CH706802A1 - An apparatus for measuring bio-electric signals, in particular signals, which are picked up by electrodes. - Google Patents

Abstract

The invention relates to a holding device (1) for measuring bioelectric signals, in particular signals which are received by electrodes, wherein the electrodes are attached to one or more fixing elements. The holding device (1) comprises a central element (3), from which bending beam-like elements (2) extend away, such that they can be arranged at the free ends of the respective electrodes (6) and the contact pressure is at least 0.5 N.

Description

Technical area

The invention relates to an apparatus for measuring bioelectrical signals picked up by electrodes, the electrodes being fixed to one or more fixing elements.

Background of the invention

Devices for the preparation of electroencephalograms are known in many designs. For this purpose, electrode assemblies are necessary for attachment to a living being, which measure the bioelectric signals on the animal. Specially designed electrodes, so-called "EEG electrodes", are used to measure the brain waves of a particular person. They are also known in various embodiments.

definitions

[0003] The term "EEG" is understood to mean electroencephalographies which are suitable, in particular, to measure brain waves.

State of the art

The electrodes themselves are arranged in holders, which in turn are placed on a cap or a net-like structure the subject on the head. Such caps or nets are often made of an elastic, preferably rubber-like material. The electrodes themselves are then fixed by clamping elements on this net-like structure. Such net-like structures, since they also contain metallic elements in particular, are perceived by the subject as very unpleasant, especially because they exert an increased pressure on the scalp. However, this increased pressure is necessary for the electrodes - preferably wet electrodes - to receive appropriate contact with the scalp. However, the pressure leads to possible obstruction of the circulation in the head and thereby the results obtained with the measurement can also be falsified. The attachment itself is done with a locally applied paste, cream or emulsion or a gel. This form is also perceived by the subject as very unpleasant.

For example, WO 2001/011857 A1 discloses an electrode arrangement. The holding means provided herein serve to attach the electrodes to the scalp of the subject, so as to attach the measuring electrode member fixed to the scalp at a defined location. The installation itself is very complex and complicated and requires a lengthy and time-consuming preparation phase.

Since nowadays not only brainwave measurements are used to measure brain activity at rest under laboratory conditions, the holding devices known to date for receiving the electrodes and thus for measuring the EEG brain waves are not suitable to carry out measurements at work or during leisure time.

Object of the invention

The object of the invention is to provide a holding device for receiving the electrode and thus to carry out measurements of brain waves, which is easy to produce and with little effort. The wearing comfort should be perceived as pleasant for the test person.

Solution of the task

The solution of the problem is provided by the characterizing features of claim 1.

Advantages of the invention

The essential idea of the invention is to provide a holding device which is simply placed on a subject's head without having to use any further fastening and fixing means. The holding device essentially comprises a central element, from which extend bending beam-like elements away, the free ends of each arrive at a head of a person to the plant. The bending beam-like elements are designed such that they rest with a defined contact pressure, regardless of the shape of the head on the surface of the head. The contact pressure is approx. 0.75 N large.

In order to provide this contact pressure, which is necessary to bring in particular electrodes with the surface of the head, it is provided to specially form the respective star-shaped elements of the central beam bending beam-like elements. The special design is that they consist of a tubular hollow-walled body in the rule, which is specially shaped depending on the respective contact point on the head. The form provides that the one end in the central element fixed, that is fixed and immovable, with the free end extending like a beam to the contact point. In this case, this can assume a corresponding arc-shaped structure, so that either the free end tangentially to the head surface or perpendicular or almost perpendicular to the head surface comes to rest. The hollow-walled cantilever-like elements are thus preferably round in cross-section. However, they can also have other cross-sections, so that different bending moments are necessary in different directions in order to carry out corresponding deflections of the free ends. This also implies that different restoring forces are possible in different directions.

The hollow-walled structure is therefore used so that, starting from the central element within the cantilever-like element electrical cables are guided, which are closed together with the electrodes arranged at a free end. The elements are designed so that it is not necessary to use a shielded cable. The tubular structure of the elements provides this shielding. Furthermore, this structure provides protection for the cable itself so that it is not accidentally destroyed. Preferably, the bending beam-like elements are metal tubes which are formed on its inside electrically insulating. They are usually made of spring steel-like material, so that when placing the fixture on the head, first the free ends must be slightly bent apart until they reach the appropriate attachment to the defined points. The bending apart happens automatically when putting on.

Due to the special configuration of the holding device, the advantage is given that fixing devices are not necessary, if the subject is preferably examined under laboratory conditions. However, if brain waves are examined outside of laboratory conditions, preferably only slight additional simple fixing elements are to be arranged, which fix the holding device on the head immovably.

Marking elements dictate which orientation the holding device must have on the head in the distal arrangement. This ensures a simple plugging.

For the subject, the postponement of arranging the holding device does not feel - as compared to the prior art - uncomfortable, but rather he feels this as a light head massage, which in turn produces a corresponding well-being in the subject.

Thus, the invention provides that the bending beam-like elements are designed such that the contact pressure of the electrodes arranged at the free ends to the scalp is the same everywhere.

Thanks to the low weight and the small size of the electrodes, head movements that are intentionally or unintentionally exerted by the subject, no artifacts in the encephalogram.

A further development can provide that at least one of the bending beam-like elements is designed such that it additionally has a corresponding holding force. This holding force can then be triggered only after placement distally on the head in the arrangement on the head by inducing a corresponding fixing movement. In addition, an additional holding force can be activated by tightening a tensioning element or by folding it over from a corresponding folding mechanism.

Another important advantage of a development of the invention provides that both in the region of the central element, both the necessary for the electrodes preamplifier and the analog-digital converter are already arranged. The so-called front-end electronics is thus already accommodated in the holding device, so that the signals recorded by the brain waves are not analog, as is the case in the prior art, but can already be transmitted digitally. As a result, it is possible either to transmit the data via a very long mobile cable without corresponding losses, for example via a serial data interface, and to evaluate these via a corresponding interface and a computer unit or also to transmit them to an interface without any hiccups. Thus, the interface has only the task of providing a galvanic isolation to the computer, which is necessary for an accurate measurement and on the other hand to adapt the data format accordingly.

Thus, a conventional from the prior art simple and adapted for each case evaluation can be used.

The bending beam-like formations also allow different use of electrode heads, in particular of wet electrodes at the respective free ends. As described above, the bending beam-like formations are designed like a cannula so that cables can be guided from the central element to the electrodes within the cannula. The electrodes are fixedly connected at the free ends and arranged there captive. In order to allow the appropriate contact with the skin, a porous foam material in the form of a cap is slipped over the electrode head. In order to produce the electrical contact between the skin and the electrode head, preferably the head-like element is impregnated with a solution, preferably potassium chloride solution. The head is preferably soft and porous and thus gives a very pleasant contact on the skin.

So that the corresponding measurement result is little distorted, the inner wall of the cannula is isolated. An inner insulation can be done for example by paint or enamel.

An optimal electrode constellation with regard to the electrochemical properties provides for using a chlorinated silver wire which is in a saturated potassium chloride solution. So that the liquid does not leak, a gel is used, which has the formation of a polymerized potassium chloride.

Another embodiment provides to design the electrode head such that the guided in the cannula silver wire is glued at the free end, so that no liquid can enter the cannula. There, the silver wire is stripped and wrapped around the insulated cannula. Subsequently, the cannula end is coated with a drop of silver or silver chloride. For example, this drop can be drawn from a suitable melt.

Preferably, the ends of the cannula are configured such that it is covered over at least over a defined distance of this with a stainless steel tube.

Alternatively it can be provided that initially a silver conductive adhesive is used, which is then coated by the silver or silver chloride droplets.

Thus, the invention provides, outgoing from a central element bending beam-like element as a holder device, the bending beam-like elements are placed distally on the head and already exert by the construction when placing the appropriate pressure on the surface of the head, so the corresponding contact the electrodes at the free ends are provided with the skin.

The design of the bending beam-like elements allows to design electrodes of different types, so that an optimal recording of the brain waves is possible even with appropriate head movement of the subject without artifacts or other interference.

Further advantageous embodiments will become apparent from the following description, the claims and the drawings:

drawings

In the drawings: <Tb> FIG. 1 <SEP> is a schematic perspective view of the holding device according to the invention; <Tb> FIG. 2 <SEP> a perspective view of the holding device mounted on a human head; <Tb> FIG. 3 <SEP> a side view of the holding device mounted on a head according to FIG. 2; <Tb> FIG. 4 <SEP> another view of the holding device according to FIG. 2; <Tb> FIG. 5 <SEP> a rear view of the holding device according to FIG. 2; <Tb> FIG. 6 <SEP> is a schematic representation of the holding device according to FIG. 1 for identifying the respective electrodes; <Tb> FIG. 7 <SEP> an enlarged view of the holding device, in particular for the representation of the central element of the holding device; <Tb> FIG. 8 is a schematic representation of the first exemplary embodiment of an electrode for the embodiments of the holding device illustrated in FIGS. 1 to 7; <Tb> FIG. 9 shows a second exemplary embodiment of an electrode for the embodiments of the holding device illustrated in FIGS. 1 to 7; <Tb> FIG. 10 shows a third exemplary embodiment of an electrode for the embodiments of the holding device illustrated in FIGS. 1 to 7; <Tb> FIG. 11 shows a fourth exemplary embodiment of an electrode for the embodiments of the holding device illustrated in FIGS. 1 to 7.

Description of the embodiments

In Figs. 1 to 5, the inventive holding device 1 is shown in perspective. The holding device 1 consists of a plurality of bending beam-like elements 2, which extend centrally from a central element 3 star-shaped away and are formed differently long depending on the corresponding position on the head. The one end 4 of the respective bending beam-like element is fixedly arranged on the central element 3, whereas the other free end 5 is provided with an electrode 6. The bending beam-like element 2 is preferably formed like a cannula, so that the electric wires not shown in detail in the drawings of the central element 3 to the free ends 5 and 6 electrodes are feasible.

The holding device 1 is placed cranial medial on the head of a subject (not shown in the drawings), so that the central element 3 is preferably arranged medially cranial (as explicitly shown in Fig. 5). From here, the corresponding bending beam-like elements 2 extend to the respective measuring points or electrodes 6 in order to measure the brain currents generated in the brain.

Preferably, the free ends 5 are bent towards the head, so that already by the cranial medial placement first the bending beam-like elements 2 must be spread. This advantageously achieves the necessary contact pressure of the electrodes on the head.

If the corresponding position, as described above, achieved and the central element 3 sits cranial medial on the skull, press the bending beam-like elements 2 to the respective measuring points of the skull.

Preferably, the bending beam-like elements 2 are designed and dimensioned such that all electrodes 6 at the free ends 5 have the same contact pressure on the skull. This is achieved in particular by the fact that the bending beam-like elements 2 extend arcuately away from the central element 3 and are preferably bent more strongly at free ends 5, in comparison to the remaining part of the element.

Only with the proper positioning of the holding device 1, the optimum contact pressure at the respective electrodes is provided. In particular, the electrode 615 attached to the nasal bone 15 indicates that the correct position has been reached.

From the central element 3, the respective guided in the cannulas wires 7, here preferably silver wires, to the corresponding measuring station (not shown here) out.

As a development (not shown in the drawings) is provided that the holding device 1 already includes a preamplifier and a corresponding analog-to-digital converter 9. The entire "front-end electronics" is thus accommodated in the holding device 1 according to the invention. The thus generated at the electrodes signals thus reach with minimal losses directly to the preamplifier and the corresponding analog-to-digital converter, so that they can then be connected digitally via a thin cable in the formation of a data interface with an interface electronics. This interface electronics only has the task to provide the galvanic isolation between a computer provided for evaluation and to adapt the data format accordingly for the evaluation. Alternatively, the data can be transmitted wirelessly. An appropriate power supply provides the necessary energy.

In Fig. 7, for example, a cavity 16 is shown, in which the front-end electronics could be arranged.

Different embodiments of electrodes 6 to 6 are shown in FIGS. 8 to 1. These electrodes 6 to 6 can each be applied to the embodiment of the holding device 1 - 1 shown in FIGS. 1 to 7.

In Fig. 8, a fixedly connected to the bending beam-like element 2 electrode head 17 of an electrode 6 is shown. This electrode head 17 is part of the bending beam-like element and has an exchangeable cap-like element 10 which can be plugged onto the electrode head in the direction of arrow 11. The cap-like member 10 is soft and porous and is preferably impregnated with potassium chloride solution to provide electrical conductivity between the skin adjacent the outer wall 12 of the cap-like member 10 and the electrode head 17.

An insulated silver wire 13 extends inside the cannula-like element 2 up to the central element 3.

The cap-like element 10 is interchangeable as needed and preferably biocompatible.

In Fig. 9, a second embodiment of an embodiment of an electrode 6 for the inventive holding device according to FIGS. 1 to 7 is shown. The electrode formation shown here is designed with respect to its electrochemical property such that it has a chlorinated silver wire, which is arranged in a saturated potassium chloride solution. Thus, the liquid does not leak within the hollow body in the bending beam-like elements 2, a gel is used for sealing, which is preferably a polymerized potassium chloride. This polymerized potassium chloride is a polyacrylamide filled with solid potassium chloride or a saturated potassium chloride solution. The silver wire is hermetically sealed approx. 1 cm behind the end of the cannulated element, whereby the closure is hydrophobic, so that the potassium chloride can not escape to the outside. The front part of the silver wire is stripped and galvanically chlorinated. This front part is completed with the previously described polymerized potassium chloride.

Here too, it is provided that the cap-like element 10 soaked with potassium chloride, as shown in FIG. 8, can be applied. This causes the electrical contact to be restored.

A significant advantage of these embodiments is that no set times must be calculated and also the "drifting" of the measurement result is avoided, which is additionally suppressed at sufficient concentration of the potassium chloride solution of the Anderson potential.

A further embodiment provides that in contrast to FIG. 9, in FIG. 10, the silver wire 13 is glued at the end of the cannula-like element, so that no liquid can penetrate into the bending beam-like element 2. The free silver wire 13 is stripped and wound around the insulated cannula-like element, wherein the free end of the cannula-like element is additionally provided with a stainless steel tube 18 at least in the region of the electrodes. Subsequently, the free end of the cannula is covered with a drop of silver or silver chloride. This drop can be drawn, for example, from a corresponding melt.

In contrast to FIG. 10, the embodiment in FIG. 11 provides that, instead of the silver chloride, a silver-epoxy layer which encloses the free end of the electrode is used first. Subsequently, an enclosure through the silver drop then takes place.

The basic idea of the invention is to use the electrodes in such a way that they can be used as dry electrodes. If a corresponding coating, as proposed in FIGS. 8 and 10, is provided, then these can be used as wet electrodes. The latter show a much better contact in practice.

LIST OF REFERENCE NUMBERS

Device for measuring bioelectric signals, in particular signals picked up by electrodes

[0049] <tb> 1., 1 <SEP> Holding device <tb> 2. <SEP> bending beam-like elements <Tb> 3 <September> central element <tb> 4. <SEP> free end <tb> 5. <SEP> free end <Tb> 6 <September> electrode <tb> 6-6 <SEP> Electrode <Tb> 6 <15> <September> electrode <Tb> 7 <September> Wire <Tb> 8 <September> <Tb> 9 <September> Analog-to-digital converter <tb> 10. <SEP> cap-like element <Tb> 11 <September> arrow <tb> 12. <SEP> outer wall <Tb> 13 <September> silver wire <Tb> 14 <September> <Tb> 15 <September> nose <Tb> 16 <September> cavity <Tb> 17 <September> electrode head <Tb> 18 <September> stainless steel tube

Claims (2)

Device for measuring bioelectric signals, in particular signals picked up by electrodes, the electrodes being fastened to one or more fixing elements, characterized in that the device is a holding device (1) comprising a central element (3), from which bending beam-like elements (2) extend away, such that they can be arranged at the free ends of the respective electrodes (6, 6, 6, 6, 6) and the contact pressure is at least 0 , 5 N is. 2. Device according to claim 1, characterized in that the electrodes (6, 6, 6, 6, 6) are wet electrodes.