Patent Description:
The rise of portable smart-devices, such as smart phones, smart watches, fitness monitors, etc. has given individuals a useful tool to monitor health parameters to address CVD symptoms, where such health parameters include blood pressure and heart rate. Such devices are also of interest to healthy individuals so that who can monitor such data to avoid the onset or progression of CVD.

Non-invasive blood pressure measuring devices including sphygmomanometers and photoplethysmography are used in monitoring patient' s blood pressures to prevent various cardiovascular diseases or provide doctors with early diagnosis. However, most of them are bulky and heavy which are inconvenient for outdoor applications and long-time monitoring. Previously, wearable blood-pressure monitoring devices that allowed for real-time monitoring and portable capability are described in <CIT> and <CIT>. However, there remains a need to more accurately measure blood pressure using a portable, non-obtrusive device.

Further wearable blood-pressure monitoring devices are known from <CIT>, <CIT> and <CIT>.

To address some of the aforementioned deficiencies, the present invention provides for a device and a method for monitoring blood pressure as defined by claims <NUM> and <NUM>, wherein preferred embodiments of the invention are laid down in the dependent claims. More particularly, the present disclosure includes a force detecting device relies on a contact member that concentrates radially directed tissue movement produced by arterial motion into a relatively small spot to compress the strain device. This concentration significantly increases the sensitivity of the force detecting device and allows further miniaturization of the device. By increasing the sensitivity with the contact member, the device can be compressed on user's skin with a smaller area being held tight against the tissue. This relatively small surface area bringing more comfort to the user. The contact member of the current is designed in such a way that the radial motion of tissue is more prominent than movement of tissue in other directions. This allows suppression of any undesirable signals, such as signals from friction or uneven motion of the tissue. The contact member also protects the strain device from damages due to large contact force and friction from user. By radial direction, it is meant in a direction radially away from the vessel being monitored.

The present disclosure includes devices for monitoring blood pressure in a blood vessel using a tissue adjacent to the blood vessel. For example, such a device includes a device body configured to extend at least partially about the digit, the device body having an interior surface adapted to be positioned adjacent or in contact with a surface of the digit; a tissue movement detecting assembly positioned on or in the device body, the transducer assembly comprising a strain device; a contact member having a tissue engaging surface protruding beyond the interior surface of the device body such that when the device body is positioned adjacent to tissue, the contact member compresses the tissue, the contact member also having a strain inducing surface adjacent to the transducer assembly; and wherein the contact member comprises a perimeter region and a central region, where the central region is configured to transmit displacement of the contact member such that, when the tissue engaging surface engages the tissue, displacement of tissue in a radial direction relative to the tissue caused by a change in a pressure in the blood vessel also displaces the tissue engaging surface causing displacement of the central region of the contact member in the radial direction so that the strain inducing surface alters a strain in the strain device to produce a change in an electrical property of the strain device.

In another variation, the contact member comprises a double layer structure having a first layer adjacent to the tissue engaging surface and a second layer spaced from the first layer, where the first and second layer are joined by a central region of the contact member.

The device body can optionally include a cavity that nests the contact member. Variations of the device include one or more power supplies electrically coupled to the transducer assembly.

In one variation of the device the contact member is configured such that the perimeter region of the contact member is reinforced such that the perimeter region transmits displacement less than the central region of the contact member.

Variations of the contact member are configured such that the perimeter region of the contact member is weakened to cause the central region to displace in the radial direction by flexure of the perimeter region. For example, perimeter region of the contact member can be softer than the central region such that the central region transmits displacement greater than the perimeter region. In additional variations, the contact member comprises at least one cavity below the tissue engaging surface, where the at least one cavity extends about the central region, wherein the at least one cavity causes the perimeter region of the contact member to be softer relative to the central region which improves an ability of the central region to transmit displacement.

Variations of the device include strain inducing surfaces that comprise at least one protrusion, wherein displacement of the central region of the contact member causes the at least one protrusion to alter the strain in the strain device. The at least one protrusion can comprise a plurality of protrusions.

Variations of the devices can further include one or more displacement limiting structures that can limit movement of the strain inducing surface or can limit movement of the strain device.

In an additional variation, a device can include a transducer assembly comprises a deformable base adjacent to the strain device, where the deformable base permits deformation of the strain device. The deformable base can comprise an elastomer that can be elastically deformable. In addition, variations of the device can include protrusion(s) adjacent, inside, or through the deformable base that increases deflection of the strain device.

In another variation of the device, the transducer assembly and contact member form a primary sensor, the device further comprising a secondary sensor comprising a second contact member and a second transducer assembly, wherein the secondary sensor is spaced a distance from the primary sensor on the interior surface of the device body.

The strain devices used herein can comprise at least a strain gauge or a conductive polymer. In one variation, the strain device comprises a first strain gauge and a second strain gauge. For example, the first strain gauge can be positioned on a first side of a deflectable base and where the second strain gauge can be positioned on a second side of a deflectable base, where a fixed end of the deflectable base is coupled to an anchoring structure and a free end of the deflectable base is positioned adjacent to the strain inducing surface.

The device body can comprise a shape selected from a group consisting of a cylinder shape, a partial cylinder shape, a ring shape, an oval shape, and a non-cylinder shape.

The device body can optionally include a biasing member configured to bias the device body against the digit to cause the contact member to at least engage tissue of the digit. In an additional variation, the biasing member comprises a mechanism selected from the group comprising a spring, a gasket, a screw, a soft polymer, and a combination thereof.

The present disclosure also includes methods for monitoring blood pressure in a blood vessel within a tissue using any of the devices described herein. For example, such a method can include positioning a device body adjacent to the tissue, where the device body comprises a contact member coupled to a transducer assembly with the contact member protruding from an interior surface of the device body; wherein the contact member comprises a tissue engaging surface protruding above the interior surface of the device body such that, when the device body is positioned adjacent to the tissue the contact member compresses a tissue in the digit, the contact member also having a strain inducing surface adjacent to the transducer assembly, where a central region of the contact member transmits displacement of the tissue in the digit to the transducer assembly at a greater degree than a perimeter portion of the contact member; generating a signal in the transducer assembly caused by a movement of the central portion of the contact member against the transducer assembly and in response to movement of the tissue caused by a pulsatile flow in the blood vessel; and transmitting the signal to a processing unit that is configured to calculate a blood pressure of the vessel from the signal.

The methods can include transmitting wirelessly. Variations of the method can comprise continuously transmitting the signal or transmitting the signal periodically.

The method can further include recording the signal on a storage device to generate a series of recorded signals on the storage device.

In another variation of the device, the device body further includes a second contact member coupled to a second transducer assembly, wherein the second contact member is spaced circumferentially away from the first contact member, the method further comprises generating a second signal in the transducer assembly caused by movement of a central portion of the second contact member against the second transducer assembly in response to movement of the tissue in the digit.

A variation of the method further comparing the first signal to the second signal to generate a rotation indicator signal. In another variation, the rotation indicator signal can inform a user to rotate the device body relative to the tissue. In another variation, the method includes comparing the first signal to the second signal to generate a device tightness signal. The method can also include providing the tightness indicator signal to a user to inform the user to adjust the device tightness adjacent to the tissue.

The method can further include using an oscillometric blood pressure cuff to calibrate the blood pressure calculation.

Another variation of the device described herein includes a device for monitoring blood pressure in a blood vessel using a tissue adjacent to the blood vessel. For example, the device can include a device body; a tissue movement detecting assembly positioned on or in the device body, the transducer assembly comprising a strain device; a contact member having a tissue engaging surface protruding beyond a surface of the device body such that when the device body is positioned adjacent to tissue, the contact member compresses the tissue, the contact member also having a strain inducing surface adjacent to the transducer assembly; and wherein the contact member comprises a perimeter region and a central region, where the central region is configured to transmit displacement of the contact member such that, when the tissue engaging surface engages the tissue, displacement of tissue in a radial direction relative to the tissue caused by a change in a pressure in the blood vessel also displaces the tissue engaging surface causing displacement of the central region of the contact member in the radial direction so that the strain inducing surface alters a strain in the strain device to produce a change in an electrical property of the strain device.

In one variation of the device the device body comprises a blood pressure cuff. Alternatively, the device body can comprise a pulse oximeter.

Methods and devices are described herein that relate to monitoring blood pressure in a vessel of a region of tissue. The methods and devices described herein can monitor blood pressure in a digit of a hand or in other areas of the body where the pulsatile flow of blood in a vessel displaces adjacent tissue that can be detected from a surface of the tissue. In addition, the methods and devices disclosed herein include improvements for detecting movement in a tissue of a region of the body, where the movement in the tissue arises from blood pressure changes within a vessel in that tissue. Optionally, the devices and methods described herein can be used wearable devices and non-invasive monitoring blood-pressure in real-time.

<FIG> illustrate respective front and oblique views of an example of a device <NUM> configured to monitor blood pressure using movement in tissue that is driven by the blood flow within a vessel located in that tissue. In the examples illustrated in <FIG>, the illustrated variation of the device <NUM> is configured with a ring-shaped body <NUM> that houses a tissue displacement measuring apparatus <NUM> having a portion that protrudes from an inner surface <NUM> of the ring shaped body <NUM>. This variation is suited for placement about a digit of an individual's hand such that it can detect movement of tissue in the digit that is caused by pulsatile flow of a vessel within the digit/tissue. However, additional variations of a blood pressure monitoring apparatus under the present disclosure are not limited to ring-type devices. The movement detecting apparatus <NUM> The device also can simply monitor movement of tissue in the digit, where the tissue movement can be caused by the oscillation of the blood vessel due to pressure changes therein. As shown, the device <NUM> can communicate <NUM> (either via a wire, wireless connection, cloudbased transmission, etc.) to a user interface <NUM>. The user interface <NUM> can comprise a body wearable apparatus or can comprise a computer, smart-phone, tablet, or other electronic apparatus. Variations of the user interface <NUM> can include a feedback portion <NUM> (either visual, audible, etc.) and/or controls <NUM>.

<FIG> shows a perspective view of the device <NUM> of <FIG>. As shown, the ring-shaped body <NUM> includes an inner surface <NUM> that can be positioned about a digit of an individual. The ring-shaped body <NUM> houses an assembly <NUM> that detects movement of tissue using a contact member <NUM> that transmit movement of tissue adjacent to the contact member into the assembly <NUM> (as will be discussed below). The contact member <NUM> can extend beyond an inner surface <NUM> of the ring-body <NUM>. The degree of extension of the contact member <NUM> can vary depending upon the application. The illustration is intended to convey the principles of the device. Furthermore, while the illustrated variation only shows a single assembly <NUM>, variations of the device can include any number of additional assemblies spaced at any interval along the body of the device <NUM>.

The tissue contact member <NUM> can comprise an elastomer that is softer than a body of the device. That is, the Young's modulus of the elastomer should be smaller than the Young's modulus of the ring body <NUM>. In such configuration, stretching of or compression to the contact member <NUM> mainly deforms the elastomer rather than the ring body itself. For example, elastomers suitable for a wearable device can include, but are not limited to natural rubber, Silicone, Neoprene, Polyurethanes, Polybutadiene, etc. In one variation, the elastomer comprises polydimethylsiloxane (PDMS) with different desired mix ratio. However, the present disclosure is not limited thereto, and any materials with elastomeric characteristic compared to the ring body can be used in the devices disclosed herein.

<FIG> illustrate additional variations of tissue displacement assemblies <NUM> for use with additional variations of blood pressure measuring devices <NUM>. The variation shown in <FIG> illustrates a finger cuff or cradle <NUM> that houses one or more assemblies <NUM>. As shown, a finger <NUM> of a hand <NUM> is positioned within or on the device body <NUM> such that the assembly <NUM> can detect movement of tissue and transmit (via a wired or wireless connection <NUM>) to a user interface device <NUM> (as described above). <FIG> illustrates a traditional blood pressure cuff <NUM> having a pump or bladder <NUM> that is used to secure the cuff <NUM> about a leg or arm of a patient. The cuff <NUM> includes any number of assemblies <NUM> that can measure displacement of tissue due to pulsatile flow of blood in a vessel within the tissue that is adjacent to the cuff <NUM>.

<FIG> illustrates a partial view of a body <NUM> of the device shown in <FIG> for purposes of illustrating one variation of a movement detecting apparatus <NUM> that can be used with any of the blood pressure detecting devices described herein. In this example, the apparatus <NUM> is positioned within the ring-shaped device body <NUM>, where the movement detecting apparatus includes a contact member <NUM> that extends beyond a tissue facing surface <NUM> of the ring body <NUM>.

<FIG> represents a cross sectional view of the movement detecting device <NUM> of <FIG> taken along the line 3B-3B. As shown, the device <NUM> includes according to the invention a contact member <NUM> that has a tissue engaging surface <NUM> protruding beyond the interior surface <NUM> of the device body <NUM> such that when the device body is positioned adjacent to tissue, the contact member compresses the tissue or is positioned in contact with tissue. In this variation, the tissue engaging surface <NUM> includes a perimeter region <NUM> that engages the inner surface <NUM> while the tissue engaging surface <NUM> is positioned adjacent to a cavity <NUM> or recess within the inner surface <NUM> of the device body. As described below, the cavity <NUM> assists in permitting displacement of the tissue engaging surface <NUM> (as a result of tissue displacement or a pressure wave caused by tissue movement). In this variation, the tissue engaging surface <NUM> extends above the perimeter region <NUM> to assist in transmitting displacement of the tissue. However, variations of devices can include perimeter regions that are flush with the tissue engaging surface. It is noted that a power supply can be positioned within the monitoring unit/display. Alternatively, a power supply (e.g., a battery, rechargeable battery, or other power source) can be positioned within the housing <NUM> of the device.

The tissue engaging surface <NUM> is adjacent to a central region <NUM> that transmits displacement of the tissue engaging surface <NUM> to a strain inducing surface <NUM>. Therefore, displacement of the tissue engaging surface <NUM> causes displacement of the strain inducing surface <NUM>. The strain inducing surface <NUM> is adjacent to/in contact with a strain device <NUM> where the displacement can be measured by the strain device <NUM>. The central region <NUM> can include a strain inducing surface <NUM> as well as a second perimeter region <NUM> that engages a portion of the body <NUM>. Moreover, a stop or displacement limiting structure <NUM> can limit displacement of the strain device <NUM>. <FIG> also illustrates a variation of the movement detecting apparatus <NUM> as having an optional stiffening member <NUM> positioned within the contact member <NUM>. The design of the contact member <NUM> increases the ability of the contact member <NUM> to transmit radial movement (i.e., movement that is parallel to a central axis <NUM>) of the contact member <NUM>. The apparatus <NUM> can also include any number of support structures <NUM> that maintains the contact member <NUM> securely within the body <NUM> structure.

<FIG> provide illustration of variations of strain devices <NUM> for use with various movement detecting devices of the present disclosure. <FIG> illustrates a strain device <NUM> comprising a deflectable base, fabricated from a metal, alloy, polymer, etc.). The deflectable base <NUM> will receive the strain inducing surface discussed herein such that movement of the strain inducing surface produces movement of the deflectable base <NUM>. The deflectable base <NUM> is coupled to a piezo resistive or similar material <NUM> that allows detection of movement by producing a change in a resistance of the material <NUM> in response to a deflection of the material <NUM>. In the variation depicted in <FIG>, the deformable base <NUM> is coupled to an anchoring structure and can include a temperature detecting element <NUM> for sensing a temperature. <FIG> shows another variation of a strain device <NUM> in which a piezo resistive or similar material <NUM> directly engages a strain inducing surface. The piezo resistive or similar material <NUM> is coupled to an anchoring structure and can optionally include a temperature detecting element.

<FIG> is an illustration of a variation of a movement detecting apparatus <NUM> applied to a region of tissue <NUM>. As noted above, the apparatus <NUM> can be used in a ring based body or other type of device. The region of tissue <NUM> will typically contain an artery <NUM> having pulsatile flow of blood therethrough. As a result of this blood flow, a pressure P within the vessel causes displacement of tissue that is adjacent to the artery <NUM>. While the displacement is depicted by arrows <NUM>, the displacement of adjacent tissue <NUM> will depend upon the anatomy that is in the vicinity of the artery <NUM>. 5A illustrates a basic example of a tissue movement detecting apparatus <NUM> placed in contact with tissue <NUM> such that the contact member <NUM> compresses a region of adjacent tissue <NUM>. Compression of the tissue increases the effect of tissue movement resulting from pressure P since the compressed region <NUM> is more prone to displacement and less likely to produce a cushion effect that would reduce deflection of the tissue. The displacement <NUM> caused by the artery <NUM> produces a radial displacement <NUM> adjacent to the contact member <NUM>. As noted above, radial displacement <NUM> of the tissue <NUM> causes displacement of the contact member <NUM> to produce a displacement in the strain device <NUM>. This allows for strain-gauge-based measurement of tissue movement that can be used to determine blood pressure. In effect, blood pressure P within the vessel <NUM> creates a radial displacement <NUM> or force that induces a strain in the strain device <NUM>. The strain changes an electrical resistance of the strain device <NUM> which alters the current in the strain device <NUM> so that a voltage across the strain device <NUM> can be measured.

As noted above, the design of the contact member <NUM> is configured to transmit radial displacement <NUM> rather than circumferential displacement (e.g., displacement that is parallel to a plane of the tissue or perpendicular to a direction of the radial displacement).

<FIG> illustrate a contact member <NUM> in respective undeflected and deflected states. <FIG> illustrates a tissue engaging surface <NUM> located at a center of the contact member having a perimeter region <NUM> and a second perimeter region <NUM> located about the central region <NUM>. As noted above, the perimeter regions <NUM> and <NUM> allow for securing the tissue contact member <NUM> within a body of the device. This construction also permits displacement of the tissue engaging surface <NUM> to produce displacement of the strain inducing surface <NUM> via movement of the central region. In one variation, the perimeter regions <NUM> and <NUM> are much softer/compliant as compared to the central region and tissue engaging surface. This design helps concentrate the radial force in the central area of the deformable skin contact <NUM>.

<FIG> illustrates a state where the tissue contact member <NUM> is in a deflected state after tissue displacement <NUM> displaces the tissue engaging surface <NUM> causing the central region <NUM> and strain inducing surface to displace in the same direction as the tissue displacement <NUM>. It is noted that this construction provides a radial force concentration construction that minimizes lateral or circumferential movement of the strain inducing surface <NUM> as a result of any lateral or circumferential forces applied by the tissue. Therefore, the radial displacement <NUM> of the strain inducing surface <NUM> alters a strain in the strain device (not shown in <FIG>) to produce a change in an electrical property of the strain device. This change in electrical property can be used to determine a change in a blood pressure of the associated artery.

<FIG> illustrates another variation of a device <NUM> in which there are at least a first movement detecting apparatus <NUM> and a second movement detecting apparatus <NUM> spaced apart on the ring body <NUM>. <FIG> illustrates the first movement detecting apparatus <NUM> and a second movement detecting apparatus <NUM> in relation to a finger <NUM>. As shown, each apparatus <NUM>, <NUM> is placed adjacent to a vessel <NUM>. However, alternative configurations and/or spacing are within the scope of this disclosure.

In one variation of the device, one or more movement detecting apparatus can be configured as a primary sensor that detects the radial force composed of the contact force the force induced by the blood pressure. A second sensor can be used to detect contact force to enhance the accuracy of the measurement. In such a case, blood pressure is determined by eliminating the contact force of the primary measurement. Moreover, the multiple apparatus configuration can be used to determine rotational error during positioning of the device. For example, gross rotation error can be detected by identifying the reduction of the blood pressure resulting from the rotation of the primary apparatus away from the artery and the increase of the blood pressure reading from the secondary apparatus.

<FIG> illustrates a partial view of another variation of a device <NUM> having a ring shaped body <NUM> with an inner surface <NUM> that includes a variation of a movement detecting apparatus <NUM>. As shown, the apparatus <NUM> includes a tissue contact member <NUM> that protrudes beyond an interior surface <NUM> of the body <NUM>. This variation of the apparatus <NUM> can be used in any of the devices discussed herein and can be used in combination with any other variation of a tissue movement detecting apparatus as described in this disclosure.

<FIG> illustrates the apparatus <NUM> of <FIG> where the tissue contact member <NUM> includes a tissue contacting surface <NUM> with a perimeter region <NUM>. The tissue contacting surface <NUM> is connected to a strain inducing surface <NUM> as discussed below. The strain inducing surface <NUM> causes strain in a strain gauge upon deflection of the tissue contact surface <NUM>. In the illustrated variation, a stress intensifier <NUM> is located adjacent to the strain inducing surface <NUM> and the strain gauge <NUM>. The apparatus <NUM> can also include a base <NUM> for securing within the body of a device.

While <FIG> illustrates a single stress intensifier <NUM>, the number of stress intensifiers <NUM> and stress inducing surfaces <NUM> between the deformable skin contact <NUM> and the strain gauge <NUM> can be varied. In other variations, the device does not require a strain intensifier.

<FIG> illustrates respective side and cross sectional views of the apparatus <NUM> of <FIG>. As shown in <FIG>, the tissue contact member <NUM> comprises a radial concentration construction as the central region <NUM> is surrounded by a cavity <NUM> that increases the ability of the tissue contact surface <NUM> to transmit radial displacement of tissue to the stress inducing surfaces <NUM> as discussed above.

<FIG> illustrate devices <NUM> and <NUM> that incorporate adjustability features to properly align the movement detecting components relative to a digit. Alternatively, or in combination, the adjustability features can adjust the degree to which the tissue contacting surface compresses adjacent tissue. <FIG> illustrates a first and second spring such as a leaf spring <NUM>. One or both leaf springs <NUM> can be adjustable as needed. <FIG> illustrates a device <NUM> as having an inner spring surface <NUM> that is adjustable by one or more screws <NUM>. One or both of the screws <NUM> can push the digit toward one of the sensors and/or loosen the device about the digit. Also, the inner spring surface <NUM> can form a smooth and movable inner surface to adjust the inner radius of the ring.

In practical use, while wearing the wearable device and measuring the blood-pressure thereby, the monitoring surfaces are preferentially placed at the lower section of the wearable device at the location of the artery besides the bone lays in an embodiment of the present invention. Therefore, the deformations of the skin due to blood pulse struck directly upon the strain gauge producing the maximum strain and signal. In a preferred embodiment, a more accurate measured blood-pressure can be retrieved if the wearer relaxes.

As described above, according to the embodiments of the present invention, a strain-gauge and pressure sensor are mounted on the inner surfaces of the wearable devices which can calculate the blood pressures based on the surface deformations due to the variations of finger arteries. Accordingly, the wearable devices and the monitoring methods according to the embodiments of the present invention are expected to be beneficial for real- time monitoring of patients and bio-medical applications.

Further, the wearable device has light-weight and compact volumes and is comfortable for human beings to wear. Thus, the wearable device is suitable for long-time wearing and accordingly long-term blood-pressure monitoring.

Claim 1:
A device (<NUM>)
for monitoring blood pressure in a body member having a blood vessel using a tissue adjacent to the blood vessel, the device comprising:
a device body configured to extend at least partially about the body member, the device body having an interior surface adapted to be positioned adjacent or in contact with a surface of the body member;
a tissue movement detecting assembly (<NUM>) positioned on or in the device body, the tissue movement detecting-assembly comprising a strain device; and
a contact member (<NUM>) formed as a single piece and comprising a perimeter region (<NUM>) and a central region (<NUM>),
the contact member adjacent to the device body and positioned to engage a surface of the tissue, where the central region of the contact member forms a tissue engaging surface (<NUM>)
protruding beyond the perimeter region of the contact member such that when the device body is positioned adjacent to tissue, the perimeter region and the central region contact the tissue to compress the tissue, the contact member also having a strain inducing surface (<NUM>) extended from a surface opposite to the tissue engaging surface and adjacent to the tissue movement detecting assembly;
wherein a compliance of the perimeter region differs from a compliance of the central region to cause the central region to transmit displacement of the contact member to a greater degree than the perimeter region such that, when the tissue engaging surface engages the tissue, displacement of tissue in a radial direction relative to the tissue caused by a change in a pressure in the blood vessel also displaces the tissue engaging surface causing displacement of the central region of the contact member in the radial direction so that the strain inducing surface alters a strain in the strain device to produce a change in an electrical property of the strain device.