FIELD OF THE INVENTION
The invention relates to a medical electrode and a garment comprising medical electrodes as described in the preamble of the corresponding independent claims.
BACKGROUND OF THE INVENTION
In a typical hospital intensive care environment, cardiac patients are monitored continuously for their physiological condition. They are physically attached to a electrocardiogram (ECG) machine through wires and become immobile. Outside an intensive care unit, patients may also be monitored continuously. Typically, wet gel passive electrodes are used for acquiring electrical signals from the body. The passive electrodes are kept in position on the body by means of adhesive. Due to the prolonged use of gel in continuous monitoring, patients develop skin allergy. The gel dries up after a few hours, and the electrodes must be replaced. The electrodes, which cannot be reused, must be disposed of.
US 4,751,471 and US 4,669,479 describe dry electrode pads incorporating an amplifying circuit. The electrodes comprise adhesive means for adhering the electrodes to the skin. Again, long term use of adhesive can irritate the skin and provoke allergic reactions.
WO 2004/086968 discloses a structure for acquiring physiological signals which may use electrodes obtained by weaving, spinning or sewing conducting fibers within the substrate of the fabric, so as to be monolithic with the fabric in which they are inserted, or in any case are composed of conducting material. The garment has to be pulled over the wearer's head. It is however not explained how the electrodes are kept in sufficient contact with the wearer's body in order to maintain signal quality.
US 6,145,551 and US 6,315,009 describe garments made by tubular weaving, i.e. as a single tube, and comprising embedded electrical and optical fibres, as well as sensors located at randomly distributed locations. US 6,381,482 describes a similar garment. The garment may consist of a rectangular piece of fabric with an opening in the centre. The opening is pulled over the wearer's head, and the front and back parts are connected at the side by zippers. Such garments are awkward to put on, and the tightness of the garment cannot be adjusted.

US 6,687?523 describes a garment for an infant, intended to be an improvement over the use of a Velcro™ belt for fastening cardiorespiratory sensors to an infant's body. The garment is closed and adjusted with Velcro™ straps. The garment comprises either two separate parts, or a single piece with a hole to be slipped over the head, or is of a tubular shape. Sensors such as standard type ECG sensors, respiration rate sensors, temperature sensors, voice sensors may be either detachable, or may be knitted into the fabric. However, the range of adjustment is fairly limited.
WO 01/02052 mentions sensor zones in the fabric of a garment, the sensor zones comprising metal fibres blended with base fibres of the garment, among others, cotton. Other zones of the garment are non-conductive and are flexible in order to ensure a tight fit of the garment.
DESCRIPTION OF THE INVENTION
It is therefore an object of the invention to create a medical electrode and a garment comprising medical electrodes of the type mentioned initially, which overcomes the disadvantages mentioned above. It is a further object of the invention to provide a medical electrode that provides good quality of the electrophysiological signals picked up, while at the same time being comfortable to wear and not requiring the use of gels or adhesives. It is a further object of the invention to provide a garment comprising medical electrodes that is easy to put on and comfortable to wear for a range of body sizes.
These objects are achieved by a medical electrode and a garment comprising medical electrodes according to the corresponding independent claims.
The medical electrode for acquiring electrophysiological signals comprises an electrode body electrically connected to a conductive fabric and to an amplifying circuit, the amplifying circuit being operationally connected to means for powering the amplifying circuit and for transmitting signals to a remote data acquisition means, the conductive fabric constituting the outer surface of at least a body side of the electrode, and the electrode further comprising a resilient padding arranged between the body side and a garment side of the electrode.

This matched combination of features allows to provide electrical body signals of good quality while at the same time having dry electrodes that have a comfortable feel and may be worn over extended periods of time.
These benefits are a consequence of the following factors:
• The use of a conductive fabric in the part of the electrode contacting the patient's skin provides a comfortable experience.
• The padding acts as a spring or cushion pressing the sensing element, i.e. the conductive fabric, against the body to give the sensing element full and close contact with the skin.
• The amplifying circuit with proper impedance matching decreases the skin impedance and provides better quality signals to the data acquisition system.
• Since the dry electrodes use neither gel nor adhesives, a patient can be monitored for long periods of time without skin irritation or discomfort.
• In combination with an adjustable form fitting garment, the electrodes are kept in place against the body, reducing or eliminating motion artifacts in the signals picked up by the electrodes.
In a further preferred embodiment of the invention, the resilient padding is, mainly on the body side of the electrode, concave, that is, in an uncompressed state the padding at the outside is thicker than the padding in the middle of the electrode. This improves conduction between the electrode and the wearerfs skin. The electrode body is typically arranged in a middle area of the electrode.
In a further preferred embodiment of the invention, the conductive fabric is made of a combination of conductive fibres with a nonconducting fibre such as cotton. For example, the conductive and nonconductive fibres or yarns are woven or knitted together to form the conductive fabric. In another preferred embodiment of the invention, the conductive fabric is made of conductive fibres alone.
Using cotton as the nonconducting fibre has the advantage that in continuous usage cotton yarn absorbs the wearer's sweat and enhances the conductivity of the electrode. The

presence of cotton also enhances the surface smoothness of the electrode, unlike electrodes made solely of conductive yarn
In a further preferred embodiment of the invention, said conductive fibres are
• metallic fibres such as stainless steel wires, or
• intrinsically conductive polymers, or
• fibres doped with conductive metallic or organic particles, or a combination of such fibres*
In a further preferred embodiment of the invention, the conductive fabric constitutes a single piece of fabric folded around the electrode body, the amplifying circuit and the padding. The conductive fabric may be connected along the edges folded over one another by e.g. sewing, gluing, heat fusing etc.
In yet a further preferred embodiment of the invention, the padding is made of hydrophobic material, in particular Polyurethane foam, or Nylon fibres or Polyester fibres.
In a further preferred embodiment of the invention, the electrode is of an elongated rectangular form. Up to a certain degree and depending on the location, increased electrode size may increase signal quality. Increasing electrode size is no problem for dry electrodes, whereas wet electrodes become even more awkward to handle and wear. The elongated form allows to conform the shape and orientation of the electrodes to be approximately parallel to typical movement vectors of the body surface which in turn reduces motion artifacts in the signals picked up. Thus, the elongated direction of the electrodes are preferably arranged at least approximately horizontally (with respect to the garment being in an upright position corresponding to the wearer standing up).
In a further preferred embodiment of the invention, the amplifying circuit comprises a high input impedance voltage follower circuit. This reduces the noise effect caused by separation distance variations between the electrode and the body. These variations would, for a passive electrode, appear as variations in impedance from the viewpoint of instrumentation amplifier inputs. The effect of these impedance variations is minimised

by having a high input impedance voltage follower circuit in-situ on the fabric electrode. The voltage follower circuit is in effect, an impedance matching device. Because the impedance variations are small when compared to the high input impedance of the voltage follower circuit, the separation distance variations have a reduced effect on the signal as received at the instrumentation amplifier in the data acquisition unit. The data acquisition unit preferably also comprises further signal processing for minimising noise and other disturbance signals.
The garment comprising medical electrodes for health monitoring comprises electrodes preferably being of the type described above. The garment consists of a single piece of fabric or of a single set of connected fabric parts, the garment being openable at the wearer's front side and comprising adjusting means for fitting the garment to the wearer's body circumference.
Thus, a back section, first front section and second front section of the garment constitute a single piece or single set of connected fabric parts. This makes the garment easy to handle and to put on, in contrast to garments in which several separate garment parts have to be put on one after the other and have to be connected mechanically and/or electrically. Since the garment can be adjusted to a variety of body sizes, in particular to the circumference of the wearer's torso and chest, reliable measurement of electrical body signals are possible.
In a further preferred embodiment of the invention, the garment comprises first fastening means for ensuring an adjustable tight fit of an electrode-carrying section of the garment against the wearer's body, and comprises second fastening means for closing a further section of the garment over the first fastening means, thereby covering the first fastening means. This protects the adjustable first fastening means from accidental manipulation or from getting entangled with other objects, and gives an esthetically satisfying appearance.
In a further preferred embodiment of the invention, the garment comprises
• a back section, a first front section and a second front section, the second front section
being the electrode-carrying section and having medical electrodes arranged on its
inside,

• wherein the second front section is attached at its inner edge to a first side of the back section and the second front section comprises first fastening means at its outer edge for connecting said outer periphery to a second side of the back section, the first fastening means being adjustable, such that, when connected, the back section and the second front section form an adjustable tubular shape around a wearer's body,
• the second front section and the first front section comprising second fastening means for connecting an outer edge of the first front section to the outside of the second front section.
In a further preferred embodiment of the invention, the first fastening means are straps in combination with slits or eyelets.
In a further preferred embodiment of the invention, the straps, in the fastened position, pass through the slits, are folded back onto themselves and are attached to themselves by means of hook and loop type fasteners such as Velcro™, the degree to which the straps are folded back onto themselves being variable and thus allowing to adjust the tightness of the electrode-carrying section around the wearer's body.
In a further preferred embodiment of the invention, the second fastening means is a zipper. The zipper preferably extends vertically over the middle of the front side of the garment, as is usual for such frontal zippers. Of course, any other type of fastening such as a variety of buttons or Velcro™ straps is applicable here, since the purpose of the first front section is to cover and protect the straps and furthermore to give an esthetical, unobtrusive appearance.
In a further preferred embodiment of the invention, the electrodes are detachably arranged on the inside of the electrode-carrying section. This allows to clean or replace the electrodes or the garment separately.
In a further preferred embodiment of the invention, the electrodes are operationally connected to a data acquisition unit by means of cables, and the data acquisition unit is arranged to transmit a representation of electrophysiological signals captured by the electrodes over a wireless communication link. A data receiver for receiving said signal

representation, or the data acquisition unit itself, is e.g. configured to store the signals, to transmit them to regular ECG equipment or to alert a caretaker or doctor when appropriate*
Further preferred embodiments are evident from the dependent patent claims.
BRIEF DESCRIPTION OF THE DRAWINGS
The subject matter of the invention will be explained in more detail in the following text with reference to preferred exemplary embodiments which are illustrated in the attached drawings, in which:
Figure 1 schematically shows a cross section through a detachable electrode; Figure 2 schematically shows a view of an electrode with its enclosing conductive
fabric opened up; Figure 3 schematically shows a cross section through an electrode permanently affixed
to a garment section; Figure 4 shows an amplifying circuit for the electrode;
Figure 5 shows a perspective view of a garment comprising medical electrodes; Figure 6 shows a front view of said garment in a closed state; Figure 7 shows a front view of said garment in an opened state; and Figure 8 shows another embodiment of a garment comprising medical electrodes.
The reference symbols used in the drawings, and their meanings, are listed in summary form in the list of reference symbols. In principle, identical parts are provided with the same reference symbols in the figures.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
Figure 1 schematically shows a cross section through an electrode 1. The electrode 1 is covered, at least on a body side 6 of the electrode 1, by a conductive fabric 3. The electrode 1 comprises an electrode body 2, that is, a conductor making the contact between a signal processing circuit and the conductive fabric 3, The electrode body 2 may be a flat metal plate or just a wire pressed or bonded against the inside surface of the conductive fabric 3. On a garment side 7 of the electrode 1, the electrode 1 is fastened to the fabric of a garment section 11. This is preferably done by means of a detachable

fastener 13, e.g. a zipper, snap fasteners, or fasteners of the hook and loop type, also known as Velcro™. On the body side 6 of the electrode 1, the electrode 1 is pressed against the wearer's skin 10. The electrode 1 comprises a padding 5 between the body side 6 and the garment side 7, ensuring a close fit of the conductive fabric 3 against the skin 10,
Figure 2 schematically shows a view of a round electrode 1 with its enclosing conductive fabric 3 opened up. The electrode 1 has a diameter of ca. 3 to 6 cm. When closing the electrode 1, as indicated by the arrow, the conductive fabric 3 on the left side, together with the padding 5, is folded over the right side, covering the amplifying circuit 4 and the electrode body 2. The adjoining edges of the body side 6 and garment side 7 of the conductive fabric 3 are joined by sewing or the like. The electrode 1 may of course also be manufactured from separate body side 6 and garment side 7 parts, made of the same or of different fabric.
Figure 3 schematically shows a cross section through an electrode 1 permanently affixed to a garment or garment section 11. The garment section 11 may be a complete garment or e.g, a textile ribbon or band wrapped around a body part such as the wearer's chest* The conductive fabric 3 covers only the body side 6 of the electrode 1, with the garment side of the electrode 1 being covered by the garment section 11 itself.
Figure 4 shows an amplifying circuit for the electrode. The circuit comprises an operational amplifier 12 configured as a voltage follower* The operational amplifier 12 has a very high input impedance, low noise and low drift. A positive input of the amplifier 12 is connected over a current limiting resistor Rl to the electrode body 2, The positive input is also connected to ground over a high frequency rejection capacitor CI. The negative input is connected to the output signal Sig Out. Power connections with voltages Vdd and Vss each comprise decoupling capacitors C2, C3 to ground.
Figure 5 shows a perspective view of a garment 20 comprising medical electrodes as described with respect to the preceding Figures, or of an other electrode or body sensor type. Figure 6 shows a front view of said garment in a closed state. The garment 20 comprises a back section 21, a right front section 22 and a left front section 23. (The terms "right" and "left" are used as seen from the wearer's side)* The right front section 22

and left front section 23 are joined in the middle of the front side by a zipper 24. The shape of the garment is essentially that of a waistcoat, i.e. tubular with arm holes 28, but in another embodiment may also comprise sleeves.
Figure 7 shows a front view of said garment in an opened state. It now is visible that the left front section 23 does not stop at the zipper 24 but extends all the way over the front side until it reaches the back section 21 at the right side of the garment 20. Here its is adjustably fastened to the right edge of the back section 21. This fastening is preferably done by means of straps 25 attached to the left front section 23 and corresponding slits 26 at the edge of the back section 21. The zipper half 24b on the left front section 23 passes over the middle of the outer side of the left front section 23. This zipper half 24b is not visible in the view of Figure 7 from the inside, which is why it is represented by a dotted line.
In this manner, when putting on the garment 20, the straps 25 can be guided through the slits 26, folded back onto themselves, forming loops, and attached to themselves by means of Velcro™ connectors. This allows to adjust the circumference of the garment according to the wearer's circumference at different heights of the upper body, i.e. torso and chest. After this is done, the right front section 22 is folded over the right half of the left front section 23, and the zipper half 24a at the outer edge of the right front section 22 and the zipper half 24b in the middle of the left front section 23 are zipped together. The straps 25 and the loops and any loose ends are covered and are no longer visible.
All the electrodes 1 are removably or permanently attached to the inside of the left front section 23, Here, elongated rectangular electrodes 1 are shown, with the longer sides being preferably at least twice as long as the shorter sides. The shorter side preferably has a length ranging from 1 cm to 6 cm, the longer side preferably has a length ranging from 4 cm to 15 cm.
Figure 8 shows another embodiment of a garment comprising medical electrodes, in which the electrodes 1 are attached to the insides of both a right front section 22 and a left front section 23. The right front section 22 and left front section 23 are symmetrical with respect to each other. In order to adjust the garment 20 to the wearer's size, under arm zippers 27 are arranged, extending downward from the arm holes.

The electrodes 1 are coupled, via signal and power cables 8, to electromedical equipment such as for measuring electrocardiograms, or to a data acquisition unit 9 for storing, converting, re-transmitting or analysing the electrode signals. For example, the acquired body signals are transmitted by the data acquisition unit 9 from the wearer wirelessly using e.g. Bluetooth to a personal computer (PC) or to handheld device such as a cellphone or personal digital assistant comprising a cellular phone communications module such as a GSM/GPRS modem. The wireless link from the data acquisition unit 9 makes the wearer mobile. In the case of any abnormality, a detection algorithm in the PC sends a SMS message to a remotely located doctor or caretaker. The doctor remotely connects to the PC or handheld device and monitors the patient's physiological condition.
In the schematic representation, the data acquisition unit 9 is depicted as a unit separate from the garment 20. The data acquisition unit 9 may however be incorporated in the garment 20, and the cables 8 as well may be incorporated by e.g. weaving conductive fibres into the garment 20.
Since the garment 20 is openable at the front, it is easily donned. The straps 25 allow quick and easy adjustment for loosening or tightening the garment 20 and give form fitness to any body shape, both male and female.
While the invention has been described in present preferred embodiments of the invention, it is distinctly understood that the invention is not limited thereto, but may be otherwise variously embodied and practised within the scope of the claims.

LIST OF DESIGNATIONS
1 electrode
2 electrode body
3 conductive fabric
4 amplifying circuit
5 padding
6 body side
7 garment side
8 cable
9 data acquisition unit
10 skin
11 garment section
12 amplifier
13 detachable fastener

20 garment
21 back section
22 right front section
23 left front section
24 zipper
24a, 24b zipper halves
25 strap
26 slit
27 arm zipper
28 arm hole

WE CLAIM:
1. A medical electrode (1) for acquiring electrophysiological signals, comprising an electrode body (2) electrically connected to a conductive fabric (3) and to an amplifying circuit (4), the amplifying circuit (4) being operationally connected to means (8) for powering the amplifying circuit and for transmitting signals to a remote data acquisition means (9), the conductive fabric constituting the outer surface of at least a body side (6) of the electrode, and the electrode further comprising a resilient padding (5) arranged between the body side (6) and a garment side (7) of the electrode (1).
2. The medical electrode (1) of claim 1, wherein the resilient padding (5) is concave, that is, in an uncompressed state the padding (5) at the outside is thicker than the padding (5) in the middle of the electrode (1).
3. The medical electrode (1) of one of the preceding claims, wherein the conductive fabric (3) is made of a combination of conductive fibres with a nonconducting fibre such as cotton.
4. The medical electrode (1) of one of claims 1 or 2, wherein the conductive fabric (3) is made of conductive fibres alone.
5. The medical electrode (1) of one of claims 3 or 4, wherein the conductive fibres are metallic fibres such as stainless steel wires, or intrinsically conductive polymers, or fibres doped with conductive metallic or organic particles.
6. The medical electrode (1) of one of the preceding claims, wherein the conductive fabric (3) constitutes a single piece of fabric folded around the electrode body (2), the amplifying circuit (4) and the padding (5).
7. The medical electrode of one of the preceding claims, wherein the padding (5) is made of hydrophobic material, in particular Polyurethane foam, Polyester fibres, Nylon fibres or Polyester fibres.

8. The medical electrode of one of the preceding claims, wherein the electrode is of an elongated rectangular form.
9. The medical electrode of one of the preceding claims, wherein the amplifying circuit (4) comprises a high input impedance voltage follower circuit.
10. A garment (20) comprising medical electrodes for health monitoring, the electrodes (1) preferably being of the type according to one of the preceding claims, the garment (20) consisting of a single piece of fabric or of a single set of connected fabric parts, the garment (20) being openable at the wearer's front side and comprising adjusting means for fitting the garment (20) to the wearer's body circumference*
11 The garment (20) of claim 10, comprising first fastening means (25) for ensuring an adjustable tight fit of an electrode-carrying section (23) of the garment (20) against the wearer's body, and comprising second fastening means (24) for closing a further section (22) of the garment (20) over the first fastening means (25), thereby covering the first fastening means (25).
12. The garment (20) of claim 11, comprising a back section (21), a first front section
(22) and a second front section (23), the second front section (23) being the
electrode-carrying section (23) and having medical electrodes (1) arranged on its
inside,
wherein the second front section (23) is attached at its inner edge to a first side of the back section (21) and the second front section (23) comprises first fastening means (25) at its outer edge for connecting said outer periphery to a second side of the back section (21), the first fastening means (25) being adjustable, such that, when connected, the back section (21) and the second front section (23) form an adjustable tubular shape around a wearer's body,
the second front section (23) and the first front section (22) comprising second fastening means (24) for connecting an outer edge of the first front section (22) to the outside of the second front section (23).
13. The garment (20) of one of claims 11 through 12, wherein the first fastening means
(25) are straps (25) in combination with slits or eyelets (26).

14. The garment (20) of claim 13, wherein the straps (25), in the fastened position, pass
through the slits (26), are folded back onto themselves and are attached to themselves
by means of hook and loop type fasteners, the degree to which the straps (25) are
folded back onto themselves being variable and thus allowing to adjust the tightness
of the electrode-carrying section (23) around the wearer's body.
15. The garment (20) of one of claims 11 through 14, wherein the second fastening
means (24) is a zipper (24).
16. The garment (20) of one of claims 11 through 15, wherein the electrodes (1) are detachably arranged on the inside of the electrode-carrying section (23).
17. The garment (20) of one of claims 10 through 16, wherein the electrodes (1) are operationally connected to a data acquisition unit (9) by means of cables (8), and the data acquisition unit (9) is arranged to transmit a representation of electrophysiological signals captured by the electrodes (1) over a wireless communication link.