Apparatus, system and method for detecting material and / or manufacturing defects in an inflatable cuff - Patent application

Abstract

The present invention relates to an apparatus, system and method for detecting material and / or manufacturing defects in an inflatable cuff.Furthermore, the present invention relates to a phantom arm device.The apparatus for detecting material and / or manufacturing defects in an inflatable cuff comprises a target pressure input configured to obtain a target pressure signal indicative of a target pressure in the cuff, a sensor input configured to obtain a cuff pressure signal indicative of the pressure in the cuff from a sensor configured to measure the pressure in the cuff, an output configured to output a warning signal, and a processing unit configured to analyze the cuff pressure signal and the target pressure signal, detect a cuff based on said analysis, and control said output to output said warning signal if said defect is detected.

Description

[Technical field]

[0001] The present invention relates to an apparatus, system and method for detecting material and / or workmanship defects in an inflatable cuff.Furthermore, the present invention relates to a phantom arm device. [Background technology]

[0002] Blood pressure (BP) is one of the most important vital signs measured during almost every medical examination. Arterial pressure can be obtained either invasively via an arterial catheter or non-invasively (NIBP). Invasive blood pressure monitoring is usually only required in high-risk patients or in complex surgical procedures. Therefore, the most used and common method to measure BP is the non-invasive method (NIBP). Two different automated NIBP methods are available on the market: the conventional method, which is deflation-based NIBP, and the second method, which is inflation-based NIBP (iNIBP). The aim of iNIBP is to substantially reduce the measurement time and patient discomfort with respect to the conventional deflation-based NIBP. In fact, using iNIBP instead of NIBP would reduce the average measurement time from 45 seconds to 20 seconds while maintaining the same measurement accuracy.

[0003] In most cases, blood pressure is monitored non-invasively by occluding the upper arm using an oscillometric blood pressure cuff. Automated oscillometric BP measurements are obtained at regular time intervals, which can vary from one minute to several hours, for example in a hospital environment. Blood pressure measurements are also very popular these days for home monitoring, where users can take measurements whenever it is convenient for them.

[0004] Inaccurate blood pressure measurements can generally lead to misdiagnosis and therefore to cardiovascular complications or clinical deterioration. In fact, overestimating true blood pressure by 5 mmHg would lead to inappropriate treatment with antihypertensive drugs in nearly 30 million Americans (see, for example, J. Handler, "The Importance of Accurate Blood Pressure Measurement", The Permanente Journal, Volume 13, No. 3, pp. 51-54, 2009). Summary of the Invention [Problem to be solved by the invention]

[0005] The accuracy of blood pressure measurements and other vital signs measurements, such as hemodynamic parameters (e.g., cardiac output or stroke volume), made using inflatable cuffs is highly sensitive to defects in the cuff materials and / or manufacturing.

[0006] The accuracy of BP measurements is affected by a sudden drop in cuff pressure caused by an artifact called "velcro crack" or "cuff crack". "Velcro crack" is usually caused by the Velcro material of the cuff, in particular by the Velcro material of the closing element of the cuff, for example by the hook and loop fastener of the cuff. "Cuff crack" is caused by other parts of the cuff, in particular other tissue parts of the cuff. For example, cuff crack is caused by cuffs that have several layers of (different) materials that are not firmly attached to each other and can move relative to each other to some extent, especially during inflation or deflation of the cuff. This is the case for cuffs with a dual bladder design, where an inner bladder is inserted inside the outer shell of the cuff. During inflation / deflation of the inner bladder, this bladder can move slightly within the outer shell. In some cases, friction between the surface of the bladder and the surface of the outer shell can lead to cuff cracks (slip-stick phenomenon). Similarly, cuff cracks are caused by the slip-stick phenomenon caused by overlapping parts of the cuff's closing elements moving relative to each other during inflation or deflation of the cuff. Additionally, closing elements having buttons, especially push buttons, can open during inflation, similarly distorting the measurement results.

[0007] Both artifacts (Velcro cracks and cuff cracks) can be understood as mechanical cracks, e.g., a sudden opening of a hook-and-loop fastener during the inflation process of a blood pressure cuff. If the artifact is very severe, it can be heard as a characteristic "ripping" sound. Moreover, these crack artifacts are superimposed on the real pressure signal, thus resulting in an erroneous estimation of the final blood pressure value (systolic and / or diastolic). Thus, the accuracy of vital signs measurements provided by using an inflatable cuff can be affected by defects in the cuff material or poor manufacturing of the materials, especially the tissue, used for the cuff.

[0008] U.S. Patent Application Publication No. 2010 / 0211096 discloses an integrated tourniquet system that allows the user to establish a separate maximum pressure level in the cuff above the normal maximum pressure level, with appropriate warnings and timely user confirmation. [Means for solving the problem]

[0009] It is an object of the present invention to provide an apparatus, phantom arm device, system and method for detecting material and / or manufacturing defects in inflatable cuffs, thus ensuring that cuffs used to measure vital signs (e.g., BP measurements) provide accurate measurement results.

[0010] In a first aspect of the present invention, an apparatus for detecting material and / or manufacturing defects in an inflatable cuff configured for blood pressure measurement is presented, the apparatus comprising: a target pressure input configured to obtain a target pressure signal indicative of a target pressure in the cuff; a sensor input configured to obtain a cuff pressure signal indicative of pressure in the cuff from a sensor configured to measure pressure in the cuff; an output configured to output a warning signal; a processing unit configured to analyze the cuff pressure signal and the target pressure signal. wherein the processing unit is configured to analyze the cuff pressure signal during inflation of the cuff or deflation of the cuff, to detect a defect in the cuff based on the analysis, and to control the output to output the warning signal if the defect is detected.

[0011] In a further aspect of the present invention, a phantom arm device for detecting material and / or manufacturing defects in an inflatable cuff configured for blood pressure measurement is presented, the phantom arm device comprising: an inner cylinder having a first material; an intermediate layer having a second material wrapped around the shell surface of the inner cylinder; and an outer layer having a third material wrapped around the intermediate layer; wherein the first material has a harderness than the second material, and the second material has a harderness than the third material.

[0012] In a further aspect of the present invention, a system for detecting material and / or manufacturing defects in an inflatable cuff configured for blood pressure measurement is presented, the system comprising: a sensor configured to measure pressure in a cuff wrapped around the phantom arm device; a pressure delivery unit configured to provide a target pressure within the cuff; and Apparatus for detecting material and / or manufacturing defects in an inflatable cuff has.

[0013] In a further aspect of the invention, there is provided corresponding methods and computer programs having program code means for causing a computer to perform the steps of the methods disclosed herein, when said computer program is run on a computer, as well as a non-transitory computer readable recording medium storing a computer program product which, when run by a processor, performs the methods disclosed herein.

[0014] Preferred embodiments of the invention are defined in the dependent claims. The claimed methods, systems, computer programs and media are understood to have similar and / or identical preferred embodiments to the claimed devices, particularly those defined in the dependent claims and disclosed herein.

[0015] The invention is based on the idea that material and / or manufacturing defects of the cuff, for example the closing element of the cuff, for example the sudden opening of the hook-and-loop fastener, affect the pressure in the cuff. For example, if the cuff becomes loose on the patient's arm due to the sudden opening of the closing element, the inner volume of the cuff that can be inflated becomes larger and therefore, upon such opening, the pressure in the cuff suddenly decreases. In particular, during inflation of the cuff, parts of the closing element may tear, causing erroneous measurements of vital signs, for example blood pressure. Similarly, a sudden movement of an air bladder in the shell of the cuff, for example caused by the slip-stick phenomenon, causes a sudden change in the volume of the inflatable part of the cuff and therefore a sudden change in the pressure in the cuff.

[0016] Thus, by analysing the pressure within the cuff, particularly against a nominal or target pressure, defects in the cuff material, for example the Velcro material of the closing element, can be detected.

[0017] The proposed system, device and method are very general and can be used for all existing commercially available cuffs, but also for new prototypes, to assess the quality of the cuff in an accurate, robust and reproducible way. In particular, the cuff material and design can be analyzed for suitability to provide reliable vital signs measurements, avoiding human experiments to assess the quality of the cuff. The proposed method, device and system can also provide insights for developing new and improved cuffs. With the present invention, new types of closing elements, e.g. new materials for hook-and-loop fasteners, can be tested. Furthermore, defects in the closing elements or defects in the shell and / or air bladder material that cannot be observed with the naked eye can be detected. Other features of the cuff can be evaluated, e.g. the cuff design.

[0018] Thus, the present invention makes it possible to detect cuffs suffering from malfunctions of the cuff closing elements or the cuff material, and to develop cuffs without malfunctions and / or defects. Thus, the accuracy of vital signs measurement using the cuff can be improved. Malfunctions and / or defects caused by the cuff material or poor workmanship related to the material, e.g., Velcro cracks, generally do not follow a specific pattern, so it is very difficult for a software algorithm to correct artifacts in the cuff pressure signal caused by these malfunctions / defects. However, the present invention provides a systematic method to test cuffs for such malfunctions / defects, thus helping to obtain sufficient information to improve software algorithms for correcting the cuff pressure signal.

[0019] In a device for detecting material and / or manufacturing defects in an inflatable cuff, the target pressure input may for example obtain a target pressure signal from a pressure delivery unit. This pressure delivery unit may comprise an air pump system configured to pump air inside the cuff and thus inflate the cuff. The target pressure signal indicative of the target pressure in the cuff may include information on the maximum (minimum) pressure at which the cuff is configured to be inflated (deflated) and the target pressure speed, i.e. the inflation speed, indicative of the pressure at which the cuff is inflated (deflated). From this information, the processing unit can deduce the target pressure (i.e. the nominal pressure that should be in the cuff at a certain time (during inflation or deflation). The target pressure signal also indicates the gas flow into the cuff during inflation (or out of the cuff during deflation), and the processing unit of the device is configured to calculate the target pressure (nominal pressure) based on the target pressure signal and to analyze the cuff pressure signal based on this target pressure. However, this target pressure signal may already indicate the target pressure, i.e. the pressure that should be in the cuff at a certain time, without the processing unit performing further calculations.

[0020] In general, the target pressure signal can be considered as a reference pressure signal for detecting defects. The target pressure signal is derived from the device using information from a pressure delivery unit. Furthermore, information from a measured cuff pressure signal can be used. However, it is also possible that the device infers or calculates the target pressure signal (alone) from the measured cuff pressure signal, for example using a certain algorithm. In this case, the target pressure input may be configured to obtain the target pressure signal, for example by processing the cuff pressure signal.

[0021] Apart from the target pressure signal, the processing unit uses the cuff pressure signal recorded during the evaluation (measurement) to detect defects. Typically, the cuff is inflated to a predefined pressure at a given pressure rate and during the inflation, the cuff pressure signal is recorded. This cuff pressure signal is then analyzed for irregularities that indicate defects in the cuff.

[0022] During the measurement time, in particular during inflation, deflation or constant pressure in the cuff, the sensor input obtains a cuff pressure signal from a sensor configured to measure the pressure in the cuff. In general, the (pressure) sensor can be located anywhere as long as it is pneumatically connected to the cuff. For example, the sensor may be located (somewhere) in a pneumatic system connected to the cuff, for example in the pneumatic system of the pressure delivery unit. However, other locations are conceivable as well. For example, the sensor may be connected to a hose (tube) that conveys air from the outlet of the pump to the outer connector of the cuff. In fact, a pressure sensor located directly in the cuff has the least pump (background) noise and is the most sensitive. However, such a positioning is difficult to achieve, since (in most cases) the cuff needs to be modified to insert the pressure sensor.

[0023] A practical location for good sensitivity is right at the inlet (for pressure measurement) of the cuff. In general, the location of the pressure sensor depends on technical feasibility and the desired sensitivity.

[0024] Both the cuff pressure signal and the target pressure signal may be analyzed by a processing unit of the device. For example, the processing unit may be configured to compare the cuff pressure signal with the target pressure signal, in particular during the measurement time, and to detect defects based on this comparison. However, the processing unit may also check whether the pressure rate at which the cuff is inflated is constant, as indicated by the target pressure signal, and analyze the cuff pressure signal taking this information into account. If the cuff pressure signal is analyzed as not indicating a constant cuff pressure rate, a defect is detected.

[0025] If a fault is detected, the output of said device is in particular configured to provide a warning signal to an output interface, which can then publish the fault detected by the device.

[0026] In one embodiment, the device further comprises a control unit configured to control the pressure delivery system to provide a target pressure in the cuff, the control unit configured to control the pressure delivery unit to inflate the cuff at a predetermined inflation rate and / or to deflate the cuff at a predetermined deflation rate and / or to maintain the target pressure at a predetermined (constant) level.

[0027] The inflation and / or deflation speed can be a constant speed. However, the control unit may be configured to control the pressure delivery unit to inflate and / or deflate the cuff at a variable speed. In particular, the control unit may be configured to control the pressure delivery unit to inflate and / or deflate the cuff at a speed that depends for example on the size of the cuff or on the material of the cuff. Furthermore, the speed may depend on the size of the rigid cylindrical shape or phantom arm device around which the cuff is wrapped during the measurement. Preferably, the inflation speed is in the range of 0.5 mmHg / s to 30 mmHg / s. Furthermore, the control unit may be configured to control the pressure delivery unit to inflate and / or deflate the cuff and / or to maintain a predefined pressure in the cuff for a predefined time.

[0028] In one embodiment of the device, the processing unit is configured to detect the defect based on a change in the cuff pressure signal, in particular the magnitude and / or shape of that change, more particularly the magnitude and / or shape of a drop or increase in the cuff pressure signal.

[0029] Preferably, the processing unit is configured to (calculate and) analyze the derivative of the cuff pressure signal and detect the defect based on this derivative. For example, the processing unit is configured to detect a negative impulse (part) in the derivative of the cuff pressure signal and detect the defect if this impulse is larger than the pump noise vibrations of the pressure delivery unit, i.e. if said impulse is larger than a predefined threshold, where the threshold depends on the magnitude of the background noise vibrations. In this way, defects caused by the closing element or other parts of the cuff are not confused with background noise.

[0030] In another embodiment, the processing unit is configured to detect a defect if the change in the cuff pressure signal is higher than a threshold, where said threshold is a static or adaptive threshold. The processing unit may for example be configured to adapt said threshold with respect to background noise (caused by the pressure delivery unit etc.). Typically, the (static or adaptive) threshold is as low as 0.1 mmHg / s. Other thresholds, for example in the range of 0.1 mmHg to 5 mmHg or 1 mmHg to 10 mmHg, are also conceivable. The threshold is adapted depending on the sensitivity of the sensor used to measure the cuff pressure signal and / or the smallest defect of interest. By increasing the threshold, not only are smaller cracks ignored, but also false positive detections due to equipment noise are reduced.

[0031] Preferably, the processing unit is configured to detect the defect based on a comparison of the change in the cuff pressure signal with the change in the target pressure signal. In particular, the processing unit is configured to detect the defect if the difference between the change in the cuff pressure signal and the change in the target pressure signal (at a particular time during the measurement time) is higher than a predefined threshold. By comparing both signals, it is possible to exclude the detection of malfunctions (defects) caused by the pressure delivery unit. This is due to the fact that if the cuff pressure signal and the target pressure signal have a sudden change at the same time, the change in the cuff pressure signal is caused by a change in the target pressure signal and not by defects in the material and / or the manufacturing of this material.

[0032] In one embodiment, the processing unit is configured to detect the defects based on any of: a spectral analysis of the cuff pressure signal, matching the cuff pressure signal with a template, and evaluating the variability of the filtered cuff pressure signal.

[0033] In other words, the processing unit is configured to perform a spectral analysis of the cuff pressure signal and to detect defects based on this analysis. More specifically, the cuff pressure signal may be analyzed using a (short-time) Fourier transform or similar spectral methods. Defects are indicated by increases in amplitude at frequencies that typically indicate defects in the cuff material or manufacturing.

[0034] Furthermore, the device may be configured to store or retrieve various templates of previous cuff pressure signals, these templates carrying information about artifacts in these signals associated with defects in the cuff. To retrieve such a template, a predefined (defect) pattern, i.e. a short signal excerpt (part) of the cuff pressure signal indicative of a defect, is searched for in the existing cuff pressure signal. The cuff pressure signal may be pre-filtered. To search for this excerpt, cross-correlation or other methods can be used. Then, by comparing the cuff pressure signal with the templates, the processing unit is able to detect similar ones and thus detect the defect.

[0035] However, the processing unit of the device may further comprise a filter unit configured for filtering the cuff pressure signal, the filter unit comprising one of a band pass filter, a low pass filter and a high pass filter, the processing unit being configured for detecting the defect based on an evaluation of the variability of the filtered signal, in particular the processing unit being configured for detecting the defect based on a change in the filtered cuff pressure signal, more particularly based on a comparison of the change in the filtered cuff pressure signal with a change in a target pressure signal.

[0036] Typically, the pressure signal is pre-processed and / or filtered before analyzing the signal. For example, high frequency noise and pump induced disturbances are removed from the signal using a low pass or band stop filter. The cuff pressure signal can similarly be filtered by a high pass filter to remove the inflation ramp, resulting in a detrended cuff pressure signal, where changes in the signal are emphasized.

[0037] In an ideal setup with an ideal cuff without any imperfections, the resulting cuff pressure signal would be a horizontal line (zero constant). However, due to background noise, there will be irregular oscillations around the baseline (zero). If the amplitude of such oscillations is greater than that of the background noise, then the imperfection will be distinguished from the oscillations. A root mean square (RMS), peak-to-peak or similar calculation of signal variability is performed on the detrended signal to obtain a score representing how much the cuff is affected by the imperfection.

[0038] More precisely, after detrending, the cuff pressure signal can be input to an algorithm configured to compare the changes in the detrended cuff pressure signal with a threshold value that is simultaneously adapted to the background noise of this signal. Each time the threshold value is exceeded, the processing unit detects (and records) the defect. Further information on the defect can also be recorded, such as the amplitude, duration and / or pressure level at which the defect occurs. On the other hand, from the detrended cuff pressure signal, some non-parametric features are calculated to evaluate the variability-unrest in the signal, such as the root mean square (RMS), peak-to-peak (the difference between the maximum and minimum value in the signal). The more defects there are, the greater the variability of the signal. The advantage of this method is that it does not require any parameters and that it works on all types of defects affecting the detrended cuff pressure signal. However, the defects are not localized or analyzed with respect to specific characteristics.

[0039] In one embodiment, the cuff is configured to be wrapped (and in particular closed during the measurement time by a closing element) into a cylindrical shape, the cylindrical shape having a phantom arm device, the phantom arm device comprising: an inner cylinder having a first material; an intermediate layer having a second material wrapped around the shell surface of the inner cylinder; and an outer layer having a third material wrapped around the intermediate layer; having The first material has a harderness than the second material, which has a harderness than the third material.

[0040] The cylindrical shape is configured to mimic a human arm. The cylindrical shape can be of plastic material or metal. By wrapping the cuff around the (non-living) shape, distortion of the cuff pressure signal caused by human movement, pulse or any other type of human factor can be prevented.

[0041] Although a simple rigid cylinder from any material that does not shrink during inflation can be used to assess the quality of the cuff, a phantom arm device with a soft outer layer has the advantage that a cuff wrapped (tightly) around this outer layer can expand towards the cylinder (as opposed to a rigid cylinder that does not collapse during inflation). Furthermore, the behavior of the cuff during inflation or deflation is closer to the behavior of a cuff when wrapped around a human arm.

[0042] In another embodiment, the defect comprises the opening, especially the sudden opening, of a closing element, where said closing element comprises any of two surfaces that contact each other, a hook and loop fastener, a magnetic fastener and a button.

[0043] An example of a button may include, among others, a push button. Thus, defects include a button coming undone, or a hook coming undone from a loop. Defects also include the slip-stick phenomenon, i.e., the spontaneous jerking motion that occurs while two objects (surfaces) are sliding against each other. Any of these defects will cause a (sudden) change in the volume inside the cuff, and thus a sudden change in the measured cuff pressure (and cuff pressure signal).

[0044] In yet another embodiment, the processing unit is configured to analyze the cuff pressure signal at different inflation and / or deflation rates. In particular, the control unit controls the pressure delivery unit to inflate the cuff at inflation rates of 6 mmHg / sec, 15 mmHg / sec and 25 mmHg / sec, and the processing unit is configured to analyze the cuff pressure signal at (any of) these rates. In this way, the behavior of the cuff can be tested in more detail.

[0045] In yet another embodiment, the processing unit is specifically configured to count the number of defects detected during the measurement time. Furthermore, the processing unit may be configured to determine the aggregate magnitude of all changes corresponding to the detected defects. Alternatively, the processing unit may be configured to evaluate the level of cuff pressure at which the defects are detected.

[0046] These analyses serve to provide meaningful statistics regarding the quality of the cuffs being tested. In particular, determining the aggregate magnitude of all dysfunctions serves to assess the quality of the cuff. For example, if the aggregate magnitude is very high, this is an indication that the cuff is severely defective and cannot be used to measure vital signs in a reliable manner.

[0047] In one embodiment of the phantom arm device, the first material comprises (rigid) polytetrafluoroethylene and the second and / or third material comprises silicone rubber, wherein the diameter of the inner cylinder is between 1 cm and 3 cm, preferably 2 cm, and / or the thickness of the middle layer is between 2 cm and 4 cm, preferably 3 cm, and / or the thickness of the outer layer is inclusive, between 0.5 mm and 1.5 mm, preferably 1 cm. In this way, the geometry of a real human arm is accurately mimicked. Preferably, the thickness of the middle and outer layers is constant and the phantom arm device has a cylindrical shape.

[0048] In another embodiment, the phantom arm device comprises one or more further layers. Any of these layers may be located below the middle layer, or above the middle layer, and / or below the outer layer, and / or above the outer layer. The further layers may be wrapped around the entire inner cylinder, or only around a portion of the inner cylinder. The material of the one or more further layers may comprise, for example, silicone rubber. In particular, the middle layer and / or the outer layer may comprise a (medical) silicone elastomer. More particularly, the middle layer may comprise Silpuran® 2420 and the outer layer may comprise Silpuran® 2400.

[0049] In a preferred embodiment, the phantom arm device comprises a cylinder having a diameter that is constant along the entire length of the phantom arm device, in other words, any point on the shell surface of said cylinder of the phantom arm device has the same distance to the inner cylinder.

[0050] In one embodiment of the system, the system further comprises a rigid cylindrical shape or phantom arm device as claimed in the present specification, which is used to mimic a human arm, and the cuff is wrapped around the rigid cylindrical shape or phantom arm device during the measurement time.

[0051] In one embodiment of the system, the pressure delivery unit is configured to maintain a predetermined constant (target) pressure rate and / or to maintain a predetermined constant gas flow rate. In general, the pressure delivery unit is configured to ensure a controlled inflation and / or deflation of the cuff. For example, the pressure delivery unit can have a programmable system configured to maintain a predetermined constant pressure rate (mmHg / sec). This programmable system can have a hardware module with universal signal inputs and outputs that executes user-defined algorithms in real time, and a personal computer that runs control, visualization and recording software. The programmable system can be used to control the inflation and / or deflation, record the inflation and / or deflation pressures, process the signals, and execute specific algorithms on the signals.

[0052] On the other hand, the pressure delivery unit provides a constant flow of gas (ml / sec or cm) into the cuff (independent of the input pressure). 3 The programmable system may have a (thermal) mass flow controller configured to maintain a constant pressure rate (g / s). Through a controller unit in the mass flow controller, a flow rate value can be defined, which can then be adjusted through a regulator unit (e.g., an electronic valve). This mass flow controller can therefore ensure a well-defined inflation behavior. The advantage of a mass flow controller is that there is no air pump (compressed air inflow is used), so there is lower background noise in the cuff pressure signal (usually caused by said air pump in the installation of the programmable system). Thus, when a mass flow controller is used, the system becomes more sensitive, i.e. even small defects such as, for example, small Velcro cracks can be detected. The advantage of a programmable system that maintains a constant pressure rate is that when the cuff is used on a patient and measurements are taken during inflation, this inflation mode is closer to the actual use of the cuff, since usually the cuff is inflated at a constant pressure rate and not at a constant flow rate.

[0053] Preferably, the pressure delivery unit of the system and / or the control unit of the device are configured to control the delivery of the target pressure in real time. [Brief description of the drawings]

[0054] These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter. [Figure 1] FIG. 1 shows a schematic diagram of an embodiment of a system for detecting material and / or manufacturing defects in an inflatable cuff according to the present invention. [Diagram 2] FIG. 2 shows a schematic diagram of an embodiment of an apparatus for detecting material and / or manufacturing defects in an inflatable cuff according to the present invention. [Figure 3A] FIG. 3A shows a standard inflatable cuff with a closing element in an open position. [Figure 3B] FIG. 3B shows the standard inflatable cuff of FIG. 3A in a closed position. [Figure 4] FIG. 4 illustrates an embodiment of a phantom arm device according to the present invention. [Diagram 5] FIG. 5 shows a schematic diagram of an embodiment of a method for detecting material and / or manufacturing defects in an inflatable cuff according to the present invention. [Figure 6] FIG. 6 is a diagram showing a cuff pressure signal. [Figure 7A] FIG. 7A shows the raw cuff pressure signal and the derived signal. [Figure 7B] FIG. 7B shows the cuff pressure signal of FIG. 7A after detrending. [Figure 7C] FIG. 7C shows the defects detected in the signal of FIG. 7B, the corresponding pressure amplitude, and the corresponding pressure in the cuff. [Figure 8A] FIG. 8A shows a similar signal to FIG. 7A. [Figure 8B] FIG. 8B shows a similar signal to FIG. 7B. [Figure 8C] FIG. 8C shows a similar signal to FIG. 7C. [Figure 9A]FIG. 9A shows the average pressure drop of various commercially available cuffs during the inflation process. [Figure 9B] FIG. 9B shows the root mean square error of the pressure signal of the cuff shown in FIG. 9A. [Figure 10A] FIG. 10A shows the average pressure drop and corresponding error for additional commercially available cuffs. [Figure 10B] FIG. 10B shows the average pressure drop and corresponding error for additional commercially available cuffs. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0055] FIG. 1 shows a schematic diagram of an embodiment of a system 1 for detecting material and / or manufacturing defects in an inflatable cuff according to the present invention.

[0056] The system 1 comprises a sensor 10, a pressure delivery unit 20 and an apparatus for detecting material and / or manufacturing defects in the inflatable cuff 30. Optionally, the system 1 further comprises a rigid cylinder or phantom arm device (not shown) and an output interface (40).

[0057] In this embodiment, the cuff is wrapped around a rigid cylinder and secured by a closing element of the cuff. However, the cuff may also be wrapped around a stick that is not (perfectly) cylindrical in shape or around a phantom arm device. Additionally, the cuff may simply be closed without wrapping around any kind of object.

[0058] Disposed within the cuff is a sensor 10 configured to measure the (gas) pressure within the cuff. The sensor 10 is further configured to provide a cuff pressure signal 11 indicative of the pressure measured within the cuff.

[0059] The pressure inside the cuff 50 is provided by a pressure delivery unit 20, i.e. the pressure delivery unit 20 is configured to inflate or deflate the cuff (e.g. via a tube) or to keep the pressure in the cuff 50 constant. In this embodiment, the pressure delivery unit 20 has a mass flow controller configured to ensure that a constant flow of gas is provided to the cuff for inflation. Based on the gas flow provided by the pressure delivery unit 20 and entering the cuff, the pressure delivery unit 20 calculates the pressure in the cuff and provides a target pressure signal 21 indicative of a target pressure in the cuff upon inflation, the target pressure being a nominal or reference pressure.

[0060] The device 30 is configured to acquire, i.e. retrieve or receive, a target pressure signal 21 from the pressure delivery unit 20 and a cuff pressure signal 11 from the sensor 10. Both signals are then used to detect defects in the cuff's material and / or in the manufacture of the cuff (e.g. in the cuff's closing elements). In particular, the device 30 may be configured to compare the pressure signal 11 with the target pressure signal 21 and detect the difference between these signals. If the difference is higher than a predefined threshold, a warning signal 31 is generated by the device 30 indicating a defect in the cuff's material and / or manufacture.

[0061] However, the device 30 is also configured to analyze whether the target pressure signal indicates a constant inflation rate of the cuff, analyze whether the cuff pressure signal has discontinuities, in particular whether the changes are higher than a predetermined threshold, and detect a malfunction if a discontinuity in the cuff pressure signal is detected.

[0062] Since the cuff is not attached to a human arm but to an inanimate object, it is possible to prevent the pressure measurement from being corrupted by arm movements, arm muscle movements or blood pressure fluctuations, or any other kind of disturbance due to human factors. If we assume that the measurement equipment is not corrupted, i.e. that the pressure delivery unit 20 and other parts of the system 1 function properly, artifacts in the cuff pressure signal, in particular differences between the measured pressure and the target pressure, can be explained by defects in the cuff 50. Furthermore, if we assume that the cuff 50 does not have any leaks, there may be a malfunction of the closing element. This is especially true if there is a sudden drop or rise in the cuff pressure signal 21.

[0063] Optionally, device 30 of system 1 may be further configured to control pressure delivery unit 20 via control signal 37, in particular to control the inflation and / or deflation of the cuff, for example the inflation rate at which the cuff is inflated.

[0064] The system 1 may further comprise an output interface 40, which is generally any means for outputting a detected malfunction based on a warning signal provided by the device. This output may be in visual or audible form, for example in text form, in images or diagrams, in voice or spoken word, etc. For example, the output interface may be a display, a speaker, a touch screen, a computer monitor, a smartphone or tablet screen, etc.

[0065] 2 shows a schematic diagram of an embodiment of a device 30 for detecting material and / or manufacturing defects in an inflatable cuff according to the present invention. The device 30 has a target pressure input 32 configured to acquire a target pressure signal 31, and a sensor input 33 configured to acquire a cuff pressure signal 11. The target pressure input 32 and the sensor input 33 may be directly coupled or connected to the pressure delivery unit 20 and the sensor 10, respectively, or may acquire (retrieve or receive) these signals from a storage device, buffer, network or bus, etc. Thus, the inputs 32 and 33 may be a communication or data interface (wired or wireless), such as, for example, a Bluetooth interface, a WiFi interface, a LAN interface, an HDMI interface, a direct cable connection, or any other suitable interface allowing for signal transfer to the device 30.

[0066] The device 30 further comprises a processing unit 34 configured to analyze the cuff pressure signal 11 based on a comparison of said cuff pressure signal 11 with the target pressure signal 21. The processing unit 34 may be any kind of means configured to process and analyze said signal and to detect therefrom a malfunction of the cuff closing element. It may be implemented in software and / or hardware, for example as an app on a programmed processor or computer or user device, such as a smartphone, smartwatch, tablet, laptop, PC, workstation, etc.

[0067] The device 30 further comprises an output 35 configured to output a warning signal 31, i.e. a signal indicating that a malfunction of the closing element 51 has been detected. The output 35 is generally any interface for providing the warning signal 31, for example for transmitting the warning signal to another device or for providing the warning signal for retrieval by another device (e.g. a smartphone, a computer, a tablet, etc.). The output can therefore generally be any (wired or wireless) communication or data interface.

[0068] Optionally, the device 30 further comprises a control unit 36 ​​configured to provide a control signal 37 to the pressure delivery unit 20 and thus control the pressure delivery unit 20 to provide a target pressure in the cuff.

[0069] Figure 3A shows a standard inflatable cuff 50 in an open state, with closing element 51. The quality of the cuff 50 can be assessed using the device 30, system 1 and method 100 according to the invention. In particular, defects in the material and / or manufacturing of the cuff are detected. The cuff 50 shown in Figure 3A has a hook and loop fastener as the closing element 51. The cuff 50 is closed by attaching a hook portion to a loop portion.

[0070] Figure 3B shows the standard inflatable cuff 50 of Figure 3A in a closed state. The cuff 50 is wrapped around a phantom arm device 60. The cuff 50 may have a tube 65 through which the cuff's air bladder (not shown) may be inflated or deflated by a pressure delivery unit (not shown).

[0071] FIG. 4 shows an embodiment of a phantom arm device according to the invention. The phantom arm device 60 is in the form of a cylinder. In this embodiment, the diameter of this cylinder is (approximately) 10 cm. However, the diameter of the cylinder of the phantom arm device 60 can generally range from 7 cm to 20 cm. The phantom arm device 60 is configured to mimic a human arm and has three different materials. A first material is used for the inner cylinder 61 of the phantom arm device 60. This inner cylinder is configured to mimic the bones of a human arm. This first material is therefore selected to be a fairly hard material, with a hardness that corresponds to the hardness of human bones. Preferably, polytetrafluoroethylene is used as the first material. Around the shell surface of the inner cylinder 61 is wrapped an intermediate layer 62 having a second material. This second material is softer than the first material and is configured to mimic the muscles of a human arm. Around the intermediate layer 62 is wrapped an outer layer 63 having a third material. The material of the outer layer is softer than the second material and is configured to mimic human skin and fat layers. The middle layer 62 and the outer layer 63 may comprise silicone rubber.

[0072] In this embodiment, the diameter of the inner cylinder is 2 cm, the thickness of the middle layer is 3 cm, and the thickness of the outer layer is 1 cm. The phantom arm device 60 further includes a base 64. This allows the phantom arm device 60 to stand stably.

[0073] The lengths of the middle layer 62 and the outer layer 63 along the axis of the cylinder may be the same or different. For example, the phantom arm device 60 shown in Figure 4 has the middle layer 62 and the outer layer 63 of the same length, and the inner cylinder 61 has a longer length than the middle and outer layers.

[0074] 5 shows a schematic diagram of an embodiment of a method 100 for detecting material and / or manufacturing defects in an inflatable cuff according to the present invention. The steps of method 100 may be performed by apparatus 30, with main steps of method 100 being performed by processing unit 34. Method 100 may be implemented as a computer program running on a computer or processor.

[0075] In a first step 101, a target pressure signal 21 is obtained, e.g. retrieved or received, from the pressure delivery unit 20. In a second step 102, which is performed before, after or in parallel with step 101, a cuff pressure signal 11 is obtained, e.g. retrieved or received, from the sensor 10. Then, in step 103, the cuff pressure signal 11 and the target pressure signal 21 are analyzed. Step 103 may in particular comprise a step of comparing both signals. Based on the analysis in step 103, in particular the comparison of both signals, a material and / or manufacturing defect of the cuff 50 is detected (determined) in step 104. Finally, in step 105, based on the determination of a defect, a warning signal 31 is output.

[0076] In a preferred embodiment of the method 100, step 103 comprises comparing the cuff pressure signal 11 with the target pressure signal 21, determining whether there is a difference between both signals, and detecting a fault if said difference is higher than a predefined threshold.

[0077] FIG. 6 shows a diagram illustrating the cuff pressure signal measured by the sensor 10 in the cuff 50. In particular, FIG. 6 shows the raw (oscillating) pressure in the cuff 50. While the cuff pressure is always increasing over time, there are also some dips in the signal. In the box on the right side of FIG. 6, a zoomed cuff pressure signal 11 is shown. This zoom shows two pressure drops at times corresponding to (approximately) 25.5 seconds and 27 seconds. Considering that the target pressure in the cuff always increases without any particular drop (e.g. due to constant inflation by the pressure delivery unit), the drop shown in the graph of FIG. 6 can be considered as a drop caused by a defect in the cuff, for example a sudden opening of a closing element that allows the cuff to stretch in a further direction. In this case, the volume V of air in the cuff increases, leading to a drop in the pressure P in the cuff. P ∝ (1 / V)

[0078] Figure 7A shows the (raw) cuff pressure signal and the derived signal. In particular, Figure 7A shows the raw cuff pressure signal measured by the sensor and the derived cuff pressure signal (after pre-processing and filtering). The signals are shown over a measurement period of approximately 45 seconds.

[0079] FIG. 7B shows the cuff pressure signal of FIG. 7A after trend removal. In particular, FIG. 7B shows the bandpass filtered cuff pressure signal. It is clear that the cuff has (faster) pressure changes other than the inflation ramp. The signal shown in FIG. 7B is used to assess the variability in this signal, with higher variability indicating more Velcro cracks or other defects in the cuff.

[0080] FIG. 7C shows the pressure levels and amplitudes of the detected defects / malfunctions. In particular, for example, the amplitudes indicate malfunctions of the closing elements of the cuff. However, defects can also be caused by other elements of the cuff. The severity of the defect / malfunction is indicated by the height of the amplitude. The higher the amplitude, the higher the severity of the corresponding malfunction. As can be seen, the cuffs used suffer from defects at different levels of pressure within the cuff. The information was evaluated using the thresholds mentioned above (as opposed to signal variability and other methods). The amplitude of the defect ("crack") is the difference between the point of highest positive or negative deflection in the crack and the pressure level immediately before the crack.

[0081] Figures 8A, 8B and 8C show similar signals to Figures 7A, 7B and 7C respectively. As can be seen from Figure 8C, the cuff used for the measurements in this case does not reveal any defects.

[0082] 9A shows the average pressure drop of various commercially available cuffs during the inflation process. As can be seen, cuff C has a higher than 25 mmHg pressure drop in the cuff pressure signal and is suffering from a pressure drop caused by (for example) a defective closing element during the inflation process.

[0083] FIG. 9B shows the root mean square error (RMS) of the cuff pressure signal shown in FIG. 9A. The RMS (similar to variance or standard deviation, which can also be used) is a measure of signal variability (instability). The main cause of this variability is cuff imperfections. In general, the root mean square level of a vector x is given by:

number

[0084] 10A and 10B show the average pressure drop and corresponding error for additional commercially available cuffs that were subjected to testing.

[0085] As can be seen from Figures 9A and 10A, none of the cuffs tested had a malfunction / defect that resulted in a pressure drop of less than 5 mmHg during the inflation time of the cuff.

[0086] While the invention has been illustrated and described in detail in the drawings and the foregoing description, such illustration and description is to be considered exemplary or explanatory and not restrictive. The invention is not limited to the disclosed embodiments. Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims.

[0087] In the claims, the term "comprising" does not exclude other elements or steps, and the absence of a plurality does not exclude a plurality of them. A single element or other unit may fulfill the functions of several items recited in the claims. The mere 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.

[0088] The computer program may be stored / distributed on a suitable non-transitory medium, such as an optical storage medium or a solid-state medium, for example supplied together with or as part of other hardware, but may also be distributed in other forms, for example via the Internet or other wired or wireless communication systems.

[0089] Any reference signs in the claims should not be construed as limiting the scope.

Claims

1. An apparatus for detecting a material and / or manufacturing defect of an inflatable cuff configured for blood pressure measurement, the apparatus comprising: a target pressure input unit configured to obtain a target pressure signal indicating a target pressure within the cuff; a sensor input unit configured to obtain a cuff pressure signal indicating the pressure within the cuff from a sensor configured to measure the pressure within the cuff; an output unit configured to output a warning signal; and a processing unit configured to analyze the cuff pressure signal and the target pressure signal The processing unit analyzes the cuff pressure signal measured during inflation or deflation of the cuff, detects a defect of the cuff based on the analysis, and controls the output unit to output the warning signal when the defect is detected.

2. The apparatus according to claim 1, further comprising a control unit configured to control a pressure delivery unit to supply the target pressure within the cuff, the control unit configured to inflate the cuff at a predetermined inflation rate and / or deflate the cuff at a predetermined deflation rate and / or control the pressure delivery unit to maintain the target pressure at a constant level.

3. The apparatus according to claim 1 or 2, wherein the processing unit is configured to detect the defect based on a change in the cuff pressure signal.

4. The apparatus according to claim 3, wherein the processing unit is configured to detect the defect when a change in the cuff pressure signal is higher than a threshold value, the threshold value being a static threshold value or an adaptive threshold value.

5. The apparatus according to claim 1, wherein the processing unit is configured to detect the defect based on any one of spectral analysis of the cuff pressure signal, matching of the cuff pressure signal with a template, and evaluation of variability of the filtered cuff pressure signal.

6. The cuff is configured to be wound in a cylindrical shape, the cylindrical shape constituting a phantom arm device, the phantom arm device comprising: an inner cylinder having a first material; an intermediate layer having a second material wound around a shell surface of the inner cylinder; and an outer layer having a third material wound around the intermediate layer having, the hardness of the first material being higher than the hardness of the second material, and the hardness of the second material being higher than the hardness of the third material, the apparatus according to claim 1.

7. The defect has the closing element opening, and the closing element has any one of two surfaces in contact with each other, a surface fastener, a magnetic fastener, and a button, the apparatus according to claim 1.

8. The processing unit is configured to analyze the cuff pressure signal at different inflation rates and / or different contraction rates, the apparatus according to claim 2.

9. The processing unit is configured to count the number of the detected defects, the apparatus according to claim 1.

10. A phantom arm device for detecting material and / or manufacturing defects of an inflatable cuff configured for blood pressure measurement, the phantom arm device comprising an inner cylinder having a first material, an intermediate layer having a second material wound around the shell surface of the inner cylinder, and an outer layer having a third material wound around the intermediate layer having, the hardness of the first material being higher than the hardness of the second material, and the hardness of the second material being higher than the hardness of the third material, the phantom arm device.

11. The first material has polytetrafluoroethylene, the second and / or third materials have silicone rubber, the diameter of the inner cylinder is 1 cm to 3 cm, and / or the thickness of the intermediate layer is 2 cm to 4 cm, and / or the thickness of the outer layer is 0.5 mm to 1.5 mm, the phantom arm device according to claim 10.

12. A system for detecting material and / or manufacturing defects of an inflatable cuff configured for blood pressure measurement, the system comprising a sensor configured to measure the pressure in a cuff having a rigid cylindrical shape or wound around the phantom arm device according to claim 10, a pressure delivery unit configured to supply a target pressure into the cuff, and the apparatus according to claim 1 having, the system.

13. A method for detecting material and / or manufacturing defects of an inflatable cuff configured for blood pressure measurement, the method comprising acquiring a target pressure signal indicating a target pressure in the cuff, acquiring a cuff pressure signal indicating the pressure in the cuff from a sensor configured to measure the pressure in the cuff, Analyzing the cuff pressure signal measured during inflation or deflation of the cuff and the target pressure signal; Detecting a defect in the cuff based on the analysis; and Controlling to output a warning signal if the defect is detected. A method comprising the above steps. **Claim 14** A computer program having program code means, which when the computer program is executed on a computer, causes the computer to execute the steps of the method according to claim 13.

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