METHOD FOR MEASURING THE INTERNAL PRESSURE OF A COMPARTMENT

Description

[0001] The invention relates to a method for measuring an internal pressure of a compartment, in particular a muscle compartment, in which an ultrasonic measuring unit coupled to a pressure measuring device is placed on a tissue under which the compartment to be measured is located and a pressure on the tissue is increased by exerting a force.

[0002] A method of the type mentioned above is known from WO2019 / 106535 A1. In this known method, an ultrasound measuring unit coupled to a pressure measuring device is placed on a tissue beneath which the compartment to be measured is located. The pressure on the tissue is increased until the ultrasound measurement indicates that the compartment reaches a predetermined degree of deformation. The pressure in the compartment is determined via the pressure measuring device based on the elasticity present at this time.

[0003] The article RM Sellei et al: «Assessment of elevated compartment pressures by pressure-related ultrasound: a cadaveric model", European Journal of Trauma and Emergency Surgery, Springer, Berlin / Heidelberg, Vol. 41, No. 6, 25 September 2014, also describes such a procedure.

[0004] US 2007 / 270720 A1 (WR Fry) also concerns the internal pressure determination of I <ompartmenten, z. B. der Zentralvene. Dabei wird das Kompartment mit einem äusseren Druck beaufschlagt, bis es kollabiert. Der notwendige äussere Druck ist dann ein Mass für den Innendruck.

[0005] In this context, the term "compartment" refers to an anatomically defined space that can be separated from the surrounding environment. In addition to muscle compartments, the abdominal cavity, for example, also represents a compartment.

[0006] CH 707046 B1 discloses a further pressure measuring device for measuring the pressure of a vein or organ, for combination with an ultrasound measuring unit, and a method for measuring the pressure of a vein. In this method, a pressure measuring device is placed on a tissue beneath which the vein or organ is located. The pressure on the tissue is increased until the ultrasound measurement indicates that the vein or organ reaches a predetermined degree of deformation. The pressure prevailing at this time is determined by the pressure measuring device as the venous pressure or organ pressure.

[0007] Based on this, the present invention is based on the object of developing a method for measuring an internal pressure of a compartment in such a way that a fast and cost-effective, non-invasive measurement of the pressure within a compartment, in particular a muscle compartment (so-called compartment syndrome), can be carried out.

[0008] The object is achieved according to the invention, inter alia, in that the internal pressure is determined from a change Δp of the pressure p acting on the compartment and a change ΔE of an extension E(p) of the compartment occurring during the action of the pressure p.

[0009] The internal pressure is determined as the pressure p at which the change ΔE of the extension in the form of a decrease in the extension E(p) due to the change Δp of the pressure p in the form of an increase in the pressure p reaches or exceeds a defined threshold value SW for the first time.

[0010] In other words, there is a correlation between the decrease in extension and the pressure p acting on the compartment, whereby the pressure p at which the decrease reaches or exceeds a defined threshold corresponds to the internal pressure.

[0011] According to the invention, during the application of the force F to the tissue, the pressure p and the extension E(p) of the compartment in the direction of the force F are measured simultaneously.

[0012] The change ΔE of the extension E(p) for a defined change Δp of the pressure p is determined by comparing the measured extension E(p) with an initial extension E0 or by comparing two consecutive measured values ​​of the extension E(p), whereby the measured pressure p at which the measured extension E(p) falls below the initial extension E0 or the immediately previously measured extension E(p) for the first time by the threshold value is determined as the internal pressure.

[0013] Preferably, the threshold value SW of the decrease in the extension is in the range of 0% < SW ≤ 10%, preferably in the range of 1% ≤ SW ≤ 8%, particularly preferably in the range of 3% ≤ SW ≤ 6%, in particular in the range of 4% relative to the initial extension E0 or relative to a measured value immediately preceding the measured extension.

[0014] Particularly preferably, at the beginning of a measurement, i.e. without exerting a force F on the compartment, the initial extension E0 is defined by pixels BP1, BP2 in an ultrasound image of the compartment, wherein the force F is subsequently introduced and preferably continuously increased and wherein the change in the extension E(p) as a function of the pressure p is continuously recorded from the recorded ultrasound images by means of an image processing unit.

[0015] Preferably, the extension E is defined by a distance of at least two pixels B1, B2 in an ultrasound image B of the compartment generated by the ultrasound measuring unit. The pixels B1, B2 are preferably defined by a user as substantially diametrically opposite each other on a border, such as the compartment skin.

[0016] The force F is continuously increased during a measurement, preferably aligned with the image points B1, B2 in the direction of the extension E.

[0017] The extension E, which changes during the examination movement, is determined in the ultrasound image B by means of an image processing unit and is continuously plotted against the measured pressure p to determine the graph or curve.

[0018] Further details, advantages and features of the invention emerge not only from the claims and the features derived therefrom - individually and / or in combination - but also from the following description of preferred embodiments derived from the drawings and their explanations.

[0019] They show: Fig. 1 a schematic representation of a measuring system with a pressure measuring device and an ultrasound measuring unit, Fig. 2a an ultrasound image of a muscle compartment without compression, Fig. 2b an ultrasound image of a muscle compartment with compression, Fig. 3 a pressure-displacement diagram with graphs of an examination movement of a muscle compartment at rest on the one hand and of a muscle compartment under tension on the other hand, and Fig. 4 a pressure-displacement diagram with a graph of a further examination movement of a compartment.

[0020] Fig. 1 shows a measuring system 10 for performing ultrasound and pressure measurements on a compartment 12, in particular a muscle compartment 12. The measuring system 10 comprises a known measuring device 14 with a pressure measuring device 16 coupled to an ultrasound measuring unit 18. The pressure measuring device 16 is coupled to a pressure evaluation unit 22 via a communication connection 20, and the ultrasound measuring unit 18 is coupled to an image processing unit 26 via a communication connection 24.

[0021] The image processing unit 26 and the pressure evaluation unit 22 are coupled to a data processing unit 28, which is designed to display the data provided by the image processing unit 26 and the pressure evaluation unit on display units 30, 32.

[0022] The method according to the invention is carried out as follows. The pressure measuring device 16, together with the ultrasound measuring unit 18, is placed on a skin surface 34 of the patient in the region of the compartment 12, optionally using contact gel. For example, a linear transducer from General Electric in combination with an ultrasound-permeable pressure measuring device 16 from VeinPress can be used as the ultrasound measuring unit 18.

[0023] Fig. 2a shows, purely schematically, an ultrasound image of compartment 12 at the beginning of a cross-sectional measurement. In the ultrasound image, an examiner marks pixels BP1, BP2 essentially diametrically opposite each other, preferably on a border 36, such as the foveal skin or fascia, of compartment 12. The pixels mark an extension E in the form of an initial extension E0 at the beginning of the examination, i.e., without compression.

[0024] Using the pressure measuring device 16, a force F is then applied to the tissue, e.g., the skin surface 34 of a lower leg. The force F is introduced into the compartment 12 in alignment with the image points BP1, BP2 and continuously increased. The force F exerts a continuously increasing pressure P on the compartment 12, which is measured by a pressure sensor 38 of the pressure measuring device 16.

[0025] Fig. 2b shows an ultrasound image of the muscle compartment 12 in cross-section during compression, ie, when the examiner exerts pressure p on the tissue. The extension E(p) changes depending on the pressure p and is continuously recorded by the image processing unit 26. For each measured value of the pressure p, an extension E(p) is measured and displayed as a graph against the pressure p.

[0026] Fig. 3 und 4 show pressure-displacement diagrams 40, in which graphs 42, 44, 50 of measurements on different muscle compartments are shown.

[0027] According to the invention, the internal pressure ICP1, ICP2 is determined from a change Δp of the pressure p acting on the compartment 12 and a change ΔE of an extension E(p) of the compartment 12 occurring during the action of the pressure p.

[0028] The internal pressure is determined as the pressure p at which the change ΔE of the extension in the form of a decrease in the extension E(p) due to the change Δp of the pressure p in the form of a preferably defined increase in the pressure p reaches or exceeds a defined threshold value SW for the first time.

[0029] In other words, there is a correlation between the decrease in extension and the pressure p acting on the compartment, whereby the pressure p at which the decrease reaches or exceeds a defined threshold corresponds to the internal pressure.

[0030] According to the invention, it is provided that during the application of the force F to the tissue, the pressure p and the extension E(p) of the compartment in the direction of the force F are measured simultaneously.

[0031] Preferably, the change ΔE of the extension E(p) at a defined change Δp of the pressure p is determined by comparing the measured extension E(p) with an initial extension E0 according to Fig. 3 or by comparing two consecutive measured values ​​of the extension E(p3) and E(p4) according to Fig. 4 The measured pressure p at which the measured extension E(p) falls below the initial extension E0 or the immediately previously measured extension E(p) for the first time by the threshold value is determined as the internal pressure. The defined change Δp in the pressure p at which the change ΔE in the extension E is determined is preferably in the range 0 < Δp ≤ 10 mmHg.

[0032] Preferably, the threshold value SW of the decrease in the extension is in the range of 0% < SW ≤ 10%, preferably in the range of 1% ≤ SW ≤ 8%, particularly preferably in the range of 3% ≤ SW ≤ 6%, in particular in the range of 4% relative to the initial extension E0 or relative to a measured value immediately preceding the measured extension.

[0033] Graph 42 shows, by way of example, the course of a relative extension Erel (p) = (E (p) × 100) / E0, which can also be referred to as the relative compartment depth, versus the compression pressure p of a resting muscle, i.e. of a muscle compartment or muscle box at rest with low internal pressure. Graph 42 shows the special feature that the relative extension Erel (p) in the case of a resting muscle is essentially constant up to a pressure ICP1 and drops from that pressure on. Studies have shown that the measured pressure p1 at which Graph 42 first drops is an internal pressure ICP1 of the muscle compartment, which can also be referred to as an intracompartmental pressure ICP1.

[0034] Graph 44 shows, by way of example, the course of a relative extension Erel (p) of a tensed muscle, i.e., a muscle compartment or muscle compartment with an increased internal pressure. According to one aspect of the invention, the measured pressure p2 is determined as the internal pressure or intracompartmental pressure ICP2 of the muscle compartment 12 at which the relative extension Erel (p) first drops.

[0035] To determine the relative extension Erel(p), the extension E(p) determined from the ultrasound image by the image processing unit 26 is continuously compared with the initial extension E0. The pressure p1, p2 at which the measured extension E(p) falls below the initial extension E0 by at least 4%, preferably 1% to 2%, is determined as the intracompartmental pressure ICP1, ICP2.

[0036] Fig. 4 shows a graph 50 of a further measurement, where the graph 50 is S-shaped and a defined drop in the relative extension, as shown in Fig. 3 is not definable. For example, if graph 50 shows the course of a circle's circumference in sections, an I <reis 52 mit Radius 54 an den Grafen 50 angepasst werden. In diesem Fall kann der Druck p, bei dem der Radius 54 in 45° Stellung bezogen auf die Abszisse (horizontale Achse - Druck p) den Grafen 50 trifft, als der Innendruck ICP3 bestimmt werden.

[0037] The invention is based on the idea that the relative extension or compartment depth initially remains unchanged during the application of pressure. A plateau forms, as can be seen in graphs 42, 44, and 50. As the pressure on the compartment increases, the compartment becomes increasingly harder. Only above a certain pressure p1, p2, p3, which corresponds to the intracompartmental pressure ICP1, ICP2, ICP3, does the relative extension Erel decrease.

[0038] According to the state of the art, the elasticity in the compartment is determined using an elasticity quotient. It has been found that the elasticity quotient is subject to high inter-individual fluctuations, which makes interpretation difficult. The method according to the invention differs from the prior art methods in that the determination of an elasticity quotient—that is, the ratio between the deformation of healthy tissue and the deformation of diseased tissue—is not necessary. In particular, the non-invasive derivation of a pressure value is medically advantageous.

Claims

1. Method for measuring an internal pressure (ICP1, ICP2) of a compartment (12), in particular a muscle compartment, in which an ultrasonic measuring unit (18) coupled to a pressure measuring device (16) is placed on a tissue (34), under which the compartment (12) to be measured is located, and a pressure p on the tissue (12) is increased by exerting a force F, characterized in that the pressure p and the extension E(p) of the compartment (12) extending in the direction of the force F are measured simultaneously during the exertion of the force F on the tissue (34), in that the change ΔE in the extension E(p) in the event of a defined change Δp in the pressure p is determined by comparing the measured extension E(p) with an initial extension E0 or by comparing two successive measured values of the extension E(p) and in that the internal pressure (ICP1, ICP2) is determined from a change Δp in the pressure p acting on the compartment (12) and a change ΔE in an extension E(p) of the compartment (12) occurring during the action of the pressure p, wherein the internal pressure (ICP1, ICP2) is determined as the pressure p at which the change ΔE of the extension in the form of a decrease in the extension E(p) by the change Δp of the pressure p in the form of an increase in the pressure p reaches or exceeds a defined threshold value SW for the first time.

2. Method according to claim 1, characterized in that the threshold value SW is in the range of 0 % < SW < 10 %, preferably in the range of 1 % < SW < 8 %, particularly preferably in the range of 3 % < SW < 6 %, especially in the range of 4 % in relation to the initial extension E0 or in relation to a measured value immediately preceding the measured extension.

3. Method according to at least one of the preceding claims, characterized in that at the beginning of a measurement, i.e. without exerting a force F on the compartment, the initial extension E0 is defined by image points (BP1, BP2) in an ultrasound image of the compartment (12), that subsequently the force F is introduced and preferably continuously increased, and that the change in the extension E(p) as a function of the pressure p is continuously recorded from the ultrasound images by means of an image processing unit (26).

4. Method according to claim 3, characterized in that the image points (BP1, BP2) on a border, such as a fascia, of the compartment (12) are defined essentially diametrically opposite one another by a user.

5. Method according to claim 3 or 4, characterized in that the force F is continuously increased in the direction of the extension E during a measurement, preferably in alignment with a line connecting the image points (BP1, BP2).

6. Method according to claim 3 or 4, characterized in that the extension E, which changes during the measurement, is determined in the ultrasound image by means of the image processing unit (26) and is continuously plotted over the measured pressure p.