Device used for non-invasive hemodynamic parameter measurement

Abstract

A cuff is provided for use in measuring hemodynamic parameters, the cuff having a shell portion for surrounding a body portion of a subject and pressure applying means surrounding the shell portion, the shell portion being positioned between the actuator and the body portion. The shell portion is formed to have at least two circumferential portions that form a closed loop around the body portion of the subject when the cuff is assembled on the body portion of the subject. For example, the shell portions overlap at their respective ends, forming at least a first overlapping region and a second overlapping region. By forming a shell structure with multiple circumferential portions, it is possible to open the shell portion from the side by sliding it to separate the shell portion at at least one tangential confluence point between the circumferential portions. For example, in some embodiments, the shell structure can be opened by sliding it tangentially to separate at least two shell portions in the first overlapping region.

Description

Technical Field

[0001] The present invention relates to the field of non-invasive hemodynamic parameter measurement.

Background Art

[0002] The most common method for non-invasive blood pressure (NIBP) measurement is the use of a blood pressure measurement cuff of the oscillometric method. This cuff has an inflatable bladder. The cuff is wrapped around the upper arm of the patient and is controlled to expand through inflation and contraction cycles. During this cycle, the pressure in the bladder is sampled, and a single set of values for systolic arterial pressure and diastolic arterial pressure is derived by processing the pressure signal.

[0003] Different techniques for non-invasive blood pressure measurement have already been proposed. This technique also uses a cuff wrapped around a body part of the patient. A cross-sectional view is shown in FIG. 1. The patient's arm 10 and the cuff 2 wrapped around the brachial artery 8 are shown. The cuff 2 includes a pressure actuator 14, which can optionally be an inflatable bladder as in a conventional NIBP cuff. Different from a conventional NIBP cuff, another cuff also includes a separate tissue pressure sensor 4 arranged to measure the pressure between the body part 10 and the cuff. The tissue pressure sensor in some examples has a sensor pad filled with fluid, and the pressure in this pad changes as a function of the pressure applied to the pad. Also, different from a conventional NIBP cuff, another cuff includes a rigid shell 12 that extends around the body part and is arranged (radially) between the actuator 14 and the body part 10.

[0004] The pulse wave of the brachial artery 8 causes a change in the movement of the skin. This change in the movement of the skin causes compression of the liquid in the sensor pad 4. The sensor pad is fluid-connected to a pressure transducer that measures the pressure signal via a flexible tube filled with the same liquid.

[0005] The pressure sensor pad 4 is surrounded by a rigid shell 12, allowing for rigidity and sufficient signal from the pressure sensor. Similar to a standard NIBP cuff, a pressure actuator 14 with an air pump-inflatable bladder compresses the arm tissue, thereby closing the brachial artery 8.

[0006] Because the rigid shell 12 includes a separate tissue pressure sensor 4 behind it, the cuff can acquire a real-time pulse signal from the patient, from which several different hemodynamic parameters, including stroke volume and cardiac output, can be obtained.

[0007] In current state-of-the-art technology, the shell structure 12 has a tangentially continuous structure, and in the most common design, it is formed from a single piece of material that is rounded and curled to define a complete (closed) loop. Figure 2 schematically shows an exemplary shell structure 12 using the latest technology. Figure 2 (left) shows a cross-section across a plane perpendicular to the longitudinal axis of the shell and parallel to the tangential and radial axes of this shell. Figure 2 (right) shows a cross-section across a plane parallel to the longitudinal axis of the shell. It can be seen that the shell structure is tangentially continuous.

[0008] In current state-of-the-art technology, due to the fact that the rigid shell 12 is relatively inflexible with respect to the diameter of the arm to which it is attached, there are multiple different cuff sizes to accommodate the various arm diameters of patients.

[0009] EP2953528B1 describes one exemplary embodiment of the various blood pressure measurement cuffs described above.

[0010] Appropriate algorithms for processing tissue pressure measurements to derive one or more hemodynamic parameters are described, for example, in references WO2018 / 210931, WO2020 / 148137, WO2019 / 211210, US10485432, EP2759258B1 and US10349849.

[0011] For example, as described in WO2018 / 210931, in some embodiments, SAP, DBP, and MAP values ​​can be obtained based on identifying peaks in the amplitude of a series of tissue pressure pulses to be measured. Then, various blood pressure measurements can be determined based on identifying the amplitude values ​​of the sequence of tissue pressure pulses at a predefined rate of decrease of the peak amplitude value. For further details, see WO2018 / 210931. [Overview of the project] [Problems that the invention aims to solve]

[0012] The inventors recognize that the problem with the current shell-back measuring cuff described above is the relative impracticality of attaching this cuff to the patient's arm. Because it is a rigid shell structure with an integrated coil structure, the cuff needs to be slid from the hand to the arm. However, in practice, the hand may have a cannula inserted for intravenous injection. Therefore, to attach the cuff, the injection must first be stopped and the cannula removed. Furthermore, the need to slide the cuff from the hand to the arm is physically difficult for the caregiver. Because the shell is a tangentially closed structure, to attach the cuff, the caregiver must first lift the arm, and then, while holding the arm, slide the cuff itself into place. However, both hands are required to properly position the cuff. In practice, this means that at least two caregivers are needed to attach a shell-back cuff to the patient's arm. [Means for solving the problem]

[0013] The inventors have devised an improved version of the known shellback cuff, aimed at addressing one or more of the problems described above.

[0014] The present invention is defined by the claims.

[0015] According to an embodiment of one aspect of the present invention, an apparatus for non-invasive hemodynamic parameter measurement is provided, the apparatus having a cuff extending around a body part, wherein the cuff has a pressure actuator for applying controllable pressure to the body part, and further has a shell structure extending around the body part and positioned between the pressure actuator and the body part when the cuff is fitted.

[0016] The shell structure can be configured in both a closed and an open state.

[0017] In the closed state, the shell structure forms a closed loop around a central lumen for receiving a body part of the subject, and in the open state, there are openings / cuts / discontinuities around the circumference of the shell structure to allow an arm to be inserted into the lumen.

[0018] The shell structure consists of at least two shell parts (at least a first shell part and at least a second shell part), each shell part defining a portion of the circumference of the shell when the shell structure is closed, and these shell parts overlap tangentially across at least the first overlapping region and the second overlapping region when closed.

[0019] Transitioning the shell structure from a closed state to an open state involves detaching the shell portion tangentially in at least one of the overlapping regions.

[0020] Therefore, we propose to provide a hemodynamic measurement cuff with a shell structure, which has two circumferential slits (discontinuities), thereby allowing the cuff to be attached to the arm laterally or laterally, instead of having to pass the arm through the central lumen from the hand to the upper arm. This makes the cuff easier to attach. In particular, it can be attached by a single caregiver, that is, one hand can be used to lift and hold the patient's arm while the other hand is used to attach and position the cuff on the arm.

[0021] Furthermore, a supplementary advantage of the proposed design is the simplification of manufacturing. State-of-the-art shell-back cuffs have a shell structure that is integrally molded, formed by coiling during manufacturing to create a tubular shape. This requires a complex molding process. According to embodiments of the present invention, since there are two or more shell parts, these shell parts can be formed more easily, for example, using a simple opening and closing injection molding process.

[0022] In some embodiments, a releaseable fixing means is provided in the first overlapping region, which, when fixed and when the shell is closed, can prevent sliding along the tangential side surface between the first and second shell portions in the first overlapping region. By providing a means for tangentially fixing the two shell portions in one of the two overlapping regions, the multi-piece design enables functional replication or imitation of the tangentially continuous shell structure of the prior art. In particular, to optimize measurement accuracy, it is best to have only one overlapping region that slides tangentially.

[0023] There are several reasons for this. First, preferably, when the cuff is attached to the arm during use, the brachial artery is positioned adjacent to a point where it does not move radially within the shell, so that changes in pressure within the artery are most effectively transmitted to the sensor pad. Therefore, it is preferable that the sensor pad is positioned below the portion of the shell that does not slide tangentially, so that it can sense changes in arterial pressure and that these changes are not easily absorbed by the sliding of the shell. Thus, by providing only one overlapping region that slides, the loss of the arterial pressure signal measured by the sensor pad is minimized.

[0024] Furthermore, since each sliding overlapping region carries the risk of skin getting caught between the moving parts of the shell and / or causing unnecessary friction, it is advantageous to have only one sliding overlapping region.

[0025] However, it is not essential to fix one of the two overlapping regions. For example, the inventors have discovered that a similar effect can be achieved by giving different rigidities to the two shell parts. The rigidity can be adjusted so that when a radial force is applied from the body part to the shell structure during operation, only one of the two overlapping regions moves, and the shell consistently and preferentially adapts to that force.

[0026] A further advantage of providing the releasable fixing means in the first overlapping region is that, optionally, in the first overlapping region, the fixing means may be provided so as to enable fixing of the first and second shell parts at a plurality of different relative tangential positions. Thereby, advantageously, the diameter of the shell (when in the closed state), and thus the entire cuff, can be adjusted to accommodate various arm sizes.

[0027] By way of example, the fixing means can have a surface fastener fixing (i.e., Velcro (registered trademark)).

[0028] In some embodiments, at least in the second overlapping region, when the shell is in the closed state, the first and second shell parts are freely slidable along the side surface in the tangential direction. Preferably, the first shell part and the second shell part are freely slidable along the side surface only in the second overlapping region, not in the first overlapping region. Thus, an overlapping region corresponding to the tangential slide is provided. Preferably, by combining this with the first overlapping region that can be releasably fixed, a shell structure is provided that includes a fixed (non-sliding in the tangential direction) overlapping region and a movable (slidable in the tangential direction) overlapping region in the operation of the device. Thus, this almost reproduces the structure of the state-of-the-art shell, but benefits from various improvements in terms of the practicality and ease of manufacture outlined above.

[0029] In some embodiments, the pressure actuator is arranged to support the shell structure radially with respect to the radial separation of at least two shell parts when the cuff is used on a body part. In other words, the pressure actuator functions to help hold together each part of the shell structure. The pressure actuator may be arranged, for example, to extend tangentially around the outside of the shell structure. The pressure actuator may be attached at one or more locations on the outside of the shell structure.

[0030] In some embodiments, the device further has a sheet product arranged to be disposed between the shell structure and the surface of the body part when the cuff is attached to the arm and arranged to contact the body part during use, where the shell structure is slidable tangentially with respect to the sheet product. In other words, a lining is provided between the inner surface of the shell structure and the body part. This prevents the skin from being pinched or wrinkled when the shell moves in the tangential direction. The shell can slide over this lining.

[0031] In some embodiments, a sheet product attached to the shell structure may be provided. Another configuration provides the sheet product as a separate item that is wrapped around the body part individually by a caregiver before attaching to the cuff. By attaching the sheet product, there is no separate attachment step. To facilitate this, in some embodiments, the sheet product is arranged to extend continuously around the radially inner surface of the shell structure between a first attachment point on the first shell part and a second attachment point on the second shell part, and preferably, the first and second attachment points are located in a first overlapping region.

[0032] The sheet product can extend uninterrupted across / throughout the second overlapping region, but is discontinuous in the first overlapping region, where the first end is attached to the first shell portion in the first overlapping region, and the second end is attached to the second shell portion in the first overlapping region. In this way, the sheet product extends around the inner surface of the shell structure, and tension is maintained by the two separable ends of the first and second shell portions.

[0033] This is an effective method for attaching the sheet product. It has the advantage that, when attaching the cuff, the lining is only attached to the shell at both ends, thus still allowing relative tangential sliding between the sheet product and the shell. Using this configuration, the sheet product has the further advantage of effectively performing a secondary function of holding the two shell sections together, at least partially, in a second overlapping area. In particular, the two shell sections cannot be completely separated from each other because the sheet product attached to both the first and second shell sections connects these two shell sections. Attaching the cuff to the patient is also much easier, as the two parts of the shell can be effectively hinged open while remaining a single structure that can be handled with one hand, as will become clearer in a later explanation.

[0034] In some embodiments, at least one of the two shell sections has greater rigidity than the other of the two shell sections. This has the advantage of effectively forcing a preferred direction of tangential movement between the two shell sections in any overlapping region. In particular, the more flexible shell section tends to be more sensitive to radial pressure applied to it than the less flexible shell section, so the more flexible shell section tends to move relative to the arm to accommodate these pressure changes, while the less flexible shell section remains relatively stationary relative to the arm. This has the advantage of maintaining consistency in the shell's motion behavior during operation.

[0035] In some embodiments, one of the two shell portions may be formed from a different material than the other shell portion, for example, a material having a different rigidity or elasticity than the other shell portion.

[0036] For example, in some embodiments, the device further includes a tissue pressure sensor that senses the pressure between the cuff and the body part when the cuff is fitted, and this tissue pressure sensor has a detection pad that is positioned between the shell structure and the body part when in use. The detection pad of this tissue pressure sensor can be positioned between a rigid shell portion and the body part, and the sliding movement of the shell during operation does not affect the pressure measurement from the sensor pad because all of these movements are absorbed by the less rigid shell portion. Furthermore, to ensure that the loss of signal from the brachial artery is minimized, it is advantageous to have a more rigid shell in close proximity to the brachial artery and therefore to the sensor pad.

[0037] In some embodiments, the shell structure includes a first shell portion and a second shell portion, and in both the first and second overlapping regions, the second shell portion is positioned radially above / above the first shell portion. This thus forms a configuration comprising a lower shell and an upper shell. In some embodiments, the second shell portion (upper shell portion) is less rigid than the first shell portion (lower shell portion). Therefore, in this set of embodiments, the first shell portion is the radially lower shell portion and is the more rigid shell portion. For example, the difference in rigidity helps to promote the effect that the upper shell follows the lower shell and does not bend outward during sliding.

[0038] In some embodiments, the first and second shell portions are formed from different materials, for example, the different materials having different rigidities.

[0039] As described above, in some embodiments, the device further includes a tissue pressure sensor that senses the pressure between the shell structure and the body portion when the cuff is attached, and this tissue pressure sensor has a detection pad that is positioned between the shell structure and the body portion when in use. In some embodiments, the tissue pressure sensor is positioned between the first (lower) shell portion and the body portion when in use.

[0040] As mentioned above, the advantage of placing the sensor pad between the less flexible shell and the body is that even if the diameter of the shell structure changes due to sliding in the second overlapping region, the sensor pad can be expected to remain relatively stationary relative to the arm. This is because a more flexible shell structure tends to absorb all sliding motions dynamically. Furthermore, placing the sensor pad radially adjacent to a more rigid shell has the advantage of improving signal strength because the shell has the effect of reducing signal loss due to radial damping.

[0041] In some embodiments, the pressure actuator is fixedly or detachably mounted to the shell structure. In some embodiments, the pressure actuator has an inflatable bladder. Other options, such as a mechanical actuator, are also possible.

[0042] In some embodiments, a pressure actuator is used to wrap around a body part when the cuff is worn. This actuator may be attached to or attachable to one of two shell sections in a first mounting area, and optionally attached to or attachable to the other of the two shell sections in a second mounting area.

[0043] The actuator can be configured in both a closed and an open state, where, in the closed state, the actuator forms a closed loop around a central lumen, and in the open state, an opening is defined around the circumference of the actuator, allowing the arm to be inserted into the lumen. The transition from the closed to the open state involves unfolding the actuator and tangentially separating both ends of the actuator. Thus, the actuator forms an additional annular layer extending circumferentially around the shell structure, which can be opened tangentially (e.g., unfolded or spread) to attach or detach the cuff from the arm.

[0044] The pressure actuator has a length portion incorporating an inflatable bladder, and may further have at least one additional length portion without an inflatable bladder. The actuator is intended to wrap around the circumference of a shell structure, and its length extends around the circumferential dimensions of the shell structure.

[0045] Even if the above example relates to a device in which the shell structure has two shell parts, in further embodiments the shell structure may have more than two shell parts, for example, three or more overlapping shell parts. The same principles as described above can be applied. For example, if there are three shell parts, these shell parts may consist of two fixed overlapping regions and one sliding overlapping region.

[0046] These and other aspects of the present invention will become apparent from and be explained with reference to the embodiments described below. [Brief explanation of the drawing]

[0047] For a better understanding of the present invention and to more clearly illustrate how the present invention is carried out, the accompanying drawings are referenced merely as examples. [Figure 1] Figure 1 shows a cross-section of a prior art hemodynamic parameter measuring device, and the embodiment of the present invention represents an advanced version of the hemodynamic parameter measuring device. [Figure 2] Figure 2 shows a cross-sectional view of an exemplary shell structure used in the apparatus shown in Figure 1. [Figure 3] Figure 3 shows the shell portion of an exemplary device according to one or more embodiments, in an open state for receiving a body part of a subject. [Figure 4] Figure 4 shows the shell portion of Figure 3 in its closed state. [Figure 5] Figure 5 shows more detailed components of an exemplary apparatus according to one or more embodiments. [Figure 6] Figure 6 shows an exemplary apparatus according to one or more embodiments, including a shell and a pressure actuator. [Figure 7] Figure 7 schematically shows exemplary structures and arrangements of pressure actuators for a shell structure according to one or more embodiments. [Figure 8] Figure 8 schematically shows exemplary structures and arrangements of pressure actuators for a shell structure according to one or more embodiments. [Figure 9] Figure 9 shows various possible positions for the tissue pressure sensor pad within the device. [Figure 10] Figure 10 shows a recessed channel on the inner surface of a shell structure for housing a fluid tube for a hydraulic tissue pressure sensor. [Modes for carrying out the invention]

[0048] The present invention will be described with reference to the drawings.

[0049] The detailed descriptions and specific examples illustrate exemplary embodiments of the apparatus, systems, and methods, but these are for illustrative purposes only and should not be understood as limiting the scope of the invention. These and other features, aspects, and advantages of the apparatus, systems, and methods of the invention will be better understood from the following description, the appended claims, and the appended drawings. The drawings are for illustrative purposes only and are not drawn to a specific scale. Also, the same reference numerals are used throughout the drawings to indicate the same or similar parts.

[0050] The present invention provides a cuff for use in measuring hemodynamic parameters, the cuff comprising a shell portion for surrounding a body portion of the subject and a pressure application means surrounding the shell portion, the shell portion being positioned between the pressure application means and the body portion. The pressure application means is operable to apply a variable pressure to the body portion during the measurement cycle. The shell portion is formed to have at least two circumferential portions that form an annular loop around the body portion of the subject when the cuff is assembled on the body portion of the subject. For example, the shell portions overlap at each end of these shell portions, forming at least a first overlapping region and a second overlapping region. By forming a shell structure comprising multiple circumferential portions, the shell can be opened from the side by pulling apart the shell portion at at least one tangential confluence point between the shell portions. For example, in some embodiments, the shell structure can be opened by tangentially pulling apart at least two shell portions in the first overlapping region.

[0051] Therefore, at least one aspect of the proposed device is to provide a shell on the cuff, where the shell is not permanently closed tangentially but can be opened tangentially around the arm. In at least one set of embodiments, this is achieved by providing the shell structure as a system of two tangentially overlapping shells, each defining a respective portion of the circumference of the tube. During cuff attachment, these shell portions can be opened by tangentially pulling apart the shell portions at at least one circumferential position. When the cuff is attached, these shell portions can be pressed to form a tangentially closed system around the arm.

[0052] This allows the cuff to be attached from the side of the arm. As mentioned above, in the latest versions of shell-back cuffs, the shell cannot be opened tangentially, so the entire cuff must be attached to the arm via the hand and slid into the correct position. This typically requires two caregivers to attach the cuff, one to hold the subject's arm and the other to slide the cuff. With the proposed device, cuff attachment can be done with only one caregiver.

[0053] As background, Figure 1 shows a schematic diagram of the basic layer structure of a prior art hemodynamic parameter measuring device, and the embodiment of the present invention represents an advanced version of the hemodynamic parameter measuring device.

[0054] The device can be used as part of a system or method for detecting blood pressure and / or other hemodynamic parameter measurements, such as cardiac output or stroke volume. The figure shows a cuff 2 attached to the patient's upper arm 10. The patient's artery 8 is schematically shown. The device has a design that differs from the most standard cuff-based blood pressure measuring devices in that it includes a dedicated tissue pressure sensor 4 that operates to ensure the cuff contacts and is held in contact with the skin tissue when the cuff is inflated. This feature is shared by embodiments of the present invention.

[0055] The cuff 2 includes an inflatable bladder-type pneumatic actuator 14 used to vary the pressure applied to the body part 10 by the cuff. A tissue pressure sensor 4 is positioned to sense the pressure between the surface of the user's body part and the cuff. Independent of the tissue pressure sensor, one or more operating parameters of the pneumatic actuator can be sampled. For example, the pressure within the inflatable bladder can be sensed. An actuator activity signal indicating the pumping capacity level or pumping speed of the pneumatic actuator's pump can also be sampled.

[0056] The cuff 2 further includes a shell structure 12, which is positioned between the pneumatic actuator 14 and the body part 10 when the cuff is attached to the body part, and is positioned to surround the body part when the cuff is attached. This shell structure can be relatively rigid. As a result, the pressure in the arm is measured by the tissue pressure sensor pad 4 in contact with a relatively rigid support, which prevents attenuation of the amplitude and shape of the signal, thus improving measurement accuracy. In particular, if the tissue pressure sensor pad 4 is at least partially positioned between the shell structure 12 and the body part 10, high accuracy of the signal measured by the tissue pressure sensor unit can be achieved. When such a configuration of the tissue pressure sensor pad 4 is used, the shell structure 12 does not absorb or attenuate the arterial pressure signal.

[0057] The device in Figure 1 differs from a standard blood pressure cuff. A standard cuff uses bladder air pressure as the sole measurement signal for sensing blood pressure. By using the tissue pressure sensor 4 additionally or as an alternative, the device shown in Figure 1 can achieve superior quality results and, in addition to blood pressure, also enables the measurement of advanced hemodynamic parameters such as stroke volume, cardiac output, and fluid responsiveness. In particular, it is assumed that in a standard pneumatic blood pressure cuff, weak air destroys more than 90% of the amplitude and contour of the tissue pressure pulse wave. In contrast, by using a dedicated tissue pressure sensor, the design shown in Figure 1 enables high-fidelity (HiFi) recording of arterial blood pressure and pulse waves.

[0058] The tissue pressure sensor 4 may be implemented, for example, as a liquid-filled bag fluid-coupled to a pressure transducer for reading tissue pressure signals. When blood pulsates in the artery 8, this generates a pressure wave 6 that can be detected by the tissue pressure sensor 4. The tissue pressure sensor 4 can be connected to the pressure transducer via a liquid-filled tube / line. This pressure transducer converts the pressure in the fluid into an electrical signal.

[0059] Therefore, the operating principle is based on coupling a pressure sensor to a body part (e.g., the arm) to transcutaneously record tissue pressure pulse waves arising from arterial pulsations (e.g., the brachial artery). Similar to conventional upper arm blood pressure cuffs, the cuff compresses the upper arm using an integrated pneumatic actuator that increases the clamping pressure. However, the actual compression is achieved by narrowing the diameter of a rigid circumferential shell 12.

[0060] The shell structure 12 has a single unitary component made of a rigid material, the ends of which overlap tangentially and curl into a loop shape. This is schematically shown in Figure 2.

[0061] Appropriate algorithms for processing tissue pressure measurements to derive hemodynamic parameters, such as systolic arterial pressure (SAP), diastolic pressure (DAP), mean arterial pressure (MAP), and cardiac output, can be found in literature such as WO2018 / 210931, WO2020 / 148137, WO2019 / 211210, US10485432, EP2759258B1, and US10349849.

[0062] For example, as described in WO2018210931, in some embodiments, the SAP, DBP, and MAP values ​​can be obtained based on identifying peaks in the amplitude of a series of measured tissue pressure pulses. Then, various blood pressure measurements can be determined based on identifying the amplitude values ​​of the tissue pressure pulse sequence by a predefined percentage reduction of the peak amplitude value. See WO2018 / 210931 for further details.

[0063] Embodiments of the present invention differ from known designs, at least with respect to the structure of the shell structure 12. More specifically, as will be further described below, it is proposed to provide a shell structure formed by at least two distinct circumferential or arcuate portions defining an overall arc or loop around a body portion.

[0064] Figures 3 and 4 schematically illustrate the principle according to one or more embodiments of the present invention.

[0065] According to one or more embodiments, an apparatus for use in non-invasive hemodynamic parameter measurement is provided.

[0066] The device has a cuff 20 that extends around a body part 10 of the subject. For illustrative purposes, Figure 3 shows a body part as the upper arm 10 of the subject. The brachial artery 8 is schematically shown.

[0067] The cuff 20 has a pressure actuator 52 (see Figures 5 and 6) for applying controllable pressure to the body portion 10. The cuff further has a shell structure 22 extending around the body portion 10, which is positioned between the actuator and the body portion when the cuff is worn. Referring to Figures 3 and 4, the actuator is radially mounted on the illustrated shell structure 22.

[0068] The shell structure 22 can be configured in a closed state or an open state. Figure 3 shows the open state. Figure 4 shows the closed state.

[0069] In the closed state, the shell structure 22 forms a closed loop around a central lumen for receiving the subject's body part 10.

[0070] When open, an opening / cut / discontinuity is defined around the circumference or periphery of the shell structure 22 to allow the arm to be inserted into the lumen.

[0071] The shell structure 22 is composed of at least a first shell portion 22a and a second shell portion 22b, and when the shell structure is in a closed state, each of these shell portions defines a respective part of the circumference of the shell structure. When the shell portions 22a and 22b are closed, they overlap in the tangential direction, forming at least a first overlapping region 32 and a second overlapping region 34.

[0072] The shell structure allows for a reversible transition between an open and a closed state. As shown in Figure 3, the transition from the closed to the open state involves separating the shell portions 22a and 22b in at least one of the overlapping regions. In the example shown, the shell portion is separable in the first overlapping region 32.

[0073] In the specific examples shown in Figures 3 and 4, the cuff further includes a lining formed from a sheet product 26 extending around the radially inward surface of the shell structure. The lining has the effect of holding the two shell portions 22a, 22b on one side of the overlapping region 34, so that the transition from a closed to an open state is achieved by moving the two shell portions apart like a hinge, where one side of the overlapping region 34 acts as a pivot / hinge, and the two shell portions are tangentially separated at the other side of the two overlapping regions 32. The lining with the sheet product 26 is not essential.

[0074] As will be described later, the main function of the sheet product 26 is to provide sliding contact between the skin and the shell. The purpose is to provide a sliding interface, so that the shell can slide tangentially against the body part without the skin wrinkling or pinching. Instead, the shell slides over the lining 26, while the lining remains stationary against the skin.

[0075] In the example shown in Figure 3, the device further includes a tissue pressure sensor that senses the pressure between the cuff and the body portion when the cuff is fitted. The tissue pressure sensor has a pressure sensing pad 4 that is positioned between the shell structure 22 and the body portion 10 when in use. For example, the pressure sensing pad 4 may be a fluid-filled pad, where the pressure sensor further includes a pressure transducer fluid-connected to the pad to detect the pressure applied to the pad. Other implementations of the pressure sensor are also possible.

[0076] In a set of preferred embodiments, though not mandatory, the first overlapping region 32 may be provided with a releaseable fixing means 42, as shown in detail in Figure 5. When fixed, this releaseable fixing means prevents tangential sliding along the side surface between the first shell portion 22a and the second shell portion 22b in the first overlapping region 32 when the shell is closed. Thus, during operation, this overlapping region is effectively fixed tangentially, thereby preventing the two shell portions 22a and 22b from sliding relative to each other. On the other hand, in the second overlapping region 34, it is preferable that the second shell portion 22a and the second shell portion are freely able to slide along the side surface tangentially when the shell is closed. Thus, this forms a sliding overlapping region during operation, allowing the shell to expand or contract as the pressure applied by the actuator decreases or increases. When pressure is applied, the volume of the arm decreases, and the diameter of the cuff can decrease accordingly so that the sliding overlap conforms to the change in the diameter of the arm. If the shell portion does not slide to allow the cuff to fit the diameter of the arm, some of the brachial artery pressure signal to the sensor pad 4 will be lost due to the inefficient mechanical connection between the artery and the sensor pad 4.

[0077] With respect to the fixable first overlapping region 32, fixing this portion during measurement provides a firm backing support to the sensor pad so that intraarterial pressure changes are maximally coupled to the sensor pad, thereby increasing the signal intensity. If the first overlapping region is slidable, the ends of the shell portion slide tangentially to each other, at least partially absorbing intraarterial pressure changes, thereby reducing the intensity of the measured arterial pressure signal.

[0078] Furthermore, in a preferred set of embodiments, the transition from a closed state (Figure 4) to an open state (Figure 3) may include tangentially separating the two shell portions 22a and 22b in the first overlapping region 32. Thus, this may involve first releasing the fixing means 42, and then pulling / sliding the two shell portions 22a and 22b apart so that a circumferential cut or opening of the shell is defined in the position where the first overlapping region 32 previously was.

[0079] Preferably, the releaseable fixing means 42 allows the first shell portion 22a and the second shell portion 22b to be fixed in a plurality of different relative tangential positions in the first overlapping region 32. In other words, the overlapping circumferential length between the two shell portions in the first overlapping region can be adjusted. In this way, the diameter or circumference of the shell portion can be adjusted to the diameter or circumference of the body portion by simply attaching the two ends of these shell portions in the first overlapping region using the fixing means at a position where the shell is optimally fitted around the body portion of the subject.

[0080] As an example, and as shown in Figure 5, the fastening means 42 may have hook-and-loop fasteners (i.e., Velcro®). Figure 5 shows a means of mounting hook-and-loop fasteners in the first overlapping region 32 by providing complementary hook-and-loop fastener surfaces 44a and 44b on the first shell portion 22a and the second shell portion 22b, respectively, where these hook-and-loop fastener surfaces are arranged in a facing relationship so that the two shell portions can be joined in the first overlapping region 32. Note that the cuff is shown divided in half for clarity and ease of numbering. However, the actual cuff is continuous, as shown in Figure 6.

[0081] When using hook-and-loop fasteners, the shear strength of the loop side is 8 to 30 PSI, more preferably 15 to 23 PSI. The peel strength of the loop side is preferably 0.2 to 4 PIW (pounds per inch width), more preferably 0.5 to 2 PIW. For the hook side, the peel strength is preferably 0.1 to 2 PIW, more preferably 0.3 to 1 PIW.

[0082] Instead of hook-and-loop fasteners, the first overlapping region 32 may be secured using other options, such as mechanical interlocks via physically engaging members on the shell, including push buttons, magnets, or cable tie (zipper wrap) based structures.

[0083] Therefore, it is understood that forming a shell structure 20 having multiple shell sections allows for the secondary advantage of making the working diameter of the entire shell structure adjustable. In particular, to achieve a tangentially open structure, a second shell section is required that can open on the opposite side of the sliding overlapping region 34. As described above, in order to maximize the signal strength to be measured, it is preferable to fix this openable overlapping region in an appropriate position during measurement.

[0084] This provides the ability to adapt the tangential length of the overlap between the two shell sections in the fixed overlapping region, allowing it to be mounted around various arms. The advantage of providing such an adaptable fixed overlapping region is that variations around the arm are captured by the fixed overlapping region rather than the sliding overlapping region, which means that the overlapping length of the sliding overlapping region can be made approximately the same for various different arm diameters. Preferably, the overlapping length of the sliding overlapping region can be minimized, thereby reducing friction between the shells.

[0085] With respect to the second (slidable) overlapping region 34, as an exemplary example, the tangential length of the overlapping region may be 20–60 mm, and the axial length (i.e., the dimension along the length of the cuff lumen) may be 80–180 mm, more preferably in the range of 120–160 mm. Note that these measurements are particularly suitable for cuffs designed for adult use. Smaller body sizes may require different dimensions.

[0086] Regarding the fixed overlap, it is preferable that the overlap has a minimum overlap length of 10 mm, and a range of 5 to 35 mm is more preferable for relatively large adult arms. This can be increased to a length in the range of 80 to 120 mm for the smallest expected adult arm.

[0087] As briefly described above, in some embodiments, the device has a sheet product 26 positioned between the shell structure 22 and the surface of the body portion 10 when the cuff is attached to the arm, and positioned to contact the body portion during use, wherein the shell structure is tangentially slidable with respect to the sheet product. In other words, a lining is provided between the shell and the body portion. The shell can slide on the lining. This prevents the skin from being pinched when the shell moves.

[0088] As shown in Figure 3-5, the sheet product 26 is attached to the shell structure 22 and is positioned to extend continuously between a first mounting point 28a on the first shell portion 22a and a second mounting point 28b on the second shell portion 22b, enclosing the radially inner surface of the shell structure. The first mounting point 28a and the second mounting point 28b are located in the first overlapping region 32.

[0089] In this example, the sheet product 26 extends uninterrupted over the second overlapping region 34 and is discontinuous in the first overlapping region 32. The first end of the sheet product is attached to the first shell portion 22a in the first overlapping region 32 (28a), and the second end 28b is attached to the second shell portion 22b in the first overlapping region (28b).

[0090] To elaborate further, compared to the conventional version of the shell back cuff, the multi-piece shell structure 22 offers an opportunity to simplify the lining. In particular, since the two shell sections 22a and 22b are positioned adjacent to each other, this allows for a lining in the form of a flat sheet 26 that folds around the two shell sections. Compared to the lining designs used in current versions of the shell back cuff (such as those described in reference EP2953528B1), this simplifies manufacturing and improves usability. In particular, the linings used in known versions of the shell back cuff must be formed as closed loops for implementation in a tangentially closed shell structure. However, the tangentially open shell structure proposed according to embodiments of this application is discontinuous and allows for the provision of a lining as a sheet product with ends that integrate into the two shell sections.

[0091] During manufacturing, with the two shell sections positioned adjacent to each other, the sheet product 26 forming the lining is placed on the radially inner surfaces of the two shell sections, extending around these inner surfaces, and finally attached to the first mounting point 28a and the second mounting point 28b on the first shell section 22a and the second shell section 28a, respectively. The attachment is performed on the underside of each shell section 22a, 22b. Thus, the lining is effectively wrapped around the inside of the shell structure. Attachment can be performed using removable fasteners such as Velcro, permanent fasteners such as adhesive, or mechanical hooks incorporated into the shell section.

[0092] When the sheet product 26 is provided as described above, the sheet product not only prevents skin pinching due to the movement of the shell structure 22, but also allows the shell structure to move freely around the arm. As described above, the sheet product extends seamlessly over the second (sliding) overlapping area 34, which means that sliding between the two shell parts is not hindered by a discontinuous lining.

[0093] The fully integrated lining described above is not mandatory. Instead, in some embodiments, a hybrid solution may be implemented in which the lining sheet product is attached to the body portion in a separate step before attaching the cuff 20. This includes, for example, wrapping the sheet product around the body portion and securing the sheet product in a closed position in the circumferential direction. For example, the sheet product is secured and released to open or close the sheet product tangentially. For example, a suitable fastener is hook-and-loop fastener or a self-adhesive material. In this case, the cuff 20 of the device may be the same as in the example described above, except for the sheet product 26.

[0094] For optimal detection functionality, it is preferable to implement two shell sections 22a and 22b such that, during operation, the tangential sliding of the cuff over the arm requires that only one of the two shell sections 22a and 22b moves while the other remains relatively stationary. In other words, one of the two shell sections moves preferentially over the other in response to radial forces. In this way, a master-slave relationship is implemented between the two shell sections, which facilitates more reliable detection operation.

[0095] In particular, the pressure sensor pad 4 is positioned between the body portion and the immovable shell portion of the two shell portions 22a and 22b relative to the arm, enabling stable measurement.

[0096] To implement this configuration, in some embodiments, one of the at least two shell portions may be provided that has greater rigidity (less flexibility) than the other of the two shell portions. For example, a first shell portion 22a is provided that has greater rigidity than the second shell portion 22b.

[0097] Additionally or alternatively, in some embodiments, in both the first overlapping region 32 and the second overlapping region 34, one of the two shell portions may be positioned radially above the other shell portion. For example, the second shell portion 22b may be positioned radially above the first shell portion 22a in both overlapping regions. This thus forms a configuration having a (radially) lower shell 22a and a (radially) upper shell 22b, in other words, an (radially) inner shell 22a and an (radially) outer shell 22b.

[0098] Examples in Figures 3-6 illustrate this configuration.

[0099] In the examples shown in Figures 3 to 6, the first shell portion 22a effectively forms the lower / inner shell portion, and the second shell portion 22b effectively forms the upper / outer shell portion 22b. In this example, the first shell portion 22a has higher rigidity than the second shell portion 22b. In this example, the first shell portion 22a supports the pressure sensor pad 4.

[0100] Positioning the sensor pad 4 on a lower, more rigid shell can be advantageous for several reasons.

[0101] One advantage of positioning the sensor pad in the center of the lower shell is improved usability. This position makes it easier to attach the cuff so that the sensor pad is aligned with the brachial artery region. In particular, for optimal measurement, during operation, the sensor pad should be offset no more than 4 cm from the position of the brachial artery, and more preferably no more than 2 cm.

[0102] Furthermore, by attaching the sensor pad to a shell with higher rigidity, it provides maximum rigidity support, which has the advantage of maximizing the absorption of body tissue movement by the sensor pad and minimizing the loss of motion signals due to absorption by the shell.

[0103] Preferably, the product of the modulus of elasticity (Emod) and the shell thickness differs between the two shell portions. Preferably, the first shell portion 22a supporting the pressure sensor pad 6 has higher rigidity than the second shell portion 22b. Preferably, the difference in the product of Emod and the shell thickness is in the range of 5 to 1000%, and more preferably in the range of 30 to 500%.

[0104] The lower shell portion 22a supporting the sensor pad 6 preferably has an Emod in the range of 100 to 7000 MPa, more preferably in the range of 300 to 5000 MPa. The thickness of the lower shell portion 22a may be in the range of 0.5 to 3 mm, more preferably in the range of 0.8 to 2 mm. The tangential length of the upper shell portion 22b may be in the range of 100 to 400 mm, more preferably in the range of 150 to 300 mm. The axial length of the lower shell portion 22a may be between 100 mm and 200 mm, more preferably between 130 mm and 170 mm.

[0105] The upper shell portion 22b preferably has an Emod in the range of 100 to 5000 MPa, more preferably in the range of 500 to 1500 MPa. The thickness of the upper shell portion is preferably in the range of 0.5 to 3 mm, more preferably in the range of 0.8 to 2 mm.

[0106] As described above, the apparatus includes a pressure actuator for applying controllable pressure to a body part, for example, to compress an arm. This pressure actuator may include an inflatable bladder, the inflation level of which determines the pressure applied. However, it is also possible to use other operating principles for the actuator. For example, any other option for applying pressure to an arm can be used, for example, by electric, hydraulic, or pneumatic means. Examples include an electric hose clamp or a pneumatic cylinder.

[0107] Figures 5 and 6 show the cuff 20 with the actuator 52 in the appropriate position. The actuator 52 is positioned to extend around the outside of the shell structure 22. The positioning and structure of the actuator are shown only schematically, and for example, the radial thickness of the actuator may be greater than shown.

[0108] In this example, the actuator 52 is positioned to wrap around a body part when the cuff is attached, and in particular, when the cuff 20 is attached, it wraps tangentially around the shell structure 22, and when the cuff is removed, the wrap can be released. Thus, the actuator can take the form of a body part wrap structure that can be folded or rolled up around a body part, similar to a typical NIBP cuff.

[0109] In other words, the actuator 52 has a closed state and an open state. In the closed state, the actuator forms a closed loop around a central lumen, and in the open state, an opening is defined around the circumference of the actuator so that the arm can be inserted laterally into the cuff. The transition from the closed state to the open state involves spreading the actuator 52 and separating both ends of the actuator tangentially.

[0110] To facilitate the process of attaching the cuff to the patient, the pressure actuator 52 may be fixedly or detachably mounted to the shell structure. In some examples, the actuator may be mounted to the shell structure 22 only in a specific, limited set of positions. In the sliding overlapping region 34, it is preferable that the actuator is not mounted to one of the two shell sections, preferably the lower shell section. This prevents wrinkles from forming in the actuator when the ends of the shell sections slide against each other.

[0111] Figure 6 shows in more detail the arrangement of the pressure actuator 52 with respect to the shell structure 22, and also shows the regions in which the actuator is fixedly or detachably attached to the shell structure 22. In particular, the actuator 52 is fixed to the second shell portion 22b across region 62. The actuator 52 is fixed to the first shell portion 22a across region 64.

[0112] The first end 72 of the actuator is shown, and the second end 74 of the actuator is shown. It can be seen that both ends of the actuator 52 are detachable from each other in order to allow overlapping and spreading of the actuator.

[0113] Therefore, the pressure actuator 52 is for wrapping around the body portion around the outside of the shell structure 22 when the cuff is fitted, and it can be seen that the actuator is mounted outside the first shell portion 22a in the first mounting area 64 and outside the second shell portion 22b in the second mounting area 62. In the example of Figure 6, the actuator is mounted over the entire tangential range of the second shell portion 22b. In other words, the second mounting area 62 extends over the entire second shell portion 22b. However, this is not mandatory. The second mounting area can extend over only a small area of ​​the second shell portion 22b. For example, in some embodiments, the second mounting area extends over a small area of ​​the shell portion that completely encloses the second overlapping area 34. This helps to avoid wrinkles in the second (sliding) overlapping area.

[0114] The actuator 52, in its extended state, includes a (length) section that implements an inflatable bladder and at least one (length) section having the form of a sheet without any bladder, and the actuator is for wrapping around the shell portion of the cuff, the length of which extends around the circumferential dimension of the cuff. The bladder portion of the actuator provides a pressure source. The non-bladder portion helps to mount the actuator to the shell to reduce slippage, allowing for the most effective pressure coupling with the shell and arm.

[0115] For example, as shown in Figure 6, in some embodiments, a portion of the inflatable bladder portion 55 of the actuator 52 is directly attached to the second shell portion 22b across a second mounting area 62, the first non-bladder portion 54a of the actuator is attached to the first shell portion 22a across the end of the shell located in a first overlapping area 32, and the second non-bladder portion 54b is positioned to overlap a portion of the inflatable bladder portion 55 when the actuator is wrapped around the shell structure 22 during use. In Figure 6, arrow 76 indicates a transition or joining point between the first non-bladder portion 54a of the actuator and the bladder portion 55 of the actuator, and arrow 78 indicates a transition or joining point between the second non-bladder portion 54b of the actuator and the bladder portion 55 of the actuator. The second non-bladder portion 54b effectively provides an additional fastening function. Attachment means such as Velcro may be provided for coupling the second non-bladder portion 54b of the actuator to the upper surface of the bladder portion 55 of the actuator below it. By strongly pulling the non-bladder portion 54b before installation, it can be used to help hold the actuator, which is fixed around the shell structure, when the cuff is in the closed position.

[0116] Figures 7 and 8 show further schematic diagrams of the arrangement of different parts of the pressure actuator 52 relative to the shell.

[0117] Figure 7 shows a closed cuff with the pressure actuator 52 wrapped around the first shell portion 22a and the second shell portion 22b. Different functional parts of the actuator are shown by different dashed lines. The portion 55 of the pressure actuator that houses the inflatable bladder, and the first portions 54a and 54b of the pressure actuator that do not house the inflatable bladder are shown. The first shell portion 22a and the second shell portion 22b are shown. For each shell portion, the portion to which the pressure actuator 52 is fixedly attached is shown by a solid line, while the portion to which the pressure actuator is not attached is shown by a dashed line. As shown, in this example, the entire circumferential range of the second shell portion 22b is fixedly attached to the pressure actuator 52, and this attachment region forms the second attachment region 62 described above. Only one portion of the first shell portion 22a is fixedly attached to the pressure actuator 52, and this portion corresponds to the first attachment region 64 described above. Further portions 66 of the first shell portion 22a that are not attached to the actuator 52 are shown. This portion extends from the end of the first shell portion 22a located in the second overlapping region 34, along the circumferential extension of the first shell portion up to a certain point.

[0118] Figure 8 shows the same cuff as in Figure 7, but in an open position.

[0119] In the closed state, it is recognized that the second non-bladder portion 54b of the actuator 52 radially overlaps with one small portion of the bladder portion 55 of the actuator 52. The second non-bladder portion 54b may be attached to or coupled to the bladder portion 55 below using attachment means such as Velcro.

[0120] In the example shown, the actuator has two functions: namely, to apply pressure to a body part to compress the artery 8, and secondly, to hold parts 22a and 22b of the shell structure radially when the cuff is attached. The first function, compression, is the primary function.

[0121] To apply the pressure actuator 52 to the shell portions 22a and 22b, it is preferable to make the actuator layer 52 (e.g., having an inflatable bladder) as thin as possible in the overlapping region 32, i.e., the first overlapping region 32, where the shell portions are fixed to each other. For this purpose, the radial end of the actuator 52 can be attached to the first shell portion 22a at a position tangentially offset from the first overlapping region. This may be done by adhesive, but other processes, namely ultrasonic welding or high-frequency welding, are also possible. During operation, when the cuff is applied to a relatively small arm, the upper shell portion 22b overlaps with the first region of the actuator 52.

[0122] With respect to the actuator 52, it is preferable for measurement accuracy that the pressure-applying portion extends completely (in a completely annular shape) around the body part when the cuff is attached. For example, if the actuator has an inflatable bladder, the portion 55 including the bladder needs to extend completely around the body part so that the pressure is applied evenly.

[0123] Furthermore, it is preferable that the pressure-applying portion of the actuator does not wrinkle in the sliding overlapping region 34. To enable this, as described above, the actuator may be mounted to the shell structure along a continuous mounting region extending tangentially along the entire length of the second overlapping region 34 (sliding overlapping region). For example, one possible mounting means is Velcro, which allows for continuous mounting along an extended strip. Other possible mounting means include adhesive, and ultrasonic or high-frequency welding of the actuator to the shell structure.

[0124] If the actuator 52 has an inflatable bladder, the actuator may be positioned relative to the shell structure such that the air tube supplying the bladder is not within the second (sliding) overlapping region 34. Preferably, the actuator is on the same side (rear) as the handle 72 of the inflatable bladder portion of the cuff.

[0125] At least a portion of the actuator 52 is permanently attached or fixed to the shell, ensuring proper positioning of the inflatable bladder of the actuator when the actuator is wrapped around the shell during use of the cuff, and also ensuring a specific relative position of the shell when the actuator is wrapped around it. As described above, the actuator plays a secondary role in holding the shell portions 22a and 22b together in a certain spatial relationship.

[0126] Each of the shell portions 22a and 22b may be made, for example, by a simple open / close injection-molded structure. In some embodiments, as will be further described below, each shell is formed from two different base materials. This can improve frictional properties, particularly in the sliding overlapping region 34. It can also help to adjust the stiffness and wall thickness.

[0127] Relevant features for implementing the sliding overlap in the second overlapping region 34 are the static and dynamic friction coefficients of the overlapping shell portions 22a and 22b. The dynamic friction coefficient is preferably in the range of 0.02 to 0.35, and more preferably in the range of 0.05 to 0.18, in order to provide low friction. The static friction coefficient is preferably close to the dynamic friction coefficient. For example, in order to reduce the stick-slip effect of the sliding shell during measurement, the difference is preferably less than 0.1, and more preferably less than 0.03.

[0128] Regarding the material properties of the shell sections 22a and 22b, there are several options to achieve the desired stiffness and coefficient of friction. One option is to use HDPE for the first shell section 22a and the second shell section 22b. Other material options include PP, POM, and polyimide. Optionally, additives such as silicone oil can be added to the material. It is also possible to use different materials for the first shell section 22a and the second shell section 22b. Options to achieve this difference include, for example, HDPE-PTFE, HDPE-polyimide, POM-HDPE, and HDPE-PP. Note that the overall coefficient of friction can be reduced by adding additives such as silicone oil.

[0129] To reduce friction between the shell parts, foil can be applied to either the first shell part and / or the second shell part. For example, PTFE foil or Kapton (polyimide) foil can be selected, and PTFE foil has the advantage of a low coefficient of dynamic friction and a small difference between the coefficient of static friction and the coefficient of dynamic friction.

[0130] Another option is to reduce friction by using a structured interface on the sliding overlapping portion of the second overlapping region 34. Preferably (when applicable), the hardest material (with the highest modulus of elasticity) has the structured interface. Preferably, the Ra value (arithmetic mean roughness of the surface, a measure of the mean deviation of the surface from the mean line or center line) is in the range of 0.03 to 20 μm, and more preferably in the range of 0.1 to 5 μm.

[0131] Another option is to provide the first shell portion 22a and / or the second shell portion 22b as a two-shot molded part, where the sliding overlapping region 34 is a reduced-thickness layer having a thickness preferably in the range of 0.05 mm to 0.6 mm, more preferably in the range of 0.2 mm to 0.3 mm. The length of the second shot material is preferably in the range of 30 mm to 120 mm, more preferably in the range of 60 mm to 80 mm.

[0132] In some embodiments, the tangential ends of the first shell portion 22a and / or the second shell portion 22b may be chamfered or rounded. This is beneficial for the shells to slide smoothly against each other. The chamfer is an angle α at the free end of the shell, where the angle α is preferably in the range of 10 to 145, and more preferably in the range of 20 to 110.

[0133] As described above, preferably the lower shell portion 22a supports or has the pressure sensor pad 4. Preferably the shell portion containing the sensor pad 6 has an elastic modulus in the range of 100 to 7000 MPa, more preferably in the range of 300 to 5000 MPa. The thickness of this shell portion is in the range of 0.5 to 3 mm, more preferably in the range of 0.8 to 2 mm. The tangential length of the upper shell 22b is in the range of 180 mm to 240 mm, more preferably in the range of 200 to 220 mm. The axial length of the lower shell 22a is preferably 100 to 200 mm, more preferably 130 to 170 mm. The upper shell portion 22b preferably has an elastic modulus in the range of 100 to 5000 MPa, more preferably in the range of 500 to 1500 MPa. The thickness of the upper shell portion 22b is in the range of 0.5 to 3 mm, more preferably in the range of 0.8 to 2 mm.

[0134] As described above, in some embodiments, the device includes a tissue pressure sensor that senses the pressure between the cuff 20 and the body portion when the cuff is worn, and the tissue pressure sensor has a detection pad 4 for positioning between the shell structure 22 and the body portion during use. As described above, in some embodiments, the pad 4 of the tissue pressure sensor is positioned between the first shell portion 22a and the body portion during use, preferably the first shell portion is more rigid than the second shell portion 22b and is radially below the second shell portion 22b.

[0135] Figure 9 shows three exemplary positions 7a, 7b, and 7c for positioning the sensor pad in the lower shell, any one of which is acceptable. However, the optimal choice is to position the sensor pad 4 in the middle of the lower shell, i.e., position 7b. This position in the lower shell facilitates the attachment of the cuff 20 around the arm so that the sensor pad is aligned with the brachial artery. In particular, Figure 7 (middle) shows the optimal positioning of the cuff relative to the brachial artery and arm when position 7b is selected for the sensor pad.

[0136] As described above, in some embodiments, the tissue pressure sensor is a hydraulic sensor having a pressure sensor pad 4, which is fluidly coupled to a pressure transducer that converts changes in fluid pressure inside the pad into pressure measurements. The fluid connection between the pad 4 and the transducer may be in the form of a fluid tube. To accommodate this, a shell portion having or supporting the pressure sensor pad 4, for example, a first shell portion 22a, may include a tube guide slot or channel into which the hydraulic tube is attached. This is illustrated in Figure 10, which shows an internal side view of the first shell portion 22a, where a tube guide slot 92 is shown.

[0137] The tube guide slot 92 prevents the tube from being pressed against the skin during measurement. This tube guide slot takes the form of a radially recessed slot or channel on the inner surface of the first shell portion 22a, where the tube is mounted and not pressed against the skin during operation. The length of the cavity may be 1 to 30 mm, and the width and depth may be in the range of 1 to 10 mm. The tube guide slot may be manufactured, for example, by injection molding and can be assembled into a single mold. A further advantage of this feature is that the hydraulic tube remains stationary during measurement, reducing the risk of artifacts caused by tube movement. This also means that, since the sensor pad 4 is mounted on the exposed inner surface of the shell portion 22a, the attachment of the sensor pad 4 to the shell portion 4 is relatively easy during assembly.

[0138] In some embodiments, the distance of the sensor pad 4 measured from the distal end of the shell structure is preferably in the range of 10 mm to 45 mm, and more preferably 20 mm to 30 mm.

[0139] In some embodiments, the shell structure, when closed, forms a tubular shape with a non-uniform diameter, for example, a linearly tapering diameter, thereby giving the closed shell structure a truncated frustoconical shape that fits better with the arm. Preferably, the cone angle is in the range of 1 to 15 degrees, more preferably in the range of 2 to 8 degrees.

[0140] Furthermore, although the drawing shows the shell structure with a roughly circular cross-section, other cross-sectional shapes, such as an ellipse, are also possible.

[0141] The apparatus may further include a processing device having one or more processors.

[0142] One or more processors can receive pressure signals from tissue pressure sensors and adapt to these pressure signals by applying one or more computational algorithms to derive one or more hemodynamic parameters.

[0143] One or more processors may be additionally or alternatively adapted to control the pressure applied by a pressure actuator in order to implement a measurement cycle. The pressure actuator has an inflatable bladder, and the control module is adapted to control the inflation / deflation cycle of this bladder. The apparatus may include a pressurized air source, such as an air pump, for use in inflating such a bladder.

[0144] The inventor constructed a test apparatus according to the principle described above. For example, the first shell portion 22a is provided with a 1.5 mm HDPE shell, and the second shell portion is provided with a 1 mm HDPE plate. A thin Kapton foil was applied to the first shell portion 22a to reduce both the dynamic and static friction coefficients.

[0145] This example device was used to measure hemodynamic parameters. The same hemodynamic parameters were also measured using a known version of the shellback cuff, specifically following the example described in reference EP2953528B1. For each cuff, measurements were recorded for three different subjects (labeled VT3, VT5, and VT9). The results are shown in Table 1 below, where all important hemodynamic parameters for all three subjects were statistically equal. Note that there is a slight difference in CO (cardiac output) between the two cuffs, which is mainly due to the difference in pulse rate (PR), and this is physiological.

[0146] The cuff according to the embodiment of the present invention was labeled A, and the cuff according to EP2953528B1 was labeled B. [Table 1]

[0147] The results show that the hemodynamic parameters measured with cuff A are statistically identical to those measured with the existing cuff version B. Therefore, the advantage of the openable and closable shell structure in the embodiment of the present invention is demonstrated to not lead to any loss of measurement quality.

[0148] In further testing, a second exemplary cuff was constructed, in which the first shell portion 22a had a 1 mm thick layer of POM material, and the second shell portion 22b had a 1 mm thick layer of HDPE material. In testing, this showed similar results to the POM-HDPE shell system described above. Furthermore, this second exemplary cuff can be made directly from injection molding and does not require foil application.

[0149] Even if the above-described example relates to a device in which the shell structure has two shell parts, in a further embodiment, the shell structure may have more than two shell parts, for example, three or more overlapping shell parts. The same principles as described above can be applied.

[0150] Some embodiments of the invention described above utilize a processing device. This processing device may generally have a single processor or multiple processors. It may be located within a single housing device, structure, or unit, or it may be distributed across multiple different devices, structures, or units. Thus, a statement that a processing device is adapted or configured to perform a particular step or task may correspond to that the step or task is performed by any one or more of the processing components, either individually or in combination. Those skilled in the art will understand how such a distributed processing device can be implemented. The processing device includes a communication module or input / output unit for receiving data and outputting data to further components.

[0151] One or more processors in a processing device can be implemented in many ways using software and / or hardware to perform various required functions. A processor typically uses one or more microprocessors programmed to perform the required functions using software (e.g., microcode). A processor may also be implemented as a combination of dedicated hardware for some functions and one or more programmed microprocessors and associated circuits for other functions.

[0152] Examples of circuits used in various embodiments of this disclosure include, but are not limited to, conventional microprocessors, application-specific integrated circuits (ASICs), and field-programmable gate arrays (FPGAs).

[0153] In various implementations, the processor may be associated with one or more storage media, such as volatile and non-volatile computer memories, including RAM, PROM, EPROM, and EEPROM. The storage media may be encoded with one or more programs that perform the necessary functions when executed on one or more processors and / or controllers. The various storage media may be mounted within the processor or controller, or they may be transportable so that one or more programs stored in the storage media can be loaded into the processor.

[0154] Modifications of the disclosed embodiments can be understood and implemented by those skilled in the art in carrying out the claimed invention by examining the drawings, this disclosure, and the appended claims. In the claims, the word “having” does not preclude other components or steps, and the absence of a statement that there are multiple components or steps does not preclude them from being multiple.

[0155] A single processor or other unit can perform the functions of several of the items listed in the claims.

[0156] The mere fact that certain means are described in mutually different dependent claims does not indicate that combinations of these means cannot be used advantageously.

[0157] When the phrase "suitable for" is used in a claim or specification, it means that the phrase "suitable for" is equivalent to the phrase "configured to".

[0158] No reference numeral in a claim should be construed as limiting its scope.

Claims

1. A device for non-invasive hemodynamic parameter measurement, The device has a cuff that extends around a part of the subject's body, The cuff has a pressure actuator for applying a controllable pressure to the body part, and further has a shell structure that extends around the body part and is positioned between the pressure actuator and the body part when the cuff is worn. The aforementioned shell structure can be configured in both a closed and an open state. In the closed state, the shell structure forms a closed loop around a central lumen for receiving the subject's body parts, and in the open state, an opening is defined around the circumference of the shell structure, allowing an arm to be inserted into the central lumen. The shell structure is composed of at least a first shell portion and a second shell portion, and each of the first shell portion and the second shell portion defines a portion of the circumference of the shell structure when the shell structure is closed, and the first shell portion and the second shell portion overlap in the tangential direction in at least the first overlapping region and the second overlapping region when the shell structure is closed. The transition from the closed state to the open state involves separating the first shell portion and the second shell portion tangentially in at least one of the first overlapping region and the second overlapping region. Device.

2. The apparatus according to claim 1, further comprising a releaseable fixing means in the first overlapping region, the releaseable fixing means for preventing tangential sliding along the side surface between the first shell portion and the second shell portion in the first overlapping region when fixed and the shell is in a closed state.

3. The apparatus according to claim 2, wherein the releaseable fixing means enables fixing of the first shell portion and the second shell portion in the first overlapping region at a plurality of different relative tangential positions.

4. The device according to claim 3, wherein the fastening means has a hook-and-loop fastener.

5. The apparatus according to any one of claims 1 to 4, wherein, when the shell structure is in a closed state, the first shell portion and the second shell portion are able to slide freely along the tangential side surface in at least the second overlapping region.

6. The apparatus according to any one of claims 1 to 5, wherein when the cuff is on the body portion during use, the pressure actuator is positioned to support the shell structure radially with respect to at least the radial separation of the first shell portion and the second shell portion.

7. The apparatus according to any one of claims 1 to 6, further comprising a sheet product positioned between the shell structure and the surface of the body portion when the cuff is attached to the arm, and positioned to be in contact with the body portion during use, wherein the shell structure is slidable tangentially with respect to the sheet product.

8. The aforementioned sheet product is attached to the shell structure, The sheet product is arranged to extend continuously around the radially inward surface of the shell structure between a first mounting point in the first shell portion and a second mounting point in the second shell portion. Preferably, the first mounting point and the second mounting point are located in the first overlapping region. The apparatus according to claim 7.

9. The sheet product extends continuously across the second overlapping region, and is discontinuous in the first overlapping region. The first end is attached to the first shell portion in the first overlapping region, and the second end is attached to the second shell portion in the first overlapping region. The apparatus according to claim 8.

10. The apparatus according to any one of claims 1 to 9, wherein at least one of the two shell portions has greater rigidity than the other of the two shell portions, and optionally, the first shell portion and the second shell portion are formed of different materials.

11. The apparatus according to any one of claims 1 to 10, wherein the shell structure includes a first shell portion and a second shell portion, and in both the first overlapping region and the second overlapping region, the second shell portion is positioned radially above the first shell portion.

12. The apparatus according to claim 11, wherein the second shell portion has lower rigidity than the first shell portion.

13. The cuff, when worn, further comprises a tissue pressure sensor that senses the pressure between the cuff and the body part, and the tissue pressure sensor has a detection pad that is positioned between the shell structure and the body part when in use. Optionally, the second shell portion is less rigid than the first shell portion, and the tissue pressure sensor detection pad is positioned between the first shell portion and the body portion. The apparatus according to any one of claims 1 to 12.

14. The apparatus according to any one of claims 1 to 13, wherein the pressure actuator is fixedly or detachably attached to the shell structure.

15. The pressure actuator has a closed state and an open state. In the closed state, the pressure actuator forms a closed loop around the central lumen. In the open state, an opening is defined around the circumference of the pressure actuator, allowing an arm to be inserted into the hollow cavity. The transition from the closed state to the open state involves extending the pressure actuator and separating both ends of the pressure actuator in the tangential direction. The apparatus according to claim 14.

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