Detecting artifacts in data

Abstract

According to one aspect, there is provided a computer-implemented method (300) for detecting artifacts in data acquired using a blood pressure measurement device, the method comprising: receiving (302) applied pressure data, the applied pressure data comprising data indicative of a pressure applied to a body part of a subject whose blood pressure is to be measured; receiving (304) tissue pressure data indicative of tissue pressure exerted by tissue of the subject on a sensor pad of the blood pressure measurement device; determining (306) a first derivative of the applied pressure data; identifying (308) that a magnitude of the applied pressure data in a first derivative of the applied pressure data satisfies a first defined threshold condition; defining a threshold condition by a first-order derivative; and in response to determining that the tissue pressure satisfies a second defined threshold condition for the predetermined duration of occurrence, determining (310) that an artifact is present in the tissue pressure data.

Description

Technical Field

[0001] The present invention relates to the general field of blood pressure measurement and, more particularly, to detecting artifacts in data obtained using a blood pressure cuff. Background Art

[0002] Non-invasive blood pressure measurement techniques can be used to measure the blood pressure of an object, and such techniques can be implemented as a cuff. In an example, the cuff is configured to wrap around the arm of the object to measure the blood pressure of the object. Figure 1 is a cross-sectional view of an example of a blood pressure cuff 100 on an arm 102 of an object. The blood pressure cuff 100 includes a housing 104 surrounded by an inflatable cuff portion 106. A sensor pad 108 on the housing 104 is configured to engage the skin of the object during use and measure the pressure wave generated by the pulse of the object as blood is pumped through an artery 110 (e.g., the brachial artery) of the object.

[0003] The pulse wave in the artery is transmitted through the tissue and skin of the object, causing movement of the skin. This movement of the skin causes compression of the sensor pad 108, and the compression of the sensor pad 108 can be registered by a pressure sensor 112 as a pressure change.

[0004] An actuator 114 (e.g., an air pump) can be provided to deliver (e.g., pump) a gas such as air into the inflatable cuff portion. As the inflatable cuff portion 106 inflates, the arm tissue is compressed, and thus the brachial artery 110 can be occluded.

[0005] Figure 2 is a schematic end view of the housing 104 of the blood pressure cuff 100 on the arm 102 of the object. During inflation of the inflatable cuff portion 106, the pressure in the inflatable cuff portion and the pressure measured by the pressure sensor 112 increase. Due to the increased pressure on the arm, the arm is compressed and thus its diameter decreases. To completely enclose the arm with the housing of the cuff, the diameter of the housing also needs to decrease, and thus an overlapping region 202 of the housing is provided. As the pressure in the inflatable cuff portion 106 increases, the amount of overlap of the housing 104 in the overlapping region 202 increases. Ideally, the overlapping portions of the housing 104 in the overlapping region 202 can slide relatively easily relative to each other, and thus the overlapping portions generally have a relatively low coefficient of friction.

[0006] In some cases, the pulse from the brachial artery can be large enough to interrupt the sliding of the overlapping region 202 of the housing 104 and can cause the housing to temporarily stick before it starts sliding again. This behavior can be referred to as a "stick-slip" event and can be responsible for a sudden and temporary artificial increase in tissue pressure. Such an increase can be referred to as an artifact in the data. If the brachial artery pulse is very severe, combined with low friction, after stopping the sliding in one direction, the overlapping region 202 of the housing 104 can be made to slightly open in the other direction before continuing to slide in the original direction. Such disturbances can lead to errors in determining hemodynamic parameters such as systolic arterial blood pressure (SAP), mean arterial blood pressure (MAP), diastolic arterial blood pressure (DAP), stroke volume (SV), heart rate, etc.

[0007] To complicate matters, the temporary increase in tissue pressure can be caused by other natural events, so it is necessary to not only identify the artifacts in the data but also distinguish the artifacts that occur as a result of stick-slip events or other non-physiological events that have an impact on the hardware (such as motion artifacts, sensor defects, touching the power cord of the device, etc.) from the artifacts that are due to natural events. Summary of the Invention

[0008] It is desirable to be able to identify artifacts in a data set obtained using a blood pressure cuff and optionally determine whether the artifacts are the result of a stick-slip event. The inventors of the present disclosure have recognized that such a determination can be made by analyzing the data obtained in a specific manner. In this way, if it is determined that one or more stick-slip events (or other artifact-causing events) have occurred, appropriate action can be taken.

[0009] According to a first specific aspect, there is provided a computer-implemented method for detecting artifacts in data obtained using a blood pressure measurement device, the method comprising: receiving applied pressure data, the applied pressure data including data indicating the pressure applied to a body part of an object whose blood pressure is to be measured; receiving tissue pressure data, the tissue pressure data indicating the tissue pressure applied by the object's tissue on a sensor pad of the blood pressure measurement device; determining a first derivative of the applied pressure data; identifying an occurrence in which the magnitude of the first derivative of the applied pressure data in the first derivative of the applied pressure data satisfies a first defined threshold condition; and determining the presence of an artifact in the tissue pressure data in response to determining that the tissue pressure satisfies a second defined threshold condition within a defined duration of the occurrence.

[0010] In some embodiments, the method may further include generating a notification that an artifact is present in the tissue pressure data for delivery to a recipient device. The applied pressure data may be received from an applied pressure sensor. The tissue pressure data may be received from a sensor pad included in the blood pressure measurement device. The tissue pressure data may be received from a sensor pad disposed between a pressurizing portion of the blood pressure measurement device (configured to apply pressure to a body portion of the device) and the body portion itself during operation of the device. The sensor pad is different / separate from the applied pressure sensor. Thus, the applied pressure data and the tissue pressure data may be independently sensed signals.

[0011] The method may further include determining a correction to be applied to the tissue pressure data to remove the artifact; and applying the correction to the tissue pressure data.

[0012] In some embodiments, determining the correction may include interpolating a first derivative of the tissue pressure data over a defined interpolation time period.

[0013] In some embodiments, the method may further include determining that the tissue pressure data includes an event indicative of a hemodynamic effect in response to determining that the tissue pressure does not meet a second defined threshold condition within a defined duration of the occurrence.

[0014] The hemodynamic effect may include, for example, at least one of a dicrotic notch event and a systole event.

[0015] The method may further include generating a notification that an action should be taken regarding the blood pressure measurement device for delivery to a recipient device in response to determining that the artifact is one of a plurality of artifacts identified in the tissue pressure data and the number of artifacts among the plurality of artifacts exceeds a defined threshold number.

[0016] In some embodiments, the method may further include applying a data flattening operation to at least one of the applied pressure data and the tissue pressure data.

[0017] In some embodiments, determining a first derivative of the applied pressure data includes determining a negative first derivative of the applied pressure data. In such cases, identifying an occurrence where the magnitude of the first derivative of the applied pressure data meets a first defined threshold condition may include identifying an occurrence where the magnitude of the first derivative is greater than 0.

[0018] The defined duration may include a duration of 100 ms before or after the occurrence.

[0019] In some embodiments, the second defined threshold condition may be satisfied when the magnitude of the tissue pressure increases to above a defined threshold pressure within the defined duration of the occurrence, the defined threshold pressure being between 0.05 and 50 mmHg.

[0020] In some embodiments, the method further includes determining one or more hemodynamic parameters of the subject based on processing of the tissue pressure data, such as by applying a parameter quantification algorithm to the tissue pressure data.

[0021] In some embodiments, the method may further include, after determining that an artifact is present in the tissue pressure data, determining whether the artifact is a stick-slip artifact. Options related to this process are outlined below. Note that regardless of the specific method for initially detecting the presence (or suspected presence) of an artifact in the signal, the processes outlined below for determining whether the artifact is a stick-slip artifact can be applied with beneficial results. In other words, the following methods / processes for determining / classifying whether an artifact is a stick-slip artifact are separate inventive concepts and can be provided as separate aspects of the present invention. Nevertheless, this concept is also compatible with any of the above embodiments or features and can be combined with any one or more of these to achieve further beneficial effects.

[0022] In some embodiments, determining whether an artifact is a stick-slip artifact may include obtaining a predefined artifact model that models the expected amplitude of a stick-slip artifact in tissue pressure data received from a sensor pad based on the position of the artifact in the data. The position of the artifact in the data may represent the temporal position of the artifact relative to one or more other features in the tissue pressure signal, such as relative to a pulse wave in the tissue pressure signal, such as relative to the start of the pulse wave that is temporally closest and prior in time to the start of the artifact in the signal. For example, the position may be defined by the time difference between the start (e.g., foot) of the pulse wave in the signal immediately preceding the artifact and the start of the artifact. For reasons discussed later, these time points can generally be assumed to correspond to the start of the stick phase of the stick-slip event associated with the stick-slip artifact and the start of the slip phase of the stick-slip event, during which the signal artifact appears.

[0023] Determining whether an artifact is a stick-slip artifact may further include: determining the position of the detected artifact in the tissue pressure data, such as relative to at least one pulse wave in the data as described above, and determining the true amplitude of the artifact in the tissue pressure data; calculating the expected amplitude of the artifact in the tissue pressure data if the artifact is a stick-slip artifact based on the use of the model and the determined position of the detected artifact; comparing the expected amplitude of the artifact with the true amplitude of the artifact; and classifying the artifact as a stick-slip artifact only if the true amplitude falls within a defined proximity range of the expected amplitude. The amplitude of an artifact or suspected artifact may represent the height of the artifact in the tissue pressure signal, i.e., the height of the pressure term.

[0024] More specifically, in some embodiments, the artifact model models the expected amplitude Δp of a stick-slip artifact in tissue pressure data received from a sensor pad according to the following equation j,理论Perform modeling:

[0025] Δp j,理论 ≈β(t 滑 -t 粘 )

[0026] wherein the tissue pressure data includes a baseline slope component associated with the increased applied pressure and an oscillatory component associated with arterial pressure oscillations, and wherein β is the gradient of the baseline slope component of the tissue pressure data, t 粘 is the time point at which the stick phase of the stick-slip artifact begins, and t 滑 is the time point at which the slip phase of the stick-slip artifact begins (or the stick phase stops). The time point t 粘 can be determined / estimated or defined as the time point consistent with the start (or foot) of the pulse wave in the tissue pressure signal immediately preceding the artifact, and the time point t 滑 can be determined as the time point at which the detected artifact begins.

[0027] In some embodiments, the artifact is classified as a confirmed stick-slip artifact only if the true magnitude Δp j (i.e., the height of the artifact in the tissue pressure signal) of the detected artifact from the sensor pad satisfies the following condition.

[0028] 0.5Δp j,理论 ≤Δp j ≤1.5Δp j,理论

[0029] wherein, Δp j,理论 is the expected magnitude of the artifact according to the model. In other words, the proximity range can be defined by the following:

[0030] 0.5Δp j,理论 ≤Δp j ≤1.5Δp j,理论 .

[0031] According to yet another particular aspect, there is provided an apparatus for detecting artifacts in data obtained using a blood pressure measurement device, the apparatus including a processor configured to perform the steps of the methods disclosed herein.

[0032] According to another specific aspect, a system for detecting artifacts in data obtained using a blood pressure measurement device is provided. The system includes a blood pressure measurement device, which includes a sensor pad and a pressurizing portion. The sensor pad is configured to measure the pressure exerted on the sensor pad by the tissue of a body part of an object wearing the blood pressure measurement device, and the pressurizing portion is configured to apply pressure to the body part of the object. The system includes: an applied pressure sensor configured to measure the pressure applied by the pressurizing portion to the body part of the object; and a processor configured to receive, from the applied pressure sensor, applied pressure data indicating the pressure applied to the body part of the object; receive, from the sensor pad, tissue pressure data indicating the pressure exerted on the sensor pad by the tissue of the body part of the object; determine a first derivative of the applied pressure data; identify occurrences where the magnitude of the first derivative of the applied pressure in the first derivative of the applied pressure data satisfies a first defined threshold condition; and determine the presence of an artifact in the tissue pressure threshold in response to determining that, during a defined duration of the occurrence, the tissue pressure satisfies a second defined threshold condition.

[0033] The sensor pad can be arranged between the pressurizing portion and the main body portion of the device during use of the device. The sensor pad is a separate / single sensing device from the applied pressure sensor. Thus, the applied pressure data and the tissue pressure data can be independently sensed signals.

[0034] The system may further include a user interface configured to present a notification indicating the presence of an artifact in the tissue pressure data to a recipient.

[0035] According to yet another specific aspect, a computer product including a non-transitory computer-readable medium having computer-readable code embodied therein is provided. The computer-readable code is configured such that, when executed by a suitable computer or processor, it causes the computer or processor to perform the steps of the methods disclosed herein.

[0036] These and other aspects will be apparent and elucidated with reference to the embodiments described hereinafter. Description of the Drawings

[0037] Exemplary embodiments will now be described by way of example only with reference to the following drawings, in which:

[0038] Figure 1 is a diagrammatic illustration of an example of a blood pressure cuff on a body part of an object;

[0039] Figure 2 is a schematic illustration of a housing of a blood pressure cuff around a body part of an object;

[0040] Figure 3A flowchart of an example of a method for detecting artifacts in data obtained using a blood pressure measurement device;

[0041] Figure 4 A flowchart of another example of a method for detecting artifacts in data obtained using a blood pressure measurement device;

[0042] FIG. 5 is a set of graphs showing a set of data obtained using a blood pressure measurement device;

[0043] FIG. 6 is a set of graphs showing another set of data obtained using a blood pressure measurement device;

[0044] FIG. 7 is a set of graphs showing another set of data obtained using a blood pressure measurement device;

[0045] FIG. 8 is a set of graphs showing another set of data obtained using a blood pressure measurement device;

[0046] Figure 9 A schematic diagram of an example of an apparatus for detecting artifacts in data obtained using a blood pressure measurement device;

[0047] Figure 10 A schematic diagram of an example of a system for detecting artifacts in data obtained using a blood pressure measurement device;

[0048] Figure 11 A schematic diagram of an example of a processor in communication with a computer-readable medium;

[0049] Figure 12 Shows an in vivo recording of the applied pressure and the tissue pressure signal; and

[0050] Figure 13 Shows a sensor pad pressure signal including several cardiac cycles, each cardiac cycle including a stick-slip event. DETAILED DESCRIPTION

[0051] The inventors of the present disclosure have recognized that by analyzing the data and specifically by looking at a combination of data related to the pressure applied to a body part of the subject during blood pressure measurement and data related to the pressure applied by the body part on the pressure sensor, artifacts in the data obtained using a blood pressure measurement device can be attributed to stick-slip events or cardiac contraction events.

[0052] Various examples will now be described with reference to a blood pressure measurement device (such as Figure 1 and Figure 2 the device shown). As shown in reference Figure 1As described, such a device may include a housing 104 that is enclosed by a pressurizing portion (also referred to as a pressure applying device or actuator) around a body part of an object (e.g., an arm). As discussed in more detail below, the pressurizing portion may include one or more straps that are wound around the housing 104 and, when tightened, apply increased pressure on the body part of the object. In other examples, such as Figure 1 the example shown in, the pressurizing portion may include an inflatable cuff that is capable of receiving a gas (e.g., air) such that when the gas pressure in the inflatable cuff portion increases, the inflatable cuff portion applies increased pressure on the body part of the object. A sensor referred to herein as an applied pressure sensor may be used to measure the pressure applied by the pressurizing portion to the body part.

[0053] It has been recognized that a stick-slip event can cause a sudden increase in tissue pressure (i.e., the pressure exerted by the tissue of the body part of the object on the sensor pad of the blood pressure measurement device). The increase in tissue pressure causes a sudden increase in the pressure applied by the blood pressure measurement device to the body part, as well as a sudden tissue compression and decrease in the diameter of the body part. As the diameter of the body part decreases, it can be seen that the pressure measured using the applied pressure sensor experiences a sudden decrease because the decreased diameter of the body part provides more space for the pressurizing portion to expand into.

[0054] It has also been recognized that as the object's heart contracts to pump blood through the arteries of its body, causing a sudden increase in the tissue pressure measured by the sensor pad, the diameter of the body part slightly increases, thereby increasing the pressure applied by the pressurizing portion to the body part (i.e., the applied pressure). Thus, it is possible to determine whether a sudden change in tissue pressure is caused by a stick-slip event or by a naturally occurring hemostatic event.

[0055] More generally, the inventors have further recognized that the same principle can also be used to detect artifacts caused by various other types of non-physiological events. As a principle of general application, it can be said that a truly physiologically induced tissue pressure fluctuation is unlikely to be accompanied by a simultaneous fluctuation in the rate of the applied pressure exerted by the pressure applicator. The simultaneous occurrence of these two conditions is an indication of a non-physiological effect on the tissue pressure sensor reading, regardless of the specific cause. A particular and most common cause of the artifacts that will be picked up by this detection mechanism is the stick-slip artifact. However, other events that may cause a similar such confluence of conditions include certain types of motion artifacts (e.g., user movement or dragging at the pressure applicator), a more global slippage of the attachment of the pressure applicator to the body part, a defect in one of the sensors, accidental touching or tapping of the pressure applicator by the user or caregiver, the pressure applicator sliding down the body part, etc. Each of these will manifest as a fluctuation in both the rate of the applied pressure and the measured tissue pressure.

[0056] According to a first aspect, a method is provided. Referring to the accompanying drawings, Figure 3 is a flowchart of an example of a method 300 for detecting artifacts in data obtained using a blood pressure measurement device. The method 300 may include a computer-implemented method and, thus, the steps of the method may be performed using one or more processors or processing circuits. The method 300 includes receiving applied pressure data at step 302. The applied pressure data includes data indicating the pressure applied to a body part of an object whose blood pressure is to be measured. As described above, the applied pressure may include the pressure applied by the pressurizing portion of the blood pressure measurement device. For example, the applied pressure data may indicate the pressure of the gas in the inflatable cuff portion or the pressure applied using some other pressurizing device. The applied pressure may be measured by an applied pressure sensor. As an example, this may be a sensor arranged to sense the pressure of the gas in the inflatable cuff portion or the pressure applied using some other pressurizing device.

[0057] At step 304, the method 300 includes receiving tissue pressure data. The tissue pressure data indicates the tissue pressure exerted by the object's tissue on the sensor pad of the blood pressure measurement device. As described above, the sensor pad (e.g., Figure 1 sensor pad 108) may be used to measure the pressure or pressure change within the tissue of the body part of the object. In an example, the sensor pad may include a flexible bag at least partially filled with a liquid such that the flexible bag is compressed when the skin and tissue of the body part move. The sensor pad may be connected to a pressure sensor via a flexible tube also filled with a liquid (e.g., the same or a similar liquid as the liquid in the sensor pad), and the pressure sensor obtains data related to the tissue pressure.

[0058] Various methods of applying pressure to a body part of an object and measuring the applied pressure and tissue pressure are described in U.S. Patent No. 8,998,817, European Patent No. 2,953,528, and International Patent Application No. PCT / EP2022 / 075999.

[0059] The applied pressure data and / or the tissue pressure data may be measured and / or received in real time or as close to real time as possible. For example, the data may be sampled (i.e., the data may be measured and / or received) at a frequency of at least 50 Hz, preferably at a frequency of at least 125 Hz, and more preferably at a frequency of at least 1 kHz.

[0060] The method 300 includes determining a first derivative of the applied pressure data at step 306. Specifically, the first derivative of the applied pressure data is determined over time. In this way, sudden changes in the gradient of the data signal containing the applied pressure data can be more easily identified.

[0061] At step 308, method 300 includes identifying an occurrence in the first derivative of the applied pressure data where the magnitude of the first derivative of the applied pressure data meets a first defined threshold condition. The first defined threshold condition can include, for example, a threshold pressure value, above which the first defined threshold condition is met. In some embodiments, an average or baseline value of the first derivative of the applied pressure data can be determined, and if the first derivative of the applied pressure data increases above the average or baseline level by more than a defined amount, the first defined threshold condition can be met. Thus, if the first derivative of the applied pressure data increases by more than a defined absolute amount or a defined relative amount, the first defined threshold condition can be met.

[0062] Once an occurrence that meets the first defined threshold condition has been identified, the data can be further investigated to determine the nature of the occurrence. According to the present invention, the tissue pressure data is analyzed over a time period corresponding to the occurrence in the applied pressure data to see if the tissue pressure data meets a specific threshold condition. Thus, method 300 includes, at step 310, in response to determining that the tissue pressure meets a second defined threshold condition during a defined duration of the occurrence, determining that the occurrence includes an artifact in the tissue pressure data. In other words, if the tissue pressure data does in fact meet the second defined threshold condition during the defined duration of the occurrence of the applied pressure data, then it can be determined that there is an artifact in the tissue pressure data. As discussed in more detail below, an artifact in the tissue pressure data can indicate a stick-slip event or other non-physiological event, and in response to detecting such an event, appropriate actions can be taken, such as performing further investigation of the blood pressure measurement device.

[0063] The second defined threshold condition can be selected based on the blood pressure measurement device used and / or the subject. In some embodiments, the second defined threshold condition is met when the magnitude of the tissue pressure increases above a defined threshold pressure during the defined duration of the occurrence. The defined threshold pressure can be between 0.05 mmHg and 50 mmHg. In other examples, the defined threshold pressure can be between 0.1 mmHg and 15 mmHg, and in other examples, different defined threshold pressures can be used.

[0064] An advantage of performing method 300 is that stick-slip events can be distinguished from some other (physiological) events that are also evident in the data, such as haemodynamic events.

[0065] Figure 4It is a flowchart of another example of a method 400 for detecting artifacts in data obtained using a blood pressure measurement device. Method 400 may include the steps of the above-mentioned method 300. In some embodiments, method 400 may further include, at step 402, applying a data flattening operation to at least one of the applied pressure data and the tissue pressure data. The data flattening operation may be applied, for example, to remove the global pressure increase of the tissue pressure as a result of increasing the applied pressure (e.g., when the inflatable cuff is inflated), so that the flattened data shows the response of the tissue pressure to the subject's heartbeat. The flattening operation may also be applied to the applied data, and this may make it easier to interpret the gradients in the applied pressure data and the tissue pressure data. Various techniques may be used to apply the data flattening operation. In some embodiments, a low-pass frequency filter may be used to filter the data. In other embodiments, the average curve of the data (e.g., calculated using a moving average) may be subtracted from the data. In other embodiments, other signal filtering techniques may be used.

[0066] In embodiments where the flattening operation is applied to the data at step 402, the subsequent steps of method 300 (e.g., step 306, step 308, and step 310) may be performed with respect to the flattened applied pressure data and / or the flattened tissue pressure data. In some embodiments, determining the first derivative of the applied pressure data may include determining the negative first derivative of the applied pressure data. In this way, the change in the applied pressure data will appear as a peak. In such an example, when analyzing the flattened data, identifying that the magnitude of the first derivative of the applied pressure data (step 308) satisfies the first defined threshold condition may include identifying that the magnitude of the first derivative is greater than 0. In other examples, different first threshold conditions may be applied. For example, when the flattening operation is not applied to the data, then the first defined threshold condition may be based on the average value of the data.

[0067] The data shows that the first derivative (e.g., pressure gradient) of the applied pressure data is generally in the range of 0.8 mmHg / s to 9 mmHg / s, and for most people, it ranges from about 2 mmHg / s to 3 mmHg / s. The pressure gradient of the received tissue data (excluding the effect of the subject's heartbeat) is generally about 50% to 95% of the applied pressure gradient. The defined threshold condition used when the flattening operation is not applied to the data may be similar to when the flattening operation is applied to the data, because the data removed as a result of the flattening operation has a substantially constant gradient. Therefore, if the change in the gradient (i.e., the increase in the first derivative of the applied pressure data is greater than 0 mmHg / s, 0.1 mmHg / s, 0.2 mmHg / s, 0.4 mmHg / s, etc.), then the first defined threshold condition may be satisfied.

[0068] In some examples, the first threshold condition may include a threshold magnitude of a first derivative of the applied pressure data that is slightly higher, such as 1 mm Hg / s, 2 mm Hg / s, etc. In this way, it is possible to account for variations in the data caused by or resulting from other factors, such as a pump used to inflate the inflatable cuff. Another way to account for variations resulting from other factors is to make the first threshold condition based on the duration for which the first derivative of the applied pressure data is greater than 80% of its peak. For example, if the duration for which the first derivative of the applied pressure data is greater than 80% of its peak is less than 0.15 s, or more preferably less than 0.1 s, then a peak in the data can be identified as a possible stick-slip event. In an example where a flattening operation is applied to the tissue data, if the tissue pressure gradient (i.e., the first derivative of the tissue pressure) increases by more than 5 mmHg / s or more preferably by more than 20 mm Hg / s, then the second defined threshold condition can be met.

[0069] At step 310 of method 300, the tissue pressure data is analyzed to determine whether it meets the second defined threshold condition within a defined duration of the occurrence of a peak in the magnitude of the first derivative of the applied pressure data. If both the first defined threshold condition and the second defined threshold condition are met within the defined duration, an artifact is determined to be present in the tissue pressure data. However, at step 404, method 400 makes a determination in the case where the second defined threshold condition is not met within the defined duration. Thus, at step 404, method 400 may also include determining that the tissue pressure data includes an event indicative of a hemodynamic effect in response to determining that the tissue pressure meets the second defined threshold condition at a time outside the defined duration of the occurrence. In other words, if there is a sudden change in pressure (e.g., a peak) in the tissue data, but no sudden change (e.g., a peak) in the defined duration of the applied pressure data, then it can be determined that the change in tissue pressure may have been caused by a hemodynamic effect rather than a stick-slip event.

[0070] Examples of hemodynamic effects that may cause pressure variations in the received pressure data include dicrotic notches and cardiac systole. Thus, a hemodynamic effect may include at least one of a dicrotic notch event and a cardiac systole event. A dicrotic notch is the result of a short period during which blood flow changes immediately before the aortic valve closes, and this may cause a sudden change in tissue pressure. Thus, a dicrotic notch may cause a sudden increase in tissue pressure, but no accompanying sudden increase (i.e., threshold condition) in the applied pressure data is seen.

[0071] In some embodiments, the defined duration discussed herein can include a duration of 100 ms before or after the occurrence (i.e., the occurrence where the magnitude of the first derivative of the pressure data applied by the cuff in the first derivative of the applied pressure data meets a first defined threshold condition). In other words, the tissue pressure data can be analyzed in a 200 ms window centered on the time at which the occurrence takes place in the applied pressure data. In other embodiments, the defined duration can include a duration of 50 ms, 25 ms, 15 ms, 10 ms, 5 ms, 2 ms, or 1 ms before and / or after the occurrence. Different defined durations can alternatively be used.

[0072] Once an artifact has been identified in the tissue pressure data (step 310), appropriate action can be taken. In some examples, method 400 can include generating a notification of the presence of an artifact in the tissue pressure data at step 406 for delivery to a receiving device. The receiving device can include, for example, a computing device, a smart phone, a wearable device, a tablet computer, etc., having an interface capable of communicating with or notifying the recipient. In an example, a healthcare professional can be notified via the receiving device of the presence of an artifact in the tissue pressure data and that this may be caused by a stick-slip event.

[0073] The stick-slip event itself is not particularly problematic as long as the occurrence in the data can be identified as a stick-slip event rather than an anomaly in the subject's heartbeat. However, if multiple stick-slip events occur (e.g., within a defined time frame, or when taking the blood pressure of a subject), this can indicate a malfunction in the blood pressure measurement device or the way the device has been attached to the subject. At step 408, method 400 can further include generating a notification for delivery to the receiving device that action should be taken by the blood pressure measurement device in response to determining that the artifact is one of a plurality of artifacts identified in the tissue pressure data and the number of artifacts in the plurality of artifacts exceeds a defined threshold number. In some embodiments, the notification to be delivered to the receiving device can indicate that the blood pressure measurement device (e.g., the blood pressure cuff) should be adjusted or refitted, or that the device should be replaced. If too many stick-slip events occur, it may be difficult to identify events occurring in the data caused by physiological problems (such as problems with the subject's heart).

[0074] In the case where a stick-slip event has been detected (i.e., it is determined at step 310 that there is an artifact in the tissue pressure data), then in some embodiments, the tissue pressure data can be corrected or adjusted to account for the stick-slip event and / or the effects of the stick-slip event can be removed from the data. Thus, method 400 can include determining at step 410 a correction to be applied to the tissue pressure data to remove the artifact. At step 412, method 400 can include applying the correction to the tissue pressure data. In some embodiments, determining the correction (step 410) can include interpolating the first derivative of the tissue pressure data over a defined interpolation time. In some embodiments, the interpolation can be done over a time window that begins at or within a short time (e.g., 0.1 second, 0.05 second, or 0.01 second) from the point where the occurrence begins. The interpolation involves interpolating the tissue pressure generated over a time window between 0.001 second and 0.5 second or more preferably between 0.01 second and 0.1 second. In some embodiments, the tissue pressure itself can be interpolated, while in other embodiments, the interpolation can be based on the first and second derivatives of the tissue pressure and / or on information related to the heartbeats adjacent to the occurrence. The interpolation continues until the point where the occurrence ends (e.g., where the negative first derivative of the flattened applied pressure data is between -0.3 mmHg / s and 0.3 mmHg / s, more preferably between -0.05 mmHg / s and 0.1 mmHg / s).

[0075] In other embodiments, other types of corrections (e.g., extrapolation) can be applied.

[0076] Figures 5, 6, 7, and 8 graphically illustrate data obtained from a blood pressure measurement sensor. In Figure 5A , line 502 represents the tissue pressure over time (e.g., the pressure applied by a body part of an object to the sensor pad 108). In this example, the data represented by line 502 has been flattened as described above. In Figure 5A , circles 504 represent the pulse maxima and triangles 506 represent the pulse minima. In Figure 5B , line 508 represents the applied pressure (which has been flattened), such as the pressure applied by a pressurizing portion (e.g., an inflatable cuff) to a body part of an object. Line 510 represents the first derivative of the flattened applied pressure data. Point 512 indicates the point where a sudden drop in the applied pressure is seen. In this case, these drops are due to global changes caused by the control of a component such as a pump that is used to inflate the inflatable cuff portion of the blood pressure measurement device, resulting in a relatively small negative applied pressure gradient. In Figure 5C , point 512 (line 502) is plotted with the tissue data. Figure 5DShows the number of artifacts detected in the data at each amplitude. Line 514 shows the total number of artifacts, and line 516 shows the number of artifacts related to the stick-slip events. The data plotted in the graph of FIG. 5 is based on real-life data, and it can be seen that the number of stick-slip events is relatively small, and the amplitude of the artifacts related to the stick-slip events is also very small: less than 0.5 mmHg.

[0077] It should be understood that the amplitude of the artifacts detected in the data is related to the difference between the static friction coefficient and the dynamic friction coefficient of the overlapping region ( Figure 1 ; 104) of the housing ( Figure 2 ; 202). The greater the difference between the static friction coefficient and the dynamic friction coefficient, the greater the amplitude of the artifacts in the data (e.g., the greater the amplitude of the peaks in the applied pressure data). The data shown in FIG. 5 was obtained by a blood pressure measurement device having a housing with a very small difference (i.e., below 0.02) between the static friction coefficient and the dynamic friction coefficient.

[0078] FIG. 6 shows a graph similar to the graph shown in FIG. 5, but the data plotted was obtained using a blood pressure measurement device having a housing with a much greater difference (i.e., between 0.05 and 0.1) between the static friction coefficient and the dynamic friction coefficient. In Figure 6A there are clearly many more peaks between adjacent minima and maxima in the tissue pressure data. Once the first derivative of the applied pressure data has been determined (shown in Figure 6B ), and the sudden drop in the applied pressure data is plotted together with the flattened tissue pressure data (shown in Figure 6C ), it is obvious that many more artifacts corresponding to stick-slip events and having a high amplitude (e.g., in the range of 0.3 mmHg to 12 mmHg) are detected. In this example, an artifact can be considered to correspond to a stick-slip event if it has an amplitude between 0.3 mmHg and 15 mmHg or more preferably between 0.5 mmHg and 10 mmHg.

[0079] More example data is shown in the graph of FIG. 7. In Figure 7A the cross 702 represents a high-amplitude artifact in the tissue pressure data corresponding to a stick-slip event. The occurrence of peaks in the tissue pressure data caused by dicrotic notches rather than stick-slip events is also indicated in FIG. 7. Importantly, the present invention is able to determine that the peak does not originate from a stick-slip event, and thus the data is not ignored or corrected.

[0080] FIG. 8 shows some of the data from FIG. 7 on a shorter time scale. In Figure 8AIn [the figure], the cross 802 indicates the peaks corresponding to the stick-slip events. The dashed line 804 represents the correction of the data using the interpolation technique described above, extending from the first time 806 when the peak starts to the second time 808 when the peak ends. The corrected data 804 removes the peaks in the tissue pressure data caused by the stick-slip events. Figure 8A and 7B Also shown are peaks 810 and 812 determined to be caused by dicrotic notches, and peak 814 determined to be caused by cardiac systole.

[0081] In a second aspect, a device is provided. Figure 9 It is a schematic illustration of an example of a device 900 for detecting artifacts in data obtained using a blood pressure measurement device. The device 900 includes a processor 902 configured to perform the steps of the methods 300, 400 disclosed herein. In some embodiments, the device 900 may include a computing device.

[0082] In a third aspect, a system is provided. Figure 10FIG. 0 is a schematic illustration of an example of a system 1000 for detecting artifacts in data obtained using a blood pressure measurement device. The system 1000 includes a blood pressure measurement device 1002, which may include, for example, a blood pressure measurement cuff or some other device capable of measuring the blood pressure of an object. The blood pressure measurement device 1002 (which may be the same as or similar to the above-mentioned blood pressure measurement device) includes a sensor pad 1004 (which may be the same as or similar to the above-mentioned sensor pad 108), and the sensor pad 1004 is configured to measure the pressure exerted on the sensor pad by the tissue of the body part of the object wearing the blood pressure measurement device. The blood pressure measurement device 1002 also includes a pressurizing portion 1006 configured to apply pressure to the body part of the object. The pressurizing portion 1006 may include, for example, an inflatable cuff portion (e.g., the inflatable cuff portion 106) or some other device for applying pressure, such as one or more straps or metal bars that can be tightened to apply pressure to the body part. The system 1000 also includes an applied pressure sensor 1008 configured to measure the pressure applied by the pressurizing portion 1006 to the body part of the object. As an example, the applied pressure sensor 1008 may be arranged to measure the pressure of the gas within the inflatable cuff portion 106. The system 1000 also includes a processor 1010 (which may be the same as or similar to the above-mentioned processor 902). The processor 1010 is configured to execute the steps of the methods 300, 400 discussed herein. Specifically, the processor 1010 is configured to receive applied pressure data indicating the pressure applied to the body part of the object from the applied pressure sensor; receive tissue pressure data indicating the pressure exerted on the sensor pad by the tissue of the body part of the object from the sensor pad; determine the first derivative of the applied pressure data; identify the occurrence in the first derivative of the applied pressure data where the magnitude of the first derivative of the applied pressure data satisfies a first defined threshold condition; and determine the presence of an artifact in the tissue pressure data in response to determining that the tissue pressure satisfies a second defined threshold condition within a defined duration of the occurrence.

[0083] In some embodiments, the system 1000 may further include a user interface 1012 configured to present a notification indicating the presence of an artifact in the tissue pressure data to a recipient. In the case where multiple artifacts (exceeding a threshold) are detected, the user interface 1012 may provide an indication to the recipient that the blood pressure measurement device should be inspected for modification or replacement. The device 900 or system 100 may include a health monitoring device or system, or a continuous patient monitoring device or system (e.g., a device or system that continuously monitors data from multiple objects).

[0084] According to a fourth aspect, a computer program product is provided. Figure 11A schematic illustration of an example of a computer-readable medium 1104 that communicates with a processor 1102. The processor 102 may include or may be similar to the above-described processors 902 and 1010. The computer program product includes a non-transitory computer-readable medium 1104 having computer-readable code embodied therein that is configured to cause a computer or processor to perform the steps of the methods 300, 400 disclosed herein when executed by a suitable computer or processor 1102.

[0085] The processors 902, 1010, 1102 may include one or more processors, processing units, multi-core processors or modules that are configured or programmed to control the apparatus 900 in the manner described herein. In certain embodiments, the processors 902, 1010, 1102 may include multiple software and / or hardware modules each configured to perform or adapted to perform individual or multiple steps of the methods described herein.

[0086] As used herein, the term "module" is intended to include a hardware component, such as a processor or a component of a processor configured to perform a particular function; or a software component, such as a set of instruction data having a particular function when executed by a processor.

[0087] To further supplement the understanding of the above-described artifact detection principle, a theoretical model will now be outlined in more detail that provides means for a finer-grained analysis of potential artifacts and their causes.

[0088] In particular, the model allows an estimation of whether a sudden increase in tissue pressure is due to an artifact, such as a stick-slip artifact, or is caused by a hemodynamic event.

[0089] Figure 12 An in vivo recording of the applied pressure signal 1202 recorded by an applied pressure sensor and the tissue pressure signal 1204 recorded by the sensor pad 1004 is shown.

[0090] The applied pressure 1202 increases linearly with time according to a certain slope α. The tissue pressure signal 1204 recorded by the sensor pad 1004 is a combination of a linear increase in pressure (referred to as the clamping pressure (due to the increase in the applied pressure)) and an oscillatory signal caused by the cardiac pulse (referred to as tissue pressure oscillation).

[0091] Primarily due to the friction of the overlapping housing of the device, the slope of the clamping pressure portion of the sensor pad 1004 signal 1204 can generally be expected to be different from the slope α of the applied pressure 1202. The slope of the clamping pressure portion of the sensor pad signal 1004 can be expressed as β = ε·α, where ε is a factor < 1.

[0092] It is possible to determine a simple relationship between the location of a potential stick-slip artifact in a heartbeat and the height of such a stick-slip artifact.

[0093] Figure 13 An in vivo recording of the tissue sensor pad pressure signal 1304 of a test device is shown, which is designed to deliberately undergo a stick-slip event, one per heartbeat.

[0094] The stick-slip artifacts are clearly visible as sudden increases in tissue pressure. The artifacts occur due to the slip phase of the stick-slip event. The start of each stick-slip artifact is an upward inflection point in the signal. The end of each stick-slip artifact is marked by an arrow and the label Δp j which represents the height of the resulting stick-slip artifact in the tissue pressure signal 1304, i.e., the pressure jump caused by the stick-slip event.

[0095] The height Δp of the pressure jump due to the stick-slip event j can be related to the location of the stick-slip event relative to the previous heartbeat.

[0096] According to the modeling, it is expected that the "stick" phase of the stick-slip event will start at the beginning of the heartbeat pulse. At this time, the overlapping portion 202 of the cuff housing 104 will stop sliding. This moment can be labeled as t 粘 . The "slip" point of the stick-slip event (where the overlapping portion 202 of the housing 104 will start sliding again) can be labeled as t 滑 . This will correspond to the start of the stick-slip artifact as it appears in the data signal.

[0097] When the overlapping portion of the housing 104 starts sliding again, the clamping pressure portion of the tissue pressure signal 1304 from the sensor pad 1004 will increase in amplitude.

[0098] Δp j,理论 ≈ β(t 滑 - t 粘 )

[0099] where β is the slope of the clamping pressure portion of the sensor pad signal 1004 and can be determined empirically.

[0100] The slope α of the applied pressure can be measured from the applied pressure sensor 1008. The slope β can be determined directly from the clamping pressure portion of the tissue pressure sensor signal 1304 from the sensor pad 1004, which is the trend line of the average increase in pressure of the tissue pressure signal measured by the sensor pad 1004 at an appropriate time (i.e., when a suspected stick-slip event occurs). In other words, instead of calculating the product β = ε·α, the slope β can be determined directly from the tissue pressure signal from the sensor pad, for example, by low-pass filtering the tissue pressure signal (to remove the arterial oscillation component) and calculating the gradient of the resulting slope. The time point t can be determined from the positive inflection point in the tissue pressure signal 1304, which indicates the foot of the blood pressure pulse immediately before the artifact. The time t can be determined from the moment of the pressure jump (i.e., the upward inflection point in the signal that is not simultaneous with the start of the blood pressure pulse) and simultaneously with the start of the suspected stick-slip artifact. 粘 Both t and t are indicated in. 滑 .

[0101] In Figure 13 t is indicated. 滑 and t 粘 both.

[0102] In Figure 13 the case shown, based on the above equation, Δp j,理论 ≈ 1.6 mmHg can be determined. This does indeed match well with the indicated value from the figure (≈ 1.5 mmHg).

[0103] According to one or more embodiments, it is proposed to use the above model to determine the expected amplitude of a suspected stick-slip artifact in the tissue pressure signal from the sensor pad 1004 based on the position of the artifact in the signal relative to at least one pulse wave in the signal, compare the expected amplitude of the artifact with the amplitude of the suspected artifact, and classify the suspected stick-slip artifact as a confirmed stick-slip artifact only when the actual amplitude falls within a defined proximity range of the expected amplitude. Note that this process for determining whether a detected or suspected artifact in the tissue pressure signal corresponds to a stick-slip artifact can be applied to obtain beneficial effects regardless of the specific method used for initially detecting or identifying the artifact or suspected artifact. In other words, this can either be applied in combination with any of the artifact detection method embodiments discussed above, or can be provided as a separate aspect of the present invention.

[0104] The amplitude of the artifact can be defined as the height Δp of the artifact (in pressure) in the tissue pressure signal from the pressure sensor pad 1004. j .

[0105] Based on the determined time points t 滑 and t 粘And the expected magnitude of the artifact is calculated using the model equation set forth above based on the determined value of the slope β.

[0106] In some embodiments, the suspected stick-slip artifact is classified as a confirmed stick-slip artifact only when the magnitude Δp of the suspected artifact in the tissue pressure signal from the sensor pad 1004 j (i.e., the height of the artifact in the tissue pressure signal) satisfies the following condition.

[0107] 0.5Δp j,理论 ≤Δp j ≤1.5Δp j,理论

[0108] where Δp j,理论 is the expected magnitude (height) of the artifact calculated based on the following:

[0109] Δp j,理论 ≈β(t 滑 -t 粘 )

[0110] where the tissue pressure data includes a baseline slope component associated with the increasing applied pressure and an oscillatory component associated with arterial pressure oscillations, and where β is the gradient of the baseline slope component of the tissue pressure data, t 粘 is the time point at which the stick phase of the stick-slip artifact begins, and t 滑 is the time point at which the slip phase of the stick-slip artifact begins, as described above. The time t 粘 can be determined as the time point consistent with the start or foot of the pulse wave signal immediately preceding the suspected artifact. The time t 滑 can be determined as the time point consistent with the start of the artifact.

[0111] As described above, regardless of the specific method used to detect the artifact, a process / method for determining / classifying whether an artifact or suspected artifact in the tissue pressure signal is a stick-slip artifact can be applied. To make this more specific, the following will outline the description of another aspect of the present invention, which can be provided alone or in combination with any of the features or embodiments discussed above.

[0112] According to one aspect of the present invention, there is provided a method for detecting / classifying stick-slip artifacts in data obtained using a blood pressure measurement device, the method comprising:

[0113] Receiving (304) tissue pressure data indicative of the tissue pressure exerted by the tissue of an object on a sensor pad of a blood pressure measurement device;

[0114] Applying an artifact detection operation to detect the presence of an artifact in the tissue pressure data;

[0115] In response to determining that there is an artifact in the tissue pressure data, determine whether the artifact is a stick-slip artifact.

[0116] In some embodiments, determining whether the artifact is a stick-slip artifact includes one or more of the following steps:

[0117] Obtain a predefined artifact model that models the expected amplitude of a stick-slip artifact in the tissue pressure data received from the sensor pad based on the position of the artifact relative to at least one pulse wave in the tissue pressure data;

[0118] Determine the position of the detected artifact in the tissue pressure data relative to at least one pulse wave in the tissue pressure data and determine the true amplitude of the artifact in the tissue pressure data;

[0119] Calculate the expected amplitude of the artifact in the tissue pressure data if the artifact is a stick-slip artifact based on the use of the model and the determined position of the detected artifact;

[0120] Compare the expected amplitude of the artifact with the true amplitude of the artifact;

[0121] Classify the artifact as a stick-slip artifact only if the true amplitude falls within a defined proximity range of the expected amplitude.

[0122] In some embodiments, the artifact model models the expected amplitude Δp of a stick-slip artifact in the tissue pressure data received from the sensor pad j,理论 as follows:

[0123] Δp j,理论 ≈β(t 滑 -t 粘 )

[0124] where the tissue pressure data includes a baseline slope component associated with an increasing applied pressure and an oscillatory component associated with arterial pressure oscillations, and where β is the gradient of the baseline slope component of the tissue pressure data, t 粘 is the time point at which the stick phase of the stick-slip artifact begins, and t 滑 is the time point at which the slip phase of the stick-slip artifact begins, and where t 粘 is defined as the time consistent with the start point of the pulse wave in the tissue pressure signal immediately preceding the artifact.

[0125] In some embodiments, the above-described artifact detection operation includes determining whether the tissue pressure meets a defined threshold condition.

[0126] In addition or alternatively, in some embodiments, the above-described artifact detection operation includes:

[0127] Receive the applied pressure data, the applied pressure data including data indicative of the pressure applied to a body part of an object, the blood pressure of which is to be measured;

[0128] Determine a first derivative of the applied pressure data; and

[0129] Identify an occurrence in the first derivative of the applied pressure data where the magnitude of the first derivative of the applied pressure data satisfies a first defined threshold condition, and in response thereto determine that an artifact is present in the tissue pressure data.

[0130] In addition or alternatively, in some embodiments, the above-described artifact detection operation includes:

[0131] Receive the applied pressure data, the applied pressure data including data indicative of the pressure applied to a body part of an object, the blood pressure of which is to be measured;

[0132] Determine a first derivative of the applied pressure data;

[0133] Identify an occurrence in the first derivative of the applied pressure data where the magnitude of the first derivative of the applied pressure data satisfies a first defined threshold condition; and

[0134] In response to determining that the tissue pressure satisfies a second defined threshold condition within a defined duration of the occurrence, determine that an artifact is present in the tissue pressure data.

[0135] Alternatively, any other method for detecting an artifact or suspected artifact in tissue pressure data may be used instead. For example, this may include detecting a threshold slope of the tissue pressure signal, detecting predefined waveform features in the tissue pressure signal, or any other artifact detection method.

[0136] Any embodiment of this aspect of the invention may be combined with any embodiment of the features outlined previously with respect to other aspects of the invention.

[0137] It should be understood that embodiments of the present invention are also applicable to computer programs suitable for putting the present invention into practice, especially computer programs on or in a carrier. The program can be in the form of source code, object code, intermediate source and object code, such as in a partially compiled form, or in any other form suitable for use in the implementation of the method according to an embodiment of the present invention. It should also be understood that such a program can have many different architectural designs. For example, the program code implementing the functions of the method or system according to the present invention can be subdivided into one or more subroutines. Many different ways of distributing the functions among these subroutines will be obvious to those skilled in the art. The subroutines can be stored together in an executable file to form a self - contained program. Such an executable file can include computer - executable instructions, for example, processor instructions and / or interpreter instructions (such as Java interpreter instructions). Alternatively, one or more or all of the subroutines can be stored in at least one external library file and linked to the main program statically or dynamically (e.g., at runtime). The main program contains at least one call to at least one subroutine. The subroutines can also include function calls to each other. Embodiments related to computer products include computer - executable instructions corresponding to each processing stage of at least one method set forth herein. These instructions can be subdivided into subroutines and / or stored in one or more files that can be linked statically or dynamically. Another embodiment related to computer products includes computer - executable instructions corresponding to each device of at least one of the systems and / or products set forth herein. These instructions can be subdivided into subroutines and / or stored in one or more files that can be linked statically or dynamically.

[0138] The carrier of the computer program can be any entity or device capable of carrying the program. For example, the carrier can include a data memory, such as a ROM, such as a CD ROM or a semiconductor ROM; or a magnetic recording medium, such as a hard disk. In addition, the carrier can be a transmissible carrier, such as an electrical or optical signal, which can be transmitted via a cable or an optical fiber or by radio or other means. When the program is embodied in such a signal, the carrier can be constituted by such a cable or other device or apparatus. Alternatively, the carrier can be an integrated circuit in which the program is embedded, and the integrated circuit is adapted to execute or for executing the relevant method.

[0139] In practicing the principles and techniques described herein, those skilled in the art can understand and implement variations of the disclosed embodiments based on a study of the drawings, this disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. A single processor or other unit may implement the functions of several items recited in the claims. The fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. A computer may be stored or distributed on a suitable medium, such as an optical storage medium or a solid-state medium supplied together with or as part of other hardware, but may also be distributed in other forms, such as via the Internet or other wired or wireless telecommunication systems. Any reference signs in the claims should not be construed as limiting the scope.

Claims

1. A computer-implemented method (300) for detecting artifacts in data obtained using a blood pressure measurement device, the method comprising: Receiving (302) the applied pressure data, the applied pressure data including data indicative of a pressure applied to a body part of an object whose blood pressure is to be measured; Receiving (304) tissue pressure data, the tissue pressure data indicative of a tissue pressure applied by the tissue of the object on a sensor pad of the blood pressure measurement device; Determining (306) a first derivative of the applied pressure data; Identifying (308) an occurrence in which an amplitude of the first derivative of the applied pressure data in the first derivative of the applied pressure data satisfies a first defined threshold condition; And Responsive to determining that the tissue pressure satisfies a second defined threshold condition within a defined duration of the occurrence, determining (310) that an artifact is present in the tissue pressure data.

2. The computer-implemented method (300, 400) according to claim 1, further comprising: Generating (406) a notification that the artifact is present in the tissue pressure data for delivery to a receiving device.

3. The computer-implemented method (300, 400) according to claim 1 or claim 2, further comprising: Determining (410) a correction to be applied to the tissue pressure data to remove the artifact; And Applying (412) the correction to the tissue pressure data.

4. The computer-implemented method (300, 400) according to claim 3, wherein, Determining the correction includes interpolating the first derivative of the tissue pressure data within a defined interpolation time period.

5. The computer-implemented method (300, 400) according to any one of the preceding claims, further comprising: Responsive to determining that the tissue pressure does not satisfy the second defined threshold condition within the defined duration of the occurrence, determining (404) that the tissue pressure data includes an event indicative of a hemodynamic effect.

6. The computer-implemented method (300, 400) according to claim 5, wherein, The hemodynamic effect includes at least one of a dicrotic notch event and a cardiac systolic event.

7. The computer-implemented method (300, 400) according to any one of the preceding claims, further comprising: Responsive to determining that the artifact is one of a plurality of artifacts identified in the tissue pressure data and the number of artifacts in the plurality of artifacts exceeds a defined threshold number, generating (408) a notification that the blood pressure measurement device should take an action for delivery to a receiving device.

8. The computer-implemented method (300, 400) according to any one of the preceding claims, further comprising: Applying a data flattening operation to (402) at least one of the applied pressure data and the tissue pressure data.

9. The computer-implemented method (300, 400) according to claim 8, wherein, Determining the first derivative of the applied pressure data includes determining a negative first derivative of the applied pressure data; and Wherein, identifying an occurrence in which an amplitude of the first derivative of the applied pressure data satisfies a first defined threshold condition includes identifying an occurrence in which the amplitude of the first derivative is greater than 0.

10. The computer-implemented method (300, 400) according to any one of the preceding claims, wherein, The defined duration includes a duration of 100 ms before or after the occurrence.

11. A computer-implemented method (300, 400) according to any one of the preceding claims, wherein, The second defined threshold condition is satisfied when the magnitude of the tissue pressure increases above a defined threshold pressure within the defined duration of the occurrence, the defined threshold pressure being between 0.05 and 50 mmHg.

12. The computer-implemented method (300, 400) according to any one of the preceding claims, wherein, The method further includes: after determining (310) that there is an artifact in the tissue pressure data, determining whether the artifact is a stick-slip artifact, wherein the determining includes: Obtaining a predefined artifact model that models an expected magnitude of a stick-slip artifact in tissue pressure data received from a sensor pad based on a position of the artifact relative to at least one pulse wave in the tissue pressure data; Determining a position of the detected artifact in the tissue pressure data relative to at least one pulse wave in the tissue pressure data and determining a true magnitude of the artifact in the tissue pressure data; Calculating an expected magnitude of the artifact in the tissue pressure data if the artifact is a stick-slip artifact based on use of the model and the determined position of the detected artifact; Comparing the expected magnitude of the artifact with the true magnitude of the artifact; Classifying the artifact as a stick-slip artifact only if the true magnitude falls within a defined proximity of the expected magnitude.

13. The computer-implemented method (300, 400) according to claim 12, wherein, The artifact model models the expected magnitude Δp of stick-slip artifacts in tissue pressure data received from the sensor pad according to the following equation j, theory: Δp j, Theory ≈ β(t_slide - t_stick) Wherein, the tissue pressure data includes a baseline slope component associated with an increased applied pressure and an oscillatory component associated with arterial pressure oscillations, and wherein β is the gradient of the baseline slope component of the tissue pressure data, t 粘 is the time point at which the stick phase of the stick-slip artifact begins, and t 滑 is the time point at which the slip phase of the stick-slip artifact begins, and wherein, t 粘 is defined as the time consistent with the start point of the pulse wave in the tissue pressure data immediately preceding the artifact.

14. An apparatus (900) for detecting artifacts in data obtained using a blood pressure measurement device, the apparatus including: A processor (902) configured to perform the method according to any one of the preceding claims.

15. A system (1000) for detecting artifacts in data obtained using a blood pressure measurement device, the system including: A blood pressure measurement device (1002) including: A sensor pad (1004) configured to measure a pressure exerted on the sensor pad by tissue of a body part of an object wearing the blood pressure measurement device; and A pressurizing portion (1006) configured to apply pressure to the body part of the object; An applied pressure sensor (1008) configured to measure the pressure applied by the pressurizing portion to the body part of the object; and A processor (1010) configured to: Receive applied pressure data indicative of the pressure applied to the body part of the object from the applied pressure sensor; Receive tissue pressure data indicative of the pressure exerted on the sensor pad by the tissue of the body part of the object from the sensor pad; Determine a first derivative of the applied pressure data; Identify an occurrence in the first derivative of the applied pressure data where the magnitude of the first derivative of the applied pressure data satisfies a first defined threshold condition; and Determine that there is an artifact in the tissue pressure data in response to determining that within the defined duration of the occurrence, the tissue pressure satisfies a second defined threshold condition.

16. The system (1000) according to claim 15, further including: A user interface (1012) configured to present a notification indicating the presence of the artifact in the tissue pressure data to a recipient.

17. A computer program product, comprising a non-transitory computer-readable medium (1104), the computer-readable medium having computer-readable code embodied therein, the computer-readable code being configured to cause a computer or a processor, when executed by a suitable computer or processor, to perform the method according to any one of claims 1 to 13.

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