Stimulation device and method of stimulating a phrenic nerve

Abstract

A stimulation device (10) configured to stimulate a Phrenic nerve (220) in a body of a patient (20) comprises a coil unit (110) configured to generate a magnetic field (30), and a holder (120) coupled to the coil unit (110). The holder (120) is arranged to position the coil unit (110) at the body of the patient (20) such that the Phrenic nerve (220) is stimulable by the magnetic field (30) generated by the coil unit (110). The coil unit (110) comprises a ferromagnetic core (1110) and a wire (1120) wound around the ferromagnetic core (1110).

Description

DESCRI PTIONTitleSTIMULATION DEVICE AND METHOD OF STIMULATING A PHRENIC NERVETechnical Field

[0001] The present invention relates to a stimulation device according to the preamble of independent claim 1 and more particularly to a method of stimulating a Phrenic nerve of a patient.

[0002] Such stimulation devices having a coil unit configured to generate a magnetic field and a holder coupled to the coil unit, wherein the holder is arranged to position the coil unit at the body of the patient such that a Phrenic nerve of a patient is stimulable by the magnetic field generated by the coil unit, can be used for stimulating the Phrenic nerve in a body of a patient, e.g., to activate a diaphragm of the patient for ventilating the patient and / or for diaphragm training during ventilation.Background Art

[0003] In medicine, it is known that for many purposes it is beneficial to activate a target tissue of a patient using stimulation by electro-magnetic, electric or magnetic fields. For achieving such activation of tissues in a patient’s body, it is known to directly stimulate the tissue or to indirectly activate the tissue via stimulation of specific parts of the neural system. For example, the target tissue being a muscular tissue can be activated by providing electric pulses directly to the muscular tissue or to nerves associated to the muscular tissue.

[0004] In critical care units or other departments of hospitals, it may be desired to activate the diaphragm for ventilating patients, typically in combination with mechanical ventilation, in order to prevent drawbacks of disuse of the diaphragm. It was shown that disuse atrophy of diaphragm muscle fibres occurs already in the first 18-69 hours of mechanical ventilation, and the muscle fibre cross-sections decreased by more than 50%in this time. Thus, it is aimed to activate the diaphragm repeatedly while the patient is given artificial or mechanical respiration such that the functioning of the diaphragm can be upheld, or to activate the diaphragm at least during the weaning period to support effective restoration of independent respiratory function.

[0005] It is known that the diaphragm can be activated by stimulating the Phrenic nerves, e.g., at the neck of a patient. In this context, US 2016 / 0310730 A1 describes an apparatus for reducing ventilation induced diaphragm disuse in a patient receiving ventilation support from a mechanical ventilator. The apparatus includes an electrode array of first and second types and comprises a plurality of electrodes configured to stimulate a Phrenic nerve of the patient.

[0006] In one example, the electrode arrays are configured as surface electrode arrays embedded in adhesive electrode patches to be placed on each side of a patient’s neck near the areas where the Phrenic nerves are located. Thus, the electrode arrays are electrically and mechanically coupled to the skin of the patient independent from each other. Therefore, the electrode arrays cover portions of a patient’s surface and may interfere with other applications required for the treatment of the patient like for example the intubation into the trachea. In case the electrode arrays need to be taken off and replaced at a later point in time, the system needs to be fully re-calibrated according the new locations of the electrode arrays to avoid undesired co-stimulation of tissue surrounding the Phrenic nerves.

[0007] In practice, also electro-magnetic stimulators are used to activate a target tissue, which are based on the principle of electro-magnetic induction. A strong current pulse (typically a monophasic or biphasic current pulse) flows through a coil winding, which produces a strong, transient magnetic field. The current pulses cause a changing magnetic field that for example alters according to the phases of the current pulses. The changing magnetic field induces a corresponding electric field, which in turn depolarizes neuronal membranes, leading to action potentials through one or more nerves. Coil windings are usually designed towards generating electric field distribution curves of the induced field, often having an electric field peak (area with maximum electric field strength) or an electric field area, which is stronger than other fields in other areas. Thus, an electric field distribution curve can generate activation pulses, which are effective periodically at time intervals, and electric field peaks or strong field areas may alternate with low field areas in the distribution curve.

[0008] However, when two target nerves inside the body in a close distance to each other, like the two Phrenic nerves, shall be stimulated simultaneously, the coil winding systems in today’s stimulators used for electro-magnetic stimulation have significant limitations. De-central coils have been designed for this purpose producing de-centralized fields. However, typically two separate stimulator devices are necessary, the electromagnetic fields of the two devices can interfere with each other, and body constraints may not allow positioning coils windings of the two devices in parallel to make use of the de-centralized design. Especially in the neck region, positioning coil windings longitudinal to the neck would force the user to choose significantly smaller coil winding sizes because the chin and chest constrain space for the coils to be placed.

[0009] For addressing such downsides of the configurations know in the art, WO 2022 / 063931 A1 suggests to provide a bracket structure coupled to first and second coil units. The coil units are configured to be positioned at the patient, in particular, at a neck of the patient where they can access the Phrenic nerves. The bracket structure is adjustable such that positions and orientations of the first field generator and of the second field generator are adapted as the need may be. The coil units comprise spiral shaped wires, which require a comparably large space such that, particularly, at the neck it may be difficult to correctly position the coil units for stimulation. Further, in order to generate a sufficiently strong electro-magnetic field for an appropriate stimulation of the Phrenic nerves, a comparably high voltage has to be provided to the coil unit. Such high voltage provision may be a security issue in particular, in an environment where also other objects of persons are located.

[0010] Therefore, there is a need for a stimulation device or method allowing a safe and targeted stimulation of Phrenic nerves, particularly at a neck region of a patient. Moreover, it may be desired to stimulate Phrenic nerves of a comparably long time period.Disclosure of the Invention

[0011] According to the invention this need is settled by a stimulation device as it is defined by the features of independent claim 1 , and by a method as it is defined by the features of independent claim 31 . Preferred embodiments are subject of the dependent claims.

[0012] In a first aspect, the invention is a stimulation device configured to stimulate a Phrenic nerve in a body of a patient. The stimulation device comprises a coil unit configured to generate a magnetic field and a holder coupled to the coil unit. The holder is arranged to position the coil unit at the body of the patient such that the Phrenic nerve is stimulable by the magnetic field generated by the coil unit. The coil unit comprises a ferromagnetic core and a wire wound around the ferromagnetic core.

[0013] The stimulation device advantageously is designed for extra-corporal application. In order to be configured to stimulate the Phrenic nerve of the patient the stimulation device has to be arranged such that it can be positioned in order that the magnetic field generated by the coil unit can reach the Phrenic nerve. This, for example, may involve a shape and dimension of the coil unit allowing holder to position the coil unit at an appropriate part of the body. In particular, the coil unit may be designed to contact or to be close to the skin of the patient where the magnetic field can be applied through the skin to the Phrenic nerve. Like this, the stimulation device can prevent any invasive action in application for stimulating the Phrenic nerve.

[0014] The term “position” as used herein refers to location and orientation. Changing the position of an element involves either relocating the element, reorienting the element or a combination thereof. If an element or component is positioned to be capable of doing something, it advantageously is located and orientated to achieve the respective function. For example, the coil unit being positioned by the holder to stimulate a Phrenic nerve typically relates to being located and oriented such that the Phrenic nerve is within the magnetic field generated by the coil unit.

[0015] The stimulation device is advantageously arranged to stimulate the Phrenic nerve at a neck of the patient. Thereby, the term “neck” may generally relate to the part of the body connecting the head to the torso. However, as used herein, the neck may also include transitional portions between head and neck or between torso and neck. In particular, it may also cover a clavicle region of the body.

[0016] The term “position at a body” or, similarly, “holding at a body” relates correspondingly to be located and oriented at the body. In connection with the coil unit these terms can relate to being physically in contact with the body of the patient and particularly with the neck, or in close distance to it. The location and orientation of the coil unit or a component thereof can thereby be predefined or distinct to be appropriate foractivating the diaphragm by stimulating the Phrenic nerve. In order to be configured for being appropriately, the coil unit can be formed to be suited to the respective position. For example, it can be formed in in correspondence to a neck of the patient such that it can conveniently be positioned at the neck, e.g., for stimulating the Phrenic nerve.

[0017] The wire of the coil unit can be a litz wire or any other wire made of any suitable material like copper or the like. It can be wound around the ferromagnetic core such that it is adjacent to and / or contacts the ferromagnetic core. Like this a compact design can be achieved and an efficient creation of the magnetic flux in the ferromagnetic core can be achieved.

[0018] The term “ferromagnetic” as used herein relates to any kind of material or structure having a sufficiently high magnetic permeability. In particular, the magnetic permeability has to essentially higher than air. Accordingly, ferromagnetic structures as described herein may include a ferromagnetic material in the literal sense (i.e. a material showing ferromagnetism) as well as materials or combinations of materials providing an appropriate magnetic permeability allowing the wound wire to generate a magnetic flux suitable to create the magnetic field (in particular a ferrimagnetic material, i.e. a material showing ferrimagnetism, such as a ferrite ceramic). As such, the term “ferromagnetic” may in particular include a ferromagnetic material in the literal sense and ferrimagnetic material. That is, the term “ferromagnetic” includes both, ferromagnetic and ferrimagnetic materials. Alternatively, the term “ferromagnetic” may be replaced by the term “magnetic”, and consequently the term “ferromagnetic core” by “magnetic core”.

[0019] For ventilation, it may be intended to activate the diaphragm of the patient. By means of the stimulation device such activation may be induced indirectly by positioning the coil unit such that the Phrenic nerve is located in the magnetic field generated by the coil unit. Like this, the Phrenic nerve can be stimulated and the diaphragm activated.

[0020] In use of the stimulation device, by providing current through the wire of the coil unit, a magnetic flux can be generated in the ferromagnetic core. Where the flux exits the ferromagnetic core, a magnetic field is generated, wherein the magnetic field may have a specifically targeted or concentrated shape. Moreover, the magnetic field generated like this typically is linearised and has a comparably high penetration depth in human tissue which may be particularly beneficial when an obese patient is involved. Further, the wire being wound around the ferromagnetic core allows for generating an amplification of themagnetic flux such that a comparably low voltage source power can be required for generating a magnetic field sufficiently strong to stimulate the Phrenic nerve. Involving comparably low voltage allows for generally increasing safety of the device and for making admission processes simpler.

[0021] The coil unit having the wire wound around the ferromagnetic core allows to create a compact design having a comparably small face to be arranged at the patient. Like this, the coil unit can efficiently be used in comparably constrained conditions such as at a neck of the patient where the Phrenic nerve can efficiently be targeted stimulated. Also, in situations where other components such as tubes, IV catheters or other medical components are arranged close to the preferred location of Phrenic nerve stimulation small faced coil units may be particularly beneficial. Therefore, the stimulation device can be useful when other treatments have to applied to the patient together with the ventilation.

[0022] Preferably, the ferromagnetic core of the coil unit has a rod portion and the wire is wound around the rod portion of the ferromagnetic core. The rod portion typically is an elongated portion of the ferromagnetic core. In particular, its axial extension typically is bigger than its diameter. In other words, where the wire is wound around the ferromagnetic core, i.e., at the rod portion, the axial extension of the ferromagnetic core typically is larger than its diameter, or largest diameter in case it is not rotational symmetric in cross-section.

[0023] Geometrically, the rod portion can be essentially cylindrical. Thereby, the cylindrical portion may have a base or cross-section in any suitable shape such as a circle, an oval, a square, a rectangle, triangle, pentagon, hexagon, or the like. When having a base or cross-section in the shape of a square or rectangle, the rod portion may be a cuboid. Particularly, the ferromagnetic core can be completely cylindrical. Also, the rod portion may be straight, i.e., having a straight axis, or bent, curved, or the like.

[0024] By having the rod portion in the ferromagnetic core, the coil unit can be efficiently positioned and re-positioned to provide and adapt the magnetic field to reach the Phrenic nerve. Also, it allows to provide a comparably small contact surface where the coil unit is applied or positioned at the body of the patient. This allows for applying the stimulation device at a location of the body where comparably narrow space constraints are present. In particular, it allows for efficiently stimulating the Phrenic nerve at the neck of the patient.

[0025] The efficient re-positioning allows to adapt the magnetic field to continuously reach the Phrenic nerve even when movements of the patient are involved. This allows for a comparably long-time stimulation. For example, the rod portion including the ferromagnetic core can be efficiently tilted. Such tilting may be desired to shape or locate the magnetic field. Like this, the Phrenic nerve can efficiently be positioned in the magnetic field generated by the coil unit.

[0026] For efficiently allowing tilting of the ferromagnetic core, the holder preferably is configured to tilt the ferromagnetic core. Such configuration can be embodied by holding the ferromagnetic core via a hinge or a similar structure. Like this, the ferromagnetic coil can be adapted to provide a magnetic field covering the Phrenic nerve even in situations, where the patient moves.

[0027] The rod portion of the ferromagnetic core of the coil unit preferably has a diameter in a range of about 1 cm to about 10 cm, of about 2 cm to about 8 cm, or of about 3 cm to about 6 cm. Such ferromagnetic coil can be designed to provide an efficient and space saving contact with the patient to apply the magnetic field.

[0028] Preferably, the wire is wound around the ferromagnetic such that it forms one or a plurality of windings. Such winding arrangement allows for a regular and compact design of the coil unit.

[0029] Thereby, in one embodiment a distance of neighboring windings of the plurality of windings preferably corresponds to a diameter of the wire or is less than the diameter of the wire. In another embodiment, neighboring windings of the plurality of windings preferably contact each other. Both embodiments of winding arrangement allow to provide a comparably high winding density. Like this, a comparably high number of windings can be provided which allows to generate a comparably high magnetic flux. In particular, the magnetic flux depends on the amount of windings such that a tight winding of the wire allows to achieve a comparably high flux.

[0030] All windings of the plurality of windings preferably comprise an identical winding diameter. In this connection, the term winding diameter relates to a diameter of one turn or one winding. In case the winding is non-circular, the winding diameter may be the maximum diameter involved. Advantageously, the plurality of windings may consist ofwindings having the same identical diameter. Like this, a single layer of windings may be embodied which allows for providing a high efficiency of generating the magnetic field.

[0031] Preferably, the plurality of windings is arranged along a winding direction and the plurality of windings comprises between about ten windings per cm winding direction and about thirty windings per cm winding direction, or about twenty windings per cm winding direction. Such winding density allows for efficiently providing a high magnetic flux to generate a sufficient magnetic field to stimulate the Phrenic nerve. It is also possible that the number of windings is lower. In particular, the plurality of windings may comprise between about one winding per cm winding direction and about ten windings per cm winding direction, or between about one winding per cm winding direction and about seven windings per cm winding direction, or between about two windings per cm winding direction and about six windings per cm winding direction. Likewise, the plurality of windings may comprise between one winding per cm winding direction and about one winding per 2 cm winding direction, or between one winding per cm winding direction and about one winding per 3 cm winding direction, or between one winding per cm winding direction and about one winding per 4 cm winding direction, or between one winding per 2 cm winding direction and about one winding per 4 cm winding direction, or between one winding per 2 cm winding direction and about one winding per 3 cm winding direction.

[0032] Preferably, the ferromagnetic core has an open face not covered by the wire wound around the ferromagnetic core. Such open face can be embodied to directly apply the magnetic field to the body of the patient or to indirectly apply the magnetic field via a further component.

[0033] In particular, in a first preferred variant the open face of the ferromagnetic core of the coil unit is configured to concentrate a magnetic flux density. The open face can be configured in that manner by being appropriately shaped and / or equipped with a suitable material.

[0034] The term “magnetic flux density” as used herein may referred to as B indicated in newton per meter per ampere (N / (m*A)), or Tesla. The magnetic field in contrast typically is indicated in ampere per meter (A / m). In vacuum, the two dimensions are related through vacuum permeability, B / no=H. In a magnetized material, the quantities on each side of this equation differ by the magnetization field of the material.

[0035] Generally, the concentrated magnetic flux density can result in the magnetic field being configured to have a targeted shape, particularly in a region just outside or adjacent said open face of the ferromagnetic core. Such targeted shape can efficiently be achieved by the magnetic flux concentrated and guided inside the ferromagnetic core. Specifically, such magnetic flux can efficiently generate a comparably narrow field, particularly in the region just outside or adjacent said open face of the ferromagnetic core. Moreover, the magnetic flux generated within the ferromagnetic core may be transformed to a different magnetic flux in terms of intensity and direction. The targeted shape can further be achieved or promoted by locally constraining the magnetic field, e.g., resulting in a peakshaped magnetic field. Like this, the magnetic field can be adapted to be active in a target area being or comprising the Phrenic nerve that shall be stimulated with the magnetic field. The targeted shape can generally be any shape of the magnetic field or a section thereof that allows to stimulate the Phrenic nerves effectively while minimizing other undesired co-stimulation effects of surrounding, above-lying or close-by tissues or nerves. A peak shape is such example, because it maximizes effects in the focality area and minimizes effects outside this focality area.

[0036] In a second preferred variant the coil unit comprises a flux head configured to concentrate the magnetic flux density and the flux head is magnetically coupled to the open face of the ferromagnetic core. To be magnetically coupled, the flux head can be in direct or indirect contact with the ferromagnetic core or it can be adjacent to the open face of the ferromagnetic core. The term “adjacent” in this connection relates to a neighboring position involving a contact or being distant or spaced. For preventing loss of efficiency, a space or gap between the open face and the flux head is to be designed sufficiently small in case air is in the space or gap.

[0037] For concentrating the magnetic flux density, in the first variant, the open face or, in the second variant, the flux head can have a specific shape. The shape can also be adapted to the location where the Phrenic nerve is to be stimulated. Further, the open face or the flux head can include a specific ferromagnetic material which may be the same as the ferromagnetic core or which may be a different material.

[0038] In the second variant, the flux head of the coil unit preferably comprises a ferromagnetic material. More specifically, the flux head may consist of the ferromagnetic material. The ferromagnetic material of the flux head can be the same as the ferromagnetic material of the ferromagnetic core.

[0039] The flux head preferably is mechanically decoupled from the ferromagnetic core such that it is displaceable relative to the ferromagnetic core. Such displacement may include an adaptation of an angle and / or distance between the flux head and the open face of the ferromagnetic core.

[0040] The stimulation device preferably comprises an adaptation module configured to detect a feedback signal representing stimulation of the Phrenic nerve and to re-arrange the coil unit when the detected signal represents a stimulation below a predefined threshold. For example, the feedback signal may be indicative for an air flow generated by the patient breathing as a reaction of the stimulation. Or, it can be indicative for a contraction of the diaphragm. By means of such adaptation module, the coil unit can be efficiently arranged or positioned and re-positioned in an automatic fashion. Specifically, the feedback signal allows for ensuring appropriate positioning of the coil unit.

[0041] In the first variant, the open face of the ferromagnetic core of the coil unit and the wire of the coil unit preferably are displaceable relative to each other. By such displacement, the magnetic field generated by the coil unit can be adapted or shaped. For example, an angle or direction into which the magnetic field is propagated can be defined.

[0042] Thereby, the adaptation module preferably is configured to re-arrange or re-position the coil unit by displacing the open face of the ferromagnetic core and wire relative to each other.

[0043] In the second variant, the flux head and the wire preferably are displaceable relative to each other. Such displacement allows for adjusting the magnetic flux or for shaping the magnetic field provided to the patient.

[0044] Thereby, the adaptation module preferably is configured to re-arrange or re-position the coil unit by displacing the flux head and the wire relative to each other.

[0045] In a third variant, the ferromagnetic core may comprise a first open face and a second open face, wherein the wire is wound around the ferromagnetic core between the first and the second open faces, and wherein each of the first and the second open faces is arranged in a half-space of the ferromagnetic core facing the body of the patient in use of the device. As such, the first open face and a second open face preferably form or arepreferably formed by a first free pole end portion and a second free pole end portion of the ferromagnetic core.

[0046] As used herein, the term “half-space” of the ferromagnetic core refers to the space in which one of two parts of the ferromagnetic core resides upon dividing the ferromagnetic core 11100 by a plane though its geometric centre (centroid).

[0047] Advantageously, having two open faces in a half-space of the ferromagnetic core facing the body of the patient in use of the device, i.e. in one and the same half-space of the ferromagnetic core facing the body of the patient in use of the device enhances the magnetic reflux between the ferromagnetic core and the patient. In particular, this reduces magnetic flux through ambient air. This in turn enhances the stimulation efficiency.

[0048] Accordingly, in use of the device at least a portion of the magnetic field generated by the coil unit may leave the ferromagnetic core at one of the first and the second open faces and re-enter the ferromagnetic core at the respective other one of the first and the second open faces. In between the first and the second open faces, at least a portion of the magnetic field outside of the ferromagnetic core, in particular a fringe magnetic field, may enter the body of the patient to stimulate the Phrenic nerve.

[0049] To guide the magnetic field (magnetic flux density), in particular the fringe magnetic field, further towards the body of the patient and to reduce leakage between the first and the second open faces, the stimulation device may preferably comprise a diamagnetic material arranged between the first and the second open faces. Preferably, the diamagnetic material is Bismuth.

[0050] For concentrating the magnetic flux density, at least one of the first and the open faces can have a specific shape (similar to the open face in the first variant and the flux head in the second variant). The shape can also be adapted to the location where the Phrenic nerve is to be stimulated. In particular, at least one of the first open face and the second open face may be tapered. Likewise, the first and the open faces may have a specific orientation to each other for optimally concentrating the magnetic flux density. Preferably, the first and the second open faces may point towards each other. Alternatively, the first and the second open faces may point away from each other. According to yet another alternative, the first and the second open faces may point in thesame direction. The specific orientation preferably is chosen in dependence of the location where the Phrenic nerve is to be stimulated.

[0051] In particular, the first open face may have at least a first surface and the second open face may have at least a second surface, wherein the wire preferably is wound around the ferromagnetic core between the first and the second surfaces, and wherein each of the first and the second surfaces preferably point into the half-space of the ferromagnetic core facing the body of the patient in use of the device. As such, the first and the second surface provide a magnetic flux interface between the ferromagnetic core and the surrounding of the core (air or body of the patient), in particular a core-patient interface or a core-air interface. More particularly, at least a portion of the magnetic field generated by the coil unit may leave the ferromagnetic core at one of the first and the second surfaces and re-enter the ferromagnetic core at the respective other one of the first and the second surface.

[0052] To adapt the magnetic field leaving and re-entering to ferromagnetic core at the first and second surfaces to the location where the Phrenic nerve is to be stimulated, the first and second surfaces may have a specific shape and / or orientation. In particular, at least one of the first surface and the second surface may be planar or curved. Likewise, the first and the second surfaces may face each other, i.e. point towards each other. Alternatively, the first and the second surfaces may be parallel to each other.

[0053] The smaller the distance between the first and the second open faces, in particular between the first and the second surfaces, the higher the magnetic flux between the first and the second open faces. Accordingly, a minimum distance between the first and the second open faces in particular between the first and the second surfaces, may be at most 150 mm, in particular at most 125 mm, more particularly at most 100 mm, preferably at most 75 mm or at most 50 mm or at most 25 mm or at most 20 mm or at most 10 mm or at most 5 mm.

[0054] In order to enable the first and second open faces being arranged in one and the same half-space of the ferromagnetic core, the ferromagnetic core preferably comprises a non-straight portion or preferably is non-straight. In particular, the ferromagnetic core may comprise a curved portion or may be curved. More specifically, the ferromagnetic core may have a bracket-shape, in particular a C-shape or a U-shape or a partial ring shape, such as a semi-ring shape or a semi-circular ring shape, or horseshoe shape.

[0055] In general, an outer cross-section of the ferromagnetic core (as seen in a cross-section perpendicular to a length extension of the ferromagnetic core) may completely fill out an inner cross-section of the one or the plurality of windings or alternatively, may be smaller than, e.g. by area half of, the inner cross-section of the one or the plurality of windings. The latter configuration may in particular facilitate to displace the wire of the coil unit and the ferromagnetic core relative to each other, which in turn allows to adapt or shape the magnetic field generated by the coil unit.

[0056] Accordingly, a filling factor of an outer cross-section of the ferromagnetic core (filling an inner cross-section of the one or the plurality of windings) may be in a range between 0.1 and 1.0, in particular between 0.2 and 0.7 or between 0.5 and 1.0, more particularly between 0.3 and 0.5 or between 0.8 and 1.0. In particular.

[0057] The plurality of windings is distributed, preferably evenly distributed, along a length extension of the ferromagnetic core, in particular between the first open face and the second open face, more particularly from the first open face to the second open face. Advantageously, having plurality of windings distributed along a length extension of the ferromagnetic core advantageously helps to reduce the reluctance of the coil unit. Preferably, the windings are distributed, especially evenly distributed, at a distance from each other along a length extension of the ferromagnetic core, in particular between the first open face and the second open face, more particularly from the first open face to the second open face. Alternatively, at least a portion of the first open face and / or at least a portion of the second open face may extend (protrude) beyond the windings to avoid interference of the winding with the patient. That is, at least a respective portion of the first free pole end portion and / or of the second free pole end portion of the ferromagnetic core may extend (protrude) beyond the windings.

[0058] Preferably, the holder is configured to be arranged around a neck of the body of the patient such that the coil unit is arranged to generate the magnetic field at the neck of the body of the patient. For example, the holder can be embodied similar as a ruff or a collar. Such a holder can be conveniently carried by the patient. Further, the coil unit can be integrated in the holder such that the do not affect comfort.

[0059] The stimulation device can comprise a plug to be connected to an external power source. However, preferably it comprises a power source. Such own power source can efficiently be adapted to suit the needs of the coil unit or of the intended application.Furthermore, it can be integrated in the stimulation device to be carried by the patient. In a mobile embodiment, the power source preferably comprises a battery.

[0060] Thereby, the power source preferably is configured to provide electric current in a range of about 2 Ampere (A) to about 10 A or in a range of about 3 A to about 7 A to the coil unit. Likewise, the power source may be configured to provide electric current in a range of about 10 Ampere to about 1000 Ampere or in a range of about 100 Ampere to about 3000 Ampere or in a range of about 100 Ampere to about 5000 Ampere. Additionally or alternatively, the power source preferably is configured to provide a voltage in a range of about 2 Volt (V) to about 10 V or in a range of about 3 V to about 7 V to the coil unit. Likewise, the power source may be configured to provide a voltage in a range of about 10 Volt to about 100 Volt or in a range of about 100 Volt to about 1000 Volt or in a range of about 100 Volt to about 5000 Volt.

[0061] Such a power source can be particularly beneficial for a safe and appropriate operation of the stimulation device. In particular, for generating a suitable magnetic flux in the ferromagnetic core such power source may suffice.

[0062] Preferably, the stimulation device preferably comprises a circuit having a capacitance and an inductance, wherein the inductance is formed by the coil unit.

[0063] In a preferred embodiment of the circuit, it is configured to charge or energetically charge the inductance by means of a current provided through the circuit. The current can be provided by the power source if the stimulation device has such power source. Or, the current may be provided by an external power source connected to the stimulation device. Such configuration and concentrating the flux allows to charge the coil unit by means of comparably low current. In particular, the provision of a high-power supply which may cause problems in terms of security can be prevented. Voltage may be generated or built up by the self-induction of the coil unit. Moreover, the comparably high inductivity obtained by the comparably high number or density of windings as described above, allow to efficiently charge the magnetic field of the coil unit.

[0064] Thereby, the circuit preferably is configured to repeatedly switch-off charging the inductance. Like this a comparably high voltage can be generated with comparably low current. The circuit preferably is configured to switch-off charging the inductance at afrequency of between 15 Hertz and 35 Hertz, of between 20 Hertz and 30 Hertz, or of 25 Hertz.

[0065] The circuit preferably is configured to charge the capacitance, e.g., through electromagnetic induction, when charging the inductance is switched-off. Thereby, the circuit preferably is configured to repeatedly convert electric charge within the capacitance to current within the inductance.

[0066] In particular, operating the coil unit by charging the inductance or coil unit, followed by switching-off the current to initiate a resonance between the inductance or coil unit and the capacitor by electromagnetic induction, allows to efficiently providing the current that generates a desired magnetic field.

[0067] In another preferred embodiment of the circuit, it is configured to charge the capacitor by means of voltage provided through the circuit. Even though such direct voltage induced charging requires comparably high-power source, it may allow efficient charging in a more familiar and robust manner. In particular, resonance can be initiated by charging the capacitor with the voltage, followed by switching the voltage to the inductance or coil unit.

[0068] Preferably, the circuit is configured to operate the coil unit in resonance with the capacitor followed by switching-off the coil current when it is close to or at zero after one or multiple resonance periods.

[0069] For switching-on and switching-off the current a Silicon-controlled switch or a Silicon-controlled rectifier such as a thyristor is preferably used. Thus, advantageously the circuit comprises such Silicon-controlled switch or a Silicon-controlled rectifier.

[0070] Operating the coil unit by providing electric current through the wire of the coil unit preferably comprises repeatedly providing current to charge the magnetic field of the coil unit, switching-off the current to initiate a resonance between the coil and the capacitance, wherein the current advantageously is switched-off close to or at zero after one or multiple resonance periods.

[0071] For an efficient ventilation, the stimulation device preferably comprises a second coil unit essentially identical to the coil unit. By means of two coil units, the two Phrenic nerves can be stimulated, e.g., at the neck of the patient. Like this, a synchronizedstimulation can be provided such that a regular and uniform activation of the diaphragm is achieved.

[0072] In a second aspect, the invention is a method of stimulating a Phrenic nerve of a patient, comprising the steps of: obtaining a coil unit comprising a ferromagnetic core and a wire wound around the ferromagnetic core; positioning the coil unit at a target surface of the body close to the Phrenic nerve; and operating the coil unit by providing electric current through the wire of the coil unit such that the coil unit generates a magnetic field and stimulates the Phrenic nerve.

[0073] The method according to the invention and its preferred embodiments described below allow to achieve the effects and benefits of the stimulation device and its preferred embodiments described above. In particular, by using the coil unit according to the invention, a particularly efficient and sophisticated stimulation of the Phrenic nerve for ventilation is possible. Thereby, the patient may be ventilated for a comparably long time such as for plural days or weeks.

[0074] Preferably, the method comprises steps of adapting the magnetic field generated by the coil unit; verifying a response of the body to generation of the magnetic field; and stopping adaptation of the magnetic field when the response of the body is appropriate.

[0075] Preferably, operating the coil unit by providing electric current through the wire of the coil unit comprises provision of the electric current in a range of about 2 Ampere to about 10 Ampere or in a range of about 3 Ampere to about 7 Ampere. Likewise, operating the coil unit by providing electric current through the wire of the coil unit may comprises provision of the electric current in a range of about 10 Ampere to about 1000 Ampere or in a range of about 100 Ampere to about 3000 Ampere or in a range of about 100 Ampere to about 5000 Ampere.

[0076] Preferably, operating the coil unit by providing electric current through the wire of the coil unit comprises provision of a voltage in a range of about 2 Volt to about 10 Volt or in a range of about 3 Volt to about 7 Volt. Likewise, operating the coil unit by providing electric current through the wire of the coil unit may comprise provision of a voltage in a range of about 10 Volt to about 100 Volt or in a range of about 100 Volt to about 1000 Volt or in a range of about 100 Volt to about 5000 Volt.

[0077] Preferably, operating the coil unit by providing electric current through the wire of the coil unit comprises charging the ferromagnetic core and the wire. In particular, operating the coil unit by providing electric current through the wire of the coil unit preferably comprises energetically charging the magnetic field of the coil unit whereby a stored energy is defined by the current and an inductivity obtained by the ferromagnetic core and the wire or plurality of windings, respectively.

[0078] Thereby, preferably operating the coil unit by charging the coil is followed by switching-off the current to initiate a resonance between the coil unit or inductance and the capacitance by electromagnetic induction, thereby providing the current of the coil unit that generates a desired magnetic field.

[0079] Alternatively, the resonance can by initiated by charging the capacitance with a voltage, followed by switching the voltage to the coil unit.

[0080] Thereby, operating the coil unit by providing electric current through the wire of the coil unit preferably comprises repeatedly switching-off charging the ferromagnetic core and the wire.

[0081] Preferably, operating the coil unit in resonance with the capacitance is followed by switching-off the current when it is close to or at zero after one or multiple resonance periods.

[0082] Preferably, for operating the coil unit by switching-off and switching-on the current a Silicon-controlled switch or Silicon-controlled rectifier such as a thyristor is used.

[0083] Thereby operating the coil unit by providing electric current through the wire of the coil unit preferably comprises repeatedly providing current to charge the magnetic field of the coil unit, switching-off the current to initiate a resonance between the coil unit or inductance and the capacitance and switching-off the current close to or at zero after one or multiple resonance periods.

[0084] Switching-off charging the ferromagnetic core and the wire is preferably performed at a frequency of between about 15 Hertz and about 100 Hertz, of between about 20 Hertz and about 30 Hertz, or of about 25 Hertz.

[0085] The capacitance is preferably charged through electromagnetic induction when charging the inductance is switched-off. Alternatively, the capacitance preferably is charged by providing a voltage.

[0086] The electric charge within the capacitance preferably is repeatedly converted to current within the inductance.

[0087] Preferably, the method comprises the steps of obtaining a second coil unit essentially identical to the coil unit; positioning the second coil unit at a second target surface of the body close to a second Phrenic nerve of the patient; and operating the coil unit by providing electric current through a wire of the second coil unit such that the second coil unit generates a second magnetic field and stimulates the second Phrenic nerve.

[0088] Preferably, the method involves or uses a stimulation device according to the invention or a preferred embodiment thereof described above.Brief Description of the Drawings

[0089] The stimulation device according to the invention and the method according to the invention are described in more detail hereinbelow by way of exemplary embodiments and with reference to the attached drawings, in which:Fig. 1 shows a schematic view of a first embodiment of a stimulation device according to the invention;Fig. 2 shows components of a coil unit of the stimulation device of Fig. 1 ;Fig. 3 shows a schematic view of a second embodiment of a stimulation device according to the invention;Fig. 4 shows a circuit scheme for operating the stimulation device of Fig. 3; andFigs. 5a-5e show various alternative examples of a coil unit according to anther embodiment of a stimulation device according to the invention.of Embodiments

[0090] In the following description certain terms are used for reasons of convenience and are not intended to limit the invention. The terms “right”, “left”, “up”, “down”, “under" and “above" refer to directions in the figures. The terminology comprises the explicitly mentioned terms as well as their derivations and terms with a similar meaning. Also,spatially relative terms, such as "beneath", "below", "lower", "above", "upper", "proximal", "distal", and the like, may be used to describe one element's or feature's relationship to another element or feature as illustrated in the figures. These spatially relative terms are intended to encompass different positions and orientations of the devices in use or operation in addition to the position and orientation shown in the figures. For example, if a device in the figures is turned over, elements described as "below" or "beneath" other elements or features would then be "above" or "over" the other elements or features. Thus, the exemplary term "below" can encompass both positions and orientations of above and below. The devices may be otherwise oriented (rotated 90 degrees or at other orientations), and the spatially relative descriptors used herein interpreted accordingly. Likewise, descriptions of movement along and around various axes include various special device positions and orientations.

[0091] To avoid repetition in the figures and the descriptions of the various aspects and illustrative embodiments, it should be understood that many features are common to many aspects and embodiments. Omission of an aspect from a description or figure does not imply that the aspect is missing from embodiments that incorporate that aspect. Instead, the aspect may have been omitted for clarity and to avoid prolix description. In this context, the following applies to the rest of this description: If, in order to clarify the drawings, a figure contains reference signs which are not explained in the directly associated part of the description, then it is referred to previous or following description sections. Further, for reason of lucidity, if in a drawing not all features of a part are provided with reference signs it is referred to other drawings showing the same part. Like numbers in two or more figures represent the same or similar elements.

[0092] Fig. 1 shows a schematic top view of a first embodiment of a stimulation device 1 according to the invention. The stimulation device 1 comprises a holder 12 with a neck ruff 121 , two coil units 11 , a dedicated power source 15 and a control unit 16. The power source 15 and the control unit are provided in a combined control-power-component.

[0093] The neck ruff 121 of the holder 1 is configured to be arranged around a neck 21 of a patient 2. Along the neck 21 , two Phrenic nerves extend between a head or brain of the patient 2 to a diaphragm of the patient 2. Each of the two coil units 11 is coupled to the holder 2 via a hinge 122. The power-control-component with its power source 15 and its control unit 16 is coupled to the wires 112 of the coil units 11 by means of respective power-connections and to the hinges 122 by respective power- and communication-connections. The power-control component is arranged external of the holder 12, wherein in other embodiments it may also be embodied integral with the holder 12.

[0094] Each of the coil units 11 comprises a ferromagnetic core 111 and a wire 112. The wire 112 is wound around the ferromagnetic core 111 such that it forms a plurality of windings. In particular, as Fig. 2 shows in more detail, the ferromagnetic core 111 is more or less completely rod-shaped. In particular, where it is wound by the wire 112, the ferromagnetic core 111 is circle-cyl indric with a diameter 114 of about 4 cm. The wire 112 is tightly wound around the ferromagnetic core 111 along a winding direction being an axis of the ferromagnetic core 111 such that neighboring windings contact each other. Like this, about 100 turns of the wire 112 are established about a winding length 113 of about 5 cm along the winding direction. Thereby, about twenty windings per cm winding direction or winding length 113 result. Moreover, all windings have an identical winding diameter such that a single layer of windings is established.

[0095] An upper end of the ferromagnetic core 111 forms an open face 115. The open face 115 is free of the wire 112 and embodied to directly apply a magnetic field to neck 21 of the patient 2. The wire 112 is arranged such that, when current runs through the wire 112 a magnetic flux 31 is generated towards the open face 115.

[0096] Turning back to Fig. 1 , it can be seen that the magnetic field 3 generated by the magnetic flux 31 is concentrated by the open face 115. The holder 12 is arranged to position each of the coil units in vicinity of one of the Phrenic nerves 22 such that the Phrenic nerves 22 are positioned in the magnetic fields 3 generated by the coil units 11 . Like this, the Phrenic nerves are stimulable by the magnetic fields 3 generated by the coil units 11.

[0097] The control unit 16 is embodied to implement a logic portion of an adaptation module configured to detect a feedback signal representing stimulation of the Phrenic nerves 22. The sensor can, e.g., be an electrode attached to the body of the patient 2 at a location suitable to identify an activity of the diaphragm such as contraction and / or distraction of the diaphragm. The control unit 16 is further configured to control re-arrangement the coil units 11 when the signal detected by the sensor represents a stimulation below a predefined threshold. For re-arranging the coil units 11 , the adaptation module comprises two drives each configured to tilt the ferromagnetic core 111 of one of the two coil units 11 about the associated hinge 122. Like this, the magnetic field 3 cancontinuously be provided to reach the Phrenic nerves 22 such that an ongoing stimulation of the Phrenic nerves 22 is possible for a comparably long time.

[0098] In addition to the mentioned tiltability of the ferromagnetic cores 11 relative to the holder 12, in each of the coil units 11 , the open face 115 of the ferromagnetic core 11 1 and the wire 112 are displaceable relative to each other. In particular, the wire 112 can be shifted along the winding direction back and forth. By such displacement, the magnetic field 3 can additionally be adapted or shaped.

[0099] In Fig. 3 a second embodiment of a stimulation device 10 according to the invention is shown. Thereby, the components and aspect not being described to be different in the following are identically embodied as in the stimulation device 1 shown in Fig. 1 . In this context it is referred to the description of Fig. 1 and Fig. 2 above.

[0100] The stimulation device 10 comprises a holder 120 with a neck ruff 1210, two coil units 110 each with a ferromagnetic core 1110, a wire 1120 and an open face 1130, a power source 150, and a control unit 160. The stimulation device 10 is arranged to be positioned at a neck 210 of a patient 20, wherein the coil units 110 are positioned such that Phrenic nerves 220 of the patient 20 are located in magnetic fields 30 generated by the coil units 110.

[0101] Different from the first embodiment of the stimulation device 1 , each of the coil units 110 of the stimulation device 10 of Fig. 3 comprises a flux head 140. More specifically, the flux head 140 is arranged adjacent to the open face 1130 of the ferromagnetic core 1110. Thereby, it is magnetic coupled to the open face 1130 and mechanically de-coupled from the ferromagnetic core 1110 such that it is displaceable relative to the ferromagnetic core 1110.

[0102] Further, the flux head of each magnetic coil 110 is made of a ferromagnetic material and configured to concentrate the magnetic field 30. To appropriately shape the magnetic fields 30 for an efficient stimulation of the Phrenic nerves 220, each of the flux heads 140 is displaceable relative to the wire 1120 of the associated coil unit 110. Moreover, the adaptation module is configured to re-arrange the coil unit 110 by displacing the flux head 140 and the wire 1110 relative to each other.

[0103] Fig. 4 shows a circuit 140 of the second embodiment of the stimulation device 10. However, even though the circuit 140 is described in connection with this embodimentit is likewise implemented in the first embodiment of the stimulation device 1 shown in Fig. 1.

[0104] The circuit 140 comprises a low power current source 1410 embodied by the power source 150 providing an initial current to an inductance 1430 embodied by the coil unit 110, a bidirectional switch 1440, and a capacitance 1420. The components of the circuit 140 are interconnected by current conductors 1450.

[0105] The low power current source 1410 is configured to provide electric current 1460 at 5 Ampere and low voltages of maximum 10 Volt into the circuit 140.

[0106] The circuit 140 is configured to charge the inductance 1430 by means of the current 1460. In particular, the inductance 1430 is charged by providing the current 1460 through the wire 1120 of the coil unit 110 such that the coil unit 110 is charged by storing energy in its magnetic field.

[0107] Further, the circuit 140 is configured to repeatedly switch-off charging the inductance 1430. More specifically, charging the inductance 1430 is switched-off at a frequency of 25 Hertz. While charging the inductance 1430 is switched-off, the capacitance 1420 is charged with a voltage by electromagnetic induction over the coil unit 110. Thus, the circuit 140 is embodied as L-C-circuit.

[0108] The embodiments of stimulation devices shown in the Figs, can be used in a method of stimulating a Phrenic nerve of a patient according to the invention. Such method involves the steps of: Obtaining the any of the two stimulation devices 1 , 10 with its two coil units 11 , 110. Arranging the holder 12, 120 at the neck 21 , 210 of the patient 2, 20 such that the coil units 11 , 110 are positioned at a target surface of the neck 21 , 210 body close to the Phrenic nerves 22, 220, and operating the stimulation device 1 , 10 by providing electric current through the wires 112, 1120 of the coil units 11 , 110 such magnetic fields 3, 30 are generated and the Phrenic nerves 22, 220 are stimulated.

[0109] The magnetic fields 3, 30 generated by the coil units 11 , 110 are regularly adapted including verifying a response of the diaphragm of the patient 2, 20 to generation of the magnetic fields 3, 30, and stopping adaptation of the magnetic fields 3, 30 when the response of the diaphragm is appropriate.

[0110] While the ferromagnetic core 111 , 1110 in the embodiments according to Fig. 1 and Fig. 3 are essentially rod-shaped with only one open face 115, 1150 or only one flux head 130 facing the body of the patient 2, 20, Figs. 5a-5e show various alternative examples of a coil unit 1100 in which the ferromagnetic core 11100 comprises two open faces to face the body of the patient. In this regard, it has been found that the magnetic through the ferromagnetic core 11100 is significantly increased if the magnetic flux is guided over the largest possible path of the closed magnetic circuit in the ferromagnetic core. In other words, the path of the closed magnetic circuit of the coil unit should pass through air as little as possible.

[0111] Accordingly, the ferromagnetic core 11100 according to all embodiments shows Figs. 5a-5e comprises a first open face 11501 and a second open face 11502, between which the wire 11200 is wound around the ferromagnetic core 11100, and each of which is arranged in a half-space 1101 of the ferromagnetic core 11000 facing the body of the patient in use of the device 100. At hand, the half-space 1101 of the ferromagnetic core refers to the space in which one of two parts of the ferromagnetic core 11100 resides upon dividing the ferromagnetic core 11100 by a plane (indicted by dashed lines in Fig. 5a) though its geometric centre (centroid). In use of the device 100, at least a portion of the magnetic field generated by the coil unit 1100 leaves the ferromagnetic core 11100 at one of the first and the second open faces 11501 , 11502 and re-enters the ferromagnetic core 11100 at the respective other one of the first and the second open faces 11501 , 11502. As such, the first and the second open faces 11501 , 11502 form or are preferably formed by a first free pole end portion and a second free pole end portion of the ferromagnetic core 11100.

[0112] The ferromagnetic cores 11000 in all five embodiments according to Figs. 5a-5e is curved substantially having a bracket-shape. While the ferromagnetic core 11000 in Fig. 5a essentially has a U-shape, the embodiments according to Fig. 5b and Fig. 5c show a rather horseshoe-like shape or C-shape, and the ferromagnetic cores 11000 in Fig. 5d and 5e have a semi-circular ring shape.

[0113] The shape and orientation of the respective first and second open faces 11501 , 11502 may be shaped and orientated differently in order to adapt the ferromagnetic core 11100 to the location where the Phrenic nerve is to be stimulated. In Fig. 5a, the first and the second open faces 11501 , 11502 have a tapered shape which proves beneficial to concentrate the magnetic flux density. In Fig. 5b and Fig. 5c, the first open face 11501and the second open face 11502 point towards each other in order to keep the air gap between them also close as possible. Preferably, a minimum distance between the first and the second open faces 11501 , 11502 is at most 150 mm, as indicated by the double arrow in Fig.5b. In Fig. 5c, the minimum distance is even smaller due to the tweezer like shape of the first and the second open faces 11501 , 11502. Here, the magnetic flux mainly leaves the ferromagnetic core 11100 at one of a first surface 11511 of the first open face 11501 or a second surface 11522 of the second open face 11502 and re-enters the ferromagnetic core 11100 at the respective other one of the first and the second surface 11511 , 11522 of the first and the second open faces 11501 , 11502, respectively. As can be seen form Fig. 5c, the first surface 11511 and the second surface 11522 are planar and face each other, yet still also directing towards the patient to be stimulated.

[0114] In contrast, Fig. 5d shows in embodiment in which the first surface 11511 of the first open face 11501 and the second surface 11522 of the second open face 11502 are parallel to each other directing into the same direction. Further in contrast to the embodiments of Fig. 5a-5c, the first surface 11511 and the second surface 11522 with the outermost windings of the coil unit 1110.

[0115] Common to all embodiments shown in Fig. 5a-5d, the outer cross-section of the ferromagnetic core 11100 (as seen in a cross-section perpendicular to a length extension of the ferromagnetic core) is smaller than the inner cross-section of the windings of the coil unit 1110. Advantageously, this facilitates to displace the wire 11200 of the coil unit 1100 relative to the ferromagnetic core 11100 which in turn allows to adapt or shape the magnetic field generated by the coil unit 1110. In the examples given, the filling factor of the ferromagnetic core 11100 is about 0.4. Alternatively, as shown in Fig. 5e, the outer cross-section of the ferromagnetic core 11100 may nearly completely fill out the inner cross-section of the windings of the coil unit 1110.

[0116] As can be further seen from Fig. 5a-5e, the windings respective the coil units 1100 are evenly distributed at a distance from each other along the length extension of the ferromagnetic core between the first open face 11501 and the second open face 11502. Advantageously, this configuration helps to reduce the reluctance of the respective coil unit 1100.

[0117] The disclosure also covers all further features shown in the Figs, individually although they may not have been described in the afore or following description. Also,single alternatives of the embodiments described in the figures and the description and single alternatives of features thereof can be disclaimed from the subject matter of the invention or from disclosed subject matter. The disclosure comprises subject matter consisting of the features defined in the claims or the exemplary embodiments as well as subject matter comprising said features. Also, the present disclosure covers intermediate generalisations of features or groups of features of the embodiments described and shown in the figures. I.e., specific features or groups of features as disclosed in the figures and the associated sections of the description may be combined with the more general embodiments of the invention disclosed in connection with the description of the invention. In particular, such specific features or groups of features may be provided in the more general embodiments of the invention in isolation from further specific features shown in the figures. For example, the specific current of 5 Ampere provided low power voltage source of the embodiments shown in the figures may also be provided by the power source of specified in connection with the description of the invention without requiring any further features of the circuit described in the figures. It is understood that those skilled in the art are able to incorporate specific features from the description of the figures into the embodiments of the description of the invention.

[0118] Furthermore, in the claims the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. A single unit or step may fulfil the functions of several features recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. The terms “essentially”, “about”, “approximately” and the like in connection with an attribute or a value particularly also define exactly the attribute or exactly the value, respectively. The term “about” in the context of a given numerate value or range refers to a value or range that is, e.g., within 20%, within 10%, within 5%, or within 2% of the given value or range. Components described as coupled or connected may be electrically or mechanically directly coupled, or they may be indirectly coupled via one or more intermediate components. Any reference signs in the claims should not be construed as limiting the scope.

Claims

CLAIMSClaim 1 : A stimulation device (1 ; 10; 100) configured to stimulate a Phrenic nerve(22; 220) in a body of a patient (2; 20), comprising: a coil unit (11 ; 110; 1100) configured to generate a magnetic field (3; 30); and a holder (12; 120) coupled to the coil unit (11 ; 110; 1100); wherein the holder (12; 120) is arranged to position the coil unit (11 ; 110; 1100) at the body of the patient (2; 20) such that the Phrenic nerve (22; 220) is stimulable by the magnetic field (3; 30) generated by the coil unit (11 ; 110; 1100), characterized in that the coil unit (11 ; 110; 1100) comprises a ferromagnetic core (111 ; 1110; 11000) and a wire (112; 1120; 11200) wound around the ferromagnetic core (111 ; 1110; 11000).Claim 2: The stimulation device (1 ; 10; 100) of claim 1 , wherein the holder (12;120) is configured to tilt the ferromagnetic core (111 ; 1110; 11000).Claim 3: The stimulation device (1 ; 10; 100) of any one of claim 1 or 2, wherein the ferromagnetic core (111 ; 1110) of the coil unit (11 ; 110; 1100) has a rod portion and the wire (112; 1120) is wound around the rod portion of the ferromagnetic core (111 ; 1110).Claim 4: The stimulation device (1 ; 10; 100) of claim 2 or 3, wherein the rod portion of the ferromagnetic core (111 ; 1110) of the coil unit (11 ; 110; 1100) has a diameter in a range of about 1 cm to about 10 cm, of about 2 cm to about 8 cm, or of about 3 cm to about 6 cm.Claim 5: The stimulation device (1 ; 10; 100) of any one of the preceding claims, wherein the wire (112; 1120; 11200) is wound around the ferromagnetic core (111 ; 1110; 11000) such that it forms one or a plurality of windings.Claim 6: The stimulation device (1 ; 10; 100) of claim 5, wherein a distance of neighboring windings of the plurality of windings corresponds to a diameter of the wire (112; 1120; 11200) or is less than the diameter of the wire (112; 1120; 11200).Claim 7: The stimulation device (1 ; 10; 100) of claim 5, wherein neighboring windings of the plurality of windings contact each other.Claim 8: The stimulation device (1 ; 10; 100) of any one of claims 5 or 7, wherein all windings of the plurality of windings comprise an identical winding diameter.Claim 9: The stimulation device (1 ; 10; 100) of any one of claims 5 to 8, wherein the plurality of windings is arranged along a winding direction (113) and wherein the plurality of windings comprises between about ten windings per cm winding direction (113) and about thirty windings per cm winding direction (113), or about twenty windings per cm winding direction (113).Claim 10: The stimulation device (1 ; 10; 100) of any one of the preceding claims, wherein the ferromagnetic core (111 ; 1110) has an open face (115; 1150) not covered by the wire (112; 1120) wound around the ferromagnetic core (111 ; 1110).Claim 11 : The stimulation device (1 ; 10) of claim 10, wherein the open face (115;1150) of the ferromagnetic core (111 ; 1110) of the coil unit (11 ; 110; 1100) is configured to concentrate a magnetic flux density.Claim 12: The stimulation device (1 ; 10) of claim 10, wherein the coil unit (11 ; 110) comprises a flux head (130) configured to concentrate a magnetic flux density and wherein the flux head (130) is magnetically coupled to the open face (115; 1150) of the ferromagnetic core (111 ; 1110).Claim 13: The stimulation device (1 ; 10) of claim 12, wherein the flux head (130) of the coil unit (11 ; 110) comprises a ferromagnetic material.Claim 14: The stimulation device (1 ; 10) of claim 12 or 13, wherein the flux head(130) is mechanically decoupled from the ferromagnetic core (111 ; 1110) such that it is displaceable relative to the ferromagnetic core (111 ; 1110).Claim 15: The stimulation device (1 ; 10) of any one of claims 12 to 14, comprising an adaptation module configured to detect a feedback signal representing stimulation of the Phrenic nerve (22; 220) and to re-arrange the coil unit (11 ; 110) when the detected signal represents a stimulation below a predefined threshold.Claim 16: The stimulation device (1 ; 10) of any one of claims 10 to 15, wherein the open face (115; 1150) of the ferromagnetic core (111 ; 1110) of the coil unit (11 ; 110) and the wire (112; 1120) of the coil unit (11 ; 110) are displaceable relative to each other.Claim 17: The stimulation device (1 ; 10) of claim 15 and 16, wherein the adaptation module is configured to re-arrange the coil unit (11 ; 110) by displacing the open face (115; 1150) of the ferromagnetic core and wire (112; 1120) relative to each other.Claim 18: The stimulation device (1 ; 10) of any one of claims 12 to 16, wherein the flux head (130) and the wire (112; 1120) are displaceable relative to each other.Claim 19: The stimulation device (1 ; 10) of claim 16 and 18, wherein the adaptation module is configured to re-arrange the coil unit (11 ; 110) by displacing the flux head (130) and the wire (112; 1120) relative to each other.Claim 20: The stimulation device (100) of any one of the preceding claims, wherein the ferromagnetic core (11100) comprises a first open face (11501 ) and a second open face (11502), wherein the wire (11200) is wound around the ferromagnetic core (11100) between the first and the second open faces (11501 , 11502), and wherein each of the first and the second open faces (11501 , 11502) is arranged in a half-space (1101 ) of the ferromagnetic core (11000) facing the body of the patient in use of the device (100).Claim 21 : The stimulation device (100) of claim 20, wherein in use of the device(100) at least a portion of the magnetic field generated by the coil unit (1100) leaves the ferromagnetic core (11100) at one of the first and the second open faces (11501 , 11502) and re-enters the ferromagnetic core (11100) at the respective other one of the first and the second open faces (11501 , 11502).Claim 22: The stimulation device (100) of any of claim 20 or 21 , further comprising a diamagnetic material arranged between the first and the second open faces (11501 , 11502) to guide a magnetic flux density further towards the body of the patient and reduce leakage between the first and the second open faces (11501 , 11502).Claim 23: The stimulation device (100) of claim 22, wherein the diamagnetic material is Bismuth.Claim 24: The stimulation device (100) of any one of claims 20 to 23, wherein at least one of the first open face (11501 ) and the second open face (11502) is tapered.Claim 25: The stimulation device (100) of any one of claims 20 to 24, wherein the first open face (11501 ) has at least a first surface (11511 ), and the second open face (11502) has at least a second surface (11522), wherein each of the first and the second surfaces (11511 , 11522) preferably point into the half-space (1101 ) of the ferromagnetic core (11000) facing the body of the patient in use of the device (100).Claim 26: The stimulation device (100) of claim 25, wherein at least one of the first surface (11511 ) and the second surface (11522) is planar or curved.Claim 27: The stimulation device (100) of claim 25 or 26, wherein the first and the second surfaces (11511 , 11522) face each other; or wherein the first and the second surfaces (11511 , 11522) are parallel to each other.Claim 28: The stimulation device (100) of any one of claims 20 to 27, wherein the first and the second open faces (11501 , 11502) point towards each other or point away from each other or point in the same direction.Claim 29: The stimulation device (1 ; 10; 100) of claim 20 to 28, wherein a minimum distance between the first and the second open faces (11501 , 11502) , in particular between the first and the second surfaces (11511 , 11522), is at most 150 mm, in particular at most 125 mm, more particularly at most 100 mm, preferably at most75 mm or at most 50 mm or at most 25 mm or at most 20 mm or at most 10 mm or at most 5 mm.Claim 30: The stimulation device (1 ; 10; 100) of any one of the preceding claims, wherein the ferromagnetic core (111 ; 1110; 11100) comprises a non-straight portion or is non-straight, in particular comprises a curved portion or is curved.Claim 31 : The stimulation device (1 ; 10; 100) of any one of the preceding claims, wherein the ferromagnetic core (111 ; 1110; 11100) has a bracket-shape, in particular a C-shape or a U-shape or a partial ring shape, such as a semi-ring shape or a semi-circular ring shape, or horseshoe shape.Claim 32: The stimulation device (1 ; 10; 100) of any one of claims 5 to 31 , wherein a filling factor of an outer cross-section of the ferromagnetic core (111 ; 1110; 11100) filling an inner cross-section of the one or the plurality of windings is in a range between 0.1 and 1 .0, in particular between 0.2 and 0.7 or between 0.5 and 1 .0, more particularly between 0.3 and 0.5 or between 0.8 and 1 .0.Claim 33: The stimulation device (1 ; 10; 100) of any one of claims 5 to 32, wherein the windings of the plurality of windings are distributed, preferably evenly distributed, along a length extension of the ferromagnetic core (111 ; 1110; 11100), in particular wherein the plurality of windings extends from the first open face to the second open face or wherein at least a portion of the first open face and / or at least a portion of the second open face extend beyond the windings.Claim 34: The stimulation device (1 ; 10; 100) of any one of the preceding claims, wherein the holder (12; 120) is configured to be arranged around a neck of the body of the patient (2; 20) such that the coil unit (11 ; 110; 1100) is arranged to generate the magnetic field (3; 30) at the neck of the body of the patient (2; 20).Claim 35: The stimulation device (1 ; 10; 100) of any one of the preceding claims, comprising a power source.Claim 36: The stimulation device (1 ; 10; 100) of claim 35, wherein the power source is configured to provide electric current in a range of about 2 Ampere to about 10Ampere or in a range of about 3 Ampere to about 7 Ampere to the coil unit (11 ; 110; 1100); or wherein the power source is configured to provide electric current in a range of about 10 Ampere to about 1000 Ampere or in a range of about 100 Ampere to about 3000 Ampere or in a range of about 100 Ampere to about 5000 Ampere to the coil unit (11 ; 110; 1100).Claim 37: The stimulation device (1 ; 10; 100) of claim 35 or 36, wherein the power source is configured to provide a voltage in a range of about 2 Volt to about 10 Volt or in a range of about 3 Volt to about 7 Volt to the coil unit (11 ; 110; 1100); or wherein the power source is configured to provide a voltage in a range of about 10 Volt to about 100 Volt or in a range of about 100 Volt to about 1000 Volt or in a range of about 100 Volt to about 5000 Volt to the coil unit (11 ; 110; 1100).Claim 38: The stimulation device (1 ; 10; 100) of any one of the preceding claims, comprising a circuit having a capacitance and an inductance, wherein the inductance is formed by the coil unit (11 ; 110; 1100) and the circuit is configured to charge the inductance by means of a current provided through the circuit.Claim 39: The stimulation device (1 ; 10; 100) of claim 38, wherein the circuit is configured to repeatedly switch-off charging the inductance.Claim 40: The stimulation device (1 ; 10; 100) of claim 39, wherein the circuit is configured to switch-off charging the inductance at a frequency of between 15 Hertz and 100 Hertz, of between 20 Hertz and 30 Hertz, or of 25 Hertz.Claim 41 : The stimulation device (1 ; 10; 100) of claim 38or 40, wherein the circuit is configured to charge the capacitance through electromagnetic induction when charging the inductance is switched-off.Claim 42: The stimulation device (1 ; 10; 100) of claim 41 , wherein the circuit is configured to repeatedly convert electric charge within the capacitance to current within the inductance.Claim 43: The stimulation device (1 ; 10; 100) of claim 38, wherein the circuit is configured to charge the capacitance by means of voltage provided through the circuit.Claim 44: The stimulation device (1 ; 10; 100) of any one of the preceding claims, comprising a second coil unit (11 ; 110; 1100) essentially identical to the coil unit (11 ; 110; 1100).Claim 45: A method of stimulating a Phrenic nerve (22; 220) of a patient (2; 20), comprising the steps of: obtaining a coil unit (11 ; 110; 1100) comprising a ferromagnetic core (111 ; 1110; 11000) and a wire (112; 1120; 11200) wound around the ferromagnetic core (111 ; 1110; 11000); positioning the coil unit (11 ; 110; 1100) at a target surface of the body close to the Phrenic nerve (22; 220); and operating the coil unit (11 ; 110; 1100) by providing electric current through the wire (112; 1120; 11200) of the coil unit (11 ; 110; 1100) such that the coil unit (11 ; 110; 1100) generates a magnetic field (3; 30) and stimulates the Phrenic nerve (22; 220).Claim 46: The method of claim 45, comprising adapting the magnetic field (3; 30) generated by the coil unit (11 ; 110; 1100); verifying a response of the body to generation of the magnetic field (3; 30); and stopping adaptation of the magnetic field (3; 30) when the response of the body is appropriate.Claim 47: The method of claim 45 or 46, wherein operating the coil unit (11 ; 110;1100) by providing electric current through the wire (112; 1120; 11200) of the coil unit (11 ; 110; 1100) comprises provision of the electric current in a range of about 2 Ampere to about 10 Ampere or in a range of about 3 Ampere to about 7 Ampere; or wherein operating the coil unit (11 ; 110; 1100) by providing electric current through the wire (112; 1120; 11200) of the coil unit (11 ; 110; 1 100) comprises provision of the electric current in a range of about 10 Ampere to about 1000 Ampere or in a range of about 100 Ampere to about 3000 Ampere or in a range of about 100 Ampere to about 5000 Ampere.Claim 48: The method of any one of claims 45 to 47, wherein operating the coil unit(11 ; 110; 1100) by providing electric current through the wire (112; 1120; 11200) of the coil unit (11 ; 110; 1100) comprises provision of a voltage in a range of about 2 Volt to about 10 Volt or in a range of about 3 Volt to about 7 Volt; or wherein operating the coil unit (11 ; 110; 1100) by providing electric current through the wire (112; 1120; 11200) of the coil unit (11 ; 110; 1100) comprises provision of a voltage in a range of about 10 Volt to about 100 Volt or in a range of about 100 Volt to about 1000 Volt or in a range of about 100 Volt to about 5000 Volt.Claim 49: The method of any one of claims 45 to 48, wherein operating the coil unit(11 ; 110; 1100) by providing electric current through the wire (112; 1120; 11200) of the coil unit (11 ; 110; 1100) comprises charging the ferromagnetic core (111 ; 1110; 11000) and the wire (112; 1120; 11200).Claim 50: The method of claim 49, wherein operating the coil unit (1 1 ; 1 10; 1100) by providing electric current through the wire (112; 1120; 11200) of the coil unit (11 ; 110; 1100) comprises repeatedly switching-off charging the ferromagnetic core (111 ; 1110; 11000) and the wire (112; 1120; 11200).Claim 51 : The method of claim 50, wherein charging the ferromagnetic core (1 11 ;1110; 11000) and the wire (112; 1120; 11200) is switched-off at a frequency of between 15 Hertz and 100 Hertz, of between 20 Hertz and 30 Hertz, or of 25 Hertz.Claim 52: The method of claim 50 or 51 , wherein the capacitance is charged through electromagnetic induction when charging the inductance is switched-off.Claim 53: The method of claim 50 or 51 , wherein the capacitance is charged by providing a voltage.Claim 54: The method of claim 52 or 53, wherein the electric charge within the capacitance is repeatedly converted to current within the inductance.Claim 55: The method of any one of claims 45 to 54, comprising obtaining a second coil unit (11 ; 110; 1100) essentially identical to the coil unit (11 ; 110; 1100);positioning the second coil unit (11 ; 110; 1100) at a second target surface of the body close to a second Phrenic nerve (22; 220) of the patient (2; 20); and operating the coil unit (11 ; 110; 1100) by providing electric current through a wire (112; 1120; 11200) of the second coil unit (11 ; 110) such that the second coil unit (11 ; 110; 1100) generates a second magnetic field (3; 30) and stimulates the second Phrenic nerve (22; 220).Claim 56: The method of any one of claims 45 to 55, wherein a stimulation device(1 ; 10; 100) of any one of claim 1 to 30 is used.

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