Methods and systems for evaluating blood flow

Abstract

The present disclosure relates to a method and system for evaluating blood flow in an area of ​​the skin and underlying tissue of a patient. The method includes the following steps: subjecting the evaluation area to at least two different pressure states, wherein the different pressure states are obtained by: the patient's weight pressing on a support on which the patient is placed, and an expandable element that at least partially surrounds the evaluation area and is expandable in the direction of the support toward the patient to substantially eliminate the pressure of the support on the patient's body in the area at least partially surrounding the evaluation area. The method also includes the following steps: obtaining (S8) blood flow data related to the evaluation area while subjecting the evaluation area to at least two different pressure states, wherein the blood flow data is obtained by optical plethysmography, and evaluating (S9) the patient's risk of pressure ulcers based on the evaluation of the blood flow data obtained for at least two different pressure states.

Description

Technical Field

[0001] The present disclosure relates to methods and systems for assessing the risk of developing a pressure ulcer. Background Art

[0002] Pressure ulcers are damage to the skin and underlying tissues caused by prolonged pressure applied to the skin. These commonly develop on the skin covering bony areas of the body such as the heels, ankles, buttocks and sacrum.

[0003] People who are most susceptible to pressure ulcers are those whose medical conditions limit their ability to change position, or those who spend most of their time in bed or a chair. Individuals who are immobile often develop painful pressure ulcers. In addition, pressure ulcers result in high costs to the healthcare system. Summary of the invention

[0004] The present disclosure relates to improved methods for assessing the risk of developing a pressure ulcer.

[0005] This is achieved by a method for evaluating blood flow in an area of ​​the patient's skin and underlying tissue. The method includes the following steps: subjecting the evaluation area to at least two different pressure states, wherein the different pressure states are obtained by pressing the patient's weight against a support on which the patient is placed and an expandable element, the expandable element at least partially surrounding the evaluation area and expandable in a direction from the support toward the patient to substantially eliminate pressure of the support on the patient's body in an area at least partially surrounding the evaluation area. The method also includes the following steps: obtaining (S8) blood flow data related to the evaluation area while subjecting the evaluation area to at least two different pressure states, wherein the blood flow data is obtained by photoplethysmography and based on the evaluation of the blood flow data obtained for at least two different pressure states, evaluating (S9) the patient's risk of developing a pressure ulcer.

[0006] The method is easy to use and reduces patient discomfort. The patient can lie in the same position during the entire measurement.

[0007] In various embodiments, substantially no pressure is provided in the evaluation region in the first pressure state. Thus, a measure of basal blood flow is obtained, and any blood flow measured under pressure can be correlated to the basal blood flow.

[0008] In various embodiments, in the second pressure state, body weight is pressed on the assessment area. Thus, a measurement is provided that at least more or less reflects the daily situation of a patient who spends most of the time in bed or in a chair.

[0009] Comparing the basal blood flow to a blood flow that reflects the patient's daily condition provides a risk assessment with improved reliability.

[0010] The first and second pressure states may be obtained in the above-described manner to reduce the risk that the measured values ​​of the basal blood flow are contaminated by previous loading of the evaluation region.

[0011] In various embodiments, the method includes the step of controlling the expandable element between at least a first expanded state corresponding to the first pressure state and a second expanded state corresponding to the second pressure state.

[0012] Through this automation, the requirements for education etc. of personnel using the method can be reduced.

[0013] In various embodiments, the method comprises the steps of obtaining pressure data and determining (S7) respective pressure states based on the obtained pressure data. Then, the step of assessing the risk of pressure ulcers based on the blood flow data obtained for the at least two different determined pressure states.

[0014] In practice, blood flow data can be obtained by illuminating the skin and underlying tissue with light from an LED, and measuring the amount of light reflected to a photodiode.

[0015] The method may also include the following steps: providing an expandable element having a controllable expansion state; providing a sensor element for obtaining blood flow data using optical plethysmography; positioning the expandable element relative to the patient so that the patient's weight provides pressure to the evaluation area depending on the expansion state of the expandable element; obtaining blood flow data related to the evaluation area using the sensor element; and evaluating the patient's risk of a pressure ulcer based on an evaluation of the blood flow data obtained for at least two different expansion states of the expandable element.

[0016] When the sensor element is not integrated with the expandable element, the method further comprises the step of attaching the sensor element to the skin of the assessment area.

[0017] The present disclosure also relates to software for performing the method as defined in any of the preceding claims.

[0018] The present disclosure also relates to a system for evaluating blood flow in an area of ​​a patient's skin and underlying tissue. The system includes a sensor board having at least one blood flow sensor obtained by optical plethysmography; and an expandable element (310) having a controllable expansion state. The expandable element is configured to form a frame that at least partially surrounds the sensor board. The construction of the expandable element ensures that the area of ​​evaluation is subjected to at least two different pressure states, which are obtained by the patient's weight pressing against a support on which the patient is placed and the expandable element expanding in a direction from the support toward the patient to substantially eliminate the pressure of the support on the patient's body in an area at least partially surrounding the evaluation area. The system also includes a computer system configured to perform data processing of the blood flow data. At least one blood flow sensor is configured to obtain blood flow data while subjecting the area of ​​evaluation to at least two different pressure states. The computer system is configured to evaluate the risk of a pressure ulcer in the patient based on the evaluation of the blood flow data of at least two different pressure states.

[0019] The system may further comprise a data acquisition system DAS connected to the sensor board, the data acquisition system being configured for data conditioning and conversion of the blood flow data, wherein the computer system is connected to the data acquisition system.

[0020] The sensor plate can be flexible and configured to conform to the curvature of the skin.

[0021] The sensor plate may be provided with an adhesive for attachment to the patient.

[0022] The sensor board may also include a plurality of LED diodes of at least two different wavelengths and at least one photodetector.

[0023] The at least one photodetector may be configured to receive data from the plurality of LEDs and to measure the data for each LED individually.

[0024] The system may further include at least one pressure sensor for acquiring pressure data. The computer system is configured to determine respective pressure states based on the acquired pressure data, and to assess the patient's risk of a pressure ulcer based on the blood flow data acquired for at least two different determined pressure states.

[0025] The present disclosure also relates to a control element for evaluating blood flow in an area of ​​a patient's skin and underlying tissue. The control element includes an interface configured to receive blood flow data from at least one sensor obtained by optical plethysmography. The blood flow data is obtained from an evaluation area that is subjected to at least two different pressure states obtained by: the patient's weight pressing against a support on which the patient is placed, and an expandable element expanding in a direction of the support toward the patient to substantially eliminate pressure of the support on the patient's body in an area at least partially surrounding the evaluation area. The control element also includes a processor configured to perform data processing on the blood flow data based on the evaluation of the blood flow data in at least two different pressure states to evaluate the patient's risk of a pressure ulcer. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 is a flow chart illustrating an example of a method for evaluating blood flow.

[0027] Figure 2 It is shown that, for example, Figure 1 Flow chart of the steps of obtaining blood flow data in a method for evaluating blood flow.

[0028] Figure 3 is a schematic diagram illustrating an example of a system for evaluating tissue under pressure.

[0029] Figure 4 An example of a design of a sensor board is schematically shown.

[0030] Figure 5a A top view of an example of an expandable element for evaluating tissue is shown.

[0031] Figure 5b Shown in an expanded state Figure 5a Side view of the expandable element.

[0032] Figure 5c Shown in an unexpanded state Figure 5a Side view of the expandable element.

[0033] Figure 6 Shows about Figure 1 Examples of applications of the disclosed methods for assessing blood flow. DETAILED DESCRIPTION

[0034] Figure 1 and Figure 6 An example of a method for evaluating blood flow in an area of ​​a patient's skin and underlying tissue is disclosed. The method evaluates a patient's risk of developing a pressure ulcer based on blood flow data.

[0035] Pressure ulcers are damage to the skin and underlying tissues caused by prolonged pressure on the skin. They usually develop on the skin covering bony areas of the body such as the heels, ankles, buttocks and sacrum.

[0036] The exemplary method for evaluating blood flow in an area of ​​skin to assess the risk of developing a pressure ulcer is easy to use and reduces patient discomfort.

[0037] The method is based on the concept that the skin area being evaluated is subjected to at least two different pressure states, wherein the different pressure states are obtained by the patient's body weight pressing against a support and an inflatable element on which the patient is placed. The inflatable element at least partially surrounds the area being evaluated. The inflatable element is inflatable in a direction from the plane of the support toward the patient to substantially eliminate the pressure of the support on the patient's body in an area at least partially surrounding the skin area being evaluated. The expansion state of the inflatable element controls the body pressure applied to the patient's skin area being evaluated.

[0038] At least two different pressure states applied to the evaluated skin area may include a first pressure state in which the evaluated skin area is substantially free of pressure. In this first pressure state, the evaluated skin area is lifted from the support on which the patient is placed by means of the inflatable element. In one example, the evaluated skin area is lifted from the support to a degree not exceeding sufficient to substantially eliminate the pressure of the support on the evaluated skin area of ​​the patient's body. If the evaluated skin area is lifted above the support height above the support by more than necessary, this requires that a higher than necessary pressure be applied to portions of the skin and underlying tissue surrounding the evaluated skin area by the inflatable element. This may result in the risk that the pressure exerted on the skin and underlying tissue portions surrounding the evaluated area may affect blood flow in the evaluated area. Generally, it is desirable that the inflatable element be designed to affect blood flow in the evaluated skin area as little as possible.

[0039] The at least two different pressure states applied to the assessment area may include a second pressure state in which body weight provides pressure to the assessment area. Characteristically, the thickness of the expandable element in this state is as thin as possible.

[0040] Blood flow data relating to the evaluation region is obtained while subjecting the evaluation region to at least two different pressure states. The blood flow data is obtained by means of optical plethysmography. The blood flow data may be obtained solely by optical plethysmography.

[0041] The patient's risk of developing a pressure ulcer is assessed based on an evaluation of blood flow data obtained for at least two different pressure conditions.

[0042] Thus, according to the method, blood flow data is obtained while applying at least two different pressures to the skin area being evaluated, wherein the pressures are obtained by using the patient's weight. In one example, one pressure at which the blood flow data is obtained corresponds to the patient's weight. Another pressure at which the blood flow data is obtained may correspond to substantially no pressure from the patient's weight.

[0043] The sensor pad is placed on the skin area to be evaluated. The sensor pad design will incorporate Figure 4 Discuss in detail.

[0044] In the example shown, the method for evaluating blood flow in the area of ​​skin and underlying tissue of a patient comprises the step of providing S1 a sensor element for obtaining blood flow data. As described above, the sensor board may comprise a blood flow sensor element configured to obtain blood flow data based on optical plethysmography.

[0045] The method further comprises the step of providing S2 an expandable element having a controllable expansion state. The expandable element may form an edge of the sensor plate. Thus, the sensor element is intended to be partially or fully surrounded by the expandable element. The expandable element may be fixed to the sensor plate, forming a unit integral with the sensor plate, or a unit physically separated from the sensor plate.

[0046] The method further comprises the step of positioning S4 the expandable element relative to the patient such that the patient's weight provides pressure to the area of ​​assessment depending on the expansion of the expandable element. Figure 6 In (above), the expandable element is shown positioned at the patient's back. In one example, the expandable element is positioned at the patient's sacrum.

[0047] Furthermore, the sensor plate is configured S3 to be at least partially surrounded by the expandable element to abut against the patient's skin. This step may include attaching the sensor plate to the skin by, for example, an adhesive. The attachment may be provided by means of, for example, a double-sided tape. The adhesive is preferably substantially transparent to radiation emitted by and reflected to the blood flow sensor element of the sensor plate so as not to interfere with the measurement.

[0048] The method further comprises a step of controlling S5 the expansion of the expandable element. Characteristically, the expandable element is controlled to different expansion states. For example, in a first expansion state, substantially no pressure is applied to the evaluated area. A second expansion state may be an unexpanded or deflated state, wherein body weight provides pressure to the evaluated area.

[0049] exist Figure 6In the lower figure, the patient lies on his back. In the lower left figure, the inflatable element is inflated. The patient's weight applies pressure to the inflatable element, but not to the evaluation area of ​​the skin where the sensor plate is arranged. Therefore, the inflated inflatable element protects the sensor element at least partially surrounded by the inflatable element from the patient's weight. Therefore, substantially no pressure is applied to the evaluation area of ​​the skin where the sensor plate is arranged.

[0050] In the lower right image, the inflatable element is not inflated and the patient's weight applies pressure to the support in the area of ​​the skin being evaluated where the sensor plate is located.

[0051] The method further comprises the step of obtaining S8 blood flow data associated with the evaluated skin area in at least two different pressure states. The acquisition of blood flow data may be provided upon determining that the expandable element is in a respective state. Accordingly, when it is determined that a respective expanded state has been reached, the acquisition of blood flow data for that expanded state may be initiated. The acquisition of blood flow data may be performed during a preset amount of time. Alternatively, the blood flow data may be acquired continuously during the entire process.

[0052] As mentioned above, blood flow data is obtained by photoplethysmography (PPG). In detail, PPG is an optically obtained volume measurement of an organ. PPG can be obtained by illuminating the skin and underlying tissues and measuring changes in light absorption.

[0053] During the systole phase of each cardiac cycle, the heart pumps blood to the tissues. Even though this pressure pulse is somewhat weakened when it reaches the skin, it is sufficient to cause the arteries and arterioles in the subcutaneous tissue to open. The volume changes caused by the pressure pulses can be detected by illuminating the skin and underlying tissue with light from a light emitting diode (LED) and then measuring the amount of light reflected to a photodiode. Each systolic cycle appears as a peak. Therefore, as described above, these pressure pulses are compared in the present disclosure while subjecting the skin to different external pressures caused by the patient's weight.

[0054] The method may further comprise the step of obtaining S6 pressure data related to the body pressure applied to the evaluated skin area. The pressure data may be provided by measuring the body pressure applied to the evaluated skin area. The pressure may be measured by means of, for example, at least one pressure sensor. The at least one pressure sensor may be formed on a sensor board that also comprises a blood flow sensor element.

[0055] The respective pressure state may be determined based on the obtained pressure data.

[0056] The determination of the respective pressure state may then be used to start acquiring blood flow data. Alternatively, the determination of the respective pressure state may then be used to select blood flow data for analysis. According to this example, blood flow data corresponding to a preset pressure interval may be selected for analysis.

[0057] The method further comprises the following steps: based on the blood flow data obtained for at least two different expansion states of the expandable element, evaluating S9 the risk of a pressure ulcer in the patient. Analyzing the blood flow in different expansion states. When the blood flow during the period of pressure applied by the body weight to the support in the evaluated skin area is greater than the blood flow during the period of no pressure, the risk of a pressure ulcer is low. On the other hand, when the blood flow during the period of pressure applied by the body weight to the support in the evaluated skin area is lower than the blood flow during the period of no pressure, the risk of a pressure ulcer is increased.

[0058] When blood flow increases as the body pressure exerted by the patient's weight increases, the risk of developing an ulcer is generally less. On the other hand, when the body pressure exerted by the patient's weight increases and blood flow decreases, the risk of developing a pressure ulcer increases. Thus, assessing a patient's risk of developing a pressure ulcer involves determining whether blood flow increases or decreases as the body pressure exerted by the patient's weight on the assessed skin area increases. Preferably, the increase or decrease in blood flow is relative to basal blood flow, i.e., blood flow measured without load.

[0059] As discussed above, the evaluation may be based on blood flow data obtained in different predetermined pressure states, such as a first pressure state in which no pressure is provided in the evaluated skin area and a second pressure state in which body weight is applied to the evaluated area, or based on continuously obtained blood flow data. In the first case, the obtained pressure data may be used to determine S7 the different predetermined pressure states. This determination may in turn be used to start blood flow measurement. In the latter case, the obtained pressure data may be continuously associated with corresponding continuously obtained blood flow data. The obtained pressure data may then be used to select an interval of blood flow data for evaluating the risk of pressure ulcers.

[0060] Figure 2 An example of details of the step of obtaining S8 blood flow data associated with the evaluated skin area is disclosed. The blood flow data is such as Figure 1The acquisition of blood flow data can include illuminating S81 the skin with light from an LED, and measuring S82 the amount of light reflected to a photodiode. The LED and the photodiode constitute a blood flow sensor element. The blood flow sensor element can be arranged on a sensor board. The LED can emit light having one wavelength. Alternatively, the LED can emit light having at least two different wavelengths. According to the latter example, a first group of LEDs emitting at a first wavelength and a second group of LEDs emitting at a second wavelength can illuminate the skin. One or more photodiodes that measure the amount of light reflected thereto can each measure light originating from a plurality of LEDs. Data from each photodiode can be obtained so that the contribution from each LED is determined S83 in the data from the respective photodiodes.

[0061] The method may further comprise the step of evaluating S84 the data associated with each LED. Based on this evaluation, it may be determined whether any LED or photodiode is faulty. The evaluation is performed by comparing the blood flow data with expected blood flow data, for example defined by upper and / or lower limits.

[0062] The S85 may report that it has detected a faulty LED and / or photodiode.

[0063] This evaluation may also be performed to determine if the LED and / or photodiode is not positioned properly, for example, against the skin.

[0064] It may be reported that the S85 detected an LED and / or photodiode that was not positioned correctly.

[0065] The method may further comprise the step of determining S86 LED data suitable for use in assessing pressure ulcer risk. The determination may comprise determining an LED that causes blood flow data that deviates from blood flow data obtained from other LEDs. The LED that causes the deviating data may, for example, lack contact with the illuminated skin portion. The LED that causes the deviating data may then be removed from use in assessing pressure ulcer risk.

[0066] Figure 3 An example of a system 300 for evaluating blood flow in an area of ​​skin and underlying tissue is disclosed. The system 300 includes a measurement system 314 including a sensor board 302. The sensor board is provided with at least one blood flow sensor element configured to obtain blood flow data. The blood flow sensor element may be composed of an LED that emits light and a photodiode that receives the emitted light and the light returned by reflection from the skin and underlying tissue. This may also be combined with Figure 2 and Figure 1 discuss.

[0067] In addition, the system 300 may also include at least one pressure sensor 315. In the example shown, the pressure sensor 315 is mounted at the sensor board 302. The pressure sensor can then be configured to sense the pressure applied to the sensor board. Alternatively, the pressure sensor 315 is a separate component physically separated from the sensor board and / or the blood flow sensor element.

[0068] An expansion element 310 having a controllable expansion state forms a frame at least partially surrounding the sensor plate 302 .

[0069] The expansion element can be designed in many different ways. The expansion element can be expanded, for example, by means of a gas such as air or a liquid. The expandable element can be expanded by means of a mechanical solution. The expansion element can be expanded by means of a magnetic solution. The expandable element can be expanded by means of a chemical solution. The expandable element can include a smart fabric with expandable properties.

[0070] The expandable element can be repeatedly expanded and retracted. Alternatively, the expandable element is disposable. A disposable expandable element is characterized as being expandable / retractable only once. For example, the expandable element can include an ampoule containing a compound that, when released, is configured to expand the expandable element.

[0071] In the example shown, the expandable element is an inflatable element. The inflatable element comprises an inflatable chamber in which the amount of air or another gas, etc., is controllable. Thus, in the example shown, the system comprises a compressor 311 in communication with the inflatable element via a pressure regulator 312 and a valve 313.

[0072] In various examples, the expandable element includes an inflatable chamber, wherein the amount of air in the inflatable chamber is controlled to provide controlled inflation. By controlling the amount of air in the inflatable chamber, the inflatable element can be controlled to at least a first inflated state and a second inflated state.

[0073] Instead of measuring the body pressure exerted by the patient's weight in the evaluated skin area or in addition thereto, at least one pressure sensor can be configured to sense the pressure inside the expansion element and / or the pressure exerted on the pressure line 316 (not disclosed). These pressures can be used to determine the body pressure exerted by the patient's weight in the evaluated skin area.

[0074] The computer system 305 is configured to perform data processing of the blood flow data. The computer system 305 is configured to evaluate the patient's risk of a pressure ulcer based on the processed blood flow data from at least two different inflation states of the inflatable chamber. Figure 1 and Figure 2An example of this has been discussed. In detail, the intensity of the pulse of the body is measured with the aid of blood flow data in at least two different inflation states. In one example, the inflation state includes a first state in which substantially no pressure is applied and a second state in which the full body weight pressure is applied to the support in the evaluated skin area. The measured pressure can be used to determine that the respective state has been reached.

[0075] The computer system can be configured to control the inflation state. Alternatively, the inflation state can be manually controlled. In the example shown, the inflation state is controlled by the control of a pressure regulator, wherein the pressure regulator can be manually controlled and / or controlled by the computer system 305.

[0076] In the example shown, the system 300 also includes a data acquisition system, DAS, 306 connected to the sensor board 314 and the computer system 305. The data acquisition system is configured for data conditioning and conversion of blood flow data.

[0077] System 300 may include memory 304 for storing measured data used by computer system 305. Memory 304 may further be configured to store evaluations made.

[0078] The system 300 also includes a user interface 303. The user interface can be configured to display information related to the pressure ulcer risk assessment. For example, the result of the assessment can be presented through the user interface. The result can be yes or no, that there is a risk of developing a pressure ulcer. Alternatively, the risk can be expressed as a percentage.

[0079] The user interface may be further configured to present information relevant to the conduct of the evaluation. For example, if a single LED or photodiode has been determined to be defective, this may be presented via the user interface. If the evaluation of the data obtained by the photodetector finds that the measurements from different parts of the sensor board are different, a warning may be displayed. For example, this may indicate that at least some parts of the sensor board are not in close contact with the skin. The warning may then indicate that the measurement should be taken again.

[0080] exist Figure 4 , an example of a sensor plate is shown. The sensor plate may be flexible and configured to conform to the curvature of the skin. The sensor plate may be made of a material that is gentle to the skin. The sensor plate may be made of rubber or a rubber-based material, for example.

[0081] In the example shown, the sensor plate is foldable along a plurality of co-linear lines to be able to conform to the curvature of the body. However, many other designs of the sensor plate can be considered so that the sensor plate can conform to the curvature of the body. If it can be ensured that the sensor plate is close to the skin when taking a measurement, the measurement results can be improved.

[0082] The sensor plate may be provided with an adhesive on its skin-facing side for attachment to the patient's skin.

[0083] The sensor board includes a blood flow sensor element, which includes a plurality of LEDs configured to emit light of at least two different wavelengths. In one example, the LED can be configured to emit red and green light. The blood sensor element also includes at least one photodetector such as a photodiode. In the example shown, the blood flow sensor element also includes a plurality of photodiodes configured to receive light emitted from the LED and reflected from the skin and underlying tissue. In the example shown, the blood flow sensor element includes a plurality of LEDs that emit light that can have at least two different wavelengths. In addition, in the example shown, the blood flow sensor element includes six photodiodes.

[0084] Each of the at least one photodetector may be configured to receive data from the plurality of LEDs and to respectively measure data from each LED.

[0085] The sensor plate may also include at least one pressure sensor (not shown) configured to measure pressure caused by the patient's weight in the evaluated skin area.

[0086] Figures 5a to 5c An example of an expansion element according to the present disclosure having a controllable expansion state is shown.The expansion element has at least two different expansion states.

[0087] As about Figure 3 As discussed above, the expandable element can be designed in many different ways. The expandable element can, for example, be expanded by means of a gas such as air or a liquid. The expandable element can be expanded by means of a mechanical solution. The expandable element can be expanded by means of a magnetic solution. The expandable element can be chemically expanded. The expandable element can include a smart fabric having expandable properties.

[0088] The expandable element can be repeatedly expanded and retracted. Alternatively, the expandable element is disposable. A disposable expandable element is typically expandable / retractable only once. For example, a disposable expandable element can include an ampoule containing a chemical compound that, when released, is configured to expand the expandable element.

[0089] The expandable element forms a frame designed to at least partially surround the sensor plate.

[0090] The expansion element may be integrally formed with the sensor plate or physically separate therefrom.

[0091] The expansion element may be integrally formed with the support on which the patient is intended to be placed, or may be physically separate from the support.The support may be a bed.

[0092] exist Figure 5aIn the view seen from above of the inflatable element, it is disclosed that the inflatable element forms a frame designed to at least partially surround the sensor plate. Thus, the inflatable element comprises a rim surrounding the area.

[0093] exist Figure 5b In the side view of the , it is disclosed that the expandable element is designed to extend above the sensor plate (dashed line in the figure) when it is arranged in the area at least partially surrounded by the expandable element when it is expanded. Thus, the edge protects the central hollow area from the pressure from the human body pressing on the expandable element.

[0094] exist Figure 5c In a side view of the , it is disclosed that the expandable element is designed to be as thin as possible when not expanded. It can be expected that the expandable element in this state is substantially aligned with the support on which the expandable element is placed. In addition, the upper surface of the expandable element in this state can be in the same plane as the surface of the sensor plate (dashed line in the figure) when arranged in an area at least partially surrounded by the expandable element. As a result, the expandable element does not substantially protect the area at least partially surrounded by the expandable element from the influence of the weight of the human body.

Claims

1. A method for evaluating blood flow in a patient's skin and underlying tissue region, the method comprising the steps of: Subjecting the evaluation area to at least two different pressure conditions, wherein the different pressure conditions are obtained by: the patient's weight on the support on which the patient is placed, and an expandable element at least partially surrounding the evaluation area and expandable in a direction of the support toward the patient to substantially eliminate pressure of the support on the patient's body in an area at least partially surrounding the evaluation area, while subjecting the evaluation region to the at least two different pressure states, obtaining (S8) blood flow data related to the evaluation region, wherein the blood flow data is evaluated by photoplethysmography, and The risk of a pressure ulcer in the patient is evaluated ( S9 ) based on the evaluation of the blood flow data obtained for the at least two different pressure states.

2. The method according to claim 1, wherein: In the first pressure state, substantially no pressure is provided in the evaluation region.

3. The method according to claim 2, wherein: In the second pressure state, the body weight applies pressure to the evaluation area.

4. The method according to claim 3, further comprising the steps of: The expandable element is controlled (S5) between at least a first expansion state corresponding to the first pressure state and a second expansion state corresponding to the second pressure state.

5. The method according to claim 1 or 2, further comprising the following steps: Pressure data are obtained (S6) and respective pressure states are determined (S7) based on the obtained pressure data, wherein the step of assessing (S9) the risk of a pressure ulcer is performed based on the blood flow data obtained for at least two different determined pressure states.

6. The method according to claim 1 or 2, wherein: The blood flow data is obtained by: Illuminating the skin and underlying tissue with light from an LED lamp, The amount of light reflected to the photodiode is measured.

7. The method according to claim 1 or 2, comprising the steps of: providing (S1) the expandable element having a controllable expansion state, providing (S2) a sensor element for obtaining said blood flow data using optical plethysmography, positioning ( S4 ) the expandable element relative to the patient such that the patient's weight provides pressure to the evaluation area depending on the expansion state of the expandable element, obtaining (S8) blood flow data related to the evaluation area using the sensor element, and The risk of a pressure ulcer in the patient is evaluated ( S9 ) based on an evaluation of the blood flow data obtained for at least two different expansion states of the expandable element.

8. The method according to claim 7, further comprising attaching (S3) the sensor element to the skin of the assessment area.

9. A computer-readable storage medium having a computer program stored thereon, wherein when the computer program is executed by a processor, the method according to any one of claims 1 to 8 is performed.

10. A system (300) for evaluating blood flow in a region of skin and underlying tissue of a patient, the system comprising: a sensor board (314) having at least one blood flow sensor for obtaining blood flow data by optical plethysmography; an expandable element (310) having a controllable expansion state, the expandable element being configured to form a frame at least partially surrounding the sensor plate (314); wherein the configuration of the expandable element ensures that the evaluation region is subjected to at least two different pressure states, the at least two different pressure states being obtained by: the body weight of the patient pressing against a support on which the patient is placed, and the expansion of the expandable element in a direction of the support toward the patient to substantially eliminate pressure of the support against the patient's body in a region at least partially surrounding the evaluation region; and A computer system (305) configured to perform data processing of the blood flow data, wherein the at least one blood flow sensor is configured to obtain the blood flow data while subjecting the evaluation region to the at least two different pressure states, and The computer system (305) is configured to evaluate the patient's risk of a pressure ulcer based on evaluating the blood flow data for the at least two different pressure states.

11. The system according to claim 10, further comprising a data acquisition system DAS (306) connected to the sensor board (314), the data acquisition system being configured for data conditioning and conversion of the blood flow data, wherein the computer system is connected to the data acquisition system.

12. The system according to any one of claims 10 to 11, wherein: The sensor plate is flexible and configured to conform to the curvature of the skin.

13. The system according to any one of claims 10 to 11, wherein: The sensor plate is provided with an adhesive for attachment to the patient.

14. The system according to any one of claims 10 to 11, wherein: The sensor board (314) also includes a plurality of LED diodes of at least two different wavelengths and at least one photodetector.

15. The system of claim 14, wherein: The at least one photodetector is configured to receive data from the plurality of LEDs and to individually measure the data from each LED.

16. The system according to any one of claims 10 to 11, further comprising at least one pressure sensor (315) for acquiring pressure data, wherein the computer system (305) is configured to determine a corresponding pressure state based on the acquired pressure data, and to evaluate the risk of a pressure ulcer of the patient based on the blood flow data acquired for at least two different determined pressure states.

17. A control element for evaluating blood flow in an area of ​​skin and underlying tissue of a patient, the control element comprising: an interface configured to receive blood flow sensor data obtained by optical plethysmography, the blood flow sensor data obtained from an evaluation region subjected to at least two different pressure states, the at least two different pressure states obtained by: the body weight of the patient pressing against a support on which the patient is positioned, and expansion of an expandable element in a direction of the support toward the patient to substantially eliminate pressure of the support against the patient's body in a region at least partially surrounding the evaluation region; and A processor is configured to perform data processing on the blood flow data to evaluate the risk of a pressure ulcer of the patient based on the evaluation of the blood flow data for the at least two different pressure states.

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