrode (9) is connected directly to at least one of a number of electrical poles in a sound transducer (8) in the detector patch

(4).

2. The detector patch of claim 1 , characterized in that said sound transducer (8) is an acoustoelectric transducer having at least two poles.

3. The detector patch of claim 2, characterized in that said transducer (8) comprises at least one piezoelectric foil as a transducer element, each foil having two electrical poles.

4. The detector patch of claim 1 , characterized in that said sound transducer (8) is mounted in a housing (7) that can be attached to the skin of a patient.

5. The detector patch of claim 4, characterized in that said housing (7) has a skin-friendly attachment tape (6) along its circumference for adhesive attachment to the skin.

6. The detector patch of claim 4, characterized in that said housing (7) has a nipple (12) for applying vacuum for suction attachment to the skin.

7. A detector unit for simultaneous pick-up of both electrical and acoustical signals from a delimited skin area on the body of a patient (1) comprising at least one electrode (9) and one sound transducer (8), characterized in that

- said detector unit is mounted in an attachment patch (4) of per se known type, and that

- each electrode (9) is connected directly to at least one of a number of poles on the sound transducer (8).

8. The detector unit of claim 7, characterized in that said sound transducer (8) is an acoustoelectric transducer having at least two electrical poles.

9. The detector unit of claim 7, characterized in that at least one among a plurality of signal conductors from said transducer (8), is adapted and connected for transmission of a picked-up voltage signal from the patient's (1) body, for instance from heart activity.