Method and device for correcting blood pressure measurements performed at a measurement site

Abstract

In order to calibrate the differential pressure measurement to a geodetic height difference of (approximately) zero, a reference position determination part (2) is brought so close to the blood pressure measuring device (1) that a calibration signal is triggered if a minimum distance between two points respectively defined on the reference position determination part (2) and on the blood pressure measuring device (1) falls below a threshold value. A control device integrated into the blood pressure measuring device (1) or connected to the blood pressure measuring device (1) performs a calibration measurement as a reaction to the trigger signal. The trigger means are implemented as a reference position determination part RFID tag (10) and an associated blood pressure measuring device near field communication reader (11). If the near field communication reader (11) in the blood pressure measuring device (1) detects a correctly encoded RFID tag in the reference position determination part (2), the near field communication reader triggers the calibration signal. The reference position determination part (2) to be attached to the patient is preferably designed as a disposable item with associated increased sterility requirements. The reference position determination part is connected to the blood pressure measuring device by means of a tube connection (12) so that a continuous liquid column exists between the liquid reservoir (13) in the reference position determination part (2) and the calibration pressure sensor (14) in the blood pressure measuring device (1).

Description

Technical Field

[0001] The invention relates to a method for correcting a blood pressure measurement performed at a measurement location which has a geodetic height difference from a reference location defined by the position of the patient's heart. Background Art

[0002] The (especially arterial) blood pressure of a patient is one of the most important measured variables in medical engineering, and the known associated measuring devices (whether invasive or non-invasive) are extremely diverse. This applies in particular to measuring devices for continuous monitoring of blood pressure over a longer period of time (for example in intensive care medicine), but also in emergency medicine and during surgery.

[0003] For reasons of good accessibility, blood pressure measuring devices are often attached to the patient's limbs, such as applanation tonometer sensors in the radial artery on the forearm or finger sensors operating based on photoplethysmography according to the so-called "vascular unloading technique" of Peňáz. Such pressure measuring devices are known, for example, from US 4,406,289, US 4,524,777, US 4,726,382, WO 2010 / 050798 A1, WO 2000 / 059369 A1, WO 2011 / 045138 A1, WO 2011 / 051819 A1, WO 2011 / 051822 A1, WO 2012 / 032413 A1 and WO 2017 / 143366 A1.

[0004] Pressure sensors for invasive measurements that are connected to a patient's artery via a fluid column using a catheter and hose system may also be connected to a patient's limb, for example by means of adhesive tape or sutures, or fastened at a distance from the patient.

[0005] In all the cases mentioned, the pressure measured locally at the measuring location changes depending on the geodetic height difference between the measuring location and the position of the patient's heart. For example, the arterial blood pressure measured at a stationary finger or wrist changes when the patient moves from a lying position to a semi-sitting position, or vice versa. Likewise, the arterial blood pressure measured at the finger or wrist changes if the hand is raised or lowered without changing the patient's position.

[0006] In order to correct corresponding position changes during continuous blood pressure measurement, so that blood pressure monitoring or blood pressure-based patient monitoring remains largely unaffected by changes in the geodetic height difference between the measurement location and the patient's heart, devices are known from the prior art that measure the static pressure difference between a blood pressure measurement device located at the measurement location and a reference position determination part that is attached to a reference position defined by the position of the patient's heart, for example fixed to the chest. For example, EP 0 465 345 A1 discloses a plethysmographic blood pressure sensor with a finger cuff, in which the hydrostatic pressure difference to the heart is measured by means of a liquid column between a ventilation reservoir of a chest unit attached close to the heart and a pressure sensor in the area of ​​the finger cuff.

[0007] US 4,779,626 describes a differential pressure sensor on a finger cuff having a hydraulic connection to a reservoir near the heart, the reservoir being designed as a flexible bag with a protective outer casing.

[0008] WO 2006 / 020917 A1 discloses a system having at least one blood pressure sensor (invasive or non-invasive) and a further pressure sensor connected to a calibration device, which may be a fluid reservoir.

[0009] No. 5,957,853 describes a height reference system having a measuring pressure sensor for measuring blood pressure and a reference pressure sensor.

[0010] Such devices usually have to be calibrated before use. In electronic measuring systems, this usually occurs when the reference position determining part is brought to as close to the same geodetic height as possible before being attached to the reference position, and the zero point adjustment is then triggered manually by the medical staff, for example using a button or a graphical user interface. To this end, either a corresponding operating element, such as a touch screen, must be located directly next to the patient, or two people are required to simultaneously bring the reference position determining part into a position suitable for calibration and trigger the zero point adjustment. Furthermore, calibration errors can occur if the reference position determining part is not kept in the correct position for calibration with sufficient care. Summary of the invention

[0011] In view of the calibration problems existing in conventional systems, the object of the present invention is to simplify the calibration of a system for taking into account geodetic pressure differences between a measurement location of blood pressure measurement and a reference location near the heart and to make it as reliable as possible.

[0012] According to one aspect of the invention, this object is achieved by a method according to claim 1 .

[0013] According to another aspect, an arrangement according to the claims is provided to achieve the underlying object of the invention.

[0014] Preferred embodiments of the invention can be implemented according to one of the dependent claims.

[0015] The invention relates to a method for correcting a blood pressure measurement performed at a measurement location which has a geodetic height difference from a reference location defined by the position of the patient's heart, wherein

[0016] - placing the reference position determination section substantially at the geodetic height of the blood pressure measurement device located at the measurement position,

[0017] - when the reference position determination part is positioned substantially at the geodetic height of the blood pressure measurement device at the measurement position, performing a calibration measurement to establish a zero point for the static pressure difference between the reference position and the measurement position,

[0018] – placing the reference position determining part at the reference position,

[0019] – when the reference position determining part is placed at the reference position, determining the static pressure difference between the measuring position and the reference position,

[0020] – Use the determined static pressure difference to correct the blood pressure measurement.

[0021] The calibration measurement is triggered by a trigger signal exchanged between the reference position determining part and the blood pressure measuring device, which is automatically triggered by placing the reference position determining part in close proximity to the blood pressure measuring device.

[0022] Therefore, the invention also provides a device for correcting a blood pressure measurement performed at a measurement location having a geodetic height difference from a reference location defined by the patient's heart location, the device comprising:

[0023] – a blood pressure measuring device, intended to be placed at a measuring location and to carry out a blood pressure measurement,

[0024] - a pressure difference determining means for determining a static pressure difference between a current position of the reference position determining portion and a current position of the blood pressure measuring device,

[0025] – calibration device for making calibration measurements to establish a zero point for static pressure difference,

[0026] - correction means for correcting the blood pressure measurement using the determined static pressure difference, and

[0027] - triggering means for automatically triggering the calibration measurement when the reference position determining part is placed in close proximity to the blood pressure measuring device.

[0028] Being placed substantially at the geodetic height of the blood pressure measuring device at the measuring position preferably means that the geodetic height deviation is 30 mm or less, preferably 20 mm or less.

[0029] Close proximity means that the distance between the first defined point on the blood pressure measuring device and the second defined point on the reference position determining part is at most 30 mm, preferably at most 20 mm.

[0030] According to a particularly advantageous embodiment, the trigger signal is triggered inductively, preferably by means of near field communication (NFC), and / or magnetically, for example using a reed switch in the blood pressure measuring device which reacts to a magnet arranged in the reference position determining part.

[0031] For implementing the near field communication, techniques known per se can advantageously be used, for example from the field of wireless payment systems or access control. Thus, according to a preferred embodiment, the reference position determination section can be equipped with a passive HF-RFID tag, which can be read by a reader integrated in the blood pressure measuring device when the distance drops below a threshold value.

[0032] In particular when near field communication is used, it is therefore advantageously possible to provide an identification means for identifying the coding of the reference position determining part. For example, the passive HF-RFID tag can store a code by means of which an associated reader in the blood pressure measuring device identifies the reference position determining part. It can thus be ensured that only reference position determining parts of suitable specifications are used and that the device outputs a warning if an incorrectly specified reference position determining part is connected and / or prevents functionality.

[0033] For technical reasons, there is often a certain distance between the measuring position and the triggering device on the side of the blood pressure measuring device. If the position of the blood pressure measuring device is changed in such a way that the plane through the measuring position and the triggering device on the side of the blood pressure measuring device is tilted relative to the horizontal, the geodetic height of the triggering device on the side of the blood pressure measuring device relative to the measuring position is also shifted.

[0034] Therefore, a change in the position and / or spatial orientation of the blood pressure measuring device relative to the horizontal is preferably detected by means of a suitable position change sensor device. If the position change sensor device detects that the difference in geodetic height between the position change sensor device and the measurement position exceeds a permissible level (i.e. a threshold value), a warning or a corresponding correction value can be output. The position change sensor device can be implemented by means of a position sensor or an acceleration sensor, as is known, for example, from the prior art for determining the spatial orientation of a smartphone.

[0035] The invention can be used particularly advantageously if the blood pressure measuring device has a finger sensor, since it is here that the difference in geodetic height between the heart and the measuring location can be particularly large and can change easily.

[0036] In particular, the blood pressure measuring device may advantageously include the following:

[0037] – a radiation source for emitting near infrared light into the finger through a light emitting surface,

[0038] – a photodetector for detecting the portion of the near-infrared light captured by the light collector surface and not absorbed by the finger,

[0039] - a cuff for receiving a finger, the cuff being assigned to the finger sensor and being fillable with a fluid, and

[0040] – A pressure regulation system for adjusting the fluid pressure in the cuff based on the detected unabsorbed portion of the near-infrared light.

[0041] A blood pressure measuring device equipped in this way can determine the arterial blood pressure in the finger according to the so-called "vascular unloading technique".

[0042] The blood pressure measuring device preferably has a base part and a cuff part including a cuff, which can be connected to the base part without using tools and can be separated from the base part without using tools, and wherein the triggering device is at least partially arranged in the base part. By separating the base part and the cuff part, the cuff part that mainly contacts the patient can be hygienically designed as a disposable item, while the complex measurement and pressure control device can be mainly accommodated in the reusable base part. The reference position determination part can also advantageously be designed as a disposable item.

[0043] According to a preferred embodiment, the device has notification means for visually and / or audibly notifying the user that a calibration measurement has been performed. The medical staff can ensure that the system has been successfully calibrated, for example by means of a light emitting diode arranged on the blood pressure measuring device, a tone generator accommodated in the blood pressure measuring device, or via another output device, such as a display of a patient monitor connected to the blood pressure measuring device. Thus, the user who initiates the calibration can specifically determine that or when the reference position determination part is brought close enough to the blood pressure measuring device to automatically trigger the calibration measurement.

[0044] According to a preferred embodiment, the device comprises switching means for activating and deactivating the trigger means.Thus, the device can be "focused" to a certain extent before use.

[0045] In principle, each variant of the invention described or indicated in the context of this application can be particularly advantageous, depending on the economic, technical and possible medical conditions in each individual case. Unless otherwise indicated or as long as it is technically feasible in principle, the individual features of the described embodiments can be exchanged or combined with each other and with features known per se from the prior art.

[0046] In particular, the device for determining the static pressure difference between a measuring position and a reference position can in principle be embodied as is known from the prior art.

[0047] The invention is explained in more detail below by way of example with reference to the accompanying schematic drawings. The drawings are not drawn to scale; in particular, for the sake of clarity, the relationships between the individual dimensions do not necessarily correspond to the dimensional relationships in actual technical embodiments. In the various figures, corresponding elements are identified by the same reference numerals. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 The general arrangement of the device according to the invention is schematically shown, wherein the position of the reference position determining part is shown once in the measuring configuration (solid line) and once in the calibration configuration (dashed line).

[0049] Figure 2 Schematically shows another device according to the invention in a calibration configuration, similar to Figure 1 The device shown.

[0050] Figure 3a Shows the horizontal support Figure 2 The device is a pressure measuring device.

[0051] Figure 3b Shown in a tilted state Figure 2 The device is a pressure measuring device.

[0052] Figure 4a Shows Figure 3a Side view of the pressure measuring device shown.

[0053] Figure 4b Shows Figure 4a Front view of the pressure measuring device (from Figure 4a center left).

[0054] Figure 5 Shows Figure 4b , in which the photoplethysmography components are schematically depicted. DETAILED DESCRIPTION

[0055] Figure 1The device shown comprises a blood pressure measuring device 1 and a reference position determining part 2 which is attached in the measuring configuration in the vicinity of the heart 3, as close as possible to the left ventricle 4 or the aorta 5 of a patient 6 which is regarded as a reference position, for example fixed to the skin of the patient 6. As is basically known from the prior art, the device measures a pressure difference ΔP resulting from a geodetic height difference h between the reference position determining part 2 and the blood pressure measuring device 1 located in the vicinity of the measuring position, for example using a pressure sensor arranged on one side of the blood pressure measuring device or pressure sensors arranged on both ends of the liquid column with the aid of a liquid column between the blood pressure measuring device 1 and the reference position determining part 2, in order to correct the blood pressure P measured by the blood pressure measuring device 1.

[0056] In the example shown, the measuring location 7 is located on a finger 9 of the patient 6 , which is enclosed by the cuff part 8 .

[0057] In order to calibrate the differential pressure measurement to a (nearly) zero geodetic height difference, the reference position determination part 2 is brought so close to the blood pressure measurement device 1 that a calibration signal is triggered if a minimum distance between two corresponding points defined on the reference position determination part 2 and the blood pressure measurement device 1 is not reached. These points can advantageously be marked on the respective housings of the reference position determination part 2 and the blood pressure measurement device 1, so that the operator can simply be instructed to bring the marked points closer together for calibration, for example to a distance of at most 3 cm, at most 2 cm or at most 1 cm as a threshold, whereby the triggering device responds with the output of a trigger signal.

[0058] A control device (not shown) integrated in or connected to the blood pressure measuring device 1 , which preferably has a microprocessor or a microcontroller, carries out the calibration measurement in response to the trigger signal.

[0059] like Figure 2 As shown, in the described example, the triggering means is implemented as an RFID tag 10 on the reference position determination part side and an associated near field communication reader 11 on the blood pressure measurement device side. If the near field communication reader 11 in the blood pressure measurement device 1 detects a correctly encoded RFID tag in the reference position determination part 2, it triggers the calibration signal. A light emitting diode unit (LED unit) 15 indicates to the user the successful triggering of the calibration signal and / or the completion of the calibration measurement.

[0060] The reference position determination part (2) to be attached to the patient is preferably designed as a disposable item, thereby meeting the associated increased sterility requirements. It is connected via a hose connection 12 (at Figure 2The reference position determining part 2 is shown with a dotted line in FIG. 1 ) connected to the blood pressure measuring device so that there is a continuous liquid column between the reservoir 13 in the reference position determining part 2 and the calibration pressure sensor 14 in the blood pressure measuring device 1. The calibration pressure sensor may be a commercially available sensor, such as a piezoelectric, piezoresistive, inductive or capacitive pressure sensor.

[0061] like Figure 3a and 3b As shown, deviations may occur when the blood pressure measuring device 1 is tilted, for example by partially resting on an elevated object 27. In the example shown, the tilt in combination with the distance between the near field communication reader 11 and the correction pressure sensor 14 results in a geodetic height difference Δh which, if the calibration is performed in an inclined position, may distort the measurement correction. Depending on the installation conditions, tilting during the blood pressure measurement may also result in a varying geodetic height difference between the measurement location 7 of the blood pressure measurement and the correction pressure sensor 14. In order to mathematically correct such distortions or to output a warning signal when a threshold tilt angle relative to the horizontal is exceeded, one or more position or position change sensors 16 may be provided in the blood pressure measuring device 1.

[0062] In the example shown, the blood pressure measuring device 1 itself is designed as a photoplethysmographic measuring system which functions according to the so-called "vascular unloading technique". The measuring components can be implemented essentially in a similar manner to the prior art mentioned at the outset. The essential components of the exemplary embodiment described are Figure 4b and especially Figure 5 Draw in Figure 5 Shown in Figure 3a and 4a Front view of the pressure measuring device 1 shown in side view (from Figure 3a and 4a ). Elements arranged within the housing are indicated by dotted lines.

[0063] The cuff part 8 is designed to accommodate two fingers, which makes it possible to measure alternately on the two fingers. For hygienic reasons, the cuff part 8 together with the palm rest 17 is designed as a disposable item, which is detachably attached to the reusable base part 18 by means of a plug-in connection.

[0064] The two inflatable finger cuffs 19a, 19b are connected to a pressure generating and pressure control system 20 via a dispenser 21 and a connection 22 at the interface between the cuff portion 8 and the base portion 18. In an alternative embodiment, the finger cuffs 19a, 19b can also be connected individually to the (optionally corresponding) pressure generating and pressure control system 20 and can thus be controlled individually.

[0065] A light source 23a, 23b and a photodetector 24a, 24b providing near infrared light for each of the two fingers, for example as a light emitting diode, are connected via a respective so-called light pipe 27 (i.e. a light guide not designed as an optical fiber bundle) to an associated light emitting surface 25a, 25b or light collector surface 26a, 26b for coupling the emitted light into the finger tissue or coupling the non-absorbed light out of the finger tissue. At the interface between the cuff part 8 and the base part 18, the cuff part-side and base part-side sections of the light pipe 27 are connected to each other via a detachable optical contact point 28.

[0066] The pressure generation and pressure control system 20 adjusts the cuff pressure according to the signal received by one of the photodetectors 24a, 24b so that the portion of the near infrared light emitted by the associated light source 23a, 23b that is not absorbed by the corresponding finger is kept as constant as possible, i.e. a corresponding pulsating portion of the arterial blood pressure is generated so that the blood volume present in the area of ​​the corresponding finger (and detected plethysmographically by the corresponding light source / detector pair 23a, 24a or 23b, 24b) is kept approximately constant. The counterpressure in the cuff 19a, 19b, which is correspondingly adjusted by the pressure generation and pressure control system 20, is detected by a sensor in the pressure generation and pressure control system 20 as a blood pressure measurement signal and is corrected using a geodesically determined pressure difference from a reference position measured by the calibration pressure sensor 14. The correction value can be output to a patient monitor via a suitable electronic interface.

Claims

1. A method for correcting a blood pressure measurement performed at a measurement location having a geodetic height difference from a reference location defined by the location of a heart (3) of a patient (6), the method comprising: placing the reference position determination section at a geodetic height of the blood pressure measurement device (1) at the measurement position (7) with a deviation of 30 mm or less in terms of geodetic height, When the reference position determination part (2) is positioned substantially at the geodetic height of the blood pressure measurement device (1) at the measurement position (7), a calibration measurement is performed to establish a zero point for the static pressure difference between the reference position and the measurement position (7), placing the reference position determination section (2) at the reference position, When the reference position determination section (2) is placed at the reference position, a static pressure difference between the measurement position (7) and the reference position is determined, using the determined static pressure difference to correct the value of the blood pressure measurement, It is characterized in that The calibration measurement is triggered by a trigger signal exchanged between the reference position determination section (2) and the blood pressure measurement device (1), When the distance between the first defined point on the blood pressure measuring device (1) and the second defined point on the reference position determining part (2) is less than a minimum distance, the trigger signal is automatically triggered, wherein the minimum distance is no more than 30 mm.

2. The method according to claim 1, wherein: The trigger signal is inductively triggered.

3. A method according to any one of the preceding claims, wherein: A change in the position and / or spatial orientation of the blood pressure measuring device (1) relative to the horizontal direction is detected.

4. The method according to claim 2, wherein: The trigger signal is by means of near field communication, and / or is magnetically triggered.

5. A device for correcting a blood pressure measurement performed at a measurement location (7) having a geodetic height difference from a reference location defined by the location of a heart (3) of a patient (6), the device comprising: a reference position determining portion (2) for attaching to said reference position, a blood pressure measuring device (1) for being placed at the measuring position and for measuring blood pressure, a pressure difference determining device (12, 13, 14) for determining a static pressure difference between a current position of the reference position determining portion and a current position of the blood pressure measuring device (1), calibration means for performing a calibration measurement to establish a zero point for said static pressure differential, and a correction device for correcting the blood pressure measurement using the determined static pressure difference, It is characterized in that The device has a trigger device for automatically triggering the calibration measurement when the distance between the first defined point on the blood pressure measuring device (1) and the second defined point on the reference position determining part (2) is lower than a minimum distance, wherein the minimum distance is not greater than 30 mm.

6. The device according to claim 5, wherein: The trigger device includes a device for detecting electromagnetic induction between a first induction device arranged in the reference position determining part and a second induction device arranged in the blood pressure measuring device, and / or a device for detecting magnetic force between a first magnetic device in the blood pressure measuring device and a second magnetic device in the reference position determining part.

7. The device according to claim 6, wherein: The triggering device includes a near field communication device (10, 11) for performing near field communication between the reference position determining section (2) and the blood pressure measuring device (1).

8. The device according to claim 7, wherein: The near field communication device comprises an identification device for identifying the code of the reference position determination part (2).

9. The device according to any one of claims 5 to 8, wherein: The blood pressure measuring device (1) comprises a position change sensor device for detecting changes in the position and / or spatial orientation of the blood pressure measuring device (1) relative to the horizontal direction.

10. The device according to any one of claims 5 to 8, wherein: The blood pressure measuring device has a finger sensor.

11. The device according to claim 10, wherein: The blood pressure measuring device comprises: a radiation source (23a, 23b) for emitting near infrared light into a finger through a light emitting surface (25a, 25b), a photodetector (24a, 24b) for detecting the portion of the near infrared light captured by the light collector surface (26a, 26b) and not absorbed by the finger, a cuff (19a, 19b) for receiving a finger, the cuff (19a, 19b) being assigned to the finger sensor and being fillable with a fluid, and A pressure regulating system is provided for regulating the fluid pressure in the cuff (19a, 19b) according to the detected non-absorbed portion of the near infrared light.

12. The device according to claim 11, wherein The blood pressure measuring device comprises a base part (18) and a cuff part (8) including the cuff (19a, 19b), wherein the cuff part (8) can be connected to the base part (18) without using tools and can be separated from the base part (18) without using tools, and wherein the trigger device is at least partially arranged in the base part (18).

13. The device according to any of claims 5-8, further comprising notification means (15) for visually and / or audibly notifying a user that a calibration measurement has been performed.

14. The device according to any one of claims 5 to 8, further comprising a switching device for activating and deactivating the trigger device.

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