Non-invasive blood pressure measurement device

Abstract

The invention relates to a measuring device for continuously determining the intra-arterial blood pressure in two fingers of a hand, the measuring device comprising a base part and a cuff part which can be connected to the base part without using tools. A light source (23a, 23b) and a light detector (24a, 24b) for near-infrared light are provided for each of the two fingers, the light source and the light detector being arranged on a common circuit board (4). By means of respective light guides (27) (i.e., light guides not in the form of a fiber bundle), the light source (23a, 23b) and the light detector (24a, 24b) are connected to an associated light-emitting surface (25a, 25b) and an associated light-collecting surface (26a, 26b), respectively, in order to couple the emitted light into the finger tissue or decouple the unabsorbed light from the finger tissue, respectively. At the interface between the cuff part (8) and the base part (18), the cuff part section and the base part section of the light guide (27) are connected to each other by means of separable optical contact points (28). On the base part, a cover glass (29) (e.g., mineral glass or sapphire glass) flush with the housing (2) of the base part (18) and as scratch-resistant as possible is mounted at each contact point.

Description

Technical Field

[0001] The present invention relates to a non-invasive blood pressure measuring device, in particular a measuring device for continuously determining the intra-arterial blood pressure on at least one finger of a hand. Background Art

[0002] The (arterial) blood pressure of a patient is one of the most important measured variables in medical technology, and the associated known measuring techniques, especially non-invasive measuring techniques, are extremely diverse. This applies in particular to measuring techniques for continuously monitoring blood pressure over a longer period of time (e.g., in intensive care medicine), but also to emergency medicine and during surgical operations.

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

[0004] In the vascular unloading technique, near-infrared light is radiated into the finger, and the pulsatile (pulse-shaped) blood flow (actually the changing blood volume) in the finger is determined based on the unabsorbed portion captured by a light detector. For this process, also known as photoplethysmography (PPG), (near-infrared) light is typically generated by one or more light-emitting diodes (LEDs) operating at one or more wavelengths and detected by one or more photosensitive receiver diodes (photodiodes). Other types of light receivers are also basically suitable to replace the diodes.

[0005] Then, the control system keeps the flow rate recorded by plethysmography (or the detected blood volume) and thus the generated photoplethysmogram signal (volume signal v(t)) constant by applying a counter-pressure in a cuff (cuff pressure) pc(t) on the finger. This counter-pressure pc(t) is usually regulated by a fast valve or a valve system together with a pump. The relevant control of the valve or valve system is performed by a control unit, which is preferably implemented with a microcomputer. The main input signals are the PPG signal v(t) and the cuff pressure pc(t). The pressure pc(t) required to keep the PPG signal v(t) constant then corresponds to the intra-arterial blood pressure pa(t).

[0006] For this purpose, it must be possible to change the cuff pressure pc(t) at least as fast as the change in the arterial blood pressure pa(t), such that the real-time condition is met. The upper limit frequency of pa(t) and thus the highest pressure change rate are at least greater than 20 Hz, which is undoubtedly a challenge for the pressure control system. As a result, the pressure control by means of a valve or valve system is advantageously located in the immediate vicinity of the cuff. If the air line is too long, there is a risk of losing this upper limit frequency condition due to the low-pass effect of the line.

[0007] A mechanical valve is known from US Patent No. 4,406,289, which regulates the counter-pressure in a finger cuff with the required precision when it is supplied with a linear pump. The valve is accommodated in a housing on the distal forearm and thus supplies the pressure pc(t) to the finger cuff via a short tube.

[0008] US Patent No. 4,524,777 describes a pressure generation system for vascular unloading techniques, where a constant cuff pressure Pc is also generated with a linear pump, and this pressure Pc is superimposed with the pressure fluctuations Δpc(t) from a vibrator or drive actuator connected in parallel.

[0009] US Patent No. 4,726,382 discloses a finger cuff for vascular unloading techniques, which has a hose connection for supplying the cuff pressure pc(t). The length of the air tube extends to the pressure generation system, which in turn is attached to the distal forearm.

[0010] WO 2000 / 059369 A1 also describes a pressure generation system for vascular unloading techniques. The valve system here consists of a separate inlet and a separate outlet valve. While relatively linear proportional pumps had to be used in US Patent No. 4,406,289 and US Patent No. 4,524,777, this system allows the use of simple and inexpensive pumps because the destructive harmonics can be eliminated by the valve arrangement. In addition, the energy consumption of the simple pump can be significantly reduced by the valve principle.

[0011] WO 2004 / 086963 A1 discloses a system for vascular unloading techniques, where the blood pressure can be continuously determined in one finger while the measurement quality (watchdog function) is checked in an adjacent finger. After a while, the system automatically replaces the measuring finger with the monitoring finger.

[0012] WO 2005 / 037097 A1 describes a control system for vascular unloading techniques, which has several interconnected control loops.

[0013] WO 2010 / 050798 A1 discloses a pressure generation system (front end) attached to the distal forearm, which has only one valve, to which a finger cuff for vascular unloading techniques can be attached.

[0014] Using the pressure generation system for vascular unloading techniques described in WO 2011 / 045138 A1, the energy consumption of the pump is reduced - similar to WO2000 / 059369 - and harmonics can be eliminated.

[0015] WO 2011 / 051819 A1 discloses an embodiment of a vascular unloading technique that has been improved with digital electronics to increase stability and further miniaturization.

[0016] WO 2011 / 051822 A1 describes a method for vascular unloading techniques in which the measured signals v(t) and pc(t) are processed to increase long-term stability and determine further hemodynamic parameters. In particular, a method for eliminating the effects caused by vasomotor changes in finger arteries and a method for determining cardiac output (CO) are disclosed.

[0017] WO 2012 / 032413 A1 describes novel finger sensors having a disposable part for single use. For hygienic reasons, the cuff that contacts the finger is housed in the disposable part, while the associated pressure generation and pressure control systems are housed in a reusable part. Therefore, in this case, a separable pneumatic connection must be provided between the disposable part and the reusable part.

[0018] Typically, the pressure generation and pressure control systems in the prior art are attached to the distal forearm, near the wrist, which has significant drawbacks: this point is often used for intravenous injections; in addition, the arterial access at the distal end of the radial artery should be patent in case of emergency. The pressure generation and pressure control systems and their attachments can block these accesses. Additionally, the system may slide or tilt during operation. This can have an adverse effect on the fit of the sensor. The fit of the sensor is also improved if the finger or the corresponding hand to be measured is in a certain static position.

[0019] To overcome this problem, the published WO 2017 / 143366 A1 proposes a measurement system for continuously determining the intra-arterial blood pressure on at least one finger of a hand. The measurement system has at least one finger sensor, a plethysmography system, at least one light source (preferably an LED having one or more wavelengths), at least one light sensor, and at least one inflatable cuff, as well as a pressure generation system having at least one valve that is adjusted in real time by means of the plethysmography system for generating a pressure in the cuff that is substantially corresponding to the intra-arterial blood pressure in the finger, wherein the measurement system has a housing having a surface that serves as a support surface for the at least one finger and the adjacent region of the palm. Here, the hand rests on a support, and under the support there are basic components that are attached to the forearm in a conventional system.

[0020] Similar to the previously mentioned WO 2012 / 032413A1, the cuff is accommodated in a disposable part that can be separated from the housing (and thus from the hand support). Therefore, in this case, a separable pneumatic connection must be provided between the disposable part and the reusable part.

[0021] In known systems, light-emitting diodes and photodiodes (possibly embedded in transparent silicone resin) for emitting and detecting near-infrared measurement radiation are arranged directly on the finger. When the light-emitting diodes and photodiodes are arranged in the reusable part, the problem is that the exposed light-emitting elements must be cleaned and disinfected before they can be reused. The need for an easily cleanable design limits the degree of freedom in design. Otherwise, the need to accommodate the light-emitting diodes and photodiodes in the immediate vicinity of the finger represents a limitation on the geometric configuration of the device. On the other hand, when the light-emitting diodes and photodiodes are arranged in the disposable part, the problem is that an electrical connection must be provided between the disposable part and the reusable base unit, and the production cost of the disposable part increases. The input of heat is also considered negative when the electrical components are in contact with the skin. Summary of the Invention

[0022] In view of the limitations existing in conventional systems, the object of the present invention is to improve the measurement device of the type mentioned at the beginning with regard to production and use.

[0023] According to one aspect of the present invention, this object is achieved by the device according to claim 1.

[0024] Preferred embodiments of the present invention can be implemented according to any of the dependent claims.

[0025] Accordingly, the present invention particularly provides a measuring device for continuously determining the intra-arterial blood pressure on at least one finger of a hand, the measuring device having a base part and a cuff part, the cuff part being connectable to the base part without using tools and detachable from the base part without using tools, the measuring device being preferably designed as a disposable article, and further providing: a radiation source for emitting light into a finger through a light-emitting surface; a light detector for detecting a portion of the light captured by a light-collecting surface and not absorbed in the finger; a cuff for receiving the finger disposed in the cuff part, the cuff part being fillable with a fluid (usually a gas, such as air, although embodiments with a liquid as the fluid are also advantageously possible); and a pressure control system at least partially disposed in the base part for controlling the fluid pressure in the cuff based on the detected non-absorbed portion of the light. In this case, the radiation source and / or the light detector are disposed in the base part, and a corresponding non-fiber optical waveguide connection (so-called light guide) is provided between the radiation source and / or the light detector disposed in the base part and the light-emitting surface or the light-collecting surface, the optical waveguide connection being at least partially disposed in the cuff part, and the corresponding optical waveguide connection member being detachable from the base part together with the cuff part and having a light contact point for coupling light from the base part into the cuff part or decoupling light from the cuff part into the base part.

[0026] In the present application, according to the usual definition, light is understood as electromagnetic radiation in the infrared, visible, and ultraviolet ranges. For typical photoplethysmography applications, this is usually near-infrared light (wavelength of approximately 700 to 1100 nm). In principle, light of different wavelengths can be used, particularly for integrating additional functions, such as measuring oxygen saturation, detecting fluorescent dyes, etc.

[0027] The light guide can be made of different glass materials, such as fused silica, or can also be made of suitable transparent plastics, such as PMMA and polycarbonate. In particular, they can be cast and possibly ground, and those skilled in the art can select the material according to the conditions in each case (optical quality, power of the radiation source or sensitivity of the light detector, material cost, biocompatibility, anti-aging property, particularly yellowing resistance, abrasion resistance, etc.). For production, depending on the material, those skilled in the art can utilize a series of suitable processing techniques, such as ultra-precision machining, glass grinding, etc.

[0028] By providing suitable reflective surfaces within the geometry of the light guide, the person skilled in the art can optimize the light beam path towards directed and loss-optimized light transmission. The light guide geometry can advantageously be individually adapted to different sizes of cuff parts. The person skilled in the art has obtained degrees of freedom in the design, which enables, for example, the use of cuff parts of different sizes for a child's hand and an adult's hand with the same base part. The angle of incidence and the light beam profile (divergence / convergence) can be adjusted according to the anatomy. The exact arrangement of the light source and the light detector is no longer determined by the anatomy. The cuff part can thus have different sizes, where it is possible that the distance between the light guides in the base part or the distance between the light source and the light detector in the base part remains constant.

[0029] Due to the fact that the radiation source and / or the light detector are arranged in the (reusable) base part, the production costs of the cuff part, which is preferably designed as a disposable article, can be kept low. Accordingly, when using a disposable cuff part, the cost per patient can be reduced.

[0030] By avoiding placing electronic components near or directly on the skin, biocompatibility can be improved. The heat input to the tissue can be significantly reduced.

[0031] Preferably, the radiation source and the light detector are arranged in the base part, and a corresponding non-fiber-optic light guide connection is provided, which is at least partially arranged in the cuff part, both between the radiation source arranged in the base part and the light-emitting surface, and between the light detector and the light-emitting surface.

[0032] Thus, the device can advantageously be implemented in such a way that there is no electrical connection between the base part and the cuff part. However, the cuff part can have electronic components for wirelessly identifying the cuff part, such as RFID tags, so that the associated interrogation element in the base part can ensure that only a suitable cuff part is used during operation. Similarly, the components for identifying the cuff part can advantageously be used to prevent the reuse of cuff parts designed as disposable components.

[0033] Eliminating the electrical contact between the base part and the cuff part can increase both the safety of the patient and the functional reliability.

[0034] Alternatively, the cuff part can advantageously have electronic components for identifying the cuff part and an interface for interrogating the electronic components as a single electrical connection between the base part and the cuff part.

[0035] According to a preferred embodiment, the radiation source and the optical detector can be arranged on a common circuit board. A driver switch for the radiation source is also particularly advantageous on the board, and / or an amplifier circuit can be arranged for the optical detector. Due to the typically low currents in the μA range, short line lengths between the photodiode (optical detector) and the amplifier circuit are particularly advantageous, which, in addition to cost-effective production and a compact design, can also be said to facilitate the provision of corresponding electronic components on the common circuit board.

[0036] At least one lens can be advantageously provided, or a lens geometry can be integrated at the transition between the radiation source and the associated optical waveguide connection and / or between the optical detector and the associated optical waveguide connection.

[0037] The optical contact points for coupling light from the base part into the cuff part and / or for decoupling near-infrared light from the cuff part into the base part can also be advantageously provided with at least one lens, or the lens geometry can be integrated into the optical waveguide at the transition.

[0038] According to an advantageous refinement, the optical contact points for coupling light from the base part into the cuff part and / or for decoupling light from the cuff part into the base part are provided with at least one cover glass.

[0039] According to a further advantageous refinement, the light-emitting surface and / or the light-collecting surface are equipped with a Fresnel structure for the directional coupling-in and coupling-out of the radiation to be measured.

[0040] The arrangement with an optical waveguide according to the invention provides the possibility of taking further technical measures to improve or adjust the light transmission path, in particular the coating of the reflective surface of the optical waveguide, for example, in particular, by vapor deposition or sputtering of a metal such as silver or gold. More advantageously

[0041] - A diffraction grating can be provided in the optical waveguide to influence the light path,

[0042] - The light transmission of interfaces, in particular contact surfaces such as emission surfaces, collector surfaces, contact points, can be improved, for example, by an anti-reflection coating made of silica,

[0043] - A band-pass filter can be introduced into the light beam path by coating the coupling surface or the collector surface,

[0044] - The optical waveguide can be coated with a material that is impermeable in the decisive wavelength range and suitable for preventing crosstalk.

[0045] To prevent crosstalk between the radiation source and the optical detector, for example, an infrared blocker can be placed between the two components. The radiation blocker in the housing can also prevent radiation from the environment from reaching the detector. This is an advantage of the installation position of the optical detector inside the base part.

[0046] In principle, each variant of the invention described or indicated in the context of the present application can be particularly advantageous, depending on the economic, technical and possible medical conditions in each case. Unless otherwise stated, or as long as technically feasible in principle, the individual features of the described embodiments can be exchanged or combined with one another, as well as combined with features known from the prior art.

[0047] In particular, the technical principles for establishing and regulating pressure in the cuff can in principle be designed according to those known from the prior art.

[0048] The invention will now be explained in more detail by way of example with reference to the accompanying schematic drawings. The drawings are not drawn to scale; in particular, the relationships between the various dimensions do not necessarily correspond to the dimensional relationships in actual technical embodiments for the sake of clarity. In the various drawings, corresponding elements are identified by the same reference numerals. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 The device according to the invention is schematically shown in a side view, with the patient's hand placed on the device.

[0050] Figure 2 Shows the same device as Figure 1 , but without the hand and in a front view, i.e., viewed from the left side of Figure 1 .

[0051] Figure 3 Shows Figure 2 in an enlarged view, in which the photoplethysmography component is schematically depicted.

[0052] Figure 4a Shows the device as shown in Figure 1 , but without the hand, and with cross-sectional plane markings for the representation from Figure 4b .

[0053] Figure 4b Is a cross-sectional view of a cutout of the device shown in cross-sectional plane A-A' from Figure 4a , where the dashed line B-B' of the cutout is also indicated in Figure 3 .

[0054] Figure 5 Similar to Figure 1 and 4a , the base part and the cuff part separated from each other are shown in a side view. DETAILED DESCRIPTION

[0055] The blood pressure measuring device 1 is designed as a photoplethysmographic measuring system operating according to the vascular unloading technique. The measuring components (that is, in particular the electronic components 23a, 23b, 24a, 24b) and the mechanical components of the pressure generation and pressure control system 20 can in principle be implemented analogously to the prior art mentioned at the beginning. The basic components of the described exemplary embodiment are in Figure 2 and in particular Figure 3 and Figure 4b are depicted, which are shown in a front view (from the Figure 1 and Figure 4a left side) or in a sectional view ( Figure 4b ) the blood pressure measuring device 1 shown in a side view in Figure 1 and Figure 4a . In Figure 3 , the elements arranged within the housing 2 of the base part or within the cuff part are indicated by dashed lines.

[0056] The cuff part 8 is designed to accommodate two fingers, which makes it possible to perform measurements alternately on the two fingers. For hygienic reasons, the cuff part 8 together with the palm rest 17 is designed as a disposable article, which is detachably attached to the reusable base part 18 by means of a plug-in connection. Figure 5 Shows the base part and the cuff part separated from each other.

[0057] The two inflatable finger cuffs 19a, 19b are connected to the pressure generation and pressure control system 20 via a distributor 21 and a connecting piece 22 at the interface between the cuff part 8 and the base part 18. In this case, the connecting piece 22 is preferably equipped with a valve (not shown), which closes the connecting piece flush with the housing 2 of the base part on the base part side when the base part 18 and the cuff part 8 are not connected to each other. In an alternative embodiment, the finger cuffs 19a, 19b can also be individually connected to (optionally also the corresponding) pressure generation and pressure control system 20 and can thus be individually controlled.

[0058] For each of the two fingers, a light source 23a, 23b for near-infrared light, for example a light-emitting diode, and a light detector 24a, 24b are provided, which are arranged on a common circuit board 4, which also supports a driver switch (not shown) for the light sources 23a, 23b and an amplifier circuit (not shown) for the light detectors 24a, 24b.

[0059] The light sources 23a, 23b and the light detectors 24a, 24b are connected to the associated light-emitting surfaces 25a, 25b or light-collecting surfaces 26a, 26b for coupling the emitted light into the finger tissue via respective light guides 27 (i.e., light guides not designed as fiber bundles), or for decoupling the unabsorbed light from the finger tissue. The light-emitting and light-collecting surfaces 25a, 25b, 26a, 26b are equipped with Fresnel structures for measuring the directional coupling-in and coupling-out of radiation.

[0060] The light emitted by the respective light sources 23a, 23b is coupled into the respective light guides 27 via respective lenses 3a, 3b.

[0061] The cuff-side and base-section-side segments of the light guide 27 are connected to each other via separable optical contact points 28 at the interface between the cuff section 8 and the base section 18. On the base-section side, a cover glass 29 (e.g., mineral glass or sapphire glass) is attached to the contact point, and the cover glass 29 closes flush with the housing 2 of the base section 18 and is as scratch-resistant as possible.

[0062] The pressure generation and pressure control system 20 adjusts the cuff pressure according to the signal received by one of the light detectors 24a, 24b such that the portion of the near-infrared light emitted by the associated light sources 23a, 23b that is not absorbed in the corresponding finger is kept as constant as possible, i.e., a counter-pressure that varies according to the pulsating portion of the arterial blood pressure is generated and transmitted via the flexible cuff membranes 9a, 9b to the respective fingers such that the blood volume area present in the respective finger regions (and detected by the respective light source-detector pairs 23a, 24a or 23b, 24b by plethysmography) remains approximately constant. The counter-pressure in the cuffs 19a, 19b adjusted accordingly 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 can be output to a patient monitor via a cable 12 via a suitable electronic interface.

[0063] The device 1 is powered via the cable 12.

Claims

1. A measuring device for continuously determining the intra-arterial blood pressure on at least one finger of a hand, having the following: A base part, A cuff part that can be connected to the base part without using tools and can be separated from the base part without using tools, A radiation source for emitting light into the finger through a light-emitting surface, A light detector for detecting the portion of the light captured by a light-collecting surface and not absorbed in the finger, A cuff that is arranged in the cuff part and can be filled with fluid for receiving the finger, and a pressure control system that is at least partially arranged in the base part for adjusting the fluid pressure in the cuff according to the non-absorbed portion of the detected light, Wherein, The radiation source and the light detector are arranged in the base part, The radiation source is connected via a corresponding non-fiber optic light guide that is at least partially arranged in the cuff part and the light-emitting surface, and the light detector is connected via another corresponding non-fiber optic light guide that is at least partially arranged in the cuff part and the light-collecting surface, and Wherein each corresponding light guide connection has a corresponding light contact point that can be separated from the base part together with the cuff part for coupling light from the base part into the cuff part or decoupling light from the cuff part into the base part.

2. The measuring device according to claim 1, Wherein, There is no electrical wire connection between the base part and the cuff part.

3. The measuring device according to claim 2, Wherein, The cuff part has electronic components for wirelessly identifying the cuff part.

4. The measuring device according to claim 1, Wherein, The cuff part has electronic components for identifying the cuff part and an interface for querying the electronic components, as a single electrical wire connection between the base part and the cuff part.

5. The measuring device according to any one of claims 1 to 4, Wherein, The radiation source and the light detector are arranged on a common circuit board.

6. The measuring device according to claim 5, Wherein, A driver switch for the radiation source and / or an amplifier circuit for the light detector are further arranged on the circuit board.

7. The measuring device according to any one of claims 1 - 4, Wherein, At least one lens or lens geometry integrated into the light guide connection is provided at the transition between the radiation source and the associated light guide connection and / or at the transition between the light detector and the associated light guide connection.

8. The measuring device according to any one of claims 1 - 4, Wherein, The light contact point for coupling light from the base part into the cuff part and / or the light contact point for decoupling light from the cuff part into the base part is provided with at least one lens or lens geometry integrated into the light guide connection.

9. The measuring device according to any one of claims 1 - 4, Wherein, At least one cover glass is provided for coupling light from the base portion to the light contact point in the cuff portion and / or for decoupling light from the cuff portion to the light contact point in the base portion.

10. The measuring device according to any one of claims 1-4, wherein the light emitting surface and / or the light collector surface is equipped with a Fresnel structure.

Images