Physiological parameter sensing system and method

Abstract

A device 100 for sensing a physiological parameter of a subject comprises a force sensor 102 and a displacement sensor 104 associated with the force sensor 102, wherein the force sensor 102 is configured to generate a first signal representing a force displacement of an organ of the subject. The displacement sensor 104 is configured to generate a second signal representing a displacement velocity of the organ of the subject. A coupling 106 is arranged on one of the force sensor 102 and the displacement sensor 104, and the coupling 106 is configured to mechanically couple the force sensor 102 and the displacement sensor 104 to the organ.

Description

Technical Field

[0001] The present disclosure relates generally to sensing of signals and, more particularly, to sensor assemblies for sensing signals related to at least one physiological parameter of a subject. Background Art

[0002] While there are a variety of sensors and systems for measuring signals when placed around a volume, particularly for measuring and monitoring physiological parameters of a living subject, providing a useful output signal representative of the parameter being measured continuously and reliably remains a challenge. Furthermore, doing so while the living subject can comfortably adapt to the sensor / system measuring the parameter is also challenging, particularly if the subject is required to wear the sensor / system for an extended period of time.

[0003] In living subjects, the use of force-sensitive resistors (FSRs) to sense muscle contraction strength has been reported.

[0004] Any discussion of documents, acts, materials, devices, articles or the like which has been included in this specification should not be taken as an admission that any or all of these matters form part of the prior art base or were common general knowledge in the field relevant to the present disclosure as it existed before the priority date of each appended claim. Summary of the invention

[0005] According to a first aspect of the present invention, there is provided a device for sensing physiological parameters of a subject, the device comprising: a force sensor configured to generate a first signal, the first signal representing a force displacement of an organ of the subject; a displacement sensor associated with the force sensor, the displacement sensor being configured to generate a second signal representing a displacement velocity of the organ of the subject; and a connector arranged on one of the force sensor and the displacement sensor, the connector being configured to mechanically connect the force sensor and the displacement sensor to the organ.

[0006] The force sensor may include a first force sensing resistor (FSR). The displacement sensor may include a piezoelectric sensor. The organ may be skin.

[0007] The coupler may have a maximum planar surface area that is smaller than the maximum planar surface area of ​​the force sensor. In addition, the maximum planar surface area of ​​the coupler may be close to the maximum planar surface area of ​​the displacement sensor.

[0008] Force sensors can be installed on displacement sensors.

[0009] The force sensor may include an operative front surface coupled to an operative rear surface of the coupler and an operative rear surface coupled to the operative front surface of the displacement sensor.

[0010] In another embodiment, the force sensor and the displacement sensor may each have an operative front surface coupled to an operative rear surface of the coupler.The force sensor and the displacement sensor may be concentrically arranged on the operative rear surface of the coupler.

[0011] The coupler may include a front surface configured to contact the organ. The front surface may be dome-shaped or mushroom-shaped or conical or pyramid-shaped. Conversely, the coupler may be cylindrical or cuboid. The coupler may include at least one of a rigid plastic material (such as an acrylic resin) and a conductive material.

[0012] The device may also include a second force sensor configured to measure a force applied to the operative rear surface of the device. The second force sensor may be a force sensing resistor (FSR). The second force sensor may be coupled to the operative rear surface of the displacement sensor.

[0013] The device may further comprise a fixing device configured to fix the device to the subject's organ. The fixing device may comprise at least one of: a) a belt member; b) a strap; c) an adhesive patch.

[0014] The device may also include at least one processor configured to determine a physiological parameter based on the first signal and the second signal.The at least one processor may be configured to calibrate the second signal received from the displacement sensor based on the first signal.

[0015] Physiological parameters may include at least one of: cardiac function parameters such as heart beats, blood pressure such as central aortic pressure or peripheral blood pressure, uterine contractions, fetal activity, breathing, body sounds such as heart sounds, the subject's heart valve opening time, the subject's heart valve closing time, the subject's heart contractility level, the subject's heart stroke volume, cardiac output, and blood flow pulse conduction time.

[0016] According to another aspect of the present disclosure, a method for measuring a physiological parameter of a subject is provided, the method comprising: receiving a first signal from a first force sensor, the first force sensor being mechanically connected to the skin at a first position on the subject; receiving a second signal from a second force sensor, the second force sensor being mechanically connected to the skin at a second position on the subject, the second position being separate from the first position; and determining the physiological parameter based on a comparison of the first signal and the second signal.

[0017] The comparison may include a difference between the first signal and the second signal.

[0018] One or more of the first force sensor and the second force sensor may be a force sensing resistor (FSR).

[0019] Physiological parameters may include at least one of: cardiac function parameters such as heart beats, blood pressure such as central aortic pressure or peripheral blood pressure, uterine contractions, fetal activity, breathing, body sounds such as heart sounds, the subject's heart valve opening time, the subject's heart valve closing time, the subject's heart contractility level, the subject's heart stroke volume, cardiac output, and blood flow pulse conduction time.

[0020] The first location may be on the upper chest of the subject, for example at or near the xiphoid process. The second location may be on the lower chest of the subject. The physiological parameter to be measured may be central arterial pressure.

[0021] In another embodiment, the first location may be on the subject's chest. The second location may be close to one of the subject's femoral artery and subclavian artery or other peripheral arteries. In this case, the physiological parameter to be measured may be peripheral blood pressure.

[0022] The method may also include receiving a third signal from a third force sensor mechanically coupled to the skin at a third location separate from the first location and the second location and determining a physiological parameter based on a comparison of the first signal, the second signal, and the third signal. The third force sensor may be a FSR.

[0023] The method may also include mechanically coupling one or more of the first sensor and the second sensor to the skin of the subject.

[0024] According to another aspect of the present disclosure, a system for measuring physiological parameters of a subject is provided, the system comprising: a first force sensor configured to generate a first signal representing a force displacement at a first position on the subject's skin; a second force sensor configured to generate a second signal representing a force displacement at a second position on the subject's skin; and at least one processor configured to determine the physiological parameters of the subject based on a comparison between the first signal and the second signal.

[0025] The comparison may include a difference between the first signal and the second signal.

[0026] At least one of the first force sensor and the second force sensor may be a force sensing resistor (FSR).

[0027] Physiological parameters may include: cardiac function parameters such as heart beats, or blood pressure such as central aortic pressure or peripheral blood pressure, uterine contractions, fetal activity, breathing, body sounds such as heart sounds, the opening time of the subject's heart valves, the closing time of the subject's heart valves, the contractility level of the subject's heart, the stroke volume of the subject's heart, cardiac output, and blood flow pulse conduction time.

[0028] The first location may be on the upper chest of the subject, for example at or near the xiphoid process. The second location may be on the lower chest of the subject. The physiological parameter to be measured may be central arterial pressure.

[0029] In another embodiment, the first location may be on the subject's chest. The second location may be close to one of the subject's femoral artery and subclavian artery or other peripheral arteries. In this case, the physiological parameter to be measured may be peripheral blood pressure.

[0030] The system may also include a third force sensor configured to generate a third signal representing a force displacement at a third location on the subject's skin separate from the first location and the second location. A physiological parameter may then be determined based on a comparison of the first signal, the second signal, and the third signal. The third force sensor may be a FSR.

[0031] One or more of the first force sensor and the second force sensor may be the first force sensor of the device as described above.

[0032] According to another aspect of the present invention, a device for sensing at least one parameter of a subject is provided, the device comprising: a flexible sensor member having an impedance that changes with bending; and a flexible carrier that surrounds the flexible sensor member and is configured to keep a contact surface of the flexible sensor member close to a surface of the subject so that a change in shape (e.g., radius) of the surface of the subject causes the flexible sensor to bend.

[0033] The flexible sensor member may include a force sensing resistor (FSR).

[0034] The carrier may be at least one of a fabric carrier and an elastic carrier. The carrier may include a belt member or an adhesive sheet. The carrier may include clothing worn by the subject. The clothing may include a shirt, or a vest, or a jacket, or a coat.

[0035] The surface of the subject may be skin, such as skin on the subject's chest. The flexible carrier may be configured to hold the contact surface close to the skin so that expansion and contraction of the skin (eg, expansion and contraction of the thorax due to breathing) causes the flexible sensor to bend.

[0036] The device may also include at least one processor configured to generate at least one parameter based on the impedance of the flexible sensor member.

[0037] Parameters may include: cardiac function parameters such as heart beats, or blood pressure such as central aortic pressure or peripheral blood pressure, or uterine contractions, fetal activity, breathing, body sounds such as heart sounds, the subject's heart valve opening time, the subject's heart valve closing time, the subject's heart contractility level, the subject's heart stroke volume, cardiac output, and / or blood flow pulse conduction time.

[0038] According to another aspect of the present disclosure, a method of sensing at least one parameter of a subject is provided, the method comprising: positioning the flexible sensor as described above at a first position proximate to an organ of the subject; and determining the at least one parameter based on impedance of the flexible sensor member. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Embodiments of the present disclosure will now be described by way of example with reference to the accompanying drawings, in which:

[0040] FIG. 1a is a schematic diagram of a first embodiment of a sensor assembly;

[0041] FIG1 b is a schematic diagram of a second embodiment of a sensor assembly;

[0042] FIG. 1c is a schematic diagram of a third embodiment of a sensor assembly;

[0043] FIG. 1d is a schematic diagram of a fourth embodiment of a sensor assembly;

[0044] Figures 2a to 2g show variations of the coupling of Figures 1a and 1b;

[0045] 3-6 illustrate embodiments of sensor assemblies in various arrangements on a human subject;

[0046] FIG7 shows a signal processing chain for processing signals received from a sensor assembly;

[0047] 8 to 10 illustrate example processing circuits implemented by the signal conditioning stages of the signal processing chain of FIGS. 7 a and 7 b for generating a force signal from a force sensor of the sensor assembly of FIG. 1 or 2 ;

[0048] 11 to 13 show circuit diagrams of example processing circuits implemented by the signal conditioning stages of the signal processing chain of FIGS. 7 a and 7 b for generating a force signal based on characteristics of the force sensor and the second force sensor of the sensor assembly of FIG. 2 ;

[0049] 14 shows a block diagram of an example processing chain implemented by the signal conditioning stage of the signal processing chain of FIGS. 7 a and 7 b for generating a conditioned velocity signal from a displacement sensor of the sensor assembly of FIGS. 1 a or 1 b ;

[0050] 15a shows a first embodiment of a processing circuit implemented by a signal conditioning stage of the signal processing chain of FIGS. 7a and 7b for generating a conditioned velocity signal from a displacement sensor of the sensor assembly of FIGS. 1a or 1b ;

[0051] 15 b shows a second embodiment of a processing circuit implemented by a signal conditioning stage of the signal processing chain of FIGS. 7 a and 7 b for generating a conditioned velocity signal from a displacement sensor of the sensor assembly of FIGS. 1 a or 1 b ;

[0052] FIG16 shows a signal processing chain for processing signals received from a plurality of sensor assemblies;

[0053] FIG17 is a graph showing force versus time recorded by the sensor assembly of FIG1a, the sensor assembly being positioned on the sternum of the subject shown in FIG3;

[0054] FIG18 is a graph showing force versus time recorded by the sensor assembly of FIG1a, the sensor assembly being positioned on the sternum of the subject shown in FIG3;

[0055] FIG19 is a graph of the sum of two force signals from force sensors of a sensor assembly located at the suprasternal notch and apex of a subject, respectively;

[0056] 20 is a graph comparing a force signal obtained from a force sensor of the sensor assembly of FIG. 1a with an integral of a displacement velocity signal obtained from a displacement sensor of the sensor assembly of FIG. 1;

[0057] FIG21 is a graph comparing an electrocardiogram (ECG) with force and displacement signals obtained from the sensor assembly of FIG1;

[0058] FIG. 22 is a graph showing a force signal obtained from the force sensor of the sensor assembly of FIG. 1a and a respiration signal obtained from the force signal together with an ECG and a respiration signal obtained from the ECG;

[0059] FIG23 is a graph showing force and accelerometer signals obtained from the sensor assembly of FIG1a together with heart sound signals, ECG, and photophethysmogram (PPG);

[0060] FIG24 is a graph showing raw data related to respiration obtained from the sensor assembly of FIG1a;

[0061] Fig. 25 is a graph showing data related to sounds and a seismocardiogram obtained from the sensor assembly of Fig. 1a;

[0062] FIG26 is a cross-sectional view of an embodiment of a sensor assembly;

[0063] FIG27 is a plan view of the embodiment of the sensor assembly shown in FIG26;

[0064] FIG28 shows a pair of the sensor assemblies of FIG26 arranged on the chest of a subject;

[0065] FIG29 is a respiration signal obtained from the sensor assembly of FIG26;

[0066] FIG30 is a cross-sectional view of another embodiment of a sensor assembly;

[0067] FIG31 is a cross-sectional view of another embodiment of a sensor assembly;

[0068] FIG32 is a graph of pulse transit time (PTT) obtained from the sensor assembly of FIG1a with a subject at rest;

[0069] FIG33 is a graph of PTT obtained from the sensor assembly of FIG1a after physical exertion by a subject;

[0070] FIG34 is a graph of cardiac activity obtained from the sensor assembly of FIG1a with a subject at rest;

[0071] FIG35 is a graph of cardiac activity obtained from the sensor assembly of FIG1a after a low amount of physical exertion by a subject; and

[0072] 36 is a graph of cardiac activity obtained from the sensor assembly of FIG. 1a following extensive physical exertion by the subject. DETAILED DESCRIPTION

[0073] Embodiments of the present disclosure relate to sensing systems and methods for monitoring physiological mechanics based on local measurements of forces exerted on the skin surface by displacements of organs, muscles, blood flow, and fluid displacement (i.e., digestion, swallowing, breathing, etc.) and their propagation speed.

[0074] Some embodiments use force sensors such as force sensitive resistors (FSRs) mechanically coupled to the subject's skin on the chest or upper abdomen to measure the recoil forces generated by the heart's contraction and blood pumping action, the so-called "forcecardiography (FCG)". Thus, embodiments can achieve continuous and non-invasive monitoring of mechanical events during each cardiac cycle of the subject. In particular, by using multiple force sensors mechanically coupled to the subject's skin, information about physiological parameters can be obtained, such as the identification and duration of each phase of the cardiac cycle, the timing of heart valve opening and closing, the level of heart contractility, stroke volume, cardiac output, pulse transit time, and central aortic pressure. Furthermore, information about heart disease and / or dysfunction can be obtained, such as but not limited to heart failure, mechanical dyssynchrony (e.g., due to bundle branch block), valvular pathology (e.g., aortic and mitral regurgitation, stenosis), etc.

[0075] When provided near a peripheral pulse point or large blood vessel (i.e., neck pulse, radial artery pulse, etc.), a force sensor can be used to measure the force of blood movement and flow and its propagation velocity. Such flow can include venous return as well as changes in hydrostatic pressure due to respiration. Thus, embodiments make it possible to infer respiration rate from force measurements of a peripheral limb.

[0076] Some embodiments use one or more force sensors (e.g., FSRs) in combination with displacement sensors (e.g., piezoelectric sensors), both of which are mechanically coupled to the subject's skin, to simultaneously measure the force displacement of the subject's skin and the speed or rate of such displacement. The compressive force (DC baseline of the force sensor signal) and the dynamic force (AC component of the force sensor signal) applied to the force sensor can be used to calibrate the displacement velocity signal generated by the displacement sensor, thereby allowing accurate and continuous direct measurement of the speed or rate of skin displacement as well as the force displacement itself. In this way, an accurate and continuous measurement of blood pulsation, and therefore heart pulsation, can be obtained based solely on skin movement.

[0077] Although the sensor assembly described herein has been specifically developed for measuring physiological parameters (e.g., cardiac activity and respiratory activity) of a living subject, it will be appreciated by those skilled in the art that the sensor assembly that is the subject of the present disclosure may be used with other objects where forces are applied by portions below the sensor assembly. Thus, the sensor assembly described herein may be used in industrial applications, such as soft robotics or other inanimate objects that apply such forces.

[0078] 1a is a cross-sectional view of a first embodiment of a sensor assembly 100 for sensing at least one physiological parameter of a subject. The sensor assembly 100 includes a force sensor 102, a displacement sensor 104, and a mechanical coupling 106. The force sensor 102 and the displacement sensor 104 are arranged on the coupling 106 so that any force applied to the front surface 108 of the coupling is transmitted to both the force sensor 102 and the displacement sensor 104.

[0079] The connector 106 includes a rigid material, such as a rigid plastic or rubber. In some embodiments, the connector 106 may include an acrylic resin. In other embodiments, the connector 106 may be partially or entirely conductive. For example, the connector 106 may partially or entirely include a conductive material, such as silver or silver chloride. The front surface 108 of the connector 106, which is configured to face and preferably be placed in contact with the surface of the subject, may be dome-shaped so as to press into a compliant surface of the subject, such as the skin. Providing a dome-shaped front surface 108 helps to improve the connection from the subject to the mechanical displacement of the force sensor 102 and the displacement sensor 104. Other shapes of the front surface 108 that provide similar effects include cones, mushrooms, etc.

[0080] The coupling 106 has a generally circular cross-section when viewed in a plane parallel to the subject-facing plane of the sensor assembly 100. In addition to coupling movement (force and displacement), the coupling 106 can be configured as a biopotential electrode and can be electrically coupled to processing circuitry (not shown) for measuring biopotentials (e.g., electrocardiogram (ECG), electromyogram (EMG), electroencephalogram (EEG), etc.).

[0081] The force sensor 102 is mounted to the rear surface of the connector 106 via a force sensor carrier 110, which includes a flexible medium. The force sensor 102 is mounted to the carrier 110 by gluing, lamination or other means. Two or more electrodes 112 are used to make electrical connections with the force sensor 102, and the two or more electrodes 112 are also used as anchor points for anchoring the force sensor 102 to the sensor carrier 110. The force sensor 102 is a force sensitive resistor (FSR) or a force sensor. As will be described in more detail below, the characteristics of the force sensor 102 change in response to the force signal applied to the force sensor, and the change represents the force displacement of the organ in contact with the front surface 108 of the connector 106. Such characteristics are, for example, the impedance or output current or voltage of the force sensor 102. As will be described in more detail below, in the case where the force sensor 102 is a FSR, the resistance change of the force sensor 102 represents the force displacement, and an output voltage can be generated according to the force displacement.

[0082] In an embodiment, the front surface of the force sensor 102 that faces the subject in use has a surface area of ​​between about 5 mm and 10 mm, for example 7 mm, 8 mm or 9 mm.

[0083] The force sensor 102 and the displacement sensor 104 are mounted together via an optional rigid interface layer 114. The rigid interface layer 114 is disposed on the rear surface of the force sensor 102. The rigid interface layer 114 may include brass, rigid plastic, or a similar rigid material. In some embodiments, the rigid interface layer 114 may be a double-sided PCB, with the force sensor 102 mounted on a first surface of the PCB (i.e., the surface facing the subject in use), and the displacement sensor 104 mounted on an opposite second surface of the PCB.

[0084] In any case, displacement sensor 104 is mechanically coupled to the rear surface of force sensor 102, as shown in FIG1a. Thus, displacement of coupler 106 due to movement of an organ in contact with coupler 106 causes displacement sensor 104 to move. Displacement sensor 104 generates a signal representing the speed or rate of displacement of sensor 104. When mechanically coupled to an organ, such as the skin of a subject, this velocity signal is proportional to the displacement velocity of the organ.

[0085] In an embodiment, the front surface of the displacement sensor 104 facing the subject has a surface area between about 5 mm and 10 mm, such as 7 mm, 8 mm, or 9 mm.

[0086] Advantageously, the surface areas of force sensor 102 and displacement sensor 104 are substantially matched to ensure uniform transfer of displacement from force sensor 102 to displacement sensor 104. Therefore, force sensor 102 and displacement sensor 104 are also preferably axially aligned along an operative central vertical axis of assembly 100 for similar reasons.

[0087] An optional protective cover 116 may be disposed around the rear surface of the displacement sensor 104. The protective cover 116 may be separated from the rear surface by a fluid gap filled with air or other gas or a vacuum. In doing so, the protective cover 116 protects the displacement sensor 104 from impacts on the non-subject-facing operative rear side of the assembly 100.

[0088] In addition to the force sensor 102 and the displacement sensor 104, the sensor assembly 100 may optionally include an accelerometer 120. The accelerometer 120 is configured to measure acceleration on one or more axes. For example, the accelerometer 120 may be configured to measure acceleration on at least an axis perpendicular to the surface of the subject to which the sensor assembly 100 is attached in use. Preferably, in addition, the accelerometer 120 measures acceleration in one or more planes parallel to the surface of the subject to which the sensor assembly 100 is attached in use, so as to measure the movement of the sensor assembly in such planes or axes. The accelerometer 120 may be positioned anywhere on the sensor assembly 100 as long as it can be mechanically coupled (directly or indirectly) to the connector 106. For example, the accelerometer 120 may be coupled to the rear of the protective cover 116.

[0089] The housing 118 encapsulates the sensor assembly 100 to protect the components of the assembly 100 from debris such as dust, grit, water, and / or any other substances that may affect the operation of the assembly 100, and to prevent foreign matter from entering the assembly 100. The operative front surface 108 of the coupler 106 extends through the aperture of the housing 118. Alternatively, the housing 118 may include at least one flexible portion (not shown) that extends over and conforms to the front surface 108 of the coupler 106, thereby completely encapsulating the force sensor 102, the displacement sensor 104, and the coupler 106.

[0090] During operation, the front surface 108 of the connector 106 of the sensor assembly 100 is placed in contact with a surface of a subject (such as the subject's skin), and the sensor assembly 100 is fixed relative to the subject by one or more fixing devices such as belts, adhesive sheets, adhesive patches, etc. (not shown). Such tape can be made of materials made of sports tape (also known as kinesio tape). By mechanically coupling the force sensor 102 and the displacement sensor 104 to the connector 106 and mechanically coupling the connector 106 to the surface of the subject, the sensor assembly 100 is configured to generate synchronized force displacement and displacement velocity signals. As will be described in more detail below, these signals are in turn used to achieve continuous and non-invasive monitoring of mechanical physiological events.

[0091] Fig. 1b is a cross-sectional view of another embodiment of a sensor assembly 200, which is a variation of the sensor assembly 100 shown in Fig. 1a. Referring to Fig. 1a, in Fig. 1b, like reference numerals refer to like components unless otherwise specified.

[0092] In addition to the elements of sensor assembly 100, sensor assembly 200 of FIG1 b also includes a second force sensor 202 that is similar to force sensor 102 and has similar features. Second force sensor 202 is operably mounted behind displacement sensor 104, for example, on an operative outer surface of protective cover 116. Similar to force sensor 102, second force sensor 202 is configured to (actively or passively) generate a signal representative of the force applied at second sensor 202. Thus, second force sensor 202 is used to measure forces applied to the operative rear portion of assembly 200, for example, as a result of applying sensor assembly 200 to a surface of a subject using one or more fixtures.

[0093] This measured external force signal can be used to compensate for carrier pressure (i.e., the force applied to the rear of the sensor assembly 200 by the fixture) and the surface elasticity of the subject (i.e., how elastic is the surface of the subject being sensed). For example, knowing the pressure applied by the operator of the external carrier or assembly 200 will allow artifacts to be eliminated. For example, a sudden impact or shearing of the sensor, i.e., during movement, may change the pressure applied by the force sensor 102, which in turn may produce artifacts in the signal from the force sensor 102. In addition, the rhythm caused by activities such as the subject running may leave baseline drift and related artifacts in the signal from the force sensor 102. As will be described in more detail below, the signals obtained from each of the two force sensors 102, 202 and the displacement sensor 104 can be used to eliminate such artifacts (either in real time or in post-processing).

[0094] Referring now to Figures 1c and 1d of the drawings, there are shown other embodiments of sensor assemblies 100 and 200. Referring again to the previous drawings, like reference numerals refer to like parts unless otherwise specified.

[0095] In both embodiments, the coupler 106 includes a collar 109 that is received within the housing 118, with the dome-shaped surface 108 of the coupler 106 protruding through an opening (not shown) in the housing 118. The diameter of the opening is smaller than the diameter of the collar 109, so that the collar 109 helps to keep the coupler 106 fixed relative to the housing 118 and prevents the coupler 106 from being separated from the housing 118.

[0096] Furthermore, in both embodiments, the diameter of the coupler 106 at its base, i.e., the diameter of the portion of the coupler 106 that contacts the sensor carrier 110 (referred to as the "base diameter"), is smaller than the diameter of the force sensor 102. However, it is desirable and preferred that the coupler 106 distributes its force over the entire surface area of ​​the displacement sensor 104. In this way, the base diameter of the coupler 106 is close to the diameter of the displacement sensor 104. Typically, the base diameter of the coupler 106 is approximately 70% to 90%, such as approximately 80%, of the diameter of the force sensor 102.

[0097] In the embodiment shown in FIG. 1d of the accompanying drawings, the sensor assembly 200 further includes a post-pressure applicator or coupling 111. Typically, in use, the coupling 111 is covered by a component of the sensor assembly 200 through which it is attached to the subject's organ, such as a belt member, a belt, a tape, etc. (not shown). This component applies a displacement force to the force sensor 202 through the coupling 111 and helps remove artifacts recorded by the sensor assembly 200 due to external factors such as movement of the sensor assembly 200 relative to the subject's organ.

[0098] Although coupling 111 is shown as a plate-like structure, it should be understood that coupling 111 may have any suitable shape, including a dome shape similar to coupling 106. Likewise, coupling 111 has a diameter that is smaller than the diameter of force sensor 202, typically about 70% to 90%, such as about 80%, of the diameter of force sensor 202.

[0099] As described above, the dome-shaped coupler 106 facilitates compression into a compliant surface of the subject, such as the skin. Thus, providing the coupler 106 with a dome-shaped front surface 108 improves the coupling of mechanical displacements from the subject to the force sensor 102 and the displacement sensor 104.

[0100] The above-mentioned sensor assemblies 100, 200 include force sensors and displacement sensors stacked in a "sandwich" arrangement with each other. However, embodiments of the present disclosure are not limited to this arrangement. For example, in other embodiments, the force sensors and displacement sensors can be arranged in a planar configuration, for example, arranged adjacent to each other or concentrically arranged (one within the other), and can be arranged on a common substrate or on different separate substrates. In each embodiment, each force sensor and displacement sensor is preferably (directly or indirectly) mechanically coupled to a connector, such as connectors 106, 111 of Figures 1a to 1d, to ensure mechanical transmission of force from the subject to each sensor.

[0101] Figures 2a to 2g show several variations of the coupling 106 of Figures 1a to 1d, which may replace the coupling 106 shown in Figures 1a and 1b. As before, like reference numerals refer to like parts unless otherwise specified.

[0102] 2a is a cross-sectional view of a sensor assembly 100 having a mushroom-shaped coupler 201 including a dome-shaped front surface 203 and a dome-shaped rear surface 205 configured to contact the force sensor 102. Providing the dome-shaped rear surface 205 creates a smaller contact surface area between the coupler 201 and the force sensor 102, thereby increasing the force per unit area applied to the sensor, which in turn increases the sensitivity of the sensor 102 to the force applied to the front surface of the coupler 201.

[0103] Figure 2b shows an embodiment of a sensor assembly 100 similar to the sensor assembly of Figure 2a, but including a coupling 111 acting on a force sensor 202 as described above with reference to the sensor assembly 202 of Figure Id.

[0104] FIG. 2c and FIG. 2d provide a perspective (enlarged) view and a side view, respectively, of a coupling 204, similar to the coupling 201 of FIG. 2a and FIG. 2b, the coupling 204 includes a dome-shaped front surface 206 and a dome-shaped rear surface 208 configured to contact the force sensor 208. Optionally, the coupling 204 is held in place relative to the housing 118 and the force sensor 102 by one or more fasteners 210 (e.g., elastic or elastomeric connectors). In other embodiments, the coupling 204 can be held in place by rear pressure on the housing 118 and in contact with the surface of the subject and a carrier (not shown). As shown in FIG. 2d, providing a dome-shaped rear surface 208 creates a smaller contact surface area between the coupling 204 and the force sensor 102, thereby increasing the force per unit area applied to the sensor, which in turn increases the sensitivity of the sensor 102 to the force applied to the front surface of the coupling 204. As described above with respect to coupler 106, it has been found that providing a domed front surface 206 improves coupling of mechanical displacements from the subject to force sensor 102 and displacement sensor 104. Other shapes of front and rear surfaces 206, 208 that provide similar effects include cones, mushrooms, and the like.

[0105] 2e and 2f show another coupler 212, which is a variation of coupler 204. Coupler 212 includes a ball portion 214 supported within housing 118 by a flange 216 extending around the periphery of ball portion 214. Flange 216 may form part of housing 118. Optionally, a seal 218, such as a gasket or O-ring, is provided between ball portion 214 and flange 216 to prevent the ingress of dust and other harmful substances.

[0106] 2g shows a coupler 220 which is a variation of coupler 212 in which ball portion 214 has been replaced by a double mushroom or waist shaped coupling member 222. The waist of coupling member 222 is engaged and held in place in coupler 220 by flange 216 which also prevents coupling member 222 from separating from housing 118.

[0107] The above-mentioned sensor assemblies 100, 200 each include a displacement sensor 104. However, it should be noted that embodiments of the present disclosure are not limited to the use of a combination of force sensors and displacement sensors. For example, various novel techniques will be described below for detecting various physiological parameters using multiple force sensors located at different locations on the subject. Such techniques do not require simultaneous displacement sensing. Such techniques may use the above-mentioned sensor assemblies 100, 200, or alternatively may use a sensor assembly that only includes a force sensor and a connector. Such a sensor assembly may include any conceivable connection arrangement, such as one of the arrangements shown in any one of Figures 1a to 2g. For example, an embodiment may use a variation of the sensor assembly 100 shown above, but omit the displacement sensor 104.

[0108] 3-6 illustrate various arrangements of a sensor assembly secured to a human subject 300, such as sensor assembly 100 of FIG. 1a, sensor assembly 200 of FIG. 1b, or variations thereof.

[0109] 3, a single sensor assembly 302 is secured relative to the xiphoid process using a chest strap 304. The chest strap 304 is configured to apply external pressure from the rear of the sensor assembly 302 and hold the sensor assembly 302 at or near the xiphoid process.

[0110] 4, multiple sensor assemblies 402 are secured to the skin of subject 300 using adhesive patches 404. Similar to chest strap 304, each adhesive patch 404 is configured to apply external pressure from the rear of sensor assembly 402 to hold it at a predetermined location on subject 300, typically the subject's chest.

[0111] 5 shows another arrangement in which a plurality of sensor assemblies 502 are secured to the chest of a subject 300 using a common adhesive patch 504, which is configured to apply external pressure from the rear of the sensor assemblies 502 to maintain them in a predetermined position relative to the subject 300. Additionally or alternatively, the plurality of sensor assemblies 502 may be secured to the back of the subject 300 in any suitable manner. By providing a plurality of sensor assemblies 502 around the torso of the subject, force tomography of the chest region may be generated based on data obtained from the sensors of the sensor assemblies 502.

[0112] 6 shows another arrangement in which a single sensor assembly 602 is secured relative to a radial vein or artery located on a wrist 604 of a subject 300. The sensor assembly 602 may be held in place on the wrist 604 by a wristband 606 (or adhesive or other means), which also applies an external force to the rear of the sensor assembly 602 to maintain contact between the assembly 602 and the wrist 606.

[0113] 7a and 7b are block diagrams showing an exemplary signal processing chain 700 for processing signals and / or parameter changes of the force sensor 102, the displacement sensor 104, the second force sensor 202, and the optional accelerometer 120 generated from a live subject. In the following examples, the force sensor 102 and the second force sensor 202 will be described below as force sensitive resistors (FSRs) FSR1 and FSR2, whose resistance is proportional to the force applied thereto. However, it should be understood that embodiments are not limited to the use of FSRs as force sensors, and that load cells or force sensors may be used in place of FSRs without departing from the scope of the present disclosure. Likewise, in the following examples, the displacement sensor 104 will be described in some examples as a piezoelectric sensor PZT, which generates a voltage in response to a change in displacement. However, again, embodiments are not limited to the use of a piezoelectric sensor as the displacement sensor 104. Other exemplary displacement sensors include, but are not limited to, resistive, inductive, capacitive, eddy current, ultrasonic, magnetoresistive, and optical encoder displacement sensors.

[0114] The displacement sensor 104, the second force sensor 202, and the accelerometer 120 are shown in dashed lines in Figures 7a and 7b because some embodiments of the present disclosure only require the force sensor 102 for operation, or require the force sensor 102 and one or more of the displacement sensor 104, the second force sensor 202, and the accelerometer 120.

[0115] The signal processing chain 700 includes a signal conditioning stage 702, an analog-to-digital conversion stage 704, and a filtering stage 706 to generate a representation of one or more physiological parameters including, but not limited to, respiration, ejection pulse, force parameters, velocity parameters, heart sounds, and blood pressure.

[0116] During the signal conditioning phase 702 , the resistance FSR1 of the force sensor 102 is converted to an output voltage Vn by hardware (processing circuitry) or by software in post-processing.

[0117] Exemplary hardware for performing this conversion is shown in Figures 8-10. Referring to Figure 8, the resistance FSR1 of the force sensor 102 forms one tail of a voltage divider 802, the output of which is provided to the input of a non-inverting amplifier 804 to generate an output voltage Vn proportional to the resistance FSR1 of the force sensor 102. In another embodiment, referring to Figure 9, a transimpedance amplifier 902 is used to convert the change in the resistance FSR1 of the force sensor 102, and the resistance FSR1 is configured as a variable input impedance of the amplifier 902. In another embodiment, as shown in Figure 10, the force sensor 102 is integrated into a current mirror 1002, and the resistance FSR1 of the force sensor 102 is configured as a bias resistor of the current mirror 1002.

[0118] As described above, the second force sensor 202 can be used to calibrate the varying forces applied by any fixation device or the subject itself to the posterior (non-subject-facing) side of the sensor assembly 200. Referring again to FIGS. 7a and 7b, a signal conditioning circuit is implemented during signal conditioning 702 to further bias the resistance of the force sensor 102 based on the resistance FSR2 of the second force sensor 202. FIGS. 11-13 each illustrate an example of a hardware layout suitable for such functionality.

[0119] FIG. 11 is a variation of the transimpedance amplifier arrangement of FIG. 9 , in which a bias voltage V2 is coupled to the non-inverting input of the amplifier 1102 , the bias voltage V2 being varied by a current sinking load through the resistor FSR2 of the second force sensor 202 .

[0120] FIG12 shows another variation of the arrangement of FIG9 , comprising a transimpedance stage 1202 having a further stage 1204 configured to inject a current proportional to the resistance FSR2 of the second force sensor 202 into the inverting input of the stage 1202, thereby reducing the output voltage Vn as the resistance FSR2 increases. The values ​​of the DC voltage V1 and the passive resistors R1 and R2 in FIGS. 11 and 12 are set according to the power supply used and the desired dynamic range of the output voltage Vn.

[0121] 13 shows another variation in which the resistance FSR2 of the second force sensor 202 is provided in the feedback loop of the transimpedance stage 1302. The gain of the stage 1302 is proportional to the resistance FSR2 and, in turn, to the pressure applied to the rear surface of the sensor assembly 200. Again, the resistance R1 is set according to the power supply used and the desired dynamic range of the output voltage Vn.

[0122] It should be understood that any of the above hardware solutions may alternatively be implemented in software, either in real time or after recording the signals from two or more of the sensors 102 , 104 , 202 .

[0123] It should also be understood that in addition to calibrating the first sensor 102, the signal obtained from the first sensor 102 can be used to determine skin compliance, such as to differentiate tissue (fat / muscle percentage, etc.) This measurement can be used to determine the amount of fat under the subject's skin.

[0124] As described above, in some embodiments, the displacement sensor 104 includes a piezoelectric sensor configured to generate a current in response to a change in displacement. In this case, the DC offset and AC voltage swing of the signal output from the displacement sensor 104 may need to be adjusted or calibrated. To this end, the signal conditioning stage 702 adjusts the signal output of the displacement sensor 104 by implementing a processing circuit such as that shown in Figures 14, 15a, and 15b.

[0125] 14, the displacement sensor 104 (PZT) is polarized using a current source 1402 (which may be digitally controlled) to adjust the AC voltage swing caused by the displacement change. A subsequent voltage amplifier 1404 is provided for adjustment of the DC offset.

[0126] FIG15a shows an exemplary implementation of signal conditioning 702 for displacement sensor 104. As with FIG14, current is injected into displacement sensor 104 and the resulting high pass filtered signal V1 is provided to voltage amplifier stage 1502 to adjust the DC offset. Note that the feedback resistor R7 and input impedance R3 of the non-inverting input of amplifier stage 1502 are selected to match the impedance of displacement sensor 104 (PZT).

[0127] FIG. 15b shows another exemplary embodiment of a signal conditioning circuit 1502 for use with the displacement sensor 104. Referring to FIG. 15a of the drawings, like reference numerals refer to like components unless otherwise noted. The signal conditioning circuit 1502 utilizes Miller's theorem to increase the input impedance (R) detected by the displacement sensor 104 based on the following equation: IN ):

[0128]

[0129]

[0130] This improves the overall low frequency response of signal conditioning circuit 1502 by lowering the high pass cutoff frequency, which is selected to reduce possible phase shifts introduced by the high pass response, even at the lowest frequencies of interest, which is the lower limit of the respiration signal band to aid comparison with the signal from force sensor 102. In some applications, the cutoff frequency is set to a range of approximately 0.01-0.05 Hz.

[0131] To enable the use of different displacement sensors 104 without the need for custom circuitry, the signal conditioning circuit 1502 can be tuned based on the specific capacitance of the selected displacement sensor 104. Using surface mount device (SMD) resistors in a pilot configuration, smaller resistance values ​​can be used to reduce the cost of the circuit 1502. As an example, a 100 MΩ resistor R1, a 100 Ω resistor R3, and a 100 kΩ trimmer R2 can be used in the circuit 1502 so that when R2 is set to 0, the displacement sensor 104 "sees" an impedance R of 100 MΩ. IN (To provide a cutoff frequency of 0.05 Hz for a displacement sensor 104 capacitance of 30 nF). By adjusting R2 to increase the resistor of the regulator, R IN Increase to 10 11 Ω.

[0132] Referring again to FIGS. 7a and 7b, during the signal conditioning stage 702, a conditioning force signal Vn representing the force applied to the coupling 106 and a conditioning displacement signal Vd representing the displacement velocity at the coupling 106 are generated. Optionally, an acceleration signal Va representing the acceleration at the coupling 106 may also be generated. These analog signals are then converted into digital representations of the force F, displacement velocity V, and acceleration A, respectively, using one or more ADCs 708 through an analog-to-digital conversion (ADC) stage 704. In some embodiments, a single ADC 708 may be provided, and the conditioning signals Vn, Vd, Va are provided to the ADC via a multiplexer (not shown). In other embodiments, the conditioning signals Vn, Vd, Va may be provided to separate ADCs 708, as shown in FIGS. 7a and 7b.

[0133] The digital signals F, V, A are then provided to a digital filter stage 706 which is configured to implement one or more filters 710, 712, 714, 716 to filter the force F, velocity V and (optionally) the accelerometer signal A to generate one or more outputs representing physiological parameters of the subject. These parameters are specific to the location on the living subject at which the assembly 100, 200 is located during measurement. For example, when located on the chest of the subject as shown in Figures 3 to 5, the digital filter stage 706 is operable to extract data related to cardiac activity (e.g., seismocardiogram, heart sounds, etc.) in addition to respiration and pulse cardiograms. In the case where the assembly 100, 200 is located on the wrist, the digital filter stage 706 may only be able to extract data related to respiration and blood pulse.

[0134] A breathing signal 720 from the subject is extracted by low pass filtering the force signal F using a low pass filter 710. The low pass filter 710 may, for example, have a low pass threshold of approximately 0.5 Hz.

[0135] A pulse signal is generated from the force signal by bandpass filtering the force signal F with a bandpass filter 712. The bandpass filter may, for example, have a passband between approximately 0.5 Hz and approximately 8 Hz.

[0136] Force and velocity parameters specific to the organ of the living subject being monitored are extracted from each of the force F and velocity signals V, respectively, by bandpass filtering the signals F, V with another bandpass filter 714. For example, for force and velocity parameters of the heart, the bandpass filter 714 may have a passband between about 8 Hz and about 40 Hz.

[0137] Body sounds can also be extracted from the force F and velocity signals V using a bandpass filter 716 having a lower threshold of about 20 Hz, about 30 Hz, about 40 Hz, or about 50 Hz in combination with an upper threshold of about 150 Hz, about 200 Hz, about 250 Hz, or about 300 Hz. In some embodiments, the bandpass filter 716 can have a passband between about 40 Hz and about 300 Hz. Depending on the location of the sensor assembly 100, 200, body sounds can include one or more of the following: heart sounds (e.g., accelerated blood flow, valve movement), bowel sounds (e.g., gas displacement), breathing, snoring, swallowing, and fetal sounds (including fetal movement, fetal heart sounds, fetal breathing, fetal gas displacement, etc.), muscle contractions around the airway (e.g., trachea).

[0138] The reduction in the size of the airway can also be monitored by monitoring changes in sounds emanating from the neck region. For example, wheezing or higher pitched sounds or vibrations in the neck can indicate respiratory insufficiency (reduced respiratory fraction), apnea, or asthma, as well as other lung and respiratory diseases. As discussed below with reference to FIG. 23 , body sounds can also be extracted from the signal received from the accelerometer 120. The body sounds can be generated based on a combination of two or more of the force F, velocity V, and acceleration signal A.

[0139] The extracted body sounds can be output to one or more speakers or headsets to be heard by the clinician. Therefore, the sensor assembly 100, 200 can be used as a digital stethoscope, providing a high-resolution digital representation of body sounds. Such extracted body sounds can be modulated and / or shifted in frequency to be more easily heard by the human ear. For example, the extracted body sounds can be shifted in frequency to the center of the human hearing range.

[0140] Note that the various filters 710, 712, 714, 716 of the digital filter stage 706 are provided merely as examples of filters that may be implemented to extract information from the force F and velocity signals V. Depending on the physiological parameters to be extracted and the location of the components 100, 200 on the subject, one or more of the filters 710, 712, 714, 716, 718 may be omitted, or other filters may be added.

[0141] Where multiple sensor assemblies are provided at different locations on the subject, each force, velocity and accelerometer signal generated by these assemblies may be filtered in a manner similar to that described above with reference to FIGS. 7a and 7b. For example, as shown in FIG. 16, where like reference numerals represent like parts, digital force F1-FN, velocity V1-VN and acceleration signals A1-AN may be provided by N sensor assemblies 1602, 1604 to a digital filter stage 1606, respectively. For simplicity, the sensor assemblies 1602, 1604 include signal conditioning and A / D conversion circuits for generating force, velocity and acceleration signals.

[0142] In addition to filtering the individual force and velocity signals from one or more of the sensor assemblies 1602, 1604, the digital filter bank 1606 is also configured to combine the force and / or velocity signals from two or more of the sensor assemblies 1602, 1604 before or after filtering. For example, the filter bank 1606 may include a bandpass filter and a combining module 1608 configured to combine the force signals F1, FN from two sensor assemblies 1602, 1604 located at different locations on the subject to generate the blood pressure signal 1610. The signals F1, FN may be bandpass filtered before combining, or the signals may be combined and a bandpass filter applied to the combined signal to generate the blood pressure signal 1610.

[0143] The filter bank 1606 is configured to combine any combination of received signals before or after filtering in any manner without departing from the scope of the present disclosure.

[0144] With the foregoing in mind, FIGS. 17-25 illustrate various signals extracted by exemplary sensor assemblies 100 , 200 affixed at various locations on a human subject.

[0145] FIG. 17 illustrates an extracted force signal 1702 obtained from the sensor assembly 300 of FIG. 3 positioned on the sternum of the subject 300 and secured at the xiphoid process by a belt 304. A corresponding ECG signal 1704 measured simultaneously is also shown for comparison. It can be seen that various cardiac parameters can be identified in the force signal 1702, including but not limited to a P wave component 1706, a QRS complex 1708, and a T wave component 1710. Thus, the sensor assembly 300 can be used to diagnose diseases such as arrhythmias (e.g., atrial fibrillation). Other parameters can also be extracted from the force signal 1702, including: the duration of each phase of the cardiac cycle, the heart valve opening time 1712 and closing time 1714, the level of cardiac contractility, stroke volume, cardiac output, and pulse transit time.

[0146] FIG. 18 illustrates an extracted force signal 1802 obtained from a sensor assembly similar to that shown in FIG. 3 using an adhesive patch instead of belt 304 at a similar location at or near the xiphoid process. A corresponding ECG signal 1804 measured simultaneously is also shown for comparison. It can be seen that, similar to FIG. 17 , the force signal 1802 provides various cardiac indications corresponding to the cardiac indications of the ECG signal 1804.

[0147] FIG. 19 illustrates a combined signal 1902, which is the sum of the force signals generated by the force sensors of the sensor assembly 402 shown in FIG. 4, wherein one of the sensor assemblies 402 is placed on the upper chest at or near the suprasternal notch and another of the sensor assemblies 402 is placed on the lower chest at or near the apex of the heart. A corresponding ECG signal 1904 is also provided for reference. It can be seen that the resulting combined signal 1902 represents an estimate of the central arterial pressure through the heart, from which various parameters can be estimated, including the peak reflected wave P1 and the jet wave P2. Therefore, it should be understood that the differential measurement of force and / or velocity using the sensor assembly described herein enables the determination of the blood pressure gradient between various parts of the subject, not just the central arterial pressure. For example, the measurement results of force and / or velocity using two or more sensor assemblies at the suprasternal notch and the femoral artery (or subclavian artery or other peripheral artery) can be compared to determine the peripheral blood pressure.

[0148] FIG. 20 illustrates a force signal 2002 generated from a force sensor 102 (FSR) of a sensor assembly 100 and an integral signal 2004 of a displacement velocity signal generated from a displacement sensor 104 (PZT) of the sensor assembly 100 located at or near the xiphoid process as shown in FIG. 3 . The figure shows the substantial similarity of the integral 2004 of the velocity signal to the force signal 2002, velocity being the first derivative of force displacement. Thus, it can be seen that the force signal 2002 can be used to calibrate the velocity signal 2004 in real time before operating the sensor or during monitoring to account for sensor drift, particularly when using piezoelectric sensors. It can also be seen from FIG. 20 that p-waves are visible in both the force signal 2002 and the integral signal 2004, highlighted in the figure by corresponding circles 2006, 2008. In addition, descending mid-wave notches can also be seen in the signals 2002, 2004, highlighted in FIG. 20 by large arrows 2010, 2012, respectively.

[0149] FIG. 21 illustrates a force signal 2102 generated by a force sensor (FSR) of the sensor assembly 602 and a displacement velocity signal 2104 generated by a displacement sensor (PZT) of the sensor assembly 602 located at or near the radial artery on the wrist 604 of the subject 300 as shown in FIG. 6. A corresponding ECG signal 2106 is also shown for comparison. The circles in each figure highlight the measured p-waves visible in each signal 2102, 2104, 2106. The large arrows identify the descending mid-wave notch in each of the force signal 2102 and the velocity signal 2104. As can be seen from FIG. 20, the p-wave is visible in the signals received from the force signal 2102 and the velocity signal 2104 measured at the wrist 604.

[0150] FIG. 22 illustrates the extraction of respiration signals 2102 , 2104 from respective force signals 2106 and ECG signals 2108 by low pass filtering (eg, using the low pass filter 710 described above with reference to FIGS. 7 a and 7 b ).

[0151] As described above, the sensor assembly 100, 200 may be provided with one or more accelerometers configured to measure the acceleration of the sensor assembly 100, 200. FIG. 23 illustrates an accelerometer signal 2302 obtained from the accelerometer 120 and a force signal 2304 obtained from the force sensor 102 of the sensor assembly 100 located at or near the xiphoid process as shown in FIG. 3. For comparison, recorded heart sounds 2306, photoplethysmogram (PPG) 2308, and ECG 2310 signals are also shown. As can be seen from the figure, the signal 2302 received at the accelerometer 120 has similar characteristics to the recorded heart sound signal 2306 having similar characteristics. Therefore, it can be seen that the accelerometer 2302 can be used to generate a sound signal representing body sounds, as described above with reference to FIGS. 7a and 7b.

[0152] Fig. 24 illustrates raw data extracted from the sensor assembly 100 of Fig. 1a. In Fig. 24, an ECG signal 2402 is provided as a reference, trace 2404 shows five respiratory cycles recorded by the displacement sensor 104, and trace 2406 shows five respiratory cycles recorded by the force sensor 102.

[0153] Similar to FIG. 23 , FIG. 25 illustrates data of sounds and seismograms extracted from the sensor assembly 100 of FIG. 1a . In FIG. 25 , trace 2502 represents raw data from the force sensor 102 after respiratory artifacts have been filtered out of the signal, trace 2504 represents raw data from the displacement sensor 104 after respiratory artifacts have been removed, and trace 2506 is a seismogram extracted from the displacement sensor 104 using the signal conditioning circuits of FIG. 7a and FIG. 7b . Trace 2508 is a sound map extracted from the displacement sensor 104 . Trace 2510 is an ECG signal provided for comparison purposes. It can therefore be seen that, with appropriate signal conditioning, a signal representing body sounds can be extracted from the displacement sensor 104 and a seismogram can be provided without the need for an ECG device. Thus, a subject wearing the sensor assembly 100 , 200 can be monitored while performing an activity, and an ECG device can be attached to the subject's body without waiting for the activity to complete.

[0154] 26 and 27 are cross-sectional and plan views, respectively, of a sensor assembly 2300 that includes a flexible sensor 2302 at least partially encapsulated in a flexible carrier layer 2304. Similar to the force sensor 102 of the assembly 100 of FIG1a, the force sensor 2302 may be a FSR whose impedance changes as the flexible sensor 2302 flexes or bends. The flexible carrier layer 2304 is able to bend, thereby enabling the sensor 2302 to conform to the curvature of the surface of the subject to which the sensor 2302 is applied.

[0155] The flexible carrier layer 2304 is preferably made of a material that, while flexible, is substantially incapable of stretching in a direction perpendicular to the surface of the subject to which the layer 2304 is conformable. Thus, bending of the carrier layer 2304 and, therefore, bending of the flexible sensor 2302 results in a change in the resistance of the flexible sensor 2302 (when it is an FSR), or in a change in the characteristics of the flexible sensor 2302. The sensor assembly 2300 also includes a fixture 2306 for holding the sensor assembly 2300 in place relative to the subject. For example, the fixture 2306 is an anchor point for attaching the sensor assembly 2300 to a carrier, such as clothing worn by the subject. The clothing may be a shirt, a belt, a waistband, a vest, etc. Similarly, the sensor assembly 2300 can be worn in a pocket of clothing without the fixture 2306. Any of the conditioning or signal processing modules or circuits described above with respect to the sensor assemblies 100, 200 can also be used to condition or generate a signal from the flexible sensor 2302.

[0156] In use, the sensor assembly 2300 is positioned at a fixed position on a surface of a subject 2500 having a radius of curvature that varies over time. For example, as shown in FIG28 , the sensor assembly 2300 is fixed to the chest of the subject 2500. The expansion of the chest during breathing causes the flexible sensor 2302 to bend, thereby changing the properties (resistance or other) of the flexible sensor 2302.

[0157] FIG. 29 illustrates a clear periodic breathing signal generated by the flexible sensor 2302 of the sensor assembly 2300 integrated in the seam of a shirt worn by the subject 2500 as shown in FIG. 28 .

[0158] FIG30 shows a schematic cross-sectional view of a sensor assembly 2700, which is a variation of the sensor assembly 2300, wherein, with reference to FIGS. 26 and 27, like reference numerals refer to like components unless otherwise indicated. The sensor assembly 2700 also includes a flexible displacement sensor 2702 configured to generate a velocity signal representing a velocity or displacement velocity of the sensor 2702. The displacement sensor 2702 is coupled to a rear surface of the flexible carrier layer 2304. The displacement sensor 2702 is optionally at least partially encapsulated in an additional flexible carrier layer 2704. In an embodiment, the displacement sensor 2702 is a piezoelectric sensor.

[0159] FIG31 shows a schematic cross-sectional view of a sensor assembly 2800, which is a variation of the sensor assembly 2700, wherein, with reference to FIG30, like reference numerals refer to like parts unless otherwise indicated. Similar to the force sensor 202 of the assembly 200 shown in FIG1 b, the sensor assembly 2800 additionally includes a second force sensor 2802 mounted on the displacement sensor 2702. Optionally, the second force sensor 2802 is at least partially encapsulated in a flexible carrier layer 2704 similar to the flexible carrier layer 2304 of the sensor assembly 2700. Similar to the force sensor 202, the force sensor 2802 changes resistance as external pressure is applied to the assembly 2800. Thus, such externally applied forces (and associated human influences) can be taken into account and the flexible sensor 2302 calibrated accordingly.

[0160] The operation of sensor assemblies 2700, 2800 is similar to the operation of corresponding sensor assemblies 100, 200 and therefore will not be described in detail here.

[0161] 32 and 33 illustrate that the sensor assemblies 100, 200 may be used to measure pulse transit time (PTT) and changes in PTT as the blood pressure of a subject increases.

[0162] The sensor assembly 100, 200 is placed on the chest wall of a healthy subject and on the right common iliac artery of the subject. Trace 3202 represents the pulse velocity detected by the displacement sensor 104 at the iliac crest after the respiratory artifact is removed, and trace 3204 represents the pulse velocity detected by the displacement sensor 104 at the chest wall of the subject near the apex of the subject after the respiratory artifact is removed.

[0163] In FIG. 32 , traces 3202 and 3204 are measured before the subject exercises, more specifically, before doing push-ups. It is noteworthy that before the subject exercises, the iliac-apex lag is approximately 146 ms based on a resting blood pressure of 123 / 68 for a healthy subject. FIG. 33 shows that the PTT hysteresis is significantly reduced after exercise, and the subject's blood pressure increases to 144 / 79. After exercise, the iliac-apex lag is reduced to approximately 59 ms. This indicates that the sensor assembly 100, 200 can be used to detect PTT when the sensor assembly 100, 200 is attached to the subject.

[0164] Figures 34 to 36 illustrate the use of sensor assemblies 100, 200 for measuring cardiac activity, and more specifically, for measuring cardiac stroke volume during exercise in healthy subjects. Figure 34 shows various parameters for a healthy subject at rest. Figure 3 shows those parameters for a subject lifting weights at a first, low rate, and Figure 36 shows the same parameters for a subject lifting weights at a second, high rate.

[0165] In this test, the sensor assembly 100, 200 is attached to the chest wall of the subject. The subject is then asked to lift a weight at two different speeds to achieve two different effort levels. In these figures, trace 3402 represents a low-frequency force cardiogram (FCG) measured by the force sensor 102 of the sensor assembly 100, 200. Trace 3404 represents a high-frequency FCG measured by the force sensor 102 of the sensor assembly 100, 200. Trace 3406 represents the respiratory effort measured by the displacement sensor 104 of the sensor assembly 100, 200. Trace 3408 represents a standard ECG, provided for comparison purposes.

[0166] The results clearly show that the amplitudes of the low-frequency and high-frequency FCGs increase consistently, which is proportional to the subject's cardiac effort level. In particular, relative to the values ​​of the FCG measured before exercise, the amplitude of the low-frequency FCG doubles when lifting weights at a low speed and triples when lifting weights at a higher speed. In contrast, the high-frequency FCG, which is known to be highly correlated with the seismogram extracted by the displacement sensor 104, increases by approximately 1.5 times when lifting weights at a low speed and almost doubles when lifting weights at a higher speed. These results indicate that the two FCG components carry different cardiac mechanics information, and the low-frequency FCG is more correlated with stroke volume than the high-frequency FCG.

[0167] One or more of the sensor assemblies described herein can be integrated into a medical device in any combination for in-situ monitoring of a subject in a variety of situations. For example, the sensor assembly can be mounted in or on a mattress, seat, or chair configured to monitor one or more physiological parameters of the subject (such as any of the above-mentioned physiological parameters). In addition, the sensor assembly can be configured to detect and monitor the movement and position of the subject relative to the sensor assembly on the bed or mattress. Such monitoring may be advantageous in preventing bedsores (where the sensor assembly is integrated into a mattress, etc.).

[0168] It should be understood that embodiments of the present disclosure can be used to diagnose and monitor a variety of human and animal diseases and symptoms, wherein these diseases and symptoms can be diagnosed and monitored by measuring the force, displacement and / or acceleration of the skin. Non-limiting examples of cardiac symptoms and diseases include: functional murmurs, cirrhosis, hypertension, angina pectoris, myocardial infarction, ventricular aneurysm, mitral valve prolapse (MVP), isolated clicks and murmurs, mitral regurgitation, mitral stenosis (MS), tricuspid regurgitation (TR), mitral regurgitation, aortic regurgitation, aortic stenosis, hypertrophic obstructive cardiomyopathy, cardiomyopathy, pericarditis, pulmonary hypertension, atrial septal defect, ventricular septal defect, patent ductus arteriosus, pulmonary artery stenosis, aortic coarctation, tetralogy of Fallot, coronary heart disease, heart failure, systolic heart failure, diastolic heart failure, pulmonary embolism, cor pulmonale, etc.

[0169] Lung diseases and lung symptoms may also be diagnosed, including pulmonary congestion. Embodiments of the present disclosure may also be used to diagnose and monitor sleep disorders such as sleep apnea, for example by placing one or more sensor assemblies described herein at or near the trachea or other locations around the neck of the subject. The sensor assembly may be configured to monitor snoring, swallowing, contraction of muscles around the airway (e.g., trachea), size reduction in the airway, optionally in addition to breathing.

[0170] Arterial and / or venous symptoms (calcification, collapse, etc.) can be diagnosed and monitored by placing one or more sensor assemblies described herein on the skin at or near the artery to be monitored. For example, in some embodiments, sensor assemblies can be placed bilaterally at the respective left and right arteries, and a comparison can be made between the left and right arteries to determine symptoms in one or the other (or both) of the arteries.

[0171] In any of the above embodiments, the sensor assembly may be integrated into a wearable device for short-term or long-term use, and force, velocity, and / or acceleration measurements may be collected and stored so that symptoms and diseases may be monitored over time.

[0172] The sensor assembly described herein can also be used to monitor uterine contractions during pregnancy. A pregnant subject can wear one or more sensor assemblies at a location on the skin near the uterus, contractions cause force displacement of the skin, and corresponding signals are obtained from the force sensors and displacement sensors of the sensor assembly and the optional accelerometer.

[0173] The sensor assemblies described herein can be used not only to measure, diagnose, and monitor human or animal subjects, but can also be used to monitor fetal activity in such subjects. For example, one or more sensor assemblies (e.g., sensor assemblies 100, 200) can be placed in locations around the abdomen to monitor movement, breathing, and cardiac signals of a fetus in the uterus of an animal or human subject in a manner similar to that described above with reference to the human or animal subject itself.

[0174] In the embodiments described herein, particularly with reference to Figures 3 to 5, the sensor assembly is secured to the front of the torso. For example, Figure 4 shows the sensor assembly positioned in a frontal auscultation position. It should be understood that one or more sensor assemblies may be secured to the back of the torso of an animal or human subject, such as a standard auscultation position on the back of the torso, without departing from the scope of the present disclosure.

[0175] In particular, those of ordinary skill in the art who benefit from this disclosure should understand that the various operations described herein (especially in conjunction with the accompanying drawings) may be implemented by other circuits or other hardware components. The order in which each operation in a given method is performed may be changed, and the various elements of the system shown herein may be added, reordered, combined, omitted, modified, etc. The present disclosure is intended to include all such modifications and variations, and therefore, the above description should be considered illustrative rather than restrictive.

[0176] Similarly, although the present disclosure refers to specific embodiments, certain modifications and changes may be made to these embodiments without departing from the scope and coverage of the present disclosure. In addition, any benefits, advantages, or solutions to problems described herein with respect to specific embodiments are not intended to be interpreted as critical, required, or essential features or elements.

[0177] Likewise, other embodiments will be apparent to one of ordinary skill in the art having the benefit of this disclosure, and such embodiments are considered to be encompassed herein.

[0178] For many applications, embodiments may be implemented on a DSP (digital signal processor), an ASIC (application specific integrated circuit), or an FPGA (field programmable gate array). Thus, the code may include conventional program code or microcode, or, for example, code for setting or controlling an ASIC or FPGA. The code may also include code for dynamically configuring a reconfigurable device such as a reprogrammable logic gate array. Similarly, the code may include code for a hardware description language such as Verilog TM or VHDL (very high speed integrated circuit hardware description language). As will be appreciated by those skilled in the art, the code may be distributed among multiple connected components that communicate with each other. Where appropriate, embodiments may also be implemented using code running on a field (re)programmable analog array or similar device to configure analog hardware.

[0179] Note that as used herein, the term "module" will be used to represent a functional unit or block that may be implemented at least in part by dedicated hardware components such as custom circuits, and / or at least in part by one or more software processors or appropriate code running on a suitable general-purpose processor, etc. A module may itself include other modules or functional units. A module may be provided by multiple components or sub-modules that need not be co-located and may be provided on different integrated circuits and / or run on different processors.

[0180] It will be appreciated by those skilled in the art that various changes and / or modifications may be made to the above embodiments without departing from the broad scope of the present disclosure. Therefore, the present embodiments are considered in all aspects to be illustrative and not restrictive.

Claims

1. A device for sensing a physiological parameter of a subject, the device comprising: A force sensor configured to generate a first signal representing a force displacement of an organ of the subject; wherein the first signal is further passed through a bandpass filter to generate a first filtered signal, the bandpass filter having a passband range of 0.5 Hz to 300 Hz; a displacement sensor associated with the force sensor, the displacement sensor configured to generate a second signal representative of a displacement velocity of the organ of the subject; and a coupler disposed on one of the force sensor and the displacement sensor, the coupler being configured to mechanically couple the force sensor and the displacement sensor to the organ; Wherein, the connector has a maximum planar surface area that is smaller than or close to a maximum planar surface area of ​​the force sensor. 2 . The device of claim 1 , wherein the force sensor comprises a first force sensing resistor (FSR).

3. The device according to claim 1 or 2, wherein the displacement sensor comprises a piezoelectric sensor.

4. The apparatus of claim 3, wherein the maximum planar surface area of ​​the coupler approximates a maximum planar surface area of ​​the displacement sensor. The apparatus according to claim 1 , wherein the force sensor is mounted to the displacement sensor.

6. The apparatus of claim 5, wherein the force sensor comprises an operative front surface coupled to an operative rear surface of the coupler and an operative rear surface coupled to an operative front surface of the displacement sensor.

7. The apparatus of claim 1, wherein the force sensor and the displacement sensor each have an operative front surface coupled to an operative rear surface of the coupler.

8. The apparatus of claim 7, wherein the force sensor and the displacement sensor are concentrically arranged on the operative rear surface of the coupling.

9. The apparatus of claim 1, wherein the coupler comprises an anterior operative surface configured to contact the organ, wherein the anterior operative surface is one of a dome-shaped, a mushroom-shaped, a cone-shaped, and a pyramid-shaped.

10. The apparatus of claim 1, wherein the coupler is cylindrical.

11. The apparatus of claim 1, wherein the coupler is a rectangular parallelepiped.

12. The apparatus of claim 1, wherein the coupler comprises at least one of a rigid plastic material and a conductive material.

13. The apparatus of claim 12, wherein the rigid plastic material comprises acrylic.

14. The device of claim 1, further comprising a second force sensor configured to measure a force applied to an operative rear surface of the device.

15. The apparatus of claim 14, wherein the second force sensor is a force sensing resistor (FSR).

16. Apparatus according to claim 14 or 15, wherein the second force sensor is coupled to an operative rear surface of the displacement sensor.

17. The apparatus according to claim 1, further comprising a fixation device configured to fix the apparatus to the organ of the subject.

18. The apparatus of claim 17, wherein the fixing means comprises at least one of: a) With components; c) Adhesive sheet.

19. The apparatus of claim 17, wherein the fixing means comprises: b) Belt.

20. The apparatus of claim 1, further comprising at least one processor configured to determine the physiological parameter based on the first filtered signal and the second signal.

21. The apparatus of claim 20, wherein the at least one processor is configured to calibrate the second signal received from the displacement sensor based on the first filtered signal.

22. The apparatus according to claim 1, wherein the physiological parameters include at least one of: cardiac function parameters, blood pressure, uterine contraction, fetal activity, respiration, heart valve opening time of the subject, heart valve closing time of the subject, heart contractility level of the subject, heart stroke volume of the subject, cardiac output, and blood flow pulse conduction time.

23. The apparatus of claim 22, wherein the physiological parameter is blood pressure, the parameter to be measured comprising at least one of central aortic pressure and peripheral blood pressure.

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