Method and system for assessing blood flow

Abstract

To provide a method and system for assessment of blood flow in an area of the skin and underlying tissue of a patient.SOLUTION: A method includes a step of subjecting an assessed area to at least two different pressure states, wherein the different pressure states are obtained by a patient's weight pressuring against a support on which the patient is placed and an expandable element at least partly circumventing the assessed area and expandable in a direction from the support against the patient to substantially eliminate the patient's body from the support in the area at least partly circumventing the assessed area. The method further includes: a step of obtaining blood flow data related to the assessed area while subjecting the assessed area to the at least two different pressure states, wherein the blood flow data is obtained by means of photoplethy smography; and a step of assessing the risk of pressure ulcers on the patient based on assessment of the blood flow data obtained for the at least two different pressure states.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] Background technology A pressure ulcer is damage to the skin and underlying tissue resulting from prolonged pressure on the skin. Pressure ulcers most often occur on the skin over bony areas of the body such as the heels, ankles, lower back and sacrum.

[0003] People at highest risk of developing pressure sores are those in medical settings with limited ability to reposition or who spend most of their time in bed or in a chair. Bedridden individuals often develop painful pressure sores. Furthermore, pressure sores represent a high cost to the healthcare system. Summary of the Invention [Means for solving the problem]

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

[0005] This has been achieved by a method of assessing blood flow in an area of ​​the skin and subcutaneous tissue of a patient, the method comprising the steps of subjecting the area to be assessed to at least two different pressure conditions, the different pressure conditions being obtained by the weight of the patient applied against a support on which the patient is placed and an expandable element at least partially surrounding the area to be assessed and expandable in a direction from the support towards the patient so as to substantially eliminate pressure from the support to the patient's body in the area at least partially surrounding the area to be assessed. The method further comprises the steps of acquiring (S8) blood flow data relating to the area to be assessed while subjecting the area to be assessed to the at least two different pressure conditions, the blood flow data being acquired by photoplethysmography, and assessing the risk of a pressure ulcer in the patient based on an evaluation of the blood flow data acquired for the at least two different pressure conditions (S9).

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

[0007] In a different embodiment, the first pressure condition provides substantially no pressure in the area being evaluated, thereby providing a measurement of basal blood flow and allowing any blood flow measured under pressure to be related to the basal blood flow.

[0008] In a different embodiment, in the second pressure state, body weight is applied against the area being evaluated, thus providing measurements that are at least somewhat reflective of everyday situations when the patient spends most of their time in bed or in a chair.

[0009] Comparing blood flow that reflects the patient's everyday situation with baseline blood flow provides a risk assessment with a high degree of certainty.

[0010] The first and second pressure conditions may be obtained in the above order to reduce the risk that measurements of basal blood flow are disturbed by previous loading on the area being evaluated.

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

[0012] This automation can reduce training requirements for personnel using the method.

[0013] In a different embodiment, the method includes the steps of acquiring pressure data and identifying respective pressure conditions based on the acquired pressure data (S7).The step of assessing the risk of a pressure ulcer is then performed based on the acquired blood flow data for the at least two different identified pressure conditions.

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

[0015] The method may further include providing an expandable element having a controllable expansion state; providing a sensor element for acquiring blood flow data using photoplethysmography; positioning the expandable element in relation to the patient such that the patient's weight provides pressure in the area to be evaluated depending on the expansion state of the expandable element; acquiring blood flow data relating to the area to be evaluated using the sensor element; and assessing the patient's risk of a pressure ulcer based on an evaluation of the blood flow data acquired for at least two different expansion states of the expandable element.

[0016] If the sensor element is not integrated with the expandable element, the method further includes attaching the sensor element to the skin in the area to be evaluated.

[0017] The present disclosure further relates to software for carrying out a method as recited in any of the preceding claims.

[0018] The present disclosure further relates to a system for evaluating blood flow in an area of ​​the skin and subcutaneous tissue of a patient. The system includes a sensor plate with at least one blood flow sensor acquired by photoplethysmography and an expandable element (310) with a controllable expansion state. The expandable element is configured to form a frame at least partially surrounding the sensor plate. The configuration of the expandable element ensures that the area to be evaluated is subjected to at least two different pressure states acquired by the weight of the patient applied against a support on which the patient is placed and an expansion of the expandable element in a direction from the support to the patient to substantially eliminate pressure from the support to the patient's body in an area at least partially surrounding the area to be evaluated. The system further includes a computing system configured to perform data processing of said blood flow data. The at least one blood flow sensor is configured to acquire blood flow data while subjecting the area to be evaluated to at least two different pressure states. The computing system is configured to evaluate the risk of a bed sore in the patient based on the evaluation of the blood flow data for the at least two different pressure states.

[0019] The system may further include a data acquisition system DAS connected to the sensor plate, said data acquisition system configured to condition data and convert said blood flow data, and a computing system connected to the data acquisition system.

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

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

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

[0023] At least one photodetector may be configured to receive data from the multiple LEDs and to measure the data from each LED individually.

[0024] The system may further include at least one pressure sensor that acquires pressure data. The computing system is configured to identify respective pressure conditions based on the acquired pressure data and to assess the patient's risk of a pressure ulcer based on the acquired blood flow data for the identified at least two different pressure conditions.

[0025] The present disclosure further relates to a control element for evaluating blood flow in an area of ​​the skin and subcutaneous tissue of a patient. The control element includes an interface configured to receive blood flow data obtained by photoplethysmography from at least one sensor. The blood flow sensor data is obtained from an area to be evaluated that is subjected to at least two different pressure conditions obtained by the weight of a patient applied against a support on which the patient is placed and the expansion of an expandable element in a direction from the support to the patient to at least substantially eliminate pressure from the support to the patient's body in an area at least partially surrounding the area to be evaluated. The control element further includes a processor configured to perform data processing of the blood flow data to evaluate the risk of a bed sore in the patient based on the evaluation of the blood flow data for the at least two different pressure conditions. [Brief description of the drawings]

[0026] BRIEF DESCRIPTION OF THE DRAWINGS [Figure 1] 1 is a flow chart illustrating an example of a method for assessing blood flow. [Diagram 2] 2 is a flow chart illustrating steps of obtaining blood flow data, for example in a method of assessing blood flow according to FIG. 1; [Diagram 3] FIG. 1 is a schematic diagram illustrating an example of a system for assessing tissue under pressure. [Figure 4] 1 shows a schematic diagram of an example sensor plate design. [Figure 5a] 1 shows a top view of one example of an expandable element for use in assessing tissue. [Figure 5b] FIG. 5b shows a side view of the expandable element of FIG. 5a in an expanded state. [Figure 5c] FIG. 5b shows a side view of the expandable element of FIG. 5a in an unexpanded state. [Figure 6] An example of the application of the method for assessing blood flow as disclosed in relation to FIG. 1 is shown. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0027] Detailed Description 1 and 6 disclose an example of a method for assessing blood flow in an area of ​​the skin and subcutaneous tissue of a patient, the method assessing the patient's risk of developing a pressure ulcer based on the blood flow data.

[0028] A pressure ulcer is damage to the skin and underlying tissue resulting from prolonged pressure on the skin. Pressure ulcers most often occur on the skin over bony areas of the body such as the heels, ankles, lower back and sacrum.

[0029] The exemplary method of assessing blood flow in an area of ​​skin to assess the risk of developing a pressure ulcer is easy to use and reduces patient discomfort.

[0030] The method is based on the concept that the skin area to be evaluated is subjected to at least two different pressure states, which are obtained by the weight of the patient and an inflatable element applied against a support on which the patient is placed. The inflatable element at least partially surrounds the area to be evaluated. The inflatable element is inflatable in a direction from the plane of the support towards the patient, so as to at least substantially eliminate pressure from the support to the patient's body in an area at least partially surrounding the skin area to be evaluated. The inflated state of the inflatable element controls the body pressure applied to the skin area to be evaluated of the patient.

[0031] The at least two different pressure states applied to the skin area to be evaluated may include a first pressure state in which the skin area to be evaluated is substantially free of pressure. In this first pressure state, the skin area to be evaluated is lifted by the expansion element from the support on which the patient is placed. The skin area to be evaluated is, in one example, merely lifted from the support sufficiently to substantially eliminate pressure from the support to the skin area to be evaluated of the patient's body. If the skin area to be evaluated is lifted above the support to a greater extent than necessary, it becomes necessary for the expansion element to provide a higher pressure than necessary to the skin and subcutaneous tissue portion surrounding the skin area to be evaluated. This may lead to a risk that the blood flow in the area to be evaluated is affected by the pressure received by the skin and subcutaneous tissue portion surrounding the area to be evaluated. It is generally desirable that the expansion element is designed to affect the blood flow in the skin area to be evaluated as little as possible.

[0032] The at least two different pressure states applied to the area being evaluated may include a second pressure state in which body weight provides pressure to the area being evaluated, wherein characteristically the thickness of the expandable element in this state is as thin as possible.

[0033] Blood flow data associated with the area being evaluated is obtained while the area being evaluated is subjected to at least two different pressure conditions. The blood flow data is obtained by photoplethysmography. The blood flow data may be obtained exclusively by photoplethysmography.

[0034] The patient's risk of a pressure ulcer is assessed based on evaluation of the blood flow data obtained for at least two different pressure conditions.

[0035] Thus, according to the method, blood flow data is acquired while at least two different pressures are applied to the skin area being evaluated, the pressures being obtained by using the weight of the patient. In one example, one of the pressures at which blood flow data is acquired corresponds to the weight of the patient. Another pressure at which blood flow data is acquired may correspond to a substantial absence of pressure from the weight of the patient.

[0036] The sensor plate is placed on the skin area to be evaluated. The design of the sensor plate is discussed in more detail in relation to FIG.

[0037] In the illustrated example, a method for assessing blood flow in an area of ​​a patient's skin and subcutaneous tissue includes the step S1 of providing a sensor element for acquiring blood flow data. As described above, the sensor plate may include a blood flow sensor element configured to acquire blood flow data based on photoplethysmography.

[0038] The method further comprises a step S2 of providing an expandable element having a controllable expansion state. The expandable element may form a rim of the sensor plate. It is therefore intended that the sensor element is partially or totally surrounded by the expandable element. The expandable element may be fixed to the sensor plate and form an integral unit therewith, or may be a physically separate unit therefrom.

[0039] The method further includes the step S4 of positioning the expandable element relative to the patient such that the weight of the patient provides pressure to the area to be evaluated in response to expansion of the expandable element. In Figure 6 (top diagram), the expandable element is shown positioned on the patient's back. In one example, the expandable element is positioned on the patient's sacrum.

[0040] The sensor plate is then positioned S3 at least partially surrounded by the expandable element and abuts against the patient's skin. This step may include attaching the sensor plate to the skin, for example by adhesive. The attachment may be provided, for example, by double-sided tape. In order not to interfere with the measurement, the adhesive is preferably substantially transparent to light emitted by and reflected by the blood flow sensor elements of the sensor plate.

[0041] The method further comprises a step S5 of controlling 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 area being evaluated. A second expansion state can be a non-inflated or deflated state in which body weight provides pressure to the area being evaluated.

[0042] In the bottom diagram of FIG. 6, the patient is lying on his back. In the bottom left diagram, the expandable element is inflated. The patient's body weight exerts pressure on the expandable element, but not on the area being evaluated where the sensor plate is provided against the skin. Thus, the inflated expandable element protects the sensor element, which is at least partially surrounded by the inflatable element, from the patient's body weight. Thus, substantially no pressure is applied to the area being evaluated where the sensor plate is provided against the skin.

[0043] In the bottom right image, the expandable element is not inflated and the patient's body weight exerts pressure on the support at the skin area being evaluated where the sensor plate is presented to the skin.

[0044] The method further includes a step S8 of acquiring blood flow data associated with the skin area being evaluated at least two different pressure states. Acquisition of blood flow data may be provided when the expandable element is determined to be in each state. Accordingly, acquisition of blood flow data for each expansion state may be initiated when it is determined that the expansion state has been reached. Acquisition of blood flow data may be performed for a preset amount of time. Alternatively, blood flow data may be acquired continuously during the entire procedure.

[0045] As mentioned above, blood flow data is obtained by photoplethysmography (PPG). In particular, PPG is an optically acquired volumetric measurement of an organ. PPG may be obtained by illuminating the skin and subcutaneous tissue and measuring the change in light absorbance.

[0046] During the systole phase of each cardiac cycle, the heart pumps blood into the tissue. This pressure pulse weakens somewhat by the time it reaches the skin, but is sufficient to distend the arteries and arterioles in the subcutaneous tissue. The volume change caused by the pressure pulse is detected by illuminating the skin and subcutaneous 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. Thus, in the present disclosure, these pressure pulses are compared while the skin is subjected to different external pressures caused by the weight of the patient, as described above.

[0047] The method may further include a step S6 of obtaining pressure data relating to a body pressure applied to the skin area being evaluated. The pressure data may be provided by measuring a body pressure applied to the skin area being evaluated. The pressure may be measured, for example, by at least one pressure sensor. The at least one pressure sensor may be formed in a sensor plate that also includes the blood flow sensor element.

[0048] Each pressure state may be identified based on the acquired pressure data.

[0049] The identification of each pressure state may then be used to initiate acquisition of blood flow data. Alternatively, the identification of each pressure state may then be used to select blood flow data for analysis. According to this example, blood flow data corresponding to a pre-set pressure interval may be selected for analysis.

[0050] The method further comprises a step S9 of assessing the risk of bed sores in the patient based on the blood flow data obtained for at least two different expansion states of the inflatable element. The blood flow in the different expansion states is analyzed. If the blood flow in the evaluated skin area during pressure with the weight against the support is greater than the blood flow during no pressure, the risk of bed sores is low. On the other hand, if the blood flow in the evaluated skin area during pressure with the weight against the support is less than the blood flow during no pressure, the risk of bed sores is high.

[0051] In general, if blood flow increases with increasing body pressure exerted by the patient's weight, the risk of bed sores is low. On the other hand, if blood flow decreases with increasing body pressure exerted by the patient's weight, the risk of bed sores is high. Thus, assessing a patient's risk of bed sores involves determining whether blood flow increases or decreases with increasing body pressure exerted by the patient's weight on the assessed skin area. Preferably, the increase or decrease in blood flow is relative to basal blood flow, i.e. blood flow measured in the absence of load.

[0052] As mentioned above, the assessment can be based on acquired blood flow data acquired at discrete predefined pressure conditions, such as a first pressure condition where no pressure is provided to the skin area to be assessed and a second pressure condition where body weight is applied to the area to be assessed, or based on continuously acquired blood flow data. In the first case, the acquired pressure data can be used to identify the discrete predefined pressure condition S7. This identification can then be used to initiate blood flow measurements. In the latter case, the acquired pressure data can be continuously associated with the corresponding continuously acquired blood flow data. The acquired pressure data can then be used to select an interval of blood flow data for assessing the risk of a pressure ulcer.

[0053] FIG. 2 discloses an example of details of step S8 of acquiring blood flow data related to the skin area to be evaluated. The blood flow data is acquired by photoplethysmography, as discussed in relation to FIG. 1. Acquiring the blood flow data may include illuminating the skin with light from an LED S81 and measuring the amount of light reflected to a photodiode S82. The LED and the photodiode form a blood flow sensor element. The blood flow sensor element may be arranged on a sensor plate. The LED may emit light having one wavelength. Alternatively, the LED may emit light having at least two different wavelengths. According to the latter example, a first set of LEDs emitting a first wavelength and a second set of LEDs emitting a second wavelength may illuminate the skin. The one or more photodiodes measuring the amount of reflected light may measure light originating from the multiple LEDs, respectively. Data from each photodiode may be acquired such that a contribution from each individual LED is identified in the data from each photodiode S83.

[0054] The method may further include a step S84 of evaluating data associated with each individual LED. Based on this evaluation, cases may be identified when any LED or photodiode is faulty. The evaluation may be performed by comparing the blood flow data with expected blood flow data defined, for example, by upper and / or lower limits.

[0055] S85 may report any faulty LEDs and / or photodiodes detected.

[0056] Evaluation may also be performed to identify if the LED and / or photodiode are not positioned correctly, for example not abutting the skin.

[0057] Any improperly positioned LEDs and / or photodiodes detected may be reported S85.

[0058] The method may further include a step S86 of identifying LED data suitable for use in assessing the risk of a pressure ulcer. The identification may include identifying LEDs that produce misaligned blood flow data from blood flow data obtained from other LEDs. LEDs that produce misaligned data may, for example, lack contact with the illuminated skin portion. LEDs that produce misaligned data may then be removed from use in assessing the risk of a pressure ulcer.

[0059] 3 discloses an example system 300 for evaluating blood flow in an area of ​​skin and subcutaneous tissue. The system 300 includes a measurement system 314 including a sensor plate 302. The sensor plate is provided with at least one blood flow sensor element configured to acquire blood flow data. The blood flow sensor element may be formed by an LED for emitting light and a photodiode for receiving the emitted light and the returned light from reflection in the skin and subcutaneous tissue. This was also discussed in relation to FIG. 2 and FIG. 1.

[0060] Additionally, the system 300 may further include at least one pressure sensor 315. The pressure sensor 315, in the illustrated example, is mounted to the sensor plate 302. The pressure sensor may then be configured to sense pressure exerted on the sensor plate. Alternatively, the pressure sensor 315 is a separate component physically separated from the sensor plate and / or the blood flow sensor element.

[0061] An expansion element 310 having a controllable expansion state forms a frame that at least partially bounds the sensor plate 302 .

[0062] The expansion element can be designed in many ways. The expansion element can be expandable by a gas, such as air, or a liquid. The expandable element can be expandable by a mechanical solution. The expansion element can be expandable by a magnetic solution. The expandable element can be expandable by a chemical solution. The expandable element can include an intelligent textile with expandability.

[0063] The expandable element may be repeatedly inflated and retracted. Alternatively, the expandable element is disposable. A disposable expandable element is characteristically inflatable / retractable only one time. For example, the expandable element may include an ampoule containing a compound configured to expand the expandable element when released.

[0064] In the illustrated example, the expandable element is an inflatable element. The inflatable element includes an inflatable chamber in which a controllable amount of, for example, air or another gas is inserted. Thus, in the illustrated example, the system includes a compressor 311 in communication with the inflatable element via a pressure regulator 312 and a valve 313.

[0065] In a different example, the inflatable element includes an inflatable chamber, and an amount of air in the inflatable chamber is controlled to provide controllable inflation. The inflatable element can be controlled to at least a first inflated state and a second inflated state by controlling the amount of air in the inflatable chamber.

[0066] As an alternative or in addition to measuring the body pressure exerted by the patient's body weight on the skin area being evaluated, the at least one pressure sensor may be configured to sense the internal pressure of the inflatable element and / or the pressure exerted across a pressure line 316 (not shown), which may be used to determine the body pressure exerted by the patient's body weight on the skin area being evaluated.

[0067] The computing system 305 is configured to perform data processing of the blood flow data. The computing system 305 is configured to assess the risk of bed sores in the patient based on the processed blood flow data from at least two different inflation states of the inflatable chamber. An example of this has been discussed in relation to Figs. 1 and 2. In particular, the strength of the body pulse is measured by the blood flow data at at least two different inflation states. In one example, the inflation states include a first state where substantially no pressure is applied and a second state where the entire body weight is applied to the support at the skin area to be evaluated. The measured pressure can be used to identify when each state has been reached.

[0068] The computing system may be configured to control the inflation state. Alternatively, the inflation state is manually controlled. In the illustrated example, the inflation state is controlled by control of a pressure regulator, which can be manually controllable and / or controllable by the computing system 305.

[0069] System 300, in the illustrated example, further includes a data acquisition system DAS 306 connected to sensor board 314 and to a computing system 305. The data acquisition system is configured to perform data conditioning and transformation of the blood flow data.

[0070] The system 300 may include a memory 304 for storing the measurement data used by the calculation system 305. The memory 304 may further be configured to store the evaluations made.

[0071] The system 300 further includes a user interface 303. The user interface may be configured to display information related to the assessment of the risk of a pressure ulcer. For example, the results of the assessment may be presented by the user interface. The result may be yes or no, i.e., there is or is not a risk of developing a pressure ulcer. Alternatively, the risk may be presented as a percentage.

[0072] The user interface may further be configured to present information related to the performance of the assessment. For example, if an individual LED or photodiode is determined to be defective, this may be presented by the user interface. If evaluation of the data acquired by the photodetector reveals that the results obtained from measurements at different parts of the sensor plate are different, a warning may be presented. For example, this may indicate that at least some parts of the sensor plate are not abutting the skin. The warning may then indicate that the measurement should be performed again.

[0073] An example of a sensor plate is shown in Figure 4. The sensor plate may be flexible and may be configured to follow the curvature of the skin. The sensor plate may be made of a material that is skin friendly. The sensor plate may be made of, for example, rubber or a rubber-based material.

[0074] In the illustrated example, the sensor plate is foldable along multiple collinear lines so that it can follow the curvature of the body. However, many other designs of the sensor plate that allow it to follow the curvature of the body are also contemplated. Measurements can be improved if it can be ensured that the sensor plate is against the skin while taking the measurements.

[0075] The sensor plate, on its side intended to face the skin, may be provided with an adhesive for attachment to the patient's skin.

[0076] The sensor plate includes a blood flow sensor element including a plurality of LEDs configured to emit light at at least two different wavelengths. In one example, the LEDs can be configured to emit red and green light. The blood sensor element further includes at least one light detector, such as a photodiode. In the illustrated example, the blood flow sensor element further includes a plurality of photodiodes configured to receive light emitted from the LEDs and light reflected from the skin and subcutaneous tissue. In the illustrated example, the blood flow sensor element includes a plurality of LEDs that emit light that can be at least two different wavelengths. Additionally, in the illustrated example, the blood flow sensor element includes six photodiodes.

[0077] At least one photodetector may be configured to receive data from each of the multiple LEDs and to measure the data from each LED individually.

[0078] The sensor plate may further include at least one pressure sensor (not shown) configured to measure pressure caused by the patient's body weight on the skin area being evaluated.

[0079] Figures 5a-5c show an example of an expansion element having controllable expansion states according to the present disclosure, the expansion element having at least two different expansion states.

[0080] As discussed in relation to FIG. 3, the expansion element may be designed in many different ways. The expansion element may be expandable by a gas, such as air, or a liquid. The expandable element may be expandable by a mechanical solution. The expansion element may be expandable by a magnetic solution. The expandable element may be chemically expandable. The expandable element may include an intelligent textile having expandability.

[0081] The expandable element may be repeatedly inflated and retracted. Alternatively, the expandable element is disposable. A disposable expandable element is characteristically inflatable / retractable only one time. For example, a disposable expandable element may include an ampoule containing a compound configured to expand the expandable element when released.

[0082] The expandable element forms a frame designed to at least partially surround the sensor plate.

[0083] The expansion element may be integrally formed with the sensor plate or may be physically separate from the sensor plate.

[0084] The inflatable element may be integral with the support on which the patient is intended to rest or may be physically separated from the support, which may be a bed.

[0085] In the top view in Fig. 5a, it is disclosed that the inflatable element forms a frame designed to at least partially surround the sensor plate, thus the inflatable element includes a rim that surrounds the area.

[0086] In the side view of Fig. 5b it is disclosed that the expandable element is designed to extend above the sensor plate (shown in dashed lines) when expanded, when the sensor plate is placed in an area at least partially surrounded by the expandable element, whereby the rim protects the central hollow area from pressure from the human body pressing against the expandable element.

[0087] In the side view of Fig. 5c, it is disclosed that the expandable element is designed to be as thin as possible when not expanded. It may be desirable for the expandable element in this state to be essentially aligned with the support on which it is placed. Furthermore, the upper surface of the expandable element may in this state be in the same plane as the surface of the sensor plate (dashed line in the figure) when placed in the area at least partially surrounded by the expandable element. Thereby, the expandable element does not substantially protect the area at least partially surrounded by the expandable element from the weight of the human body.

Claims

1. 1. A method of operating a system for assessing blood flow in an assessed area of ​​a patient's skin and subcutaneous tissue, comprising: subjecting the area of ​​the patient's skin and subcutaneous tissue to at least two different pressures with an expandable element expandable in a direction from the support towards the patient so as to at least partially surround the area of ​​the patient's skin and subcutaneous tissue to be evaluated and to substantially eliminate pressure from the support to the patient's body in the area of ​​the patient; (S8) while the expandable element subjects the area to be evaluated to the at least two different pressures, at least one blood flow sensor acquiring blood flow data relating to the area to be evaluated by photoplethysmography; and (S9) a computing system assessing the patient's risk of a pressure ulcer based on evaluation of the blood flow data obtained for the at least two different pressures.

2. The operating method of claim 1, further comprising a step (S5) of expanding the expandable element to a state between a first expanded state corresponding to a first pressure among the at least two different pressures and a second expanded state corresponding to a second pressure among the at least two different pressures.

3. the first pressure of the at least two different pressures is substantially absent; and / or The method of claim 2 , wherein the second of the at least two different pressures is caused by the weight of the patient's body applied against the area being evaluated.

4. An operating method as described in any one of claims 1 to 3, further comprising a step (S6) of at least one pressure sensor acquiring pressure data, and a step (S7) of the computing system identifying the respective pressures based on the acquired pressure data, wherein the step (S9) of assessing the risk of bedsore is performed based on blood flow data acquired for the identified at least two different pressures.

5. The blood flow data is illuminating the skin and subcutaneous tissue with light from an LED; A method according to any one of the preceding claims, wherein the intensity is obtained by measuring the amount of light reflected onto a photodiode (S8).

6. Method according to any one of the preceding claims, wherein the expandable element forms an integral unit with a sensor element in the form of a sensor plate.

7. Software for carrying out the operating method according to any one of claims 1 to 6.

8. 1. A system (300) for assessing blood flow in an area of ​​a patient's skin and subcutaneous tissue, comprising: a sensor plate (314) having at least one blood flow sensor for acquiring blood flow data by photoplethysmography; an expandable element (310) having a controllable expansion state, configured to form a frame at least partially surrounding said sensor plate (314); an expandable element (310) whose configuration ensures that the area to be evaluated is subjected to at least two different pressures obtained by the weight of the patient applied against a support on which the patient is placed and by the expansion of the expandable element in a direction from the support to the patient to substantially eliminate pressure from the support to the patient's body in the area to be evaluated; and a computing system (305) configured to perform data processing of the blood flow data; the at least one blood flow sensor is configured to acquire the blood flow data while subjecting the area to be evaluated to the at least two different pressures; The computing system (305) is configured to assess the patient's risk of a pressure ulcer based on evaluation of the blood flow data for the at least two different pressures.

9. 9. The system of claim 8, further comprising a data acquisition system (DAS) (306) connected to the sensor plate (314), the data acquisition system configured to condition data and convert the blood flow data, and the computing system connected to the data acquisition system.

10. 10. The system of claim 8 or 9, wherein the sensor plate is flexible and configured to follow the curvature of the skin.

11. The system of any one of claims 8 to 10, wherein the sensor plate is provided with an adhesive for attachment to the patient.

12. The system of any one of claims 8 to 11, wherein the sensor plate (314) further comprises a plurality of LED diodes of at least two different wavelengths and at least one photodetector.

13. The system of claim 12 , wherein the at least one photodetector is configured to receive data from a plurality of LEDs and to measure the data from each LED individually.

14. The system of any one of claims 8 to 13, further comprising at least one pressure sensor (315) for acquiring pressure data, wherein the calculation system (305) is configured to identify the respective pressures based on the acquired pressure data, and to assess the patient's risk of a pressure ulcer based on blood flow data acquired for the identified at least two different pressures.

15. A system according to any one of claims 8 to 14, wherein the expandable element forms an integral unit with the sensor plate.

Images