Displacement sensor, sensor belt, and sensor belt system

Abstract

A displacement sensor comprising: a base having a fixed input mount; a displacement arm having a fixed end for fixing the displacement arm to the base; and a free end, the free end having a displaceable input mount aligned with the fixed input mount, the displacement arm having one degree of freedom along a displacement axis perpendicular to the displacement arm, allowing substantially linear translation of the free end of the displacement arm along the displacement axis; and a sensor configured to determine the displacement of the free end of the displacement arm along the displacement axis. The displacement sensor may be part of a sensor belt, for example, a sensor belt for monitoring the state of a human object such as respiratory status. The sensor belt may be part of a sensor belt system.

Description

Background Art

[0001] The health state of a human subject, particularly the respiratory state, is currently evaluated using methods such as spirometry and end-tidal carbon dioxide measurement. In the case of a subject in a specific clinical situation such as after surgery and / or intensive care, the respiratory state is mainly monitored through pulse oximetry, that is, by measuring the peripheral arterial oxygen saturation (SpO2) using a pulse oximeter probe adapted to the earlobe or fingertip.

[0002] These monitoring techniques are associated with certain drawbacks and limitations. For example, end-tidal carbon dioxide can be useful for monitoring anesthetized or ventilated subjects, but is somewhat inaccurate when used for non-ventilated subjects. Spirometry, such as the use of a spirometer, is somewhat unreliable in that the results substantially depend on the effort made by the subject during the test and thus on other highly variable factors such as instructions that the subject can receive, understand, or follow while performing the measurement. The measurement of peripheral arterial oxygen saturation is relatively accurate and reproducible. However, a decrease in oxygen saturation is a marker that appears only at a rather late stage in the cascade of events frequently associated with the occurrence of life-threatening respiratory problems, which limits the possibility of applying effective therapeutic interventions with low side effects to the subject.

[0003] Therefore, there is a need for techniques and means for monitoring the respiratory state of a subject such that the occurrence of respiratory deterioration is detected earlier and more reliably than is currently possible. Furthermore, there is a need for improved means for monitoring the respiratory state of a human subject with high sensitivity. These and other needs are addressed by various aspects and embodiments of the present disclosure as described below.

Summary of the Invention

[0004] A sensor belt is provided which is adapted to sense signals characterizing one or more respiratory parameters of an object that is a human being performing at least one respiratory operation. The sensor belt includes (a) a band having longitudinal dimensions adapted to surround the chest of the object, the band being intrinsically inelastic. The belt further includes (b) fastening means for fastening the band around the chest of the object by directly or indirectly connecting a first position of the band to a second position of the band, and (c) a sensing device attached to the band, which is referred to herein as the first sensing device, the first sensing device being adapted to acquire and transmit signals characterizing one or more respiratory parameters of the object, including tidal volume (Vt), inspiratory time (Ti), expiratory time (Te), total cycle time (Ttot), respiratory rate (RR), and / or work of breathing (WoB). The first sensing device is capable of sensing forces acting on the band, the force being further characterized in that it arises from the expansion of the object's chest caused by the object's respiratory operation.

[0005] Optionally, the sensor belt may include a second sensing device adapted to sense the electrical activity of one or more muscles involved in the subject's respiratory operation.

[0006] In another aspect, the disclosure provides the use of a sensor belt, such as for use in acquiring and transmitting signals characterizing one or more respiratory parameters selected from Vt, Ti, Te, Ttot, RR, WoB, and / or any derived parameters thereof, and / or signals characterizing the electrical activity of one or more muscles involved in the respiratory operation of the subject.

[0007] In yet another embodiment, a method is provided that includes the use of a sensor belt.

[0008] In a first sensing device for a sensor belt, the Disclosure provides a displacement sensor comprising: a base having a fixed input mount; a displacement arm having a fixed end for fixing the displacement arm to the base; a free end having a displaceable input mount aligned with the fixed input mount, the displacement arm having one degree of freedom along a displacement axis perpendicular to the displacement arm, and allowing substantially linear translation of the free end of the displacement arm along the displacement axis; and a sensor configured to determine the displacement of the free end of the displacement arm along the displacement axis.

[0009] In a further embodiment of the sensor belt, the sensor belt comprises a displacement sensor, further comprising a band, one end of which is fastened to a fixed input mount of the displacement sensor and the other end of which is fastened to a displaceable input mount, wherein the band is configured to transmit forces acting on the band to the displaceable input mount, thereby translating the free end of a displacement arm along the displacement axis. Preferably, according to this embodiment, the sensor belt comprises a displacement sensor configured to determine the displacement of the free end of a displacement arm along the displacement axis from forces acting on the band, which are converted to a displaceable input mount.

[0010] In a further embodiment of the sensor belt, a sensor belt for monitoring a subject's respiration comprises a displacement sensor, the sensor belt further comprising a band configured to be applied around the subject's chest, one end of which is fastened to a fixed input mount of the displacement sensor and the other end of which is fastened to a displaceable input mount, and when the subject breathes, the band is configured to transmit force from the expansion of the subject's chest to the displaceable input mount, causing the free end of the displacement arm to translate along the displacement axis. Preferably, according to this embodiment, the sensor belt for monitoring respiration comprises a displacement sensor configured to determine the displacement of the free end of the displacement arm along the displacement axis from the force acting on the band, which is converted into a displaceable input mount.

[0011] In a further embodiment, the sensor belt system comprises a sensor belt, and the sensor belt system further comprises a processor connected to a displacement sensor, and a power supply connected to the displacement sensor. Preferably, according to this embodiment, the sensor belt system comprises a processor configured to determine one or more respiratory parameters based on the outputs of the displacement sensor and / or electrical sensor.

[0012] Further embodiments and features are disclosed in the detailed description, drawings, and claims. [Brief explanation of the drawing]

[0013] [Figure 1] This is a simplified diagram of a human subject wearing a sensor belt fastened around their chest. [Figure 2] This depicts a portion of a sensor belt band, including fastening means and a pretensioner. [Figure 3] An example of a first sensing device in a specific form is shown. [Figure 4] A portion of a sensor belt band in another embodiment, including fastening means and pretensioners, is depicted, and an EMG sensor is also shown as part of an example of a second sensing device. [Figure 5A] This describes an embodiment of a first sensing device as an exemplary displacement sensor. [Figure 5B] This describes an embodiment of a first sensing device as an exemplary displacement sensor. [Figure 5C] This describes an embodiment of a first sensing device as an exemplary displacement sensor. [Figure 6A] This illustrates an example of a displacement sensor. [Figure 6B] This illustrates an example of a displacement sensor. [Figure 7A] This illustrates an example of a displacement sensor. [Figure 7B] This illustrates an example of a displacement sensor. [Figure 8A] This illustrates an example of a displacement sensor. [Figure 8B]Describes an example of a displacement sensor. [Figure 9] Describes an example of one or more planar coils. [Figure 10] Describes an example of an aspect of a sensor that is a displacement sensor. [Figure 11A] Describes an example of a displacement sensor. [Figure 11B] Describes an example of a displacement sensor. [Figure 12] Describes an example of an aspect of a sensor that is a displacement sensor. [Figure 13] Describes an exemplary strain gauge. [Figure 14] Is a diagram of an exemplary bridge circuit. [Figure 15] Describes a sensor belt system.

[0014] None of the figures presented in this specification are drawn to scale.

Mode for Carrying Out the Invention

[0015] In a first aspect, a sensor belt is provided. The sensor belt is adapted to sense a signal characterizing one or more respiratory parameters of a subject, who is a human performing at least one respiratory operation. The belt includes (a) a band having a longitudinal dimension adapted to surround the chest of the subject, the band being substantially inelastic. The belt further includes (b) fastening means for directly or indirectly connecting a first position of the band to a second position of the band to fasten the band around the chest of the subject, and (c) a sensing device attached to the band, referred to herein as a first sensing device, the first sensing device being adapted to acquire and transmit a signal characterizing one or more respiratory parameters of the subject, including tidal volume (Vt), inspiratory time (Ti), expiratory time (Te), total cycle time (Ttot), respiratory rate (RR), and / or work of breathing (WoB). The first sensing device is further characterized in that it can sense a force acting on the band, said force resulting from the expansion of the chest of the subject caused by the respiratory operation of the subject.

[0016] The sensor belt provided herein enables a very accurate assessment of the health status of a human subject, particularly of the lung function and / or respiratory function of the subject, and enables the very early detection of any deterioration of the respiratory system of the patient, as will be described in more detail below.

[0017] The belt comprises a sufficiently long band so as to be worn around the chest of a human subject. Typically, the band is flexible so as to be able to take the shape around the chest. Further, the band is substantially inelastic by virtue of its material, its structure and / or its dimensions. This enables a more accurate measurement of the mechanical force applied by the subject during the inspiration phase of the respiratory operation through which the chest expands, unlike an elastic sensor belt. Due to the substantial lack of elasticity of the band, said mechanical force can be selectively measured by a first sensing device adapted to sense such a force acting on the band.

[0018] In this regard, essentially inelastic means that the length of the band does not increase significantly when the belt is tightened around the chest of a human subject during a breathing operation. In some embodiments, the increase in the length of the band between a first position and a second position during a breathing operation is about 5% or less, with the percentage being based on the resting length of the band between the first and second positions. In some preferred embodiments, the increase in length is about 3% or less, or about 2% or less, or about 1% or less, respectively. Some embodiments are also preferred in which the increase in length between the first and second positions is about 3 cm or less, about 2 cm or less, or about 1 cm or less, as measured as described above. This does not preclude the possibility of bands that are more stretchable when subjected to higher tensile forces than those that occur when the band, as part of a belt as described herein, is fastened around the chest of a human subject performing a breathing operation.

[0019] Potentially suitable band materials are generally known to those skilled in the art. For example, woven polyester fibers, such as those used in car or aircraft safety belts, can be used.

[0020] The band may have any suitable width in the range of, for example, about 20 to about 100 mm. In other embodiments, the widths are about 30 to about 80 mm, or it is about 40, 45, 50, 55, 60, 65, or 70 mm. With respect to the band width, the expression "about" preferably means ±5 mm.

[0021] The band thickness can be selected while paying attention to the band material and its structure. For some useful band materials, thicknesses in the range of approximately 0.5 to 3 mm are considered useful. Further examples of potentially useful thicknesses are approximately 1 mm, 1.2 mm, 1.4 mm, 1.6 mm, 1.8 mm, or 2 mm, respectively. Regarding band thickness, the expression "approximately" should preferably be understood as ±0.2 mm.

[0022] As described above, the belt includes fastening means for directly or indirectly connecting a first position of the band to a second position of the band, so that the band can be fastened around the chest of a human subject. In some embodiments, the first or second position is at or near one end of the band, and the other position is at or near the other end of the band. Thus, the length of the band from the first to the second is sufficient to cover a large portion (e.g., about 60% or more, or about 70% or more) of the circumference of the chest to which the belt is fastened.

[0023] The fastening means may be attached, for example, directly to a first position at the first end of the band, or indirectly to a first sensing device via one or more members near or at the opposite end, or vice versa.

[0024] Any suitable type of fastening means can be used, including any combination of different types of fastening means. For example, the fastening means may comprise a tongue member attached to the band and a buckle member integrated into a housing that also holds the first sensing device.

[0025] As described above, the first sensing device is adapted to acquire and transmit signals characterizing one or more respiratory parameters of the subject. In particular, the sensing device is adapted to be able to sense a force acting on the band, the force arising from the expansion of the subject's chest caused by the subject's respiratory operation. Such a force typically acts on the band longitudinally with respect to the band's orientation.

[0026] Respiratory parameters may be at least one of the following: tidal volume (Vt), inspiratory time (Ti), expiratory time (Te), total cycle time (Ttot), respiratory rate (RR), and / or work of breathing (WoB). As used herein, Vt is understood as the amount of air entering and leaving the lungs of a subject with each respiratory operation when breathing normally, i.e., when no effort is being made, such as deep breathing. Ti is preferably understood as the time interval between respiratory operations from the start of inspiratory airflow to the start of expiratory airflow. The primary period of inspiratory time is the time of actual positive airflow to the lungs, typically followed by a very short inspiratory pause with no airflow, which forms the second phase of Ti. Similarly, Te is preferably understood as the time interval between respiratory operations from the start of expiratory airflow to the start of inspiratory airflow, and includes a short expiratory pause with no airflow after the expiratory airflow time. Ttot should be interpreted as the total time of a breathing operation, measured, for example, from the start of the exhaled airflow of a given breathing operation to the start of the inspiratory airflow of a subsequent breathing operation. RR refers to the number of breathing operations per minute. Work of breathing, or WoB, sometimes called the work of breathing, should preferably be understood as the energy required for the subject's respiratory activity, i.e., the energy required to inhale and exhale air or respiratory gases, in the case of a human subject not on a ventilator. WoB can be expressed as work per unit volume, such as joules / liter, or as power, for example, joules / minute.

[0027] In some preferred embodiments, the signal obtained by the first sensing device relates to a combination of respiratory parameters. In some cases, after appropriate calibration, the same raw signal obtained by the sensing device can be used to derive or characterize two or more respiratory parameters. In some preferred embodiments, the first sensing device is adapted to obtain a signal characterizing WoB, as well as at least one further parameter selected from Vt, Ti, Te, Ttot, and RR. Such signals may be generated in response to force, deflection, motion, or changes in any of these over time.

[0028] In some further embodiments, the first sensing device comprises a member that becomes movable or deformable by a force acting on the band as a result of the expansion of the subject's chest when the subject performs a breathing operation. In this context, the expression “movable or deformable” should be interpreted as movable and / or deformable. In other words, each member can be both movable and deformable simultaneously by force. For the movable or deformable member to respond to force, it is positioned between a first position and a second position of the band. More specifically, the movable or deformable member has a first end fixed to the first position of the band and a second end fixed to the second position of the band. In this context, the fasteners may be direct or indirect. In other words, the first and second positions are connected by a substantially inelastic band and via the movable or deformable member of the first sensing device, forming a belt that can be fastened, for example, around the subject's chest, in which case the movable or deformable member moves or deforms in response to the expansion of the chest during a breathing operation. Preferably, the movement or deformation of a movable or deformable member is reversed during the exhalation phase of the subject's breathing operation.

[0029] In a more preferred embodiment, the first sensing device comprises a housing for holding or housing a movable or deformable member. For example, it can hold a movable or deformable member such that one end thereof, for example, either a first or a second end, is fixedly attached to the housing, and the other end is movable relative to the housing. By example, the first position of the band, the first end of the movable or deformable member, and the housing of the first sensing device may all be fixed to each other, while the second position of the band may be fixed to the second end of the movable or deformable member but movable relative to the housing.

[0030] Optionally, a movable or deformable member is completely enclosed by a housing, and as a result, the position of the band, which is movable relative to the housing, is at least partially insertable into the housing, for example, through an opening provided in the housing. Such an opening may be shaped and sized to provide a guide for the insertable portion of the band and to restrict or avoid lateral movement of the band. Optionally, a guide member may be placed inside the housing to further restrict or avoid lateral movement of the insertable portion of the band.

[0031] In some embodiments, the movable or deformable member is or includes a spring, such as a disc spring, helical spring, compression spring, torsion spring, gas spring, or leaf spring. Optionally, two or more springs of the same or different types may be combined with the movable or deformable member. The springs can be made of any suitable material, such as metal, polymer, or composite material such as fiber-reinforced composites.

[0032] In some more preferred embodiments, the movable or deformable member is or includes a leaf spring. In some preferred versions of the leaf spring, there are at least two leaves, in particular two metal leaves. In a further embodiment, the movable or deformable member is a leaf spring comprising two stainless steel leaves.

[0033] Furthermore, the movable or deformable member may be a leaf spring comprising two or more metal (such as stainless steel) leaves mounted together to form a four-bar link. As used herein, a four-bar link is a closed movable link comprising four members, sometimes called bars or links, connected in a loop by four joints. In the context of this embodiment, the joints are preferably configured such that the links move in parallel planes, thereby forming a four-bar link in the plane. Two of the four links or bars may be represented by two leaves of a leaf spring, with the other two being auxiliary links. This type of assembly is advantageous in that it prevents or minimizes lateral movement of the leaves.

[0034] Furthermore, the first sensing device preferably comprises a transducer adapted to generate an electrical signal in response to the movement or deformation of a movable or deformable member. A transducer is generally understood as a device capable of converting a signal of one form of energy into a signal of another form. For example, in this context, the transducer may be adapted to convert a mechanical signal based on the movement and / or deformation of a leaf spring into an electrical signal, which can then be transmitted and processed.

[0035] In some preferred embodiments, the transducer is adapted to generate an electrical signal without friction with a movable or deformable member. Such an arrangement has the advantage of reducing noise associated with the electrical signal generated by the transducer. In some embodiments, electricity is generated without direct contact between the transducer and the movable or deformable member.

[0036] This can be achieved, for example, by a non-contact transducer device having an inductive sensor comprising at least one coil, each coil consisting of a helical conductor arranged on a plane and having two flat surfaces, one of which forms a measuring surface that covers a sample in various ways, and is positioned at a certain distance according to movement parallel to the measuring surface. Furthermore, the sensor electronics system supplies an alternating current to the inductive sensor and evaluates the change in the alternating current caused by the sample. The sample is induced at a constant distance across the surface of the flat coil. The sensor electronics system of this device is formed to detect the change in attenuation caused by the fluctuating region of the flat coil covered by the sample. Furthermore, the sample affecting the measuring surface is conductive, or the sample has a conductive target or measuring collar and covers a coil region of the flat coil that can be geometrically predetermined depending on the position of the target or measuring collar. The device is further characterized in that the rectangular measuring surface is diagonally divided into two triangular flat coils, thereby their inductance and ohmic resistance forming half of a bridge circuit, and the other half is complemented by resistors to produce a full bridge.

[0037] A potentially useful alternative type of transducer in the first sensing device is based on one or more strain gauges attached to a movable or deformable member. In some embodiments, the movable or deformable member is a leaf spring, such as a spring with two or more metal leaves, or a leaf spring, where at least one of the leaves is fitted with at least one strain gauge. Although the strain gauges are not non-contact, they function without generating undesirable friction. Furthermore, they primarily respond to the deformation of the component to which they are attached, such as the leaf spring.

[0038] In certain embodiments, two or more strain gauges are mounted on the surface of a movable or deformable member, such as the surface of a metal leaf contained in a leaf spring. In particular, the strain gauges should be positioned or fixed in response to longitudinal deformation of the leaf. In this regard, the longitudinal direction is the same as the longitudinal direction of the band, and is the same direction in which the forces resulting from the expansion of the chest of the object caused by the breathing motion act on the movable or deformable member.

[0039] When one or more strain gauges are used as transducers to generate electrical signals in response to the mechanical deformation of one or more metal leaves, they may also be arranged in a double-bent beam configuration. In such an assembly, two spring elements (i.e., leaves or beams) are coupled via a rigid element. The strain gauges may be mounted on at least one surface of the leaf at a location of maximum strain, optionally, and more preferably at a location that does not exceed the maximum strain of the strain gauge.

[0040] In some more preferred embodiments, the first sensing device comprises a transmitter adapted to transmit an electrical signal generated by a transducer via wire or wirelessly. The signal may be transmitted directly or after initial signal processing, i.e., by amplification or filtering, which may be performed by further electronic elements arranged as part of the sensing device, for example, inside an optional housing.

[0041] Signal transmission may typically occur from the sensing device to an external control unit, which is not part of the sensor belt, as claimed herein. Alternatively, the control unit may actually be integrated into the sensor belt. For example, it may be integrated inside the housing of the first sensing device. The control unit may comprise a central processing unit and other electronic devices necessary to perform further signal processing, such as calculating the aforementioned respiration parameters, or any parameters derived therefrom. The control unit may further comprise, or be associated with, a display for displaying one or more parameters, their changes over time, or messages relating to the state of the object or the function of the sensor belt.

[0042] In some embodiments, the first sensing device may be positioned as part of a belt to bridge or connect the first and second positions. In related embodiments, fastening means are configured to connect the first position to the second position via the first sensing device. The fastening means may be associated with the housing of the first sensing device or may be integrated inside the housing of the first sensing device.

[0043] In some preferred embodiments, for example, the housing of the first sensing device comprises a first end fixed to a first position of the band and together with the first end of a movable or deformable member, and a second end movable to a second position of the band and the second end of the movable or deformable member. The second position of the band may be connectable to the second end of the movable or deformable member, for example, by fastening means or members thereof. For example, a tongue-shaped member may be attached to the band at its second position, and a buckle member may be attached to the second end of the movable or deformable member, and the tongue-shaped member and the buckle are rigid but reversibly connectable.

[0044] In some embodiments, the buckle member is secured to a movable or deformable member via a portion of an inelastic band. In other words, the band may be interrupted by the fastening means.

[0045] In some more preferred embodiments, the sensor belt includes a pretensioner for adjusting the longitudinal extension of the band around the chest of the subject. The pretensioner may be a simple manually adjustable means for pre-adjusting the effective length of the band, such as a slide like a webbing buckle slide.

[0046] Powering the first sensing device can be achieved, for example, by connecting the sensing device to an external power source using a suitable power cord. Alternatively, according to some preferred embodiments, the sensor belt is configured to house an internal power source. For example, the sensor belt may include a battery holder. Such a battery holder may be advantageously located in a housing that also holds a movable or deformable member, i.e., the housing of the first sensing device.

[0047] In certain further embodiments, the sensor belt preferably comprises a second sensing device adapted to sense the electrical activity of one or more muscles involved in the subject's respiratory operation. This further sensing device preferably comprises at least one electronic amplifier and at least three skin electrodes configured to perform surface electromyography (EMG). The electrodes are connected to the amplifier by wires dimensioned to allow the electrodes to be positioned on the subject's skin independently of the band, i.e., independently of the precise position of the chest band. The amplifier may optionally be located in the housing of the first sensing device.

[0048] Electromyography (EMG) involves detecting the electrical potentials generated by muscle cells when they are electrically or neurologically activated. EMG can be performed using needle sensors, but in the context of this embodiment, the use of skin electrodes or surface electrodes is preferred.

[0049] A sensor belt further equipped with a second sensing device is particularly advantageous because it allows for the simultaneous analysis and correlation of respiratory parameters derived from mechanical signals obtained via the first sensing device with electrical signals from the muscles involved in respiration, which reflect the degree of physiological stimulation required to generate the respiratory parameters. Such analysis and correlation has been shown to enable a more accurate assessment of the health status of a human subject, particularly the state of the respiratory system. Furthermore, the inventors have found that this also enables earlier detection of deterioration in health status compared to conventional monitoring techniques.

[0050] In this regard, human subjects may preferably be patients receiving postoperative care and / or intensive care. In particular, subjects may be patients at risk of developing pulmonary complications, such as postoperative pulmonary complications. As used herein, "at risk" should be understood as a higher risk compared to healthy human subjects.

[0051] In further embodiments, the disclosure relates to the use of a sensor belt for monitoring an object. More specifically, the sensor belt described above can be used to acquire and transmit signals characterizing one or more respiratory parameters of an object that is a human. In particular, the respiratory parameters can be selected from Vt, Ti, Te, Ttot, RR, WoB, and / or derived parameters of any of these. Furthermore, some preferred embodiments relate to the use of a sensor belt comprising a second sensing device, such as those disclosed above, for acquiring and transmitting signals relating to electromuscular activity, particularly the electromuscular activity of one or more muscles involved in respiration.

[0052] In yet another aspect, the disclosure relates to a method for evaluating signals generated by a sensor belt. Such a method includes, continuously and simultaneously, (i) receiving from a first and / or second sensing device, and (ii) processing a plurality of signals characterizing one or more respiratory parameters selected from Vt, Ti, Te, Ttot, RR, WoB, and / or electromuscular activity. In other words, while the signals are continuously received from the first and / or second sensing device, they are processed simultaneously. The processing includes calculating one or more statistical variability measures of Vt, Ti, WoB, electromuscular activity, or any ratio thereof. As used herein, continuous processing should be broadly interpreted to include persistent and repetitive or iterative processing, such as when a particular calculation step is repeated at a particular time interval, for example, every second or every five seconds.

[0053] The period during which the continuous and simultaneous reception and processing of signals occur can be selected by focusing on the specific circumstances. Typically, the period is at least about 1 minute. For example, the period may be set in the range of about 1 minute to about 14 days. In some more preferred embodiments, the period is about 1 hour to about 7 days. If the method is performed during postoperative and / or intensive care, the period during which the method is performed may essentially encompass the period during which the subject receives postoperative and / or intensive care. Alternatively, the period during which the method is performed may extend to at least about 50%, 60%, 70%, 80%, or 90% of the postoperative and / or intensive care period.

[0054] In some embodiments, the continuous processing of signals received from a first sensing device includes the continuous calculation of a variability scale, such as Vt and / or the ratio Vt / Ti, e.g., the coefficient of variation. Optionally, the method further includes the step of continuously displaying the variability scale on an electronic display, e.g., in numerical form or in the form of a graph depicting the variability scale over time.

[0055] In a more preferred embodiment, the continuous processing of the signal includes performing one or more Fast Fourier Transforms (FFTs) on the signal received from the first sensing device. Preferably, this may further include the continuous calculation of a correlation scale indicating the degree of correlation between the FFT-transformed signal and a previously acquired and FFT-transformed reference signal. The results of the continuous calculation can be displayed on a display in real time or with minimal delay. The inventors have found that this use of FFT can significantly improve the ability of a notified observer to recognize that the condition of the subject being monitored, which is a human being, has begun to deteriorate, compared to conventional monitoring techniques.

[0056] In a more preferred embodiment, the continuous processing includes calculating at least one ratio of respiratory parameters to parameters describing the electrical activity from signals received from a first sensing device and signals received from a second sensing device. For example, a particularly relevant ratio reflecting the state of the monitored subject may be the ratio of WoB calculated from signals obtained from the first sensing device to parameters describing the electrical activity of one or more muscles involved in respiration based on signals obtained from the second sensing device, or vice versa. The inventors have found that such ratios are particularly sensitive in evaluating the state of a human subject or in the early detection of changes in state.

[0057] The following numbered items are embodiments included in this disclosure.

[0058] 1. A sensor belt for sensing signals characterizing one or more respiratory parameters of a human subject performing at least one respiratory operation, (a) A band having longitudinal dimensions that are fitted to surround the chest of the subject, wherein the band is essentially inelastic, (b) Fastening means for securing the band around the chest of the subject by directly or indirectly connecting the first position of the band to the second position of the band, and (c) A belt comprising a first sensing device attached to the band, the first sensing device being adapted to acquire and transmit signals characterizing one or more respiratory parameters of the subject, including tidal volume (Vt), inspiratory time (Ti), expiratory time (Te), total cycle time (Ttot), respiratory rate (RR), and / or work of breathing (WoB), the first sensing device being able to sense a force acting on the band, the force resulting from the expansion of the subject's chest caused by the subject's respiratory operation.

[0059] 2. The sensor belt according to item 1, wherein the first sensing device comprises a member that is movable or deformable by the force, the member having a first end and a second end, the first end being fixed in a first position and the second end being fixed in a second position on the band, and the first sensing device optionally comprises a housing for holding the movable or deformable member.

[0060] 3. The sensor belt according to item 1 or 2, wherein the movable or deformable member is preferably a leaf spring having one or more leaves, or a leaf spring having two or more leaves preferably mounted to each other to form a four-bar link.

[0061] 4. The sensor belt according to any one of the preceding items, wherein the first sensing device comprises a transducer adapted to generate an electrical signal in response to the movement or deformation of 19 movable or deformable members, the transducer preferably adapted to generate an electrical signal without direct contact with the movable or deformable members.

[0062] 5. The transducer comprises an inductive sensor comprising at least one coil, each coil consisting of a helical conductor arranged in a plane and having two flat surfaces, one of the two flat surfaces forming a measuring surface that covers the object to be measured in various ways, and the two flat surfaces being spaced apart in accordance with movement parallel to the measuring surface; the sensor electronics system supplies an alternating current to the inductive sensor and evaluates the change in the alternating current caused by the object to be measured; the object to be measured is induced at a constant distance across the surface of the flat coil; the sensor electronics system is formed to detect the change in attenuation caused by the changing region of the flat coil covered by the object to be measured; the object to be measured affecting the measuring surface is conductive, or the object to be measured has a conductive target or measuring collar; covering a coil region of the flat coil that can be geometrically predetermined depending on the position of the target or measuring collar; the rectangular measuring surface is diagonally divided into two triangular flat coils, thereby their inductance and ohmic resistance forming half of a bridge circuit, and the other half being complemented by resistors to produce a full bridge, as described in item 4.

[0063] 6. A sensor belt according to item 4 or 5, wherein the transducer includes one or more strain gauges fixed to a movable or deformable member.

[0064] 7. A sensor belt according to any one of the preceding items, wherein the first sensing device comprises a transmitter adapted to transmit an electrical signal generated by a transducer via wire or wireless means.

[0065] 8. A sensor belt according to any one of the preceding items, wherein the fastening means is configured to connect a first position to a second position via a first sensing device.

[0066] 9. The sensor belt according to any one of items 2 to 8, wherein the housing of the first sensing device comprises a first end fixed to a first position of the band and a first end of a movable or deformable member, and a second end that is movable to a second position of the band and a second end of a movable or deformable member.

[0067] 10. A sensor belt according to any one of the preceding items, comprising a pretensioner for adjusting the longitudinal extension of the band to the circumference of the chest of a subject, and / or a battery holder, wherein the battery holder is optionally disposed in a housing that holds a movable or deformable member.

[0068] 11. A sensor belt according to any one of the preceding items, comprising a second sensing device, the second sensing device being adapted to sense the electrical activity of one or more muscles involved in the respiratory operation of the subject; the second sensing device preferably comprising at least one electronic amplifier and at least three skin electrodes arranged to perform surface electromyography (EMG), wherein the electrodes are connected to at least one amplifier by wires sized to allow the electrodes to be placed on the subject's skin independently of the band, and the amplifier is preferably located inside the housing of the first sensing device.

[0069] 12. A sensor belt described in any one of the preceding items, in which the subject is a patient receiving postoperative treatment and / or intensive care, and the subject is at risk of developing pulmonary complications such as postoperative pulmonary complications.

[0070] 13. Use of a sensor belt as described in any one of items 1 to 12 to acquire and transmit signals characterizing one or more respiratory parameters selected from Vt, Ti, 21 Te, Ttot, RR, WoB, and / or signals characterizing electromuscular activity, or any derived parameters thereof.

[0071] 14. A method for evaluating signals generated by a sensor belt described in any one of items 1 to 12, the method comprising, in a continuous and simultaneous manner, (i) receiving from a first and / or second sensing device, and (ii) processing a plurality of signals characterizing one or more respiratory parameters selected from Vt, Ti, Te, Ttot, RR, WoB [and / or electromuscular activity], wherein the processing comprises calculating one or more measures of statistical variability of Vt, Ti, Wb, electromuscular activity, or any ratio thereof.

[0072] 15. The method of item 14, wherein processing includes: - performing a fast Fourier transform (FFT) on one or more signals received from a first sensing device; - calculating a correlation measure indicating the degree of correlation between the FFT-transformed signals and a previously acquired and FFT-transformed reference signal; and optionally - calculating a ratio of at least one respiratory parameter to a parameter describing the electrical activity from the signals received from the first sensing device and from the signals received from the second sensing device.

[0073] In the first sensing device embodiment described in detail above, the first sensing device may be a displacement sensor. The physical structure and arrangement of the displacement sensor offer many advantages, which can also be described in detail above with respect to the first sensing device. In one embodiment, the displacement sensor can output a highly accurate and low-noise signal for measuring displacement because there is no inter-member friction between the components of the displacement sensor structure. Furthermore, also due to the physical structure and arrangement of the displacement sensor, a system with no or negligible mechanical hysteresis is possible by mechanically isolating the relevant input forces. These embodiments, individually and cumulatively, enable the sensor to output a highly accurate and low-noise signal for measuring displacement. The structure of the displacement sensor and various related embodiments will be described in further detail below.

[0074] Displacement sensor comprising: a base having a fixed input mount; a displacement arm having a fixed end for fixing the displacement arm to the base; a free end having a displaceable input mount aligned with the fixed input mount, the displacement arm having one degree of freedom along a displacement axis perpendicular to the displacement arm, and enabling substantially linear translation of the free end of the displacement arm along the displacement axis; and a sensor configured to determine the displacement of the free end of the displacement arm along the displacement axis.

[0075] The base of the displacement sensor comprises a reference frame for various features of the displacement sensor, including the orientation of various features, as well as a physical structure to which other features are attached or integrally formed. The base may be part of the housing described above, or it may be a separate structure provided within the housing. Since the base is the reference frame of the displacement sensor, the base may be formed of a material that does not undergo plastic deformation due to forces acting on the input to the displacement sensor or forces acting on the displacement sensor in general. Considering the various applications of the displacement sensor, the base may be formed of one or more metals, plastics, ceramics, and / or composite materials. The base comprises a fixed input mount. The fixed input mount may be a separate structure attached to the base, or it may be integrally formed with the base, i.e., monolithically, so that the base is immovable and has a fixed position relative to the base. An external input that transmits physical forces may be attached, for example, by being detachably or irreversibly fixed to the fixed input mount. A detachably fixed external input may have a structure that allows for a secure connection when attached, but has a structure that allows for reversible disconnection of the external input to the fixed input mount. In contrast, an irreversibly fixed external input cannot be removed without causing physical damage to the external input or fixed input mount.

[0076] The displacement sensor also comprises a displacement arm, which is also referred to herein as a movable or deformable member of the first sensing device. The displacement arm extends from a fixed end, which is also referred herein as the first end of the movable or deformable member, to a free end, which is also referred herein as the second end of the movable or deformable member.

[0077] The fixed end of the displacement arm is fixed to the base such that the displacement arm, i.e., the free end of the displacement arm, has one degree of freedom along a displacement axis perpendicular to the displacement arm, and that substantially linear translation of the free end of the displacement arm along the displacement axis is possible.

[0078] For reference, one degree of freedom refers to the six degrees of freedom of an object with respect to the X, Y, and Z axes, including translation along or relative to any of the axes, and rotation along or relative to any of the axes. Thus, as used herein, the free end of a displacement arm has only one translational degree of freedom along a single axis referred to herein as the displacement axis. Since a displacement arm is an elongated structure extending from a free end to a fixed end, the structure can have an overall deflection profile that has an arc-shaped or curved shape from one maximum deflection point to another (elastic or plastic). However, the substantially linear translation of the free end of the displacement arm points to a target region for displacement measurement, where the movement of the free end of the displacement arm follows a substantially linear path, for example, the deflection profile inside the target region has a sufficiently large radius of curvature, and the movement of the free end is substantially linear for measurement purposes. Therefore, the physical parameters of the displacement arm (e.g., dimensions, shape, material properties, and interactions between them) ensure substantially linear translation of the free end of the displacement arm along the displacement axis within the target region. The target region can be determined by the length of a predetermined maximum displacement, which the displacement sensor is configured to measure / determine. In this configuration, a guide structure that traces a single axis by physically blocking non-axial movement of the target of measurement is not required, thus eliminating friction between the target of measurement and the guide structure.

[0079] Furthermore, the displacement sensor may have one or more stoppers to prevent the free end of the displacement arm from translating beyond the target area of ​​measurement and / or to a position that could cause plastic deformation of the displacement arm. One or more stoppers may be fixed to the base, fixed to the housing, and / or formed integrally with the base and / or housing. One or more stoppers are configured to physically block or limit the movement of the free end of the displacement arm in one or both directions along the displacement axis.

[0080] The free end of the displacement arm is equipped with a fixed input mount and a displaceable input mount that is aligned with it. The displaceable input mount and the fixed input are aligned such that the force acting on one or both mounts does not produce a moment of force that could result in torque or rotation of the displacement sensor, which would also reduce the accuracy of the displacement sensor. The displacement input mount and the fixed input mount may be aligned such that the force acting on one or both mounts is aligned with the displacement axis.

[0081] The displaceable input mount may be a separate structure attached to the free end of the displacement arm, or it may be formed integrally with the free end, i.e., monolithically, so that it is immovable and has a fixed position relative to the free end of the displacement arm. An external input that transmits physical force can be attached, for example, to the displaceable input mount in a removable or irreversible manner. A removable external input may have a structure that allows for a secure connection when attached, but has a structure that allows for reversible disconnection of the external input to the displaceable input mount. In contrast, an irreversibly attached external input cannot be removed without causing physical damage to the external input or the displaceable input mount.

[0082] Since the fixed end of the displacement arm is the only part of the displacement arm attached to the base, the free end of the displacement arm is not in physical contact with any other structure of the displacement sensor; that is, there is a gap between the free end of the displacement arm and any other structure of the displacement sensor that would introduce friction during movement. This allows for frictionless movement (excluding internal friction) of the free end of the displacement arm due to the force acting on the displaceable input mount. Therefore, the mechanical force acting on the displaceable input mount is accurately transmitted as translation of the free end of the displacement arm without any loss due to friction.

[0083] The displacement arm may comprise a leaf spring (as described elsewhere herein) extending from a fixed end to a free end, the leaf spring cantilevering at the fixed end, i.e., along the longitudinal axis / longest dimension of the leaf spring, with only one end of the leaf spring (the fixed end) fixed to the base, and the free end not in physical contact with any other structure of the displacement sensor that would introduce friction during movement, and the planar shape of the leaf spring is oriented perpendicular to the displacement axis. When the planar shape of the leaf spring is oriented perpendicular to the displacement axis and cantilevering at the fixed end, the free end of the leaf spring can translate along the displacement axis with the shape of the leaf spring oriented such that the shape of the leaf spring allows it to deflect in the direction in which it has maximum elasticity, while simultaneously suppressing or preventing deflection in other directions, such as perpendicular to the displacement axis and aligned with the planar shape of the leaf spring. When the free end of a leaf spring translates along the displacement axis, the overall plane shape of the leaf spring deflects into an "S" shape when viewed along the plane shape of the leaf spring. The leaf spring parameters, such as the spring constant, shape, dimensions, and their interactions, are selected to have a minimal or negligible effect on the force applied to the displaceable input mount, ensuring that the mechanical force acting on the displaceable input mount is accurately transmitted as the translation of the free end of the displacement arm along the displacement axis, eliminating or reducing force components in other directions. As an example, a leaf spring may have dimensions ranging from 10 to 200 mm, optionally from 50 to 150 mm, preferably 80 mm in length; from 1 to 50 mm, optionally from 10 to 20 mm, preferably 16 mm in width; and from 0.1 to 1.0 mm, optionally from 0.1 to 0.3 mm, preferably 0.25 mm in thickness. The leaf spring may have a linear spring constant. Alternatively, a leaf spring may have a nonlinear spring constant, for example, a variable spring constant that changes based on the deflection of the leaf spring. The nonlinear spring constant may be progressive, i.e., increase with deflection, or progressive, i.e., decrease as it deflects. As an example, the spring constant may have a nonlinear spring constant according to Table 1. The leaf spring may contain one or more metals and / or metal alloys, such as spring steel, etc., conforming to one or more of the standards BS 1449, CS 80, and BS 970.

[0084] [Table 1]

[0085] In other embodiments described elsewhere in this specification, for example, as a four-bar linkage, the displacement arm may further comprise a mounting member fixed to a base, a plurality of leaf springs extending from a fixed end to a free end, the plurality of leaf springs cantilevering outwards from the mounting member at the fixed end of the displacement arm, the planar shapes of each leaf spring of the plurality of leaf springs being oriented perpendicular to the displacement axis and parallel to one another, and a connecting member attached to the free ends of the plurality of leaf springs to translate the free ends of the plurality of leaf springs together. The leaf springs of the plurality of leaf springs may be spaced apart from one another, for example, each leaf spring of the plurality of leaf springs may be considered to be in a parallel plane, that is, the planar shapes of the plurality of leaf springs are aligned to be substantially parallel. The plurality of leaf springs may be spaced apart from one another by a range of 1 to 100 mm, optionally 10 to 30 mm, preferably 26 mm.

[0086] The mounting member may be a separate structure attached to the base, or it may be formed integrally with the base, i.e., monolithically, so that the mounting member is immovable and has a fixed position relative to the base. The mounting member is configured to be the sole structure of the displacement arm that contacts the base or other structures of the displacement sensor that may cause friction when the displacement arm is moving. The mounting member may be made of a rigid or substantially inflexible material, i.e., forces acting on the displacement arm should not cause deflection or other movement of the mounting member.

[0087] The connecting member attaches the free ends of multiple leaf springs to each other so that their free ends translate simultaneously. Therefore, like the mounting member, the connecting member may be made of a rigid or substantially inflexible material; that is, forces acting on the displacement arm should not cause deflection or other movement of the connecting member. In this configuration, the multiple cantilevered leaf springs are configured as a displacement arm structure intended to deflect by the substantially linear translation of the free ends of the multiple leaf springs. As the free ends of the multiple leaf springs translate along the displacement axis, the plane shape of the individual leaf springs as a whole deflects into a parallel "S" shape when viewed along the plane shape of the leaf springs.

[0088] When the planar shapes of each leaf spring in a multi-leaf spring configuration are oriented perpendicular to the displacement axis and parallel to one another, and the fixed end cantilevered outwards, the free end of the leaf spring can translate along the displacement axis with a shape that allows the leaf spring to deflect in the direction in which it has maximum elasticity, while simultaneously suppressing or preventing deflection in other directions, such as perpendicular to the displacement axis and aligned with the planar shape of the leaf spring. In addition, this configuration further simultaneously suppresses or prevents torsional / rotational motion of the displacement arm, making it more stable compared to a single leaf spring. The leaf spring parameters, e.g., spring constant, shape, dimensions, and their interactions, are selected to act minimally or negligibly on the force applied to the displaceable input mount, ensuring that the mechanical force acting on the displaceable input mount is accurately transmitted as translation of the free end of the displacement arm along the displacement axis, eliminating or reducing linear and torsional force components in other directions.

[0089] The displacement sensor further comprises a sensor configured to determine the displacement of the free end of a displacement arm along a displacement axis. The sensor may include, but is not limited to, any of the sensor circuits mentioned elsewhere in this specification, such as transducers, non-contact transducers, transmitters, electronic components, inductive sensing elements, and / or iron core pieces; that is, the sensor means any electrical circuit described elsewhere in this specification, and any electrical circuit that implements this function, configured to output an electrical signal based on a mechanical input to the entire displacement sensor, for example, to determine / measure the displacement of the free end of the displacement arm of the displacement sensor. For example, the sensor may further comprise a controller, an integrated circuit, electrical hardware and components such as one or more resistors, one or more capacitors, one or more coils, one or more diodes, one or more amplifiers, one or more regulators, software, firmware, and any combination thereof.

[0090] While various advantages of the physical structure of a displacement sensor have been noted above in relation to its ability to accurately transmit the mechanical force acting on the displaceable input mount as translation of the free end of the displacement arm along the displacement axis, and to eliminate or reduce linear and / or torsional force components in other directions and / or friction, these advantages are also beneficial to the accuracy of the sensor. In particular, friction due to the structural components of the entire displacement sensor will increase the noise level of the output signal of the sensor itself. Furthermore, the nonlinear motion of the free end of the displacement arm can also reduce the accuracy of displacement measurement, as the sensor may be configured to determine the linear motion of the free end of the displacement arm along the displacement axis, and therefore input forces resulting in other motions are not determined or considered, thus reducing the accuracy of the measurement. In addition, the physical structure of a displacement sensor allows the sensor to be configured to convert the input force into a substantially linear electrical signal.

[0091] The sensor may include a measurement target attached to the free end of a displacement arm to move the measurement target substantially linearly together along the displacement axis, and a sensing circuit attached to a base and spaced apart from the free end of the displacement arm and the measurement target, forming a gap between the sensing circuit and the measurement target and the free end of the displacement arm, the sensing circuit being configured to determine the translation of the measurement target along the displacement axis.

[0092] The measurement target may be a separate structure or a predetermined part of the free end of the displacement arm, on which the sensing circuit can sense, i.e., determine and / or measure any translation of the measurement target. The measurement target is attached, i.e., fixed to the free end of the displacement arm such that any translation of the free end of the displacement arm also translates substantially linearly together with the measurement target along the displacement axis.

[0093] The sensing circuit is mounted on a base and spaced away from the free end of the displacement arm and the target of measurement, creating a gap between the sensing circuit and the target of measurement and the free end of the displacement arm. Therefore, the sensing circuit does not physically contact the target of measurement or the free end of the displacement arm, and thus no friction occurs when the displacement arm is moving. Thus, the target of measurement can move along the displacement axis relative to the sensing circuit without friction. The gap may be in the range of 0.1 to 10 mm, optionally 0.1 to 1.0 mm or 0.5 to 1.0 mm, preferably 0.5 mm or 1.0 mm.

[0094] The sensing circuit is configured to determine the movement of the target to be measured frictionlessly, i.e., without direct physical contact with the target to be measured. The sensing circuit may be an optical sensor capable of optically distinguishing the target to be measured and determining the movement of the target to be measured via a photosensitive receptor. The sensing circuit may be an electric field sensor relating to the target to be measured, which causes a measurable variation in the electric field between the sensing circuit and the target to be measured in order to determine the movement of the target to be measured. The sensing circuit may be a magnetic field sensor relating to the target to be measured, which causes a measurable variation in the magnetic field between the sensing circuit and the target to be measured in order to determine the movement of the target to be measured. The sensing circuit may be a combination of an optical sensor, an electric field sensor, and / or a magnetic field sensor. For example, the sensing circuit may be an electromagnetic sensor relating to the target to be measured, which causes a measurable variation due to the interaction effect of magnetic and electrical systems in order to determine the movement of the target to be measured. The sensing circuit may be, for example, an eddy current sensor or an inductive sensor.

[0095] Therefore, the measurement target may include an optical pattern and / or optically distinguishable material and / or color, such as a contrasting color and / or phosphorescent material. The measurement target may include a conductive material. The measurement target may include an electrical component having an electrically configured structure that capacitively interacts with another electrically configured structure of the sensing circuit, such as a capacitor plate or a capacitive comb structure. The measurement target may include a metal, such as aluminum, and / or a metal alloy, such as brass. The measurement target may include a ferromagnetic material, such as steel.

[0096] The sensing circuit may comprise one or more planar coils arranged parallel to the displacement axis, with the one or more planar coils at a fixed distance from the displacement axis, and configured such that the target of measurement translates along the displacement axis together with the free end of the displacement arm. Thus, the size of the gap between the sensing circuit and the target of measurement, as well as the free end of the displacement arm, are constant along the displacement axis. The area covered by the one or more planar coils can define a target area along the displacement axis in which the displacement sensor is configured to measure displacement. Since the free end of the displacement arm on which the target of measurement is located has one degree of freedom along the displacement axis, the physical structure of the displacement sensor ensures that the target of measurement moves along the displacement axis at a fixed distance from the one or more planar coils, thereby ensuring a constant effect on the one or more planar coils. In the configuration of the sensing circuit relating to one or more planar coils, the target of measurement may include a ferromagnetic material.

[0097] One or more planar coils may include a conductive material. The conductive material may include one or more metals, for example, copper, or an alloy, for example, a copper alloy. One or more planar coils may be placed on a substrate or carrier. The substrate or carrier may include a non-conductive material relative to the conductive material of one or more planar coils. The substrate or carrier material may include, for example, a resin, for example epoxy resin, silicon, ceramic, glass, and / or composite materials such as FR4.

[0098] One or more planar coils may include multiple planar coils arranged in parallel planes. Multiple planar coils arranged in parallel planes may be electrically isolated from each other and stacked on top of each other, i.e., stacked, and aligned perpendicularly to each other. A stacked coil system can reduce the power input required to the sensing circuit due to the higher impedance of the stacked coil system. This is particularly advantageous, for example, when the displacement sensor is connected to a fixed-volume power source, such as a battery, thereby extending the operating time of the displacement sensor.

[0099] The turns of one or more planar coils may be arranged in a triangular shape, and the measuring target may have the shape of a right-angled rectangular prism. In another aspect of the present disclosure, two or more planar coils have turns arranged in a triangular shape, and the hypotenuses and sides of the triangular shapes of the two or more planar coils are arranged parallel to each other, forming a quadrilateral shape as a whole. The measuring target may have a narrow rectangular profile facing one or more planar coils, with the maximum length of the measuring target positioned perpendicular to the displacement axis and the minimum dimension of the right-angled rectangular prism shape positioned parallel to the displacement axis. The maximum length of the measuring target may extend beyond the maximum width of the planar coils (i.e., as one or more planar coils or two or more planar coils) to compensate for any curvature in the substantially linear path of the free end of the displacement arm, by ensuring that the maximum width of the planar coils is always covered by the measuring target. For example, the narrow rectangular profile may have adjacent sides, e.g., length and width, in a ratio of about 4:1. The narrow rectangular profile may have a length ranging from 1 to 100 mm, optionally from 10 to 30 mm, preferably 20 mm, and a width ranging from 1 to 25 mm, optionally from 1 to 10 mm, preferably 5 mm. The sensing circuit may include a bridge circuit, such as a Wheatstone bridge circuit, and the planar coil forms a half-bridge of the bridge circuit. The planar coil may be configured to generate a high-frequency electromagnetic field that induces eddy currents in the target of measurement moving over the planar coil, thereby causing an attenuation effect on the high-frequency electromagnetic field determined by the sensing circuit. Due to the triangular shape of the planar coil and the right-angled rectangular prism shape of the target of measurement, path-dependent attenuation due to the translation of the target of measurement on the planar coil is made possible by a linear output signal from the sensing circuit including the bridge circuit.

[0100] The sensing circuit may further include a ferromagnetic structure on the side of the planar coil opposite the measurement target. The ferromagnetic structure reduces interference to the planar coil from the electromagnetic field opposite the planar coil side, thereby improving the accuracy of the sensing circuit.

[0101] In alternative embodiments of the present disclosure, the sensor may comprise one or more strain gauges (as described in more detail above) mounted on a displacement arm. The one or more strain gauges may be mounted on a leaf spring of the displacement arm, preferably on the plane of the leaf spring of the displacement arm. The first strain gauge may be mounted on the leaf spring closer to the fixed end than to the free end, and the second strain gauge may be mounted on the leaf spring closer to the free end than to the fixed end. In this configuration, one of the first and second strain gauges is mounted in a region of the leaf spring under compression, and the other strain gauge is mounted in a region of the leaf spring under tension, during the deflection of the leaf spring, i.e., the associated translation of the free end along the displacement axis. The measuring regions of the first and second strain gauges may be located equidistant from the neutral zone of the leaf spring. The neutral zone of the leaf spring is the region of the leaf spring where the compressive and tensile stresses transition. In a configuration with multiple leaf springs, the first and second strain gauges may be mounted on different leaf springs among the multiple leaf springs.

[0102] The sensor may include a bridge circuit, such as a Wheatstone bridge circuit, where a first strain gauge and a second strain gauge form a half-bridge of the bridge circuit. In another aspect of the present disclosure, the bridge circuit, such as a Wheatstone bridge circuit, may be formed by four strain gauges, where third and fourth strain gauges are mounted on another leaf spring among a plurality of leaf springs in a mirror image relationship with the first and second strain gauges.

[0103] Similar to the sensors described above, which include a measurement target and one or more planar coils, a sensor comprising one or more strain gauges mounted on a displacement arm allows frictionless translation of the free end of the displacement arm, as the free end of the displacement arm does not come into contact with other structures of the displacement sensor that would cause friction during movement. The one or more strain gauges may have wires connecting each strain gauge to an additional sensing circuit, but the geometric shape and characteristics of the wires may be such that their influence on the movement of the displacement arm is negligible, for example, by selecting thin or small gauge wires.

[0104] As shown above, displacement sensors according to various embodiments of this disclosure may be incorporated into a sensor belt. The sensor belt may further comprise a band (described in more detail elsewhere) having one end fixed to a fixed input mount of the displacement sensor and the other end fixed to a displaceable mount at the free end of the displacement arm of the displacement sensor. The band is configured to transmit forces acting on the band to the displaceable input mount, thereby translating the free end of the displacement arm along the displacement axis. The displacement sensor is configured to determine the displacement of the free end of the displacement arm along the displacement axis from the forces acting on the band, which are converted to the displaceable input mount.

[0105] As described in detail above, an advantageous aspect of the present disclosure involves applying a sensor belt to monitor the respiration and / or respiratory parameters of an object. Thus, the band is configured to be applied around the object's chest, with one end fixed to a fixed input mount of a displacement sensor and the other end fixed to a displaceable input mount. When the object breathes, the band is configured to transmit force from the expansion of the object's chest to the displaceable input mount, causing the free end of the displacement arm to translate along the displacement axis. During exhalation, the object's chest contracts, reducing the force acting on the band, and the displacement arm of the displacement sensor returns to its initial position. The displacement sensor is configured to determine the displacement of the free end of the displacement arm along the displacement axis from the force acting on the band, which is converted to the displaceable input mount due to the object's respiration. Thus, when the object breathes, the displacement sensor can output a sinusoidal wave dependent on the object's respiratory input.

[0106] The sensor belt may further comprise an electrical sensor, also referred to herein as a second sensing device. The electrical sensor may comprise multiple electrodes and be configured to determine the potential difference between the multiple electrodes. As discussed elsewhere herein, the electrical sensor may also be an electromyogram sensor. The electrical sensor may be co-located in a housing that also comprises a displacement sensor. Alternatively, the electrical sensor may be located separately from the displacement sensor on the band.

[0107] A sensor belt may be part of a sensor belt system. The sensor belt system may further include a processor connected to a displacement sensor. The processor is configured to receive outputs from the displacement sensor and / or electrical sensor and / or determine one or more respiratory parameters (described in detail elsewhere in this specification) based on the outputs of the displacement sensor and / or electrical sensor. The processor may be configured to perform the processing methods described herein.

[0108] The sensor belt system may further include a power supply connected to the displacement sensor. The power supply may be directly or indirectly connected to the displacement sensor and / or processor. The power supply may be a finite power source, such as a battery, or it may be directly or indirectly connected to the power grid, for example, "plugged into" an electrical system that provides on-demand electricity.

[0109] Detailed description of the drawing Figure 1 depicts a sensor belt (10) in several embodiments disclosed herein, worn by a subject (1) which optionally represents a human patient. The sensor belt (10) is secured around the chest of the subject (1), although only partially visible. The sensor belt (10) comprises a band (12) and a first sensing device (20) (e.g., a displacement sensor (20)).

[0110] Figure 2 illustrates a portion of a sensor belt according to some embodiment disclosed herein, having a band (12) and fastening means (15) connecting a first position (17) and a second position (18) of the band. The first position (17) and the second position (18) may represent opposing ends of a single, continuous band segment, or they may be located on different segments of the band (10), namely the first segment and the second segment, with the fastening means also connecting two such segments of the band (12). Furthermore, the sensor belt (10) includes a pretensioner (16) for adjusting the longitudinal extension of the band (12) around the chest of a subject (not shown).

[0111] Figure 3 illustrates an example of a first sensing device (20) (e.g., a displacement sensor (20)) according to several aspects of the present disclosure. A portion of a band (12) connected to the first sensing device (20) (e.g., a displacement sensor (20)) is visible via a connector (14), one end of which fastens the band (12) to the housing (22) of the sensing device (20), and the other end of which fastens the band (12) to a movable structure, in this case a core piece (30) (which may be an example of a measurement target, e.g., a measurement target (141)). If the function of the fastening means is incorporated into the first sensing device (20), the band portion connected in this manner via the sensing device (20) potentially represents a first position (17) and a second position (18) of a single band segment, e.g., opposite ends. Alternatively, if the fastening means is located separately from the first sensing device (20), the band portion connected in this manner via the sensing device (20) represents two different segments of the band (12) of the sensor belt.

[0112] Inside the housing (22) is a functional sensor unit (e.g., sensor (140)) which includes an inductive sensing element (28) (which may be an example of a sensing circuit, such as a sensing circuit (142)) that slidably receives an iron core piece (30) that is at least partially insertable into the inductive sensing element (28). The movement of the inductive sensing element (28) and the iron core piece (30) relative to each other is caused by the expansion of a band (12) in response to the breathing operation of an object (not shown), with direction (38) shown in the figure. The movement of the iron core piece (30) relative to the inductive sensing element (28) generates an electrical signal that can be transmitted to an electronic component (32), which may include, for example, one or more amplifiers and / or transducers.

[0113] Furthermore, for example, a leaf spring (24) having two metal leaves mounted to each other to form a four-bar link is shown (this could be an example of a displacement arm (120) comprising multiple leaf springs (121, 122)). Thus, the leaf spring (24) represents part of a deformable member (e.g., a displacement arm (120)) that responds to the movement of the band (12). As shown in the figure, one of the two ends of the leaf spring (24) is immovable (e.g., fixed end (125)) relative to the housing (22) (e.g., relative to the base (100), which may be part of the housing (22)) by its fixing (26) (which could be an example of a mounting member (124)), and thereby is also immovable relative to a first position (17) or segment of the band (12). Meanwhile, the other end of the leaf spring (24) is movable (e.g., free end (126)) relative to the housing (22) (e.g., relative to the base (100), which may be part of the housing (22)) and is connected to a second position (18) or segment of the band (12) via a core piece (30) (as discussed elsewhere, the free end (126) of the displacement arm (120) is equipped with a displaceable input mount (130) to which the band (12) can be attached, and the measurement target (141) can be attached to the free end (126) of the displacement arm (120)). A guide member (36) is configured to guide the movement of the movable connector (14) and the associated band portion at the second position (18) or segment. At the second position (18) of the band (12), which is movable relative to the housing (22) and can partially slide into and out of the housing (22), a gasket (34) is positioned to protect the inside of the housing (22) from contamination.

[0114] Figure 4 illustrates an example of a second sensing device (40) (e.g., an electrical sensor (40)) according to several aspects of the present disclosure. A segment of a sensor belt having a band (12), fastening means (15), and a pretensioner (16) is also shown, as previously described. In this example, the second sensing device (40) comprises three electromyography (EMG) sensor patches (42), each patch comprising an electrode (44) adapted to surface EMG. Each electrode (44) is connected to a signal distributor (40) by a wire (52), which is electrically connected to, for example, an amplifier (not shown) by a wire (52).

[0115] Figures 5A, 5B, and 5C illustrate embodiments of the first sensing device (20) as an exemplary displacement sensor. Figure 5A shows the displacement sensor (20) from above, and Figures 5B and 5C show the displacement sensor (20) from a side view. The displacement sensor (20) comprises a base (100) which may be part of the housing (22) or may be a separate structure. A fixed input mount (110) is fixed to the base (100).

[0116] The displacement arm (120) extends from a fixed end (125) to a free end (126). The fixed end (125) is fixed to the base (100). The free end (126) is equipped with a displaceable input mount (130) which is aligned with a fixed input mount (110), for example, along the displacement axis (150). The displacement arm (120) has one degree of freedom along the displacement axis (150) as described above. The displacement axis (150) is oriented perpendicular to the displacement arm (120), and the free end (126) of the displacement arm (120) translates substantially linearly along the displacement axis (150) as described above. For illustrative purposes, the displacement axis (150) can be considered as the x-axis. The y-axis is perpendicular to the displacement axis (15) and lies on the same plane, for example, the longitudinal axis of the displacement arm 120, or an axis parallel to that longitudinal axis, and the z-axis can be considered to be perpendicular to the plane formed by the x-axis and y-axis.

[0117] The displacement sensor (20) includes a sensor (140). The sensor (140) is configured to determine the displacement of the free end (126) of the displacement arm (120) along the displacement axis (150). The sensor (140) can be configured to determine the displacement of the free end (126) of the displacement arm (120) along the displacement axis (150) within a target region (151), which can also correspond to a region where the free end (126) of the displacement arm (120) moves substantially linearly along the displacement axis (150). One or more stoppers (160) can be fixed to the base (100) to restrict the translation of the free end (126) of the displacement arm (120), for example, to restrict translation into the target region (151).

[0118] Figures 5B and 5C show side views of the displacement sensor (20). Various elements have been omitted for illustrative purposes. Figure 5C differs from Figure 5B in that the fixed end (125) of the displacement arm (120) may be fixed to the base (100) in any orientation, and is not limited to, for example, an arrangement in which the displacement arm (120) is parallel to the base (100). Thus, the displacement arm (120) may cantilever directly from the base (100) without the fixed end (125) orienting the displacement arm (120) in a particular orientation. Alternatively, the fixed end (125) may orient the displacement arm (120) in a particular orientation, as may be shown in Figure 5B.

[0119] Figures 6A and 6B illustrate examples of the displacement sensor (20). Figure 6A shows the displacement sensor (20) from above, and Figure 6B shows the displacement sensor (20) from a side view. Various elements have been omitted for illustrative purposes, and for brevity, the same or similar features are not repeated here.

[0120] Figures 6A and 6B show a displacement arm comprising a leaf spring (121) extending from a fixed end (125) to a free end (126), the leaf spring (121) having a planar shape perpendicular to the displacement axis (150) and cantilevering over the fixed end (125). The displacement arm (120) may further comprise a mounting member (124) that cantilevering over the fixed end (125) of the leaf spring (121) to a base (100). In this embodiment of the present disclosure, the mounting member (124) can orient the displacement arm (120) in a particular configuration.

[0121] Figures 7A and 7B illustrate examples of the displacement sensor (20). Figure 7A shows the displacement sensor (20) from above, and Figure 7B shows the displacement sensor (20) from a side view. Various elements have been omitted for illustrative purposes, and for brevity, the same or similar features are not repeated here.

[0122] Figures 7A and 7B show a displacement arm (120) comprising a mounting member (124), a plurality of leaf springs (121, 122), and a connecting member (123). The mounting member (124) is fixed to the base (100). The plurality of leaf springs (121, 122) extend from a fixed end (125) to a free end (126) and cantilever out from the mounting member (124) at the fixed end (125) of the displacement arm (120). The planar shape of each leaf spring (121, 122) is oriented perpendicular to the displacement axis (150) and parallel to one another. The connecting member (123) is attached to the free ends (126) of the multiple leaf springs (121, 122) in order to cause the free ends (126) of the multiple leaf springs (121, 122) to be translated simultaneously along the displacement axis (150).

[0123] Figures 8A and 8B illustrate examples of the displacement sensor (20). Figure 8A shows the displacement sensor (20) from above, and Figure 8B shows the displacement sensor (20) from a side view. Various elements have been omitted for illustrative purposes, and for brevity, the same or similar features are not repeated here.

[0124] Figures 8A and 8B show a displacement sensor (20) relating to an embodiment of a sensor (140) comprising a measurement target (141) and a sensing circuit (142). The measurement target (141) is attached to the free end (126) of a displacement arm (120) to substantially linearly translate the measurement target (141) together along a displacement axis (150). The sensing circuit (142) is attached to a base (100) and spaced away from the free end (126) of the displacement arm (120) and the measurement target (141), forming a gap (170) between the sensing circuit (142) and the measurement target (141) and the free end (126) of the displacement arm (120). The sensing circuit (142) is configured to determine the translation of the measurement target (141) along the displacement axis (150). A sensing circuit (142) may be positioned in the target region (151) to determine the translation of a measurement target (141) attached to the free end (126) of the displacement arm (120).

[0125] The sensing circuit (142) may comprise one or more planar coils (143) arranged parallel to the displacement axis (150), the one or more planar coils (143) being positioned at a fixed distance from the displacement axis (150), and the measurement target (141) being configured to translate along the displacement axis together with the free end (126) of the displacement arm (120). The one or more planar coils (143) may be coplanar, as may be shown in Figure 8B.

[0126] Alternatively, as may be shown in Figure 9, one or more planar coils (143) may include a plurality of planar coils (143-1, 143-2) arranged in parallel planes. The plurality of planar coils (143-1, 143-2) are electrically insulated from each other by their respective substrates (142-1, 142-2). For example, the substrate may be formed by separate layers, or it may be formed monolithically as a single substrate having one or more planar coils embedded within the substrate. The sensing circuit (142) may further include a ferromagnetic structure (148) on the side of one or more planar coils opposite to the target of measurement (141).

[0127] Figure 10 illustrates an example of a sensor (140) comprising a measurement target (141) and one or more planar coils (143). Various elements have been omitted for illustrative purposes, and for brevity, the same or similar features are not repeated here.

[0128] Figure 10 depicts a sensing circuit (142) comprising one or more planar coils (143) corresponding to a target region (151), and a measurement target (141) aligned on the target region (151) and the displacement axis (150). For illustrative purposes, a two-dimensional contour of the measurement target (141) is shown. The planar coils (143) may further comprise one or more contact points (144).

[0129] The turns of one or more planar coils (143) may be arranged in a triangular shape, and the measurement target (141) may have the shape of a right-angled rectangular prism, as illustrated in Figure 10. Furthermore, as illustrated in Figure 10, the sensing circuit (142) may comprise two or more planar coils (143) having turns arranged in a triangular shape, where the hypotenuses and sides of the triangular shapes of two or more planar coils are arranged parallel to each other, forming a quadrilateral shape overall.

[0130] Figures 11A and 11B illustrate examples of the displacement sensor (20). Figure 11A shows the displacement sensor (20) from above, and Figure 11B shows the displacement sensor (20) from a side view. Various elements have been omitted for illustrative purposes, and for brevity, the same or similar features are not repeated here.

[0131] In Figures 11A and 11B, the sensor (140) may be mounted on the side of the displacement arm (120). Although Figures 11A and 11B depict the sensor (140) on a specific side of the displacement arm (120), the position of the sensor (140) is not limited thereto and may be located, for example, on the opposite side of the displacement arm (120) or on a side adjacent to the side depicted in Figures 11A and 11B. In this embodiment of the displacement sensor (20), the sensor (140) may comprise one or more strain gauges mounted on the displacement arm (120). Since the strain gauges can directly determine the compressive and tensile forces on the displacement arm (120), the components of the sensor (140) do not need to be located within a target area having a aligned sensing circuit and a target for measurement. However, the free end (126) of the displacement arm (120) is still configured to move along the displacement axis (150) and its movement may be restricted by one or more stoppers (160).

[0132] Figure 12 illustrates an example of a sensor (140) comprising one or more strain gauges (145, 146) attached to a displacement arm (120) having a leaf spring (121). Various elements have been omitted for illustrative purposes, and for brevity, the same or similar features are not repeated here.

[0133] As shown in Figure 12, the sensor (140) includes one or more strain gauges (145, 146) attached to the displacement arm (120). The first strain gauge (145) may be attached to leaf spring (121) of a plurality of leaf springs (121, 122) closer to the fixed end (125) than to the free end (126), and the second strain gauge (146) may be attached to leaf spring (121) of a plurality of leaf springs (121, 122) closer to the free end (126) than to the fixed end (125). The first strain gauge (145) and the second strain gauge (146) may be positioned equidistant from the neutral zone (147) of the leaf spring (121).

[0134] Figure 13 depicts exemplary strain gauges, e.g., a first strain gauge (145) and / or a second strain gauge (146). The strain gauge includes a contact pad (181) and an active region (182) having a conductive pattern configured to elastically deform based on stress applied to the strain gauge, thereby changing the resistivity of the conductive pattern.

[0135] Figure 14 shows an exemplary bridge circuit (300). For example, the sensing circuit (142) of the sensor (140) may comprise a bridge circuit (300) having two or more planar coils (e.g., 143-1, 143-2) that form a half-bridge of the bridge circuit (300). Alternatively, the sensor (140) may comprise a bridge circuit (300) having two or more strain gauges (e.g., 145, 146) that form a half-bridge of the bridge circuit (300).

[0136] The bridge circuit 300 is attached to a power supply, which is exemplary an AC power supply, as shown in Figure 14. The diagram of the bridge circuit (300) depicts the contact node (370), typical resistances (310, 320, 330, and 340), and typical inductances (350, 360). Thus, half-bridges formed by two or more planar coils or two or more strain gauges can be represented by typical resistances and inductances (330, 350) and (340, 360), respectively.

[0137] In aspects of the present disclosure, the sensor belt system depicted in Figure 15 is provided comprising a sensor belt (10) equipped with a displacement sensor (20), a processor (80) connected to the displacement sensor (20) and optionally an electrical sensor (40), and a power supply (90). The processor (80) is configured to receive outputs from the displacement sensor (20) and / or the electrical sensor (40) and to determine one or more respiratory parameters based on the outputs of the displacement sensor (20) and / or the electrical sensor (40).

[0138] None of the figures presented in this specification are drawn to scale. [Explanation of Symbols]

[0139] 1. Target 10 Sensor Belt 12 bands 14 connectors 15 Fastening means 16 Pretensioners 17. First position of the band 18 Bands, 2nd position 20 First sensing device / displacement sensor 22 Housing of the first sensing device / displacement sensor 24 leaf springs 26. Fixing of leaf springs / mounting components 28 Inductive sensing element / sensing circuit 30 iron core pieces / measurement targets 32 Electronic Components 34 Gasket 36 Guide member 38 Direction of movement 40. Second sensing device / electrical sensor 42 EMG sensor patches 44 electrode 50 EMG signal splitter 52 EMG wires

Claims

1. It is a displacement sensor, Base with fixed input mount, It is a displacement arm, The displacement arm has a fixed end that secures it to the base, The free end is equipped with a displaceable input mount that is aligned with the fixed input mount, The displacement arm has one degree of freedom along a displacement axis perpendicular to the displacement arm, and allows substantially linear translation of the free end of the displacement arm along the displacement axis, and A displacement sensor comprising a sensor configured to determine the displacement of the free end of the displacement arm along the displacement axis.

2. The displacement sensor according to claim 1, wherein the displacement arm comprises a leaf spring extending from the fixed end to the free end, and the leaf spring cantilevered out from the fixed end in a planar shape perpendicular to the displacement axis.

3. The displacement arm is Mounting member fixed to the base, A plurality of leaf springs extending from the fixed end to the free end, wherein the plurality of leaf springs cantilever outwards from the mounting member at the fixed end of the displacement arm, and the planar shape of each of the plurality of leaf springs is oriented perpendicular to the displacement axis and parallel to each other, and The displacement sensor according to claim 1, further comprising connecting members attached to the free ends of the plurality of leaf springs in order to integrally translate the free ends of the plurality of leaf springs.

4. The aforementioned sensor is A measurement target attached to the free end of the displacement arm is used to move the measurement target substantially linearly along the displacement axis, The sensing circuit is mounted on the base and is spaced apart from the free end of the displacement arm and the measurement target, and comprises a sensing circuit that forms a gap between the measurement target and the free end of the displacement arm, The displacement sensor according to any one of claims 1 to 3, wherein the sensing circuit is configured to determine the translation of the target of measurement along the displacement axis.

5. The displacement sensor according to claim 4, wherein the sensing circuit comprises one or more planar coils arranged parallel to the displacement axis, the one or more planar coils being at a fixed distance from the displacement axis, and the measurement target is configured to translate along them together with the free end of the displacement arm.

6. The displacement sensor according to claim 5, wherein the one or more planar coils include a plurality of planar coils arranged in parallel planes.

7. The turns of the one or more planar coils are arranged in a triangular shape. The displacement sensor according to any one of claims 5 or 6, wherein the target of the measurement is in the shape of a right-angled rectangular prism.

8. The displacement sensor according to any one of claims 5 to 7, wherein the sensing circuit comprises a bridge circuit, and the one or more planar coils form a half-bridge of the bridge circuit.

9. The sensing circuit comprises two or more planar coils, each of which has turns arranged in a triangular shape, and the hypotenuses and sides of the triangular shape of the two or more planar coils are arranged parallel to each other, forming a quadrilateral shape overall. The displacement sensor according to any one of claims 5 or 6, wherein the target of the measurement is in the shape of a right-angled rectangular prism.

10. The displacement sensor according to claim 9, wherein the sensing circuit comprises a bridge circuit, and the two or more planar coils form a half-bridge of the bridge circuit.

11. The displacement sensor according to any one of claims 5 to 10, wherein the sensing circuit further comprises a ferromagnetic structure on the side of the one or more planar coils opposite to the target of measurement.

12. The aforementioned sensor is The displacement sensor according to any one of claims 1 to 3, comprising one or more strain gauges attached to the displacement arm.

13. The displacement sensor according to any one of claims 2 or 3, wherein the sensor comprises one or more strain gauges attached to the leaf spring or to one of the leaf springs among the plurality of leaf springs.

14. The one or more strain gauges described above are The first strain gauge is attached to one of the leaf springs among the plurality of leaf springs, closer to the fixed end than to the free end, and The displacement sensor according to claim 13, further comprising the fact that a second strain gauge is attached to one of the leaf springs among the plurality of leaf springs, closer to the free end than to the fixed end.

15. A sensor belt comprising a displacement sensor according to any one of claims 1 to 14, wherein the sensor belt is The system further comprises a band, one end of which is fastened to the fixed input mount of the displacement sensor and the other end of which is fastened to the displaceable input mount, The band is configured to transmit the force acting on the band to the displaceable input mount, thereby translating the free end of the displacement arm along the displacement axis, in a sensor belt.

16. The sensor belt according to claim 15, wherein the displacement sensor is configured to determine the displacement of the free end of the displacement arm along the displacement axis from the force acting on the band, which is converted into the displaceable input mount.

17. The aforementioned sensor belt The sensor belt according to claim 15 or 16, further comprising an electrical sensor having a plurality of electrodes, configured to determine the potential difference between the plurality of electrodes.

18. The sensor belt according to claim 17, wherein the electrical sensor is an electromyography sensor.

19. A sensor belt for monitoring the respiration of a subject, wherein the sensor belt comprises a displacement sensor according to any one of claims 1 to 14, and the sensor belt is A band configured to be applied around the chest of a subject, further comprising a band having one end fastened to the fixed input mount of the displacement sensor and the other end fastened to the displaceable input mount, A sensor belt configured such that when the subject breathes, the band transmits force from the expansion of the subject's chest to the displaceable input mount, causing the free end of the displacement arm to translate along the displacement axis.

20. The sensor belt according to claim 19, wherein the displacement sensor is configured to determine the displacement of the free end of the displacement arm along the displacement axis from the force acting on the band, which is converted into the displaceable input mount.

21. The aforementioned sensor belt The sensor belt according to claim 19 or 20, further comprising an electrical sensor having a plurality of electrodes, configured to determine the potential difference between the plurality of electrodes.

22. The sensor belt according to claim 21, wherein the electrical sensor is an electromyography sensor.

23. A sensor belt system comprising a sensor belt according to any one of claims 15 to 22, wherein the sensor belt system is A processor connected to the displacement sensor, configured to receive output from the displacement sensor and / or the electrical sensor, and A sensor belt system further comprising a power supply connected to the displacement sensor.

24. The sensor belt system according to claim 23, wherein the processor is configured to determine one or more respiratory parameters based on the output of the displacement sensor and / or the electrical sensor.

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