Intracranial catheter for measuring blood flow

Abstract

The invention relates to an intracranial catheter (2) for measuring blood flow through body tissue, comprising a longitudinal body (4) adapted to be inserted into a skull chamber, the device comprises a longitudinal body (4) having a tip element (6) forming a distal end of the longitudinal body (4) and preferably having a channel extending from a proximal end of the longitudinal body (4) to at least one opening (18) of the tip element (6), and a sensor (22) configured to detect a pulsating pressure profile, the pulsating pressure profile is analyzed via a pulse profile analysis performed by a processing unit (44) coupled to the sensor (22).

Description

[0001] The present invention relates to an intracranial catheter for measuring blood flow through body tissue, wherein the intracranial catheter comprises a longitudinal body adapted to be inserted into a skull chamber and having a tip element forming the distal end of the longitudinal body. Such intracranial catheters are known, for example from US 5024226A.

[0002] US 5024226A relates to an intracranial catheter comprising a sensor for determining the oxygen availability of tissue within the skull, wherein the sensor is placed epidurally through the skull to measure the oxygen availability. During neurological and neurological-related surgical procedures, it is often desirable to continuously monitor the oxygenation of blood supplied to the brain. Typically, access to the brain is obtained through a burr hole in the skull, and a sensor that optically measures oxygenation can then be inserted through this burr hole. Then, the optical sensor should exhibit a number of design and performance criteria in order to operate satisfactorily in this environment. The sensor must be able to be inserted through the burr hole so as to contact the tissue to be measured for oxygen availability. The sensor must be soft so that it does not damage the neural tissue, but rigid enough in certain dimensions so that it can be manipulated from outside the skull. It must also be sized to fit within the burr hole and in the position where the measurement is made. In addition, the sensor must be designed so that the detection of ambient light is eliminated, which will interfere with the detection of the desired optical signal. The sensor must also prevent detection of direct transmitted light from the sensor's light source.

[0003] While US 5024226 A focuses on monitoring oxygen availability in cerebral blood flow by optical measurements, the present invention aims at measuring cerebral blood flow (CBF).

[0004] As a solution to the above-mentioned object, the present invention proposes an intracranial catheter for measuring blood flow having the features of claim 1 .

[0005] The intracranial catheter is characterized by a sensor configured to detect a pulsating pressure curve, which is analyzed via a pulse profile analysis performed by a processing unit coupled to the sensor, the sensor preferably comprising a plurality of sensor devices. Since blood volume is proportional to the area under the contraction portion of the pressure curve, analyzing the pulsating pressure curve via pulse profile analysis allows the determination of cerebral blood flow.

[0006] The viscoelastic properties of blood vessels also affect cerebral blood flow. The Moens–Koteweg equation models the relationship between the incremental elastic modulus of the arterial wall and the pulse wave velocity (PWV). PWV in m / s can be measured using the signals of sensor devices by exploiting the distance between them.

[0007] Using absolute CBF measurements, for example by indocyanine green spectroscopy or CT or MRI perfusion measurements, and calculated patient-specific viscoelasticity, the pulse profile algorithm can be calibrated to calculate absolute CBF values, updated for each heartbeat, ie continuously.

[0008] Preferably, the sensor comprises a pressure sensor device configured to detect a pulsating pressure curve. In particular, an absolute pressure sensor, a gauge pressure sensor, a vacuum pressure sensor, a differential pressure sensor or a sealed pressure sensor can be used to detect the pulsating pressure curve. The working principle of the pressure sensor device is not particularly limited by the present invention. For example, an optical pressure sensor can be used. Alternatively or additionally, the pulsating pressure curve can be derived from a light absorption measurement, in particular by using a photoplethysmogram.

[0009] The sensor may be a piezoresistive sensor that uses the piezoresistive effect (ie, a change in resistivity when pressure is applied) to detect a pulsating pressure curve.

[0010] The sensor may be disposed in or on the longitudinal body, and the processing unit may be disposed at a distance from the longitudinal body. For example, the processing unit may be provided by an external device coupled to the sensor for receiving the sensor signal via a cable or wirelessly. However, in one embodiment, the processing unit may be disposed within the longitudinal body.

[0011] Preferably, a channel is formed in the longitudinal body, wherein the channel extends from the proximal end of the longitudinal body to at least one opening of the tip element. The channel can be used as a drainage channel for cerebrospinal fluid. However, in one embodiment of the present invention, the tip element may not have an opening and / or the longitudinal body may not have a channel. The longitudinal body may be formed in a manner similar to or identical to the longitudinal body disclosed in US 5024 226A or WO 2016 / 192958A1, the contents of which are incorporated herein by reference.

[0012] In a preferred embodiment of the intracranial catheter, the sensor comprises an optical sensor device comprising at least one light emitter for emitting light (preferably in the near infrared range) into body tissue and at least one light receiver for receiving light reflected in the body tissue and returned to the longitudinal body and for generating a signal. Preferably, a light source with coherent light in the near infrared range is used, which is able to penetrate biological tissue. It is particularly preferred to specifically use a wavelength suitable for the selected measurement technique. Preferably, light with wavelengths of 690nm, 760nm, 808nm and 905nm is used.

[0013] Typically, indocyanine green is used as an indicator substance in medical diagnostics, which is administered intravenously. The absorption and fluorescence spectra of indocyanine green are in the near-infrared region. Both depend primarily on concentration, and the concentration curve measured by the intracranial catheter depends strongly on blood flow. The optical sensor device is preferably arranged in a groove formed in the longitudinal body and covered by a translucent window. The pressure sensor device can be arranged in a similar groove. These grooves can be formed, and the optical sensor devices and the pressure sensor device can be arranged in a manner similar to or identical to those disclosed in WO 2016 / 192958A1, the contents of which are incorporated herein by reference.

[0014] In a preferred embodiment of the intracranial catheter, the signal generated by the optical receiver contains information about the difference between the oxygenated and deoxygenated hemoglobin concentrations, which signal is processed to monitor continuous cerebral blood flow.

[0015] In a further preferred embodiment, the intracranial catheter comprises a first group of at least two LEDs, wherein a first LED of the first group emits light of a different wavelength than a second LED of the first group, and wherein the LEDs of the first group are adapted to emit light in the near infrared range, and wherein a light receiver adapted to receive reflected light of the first group generates a signal that is processed to monitor cerebral blood flow. Specifically, it is preferred that the first LED of the first group emits light of a wavelength of 808 nm, and the second LED of the first group emits light of a wavelength of 905 nm.

[0016] In a further preferred embodiment, the intracranial catheter comprises a second group of at least two LEDs, wherein a first LED of the second group emits light of a different wavelength than a second LED of the second group, and wherein the LED of the second group is adapted to emit light in the near infrared range, and wherein a light receiver adapted to receive reflected light of the second group generates a signal that is processed to monitor cerebral blood sample saturation. Specifically, it is preferred that the first LED of the second group emits light of a wavelength of 690 nm, and the second LED of the second group emits light of a wavelength of 760 nm or 905 nm.

[0017] In a further preferred embodiment, the intracranial catheter comprises a third group of at least two LEDs, wherein the first LED of the third group emits light of a different wavelength from the second LED of the third group, and wherein a light receiver adapted to receive reflected light of the third group generates a signal, which is processed to monitor brain cytochrome-c-oxidase and / or water content. Specifically, it is preferred that the first LED of the third group emits light of a wavelength of 520 nm, and the second LED of the third group emits light of a wavelength of 550 nm for monitoring brain cytochrome-c-oxidase. Alternatively, the wavelength of the third group of LEDs may be any one of 740 nm, 840 nm and 960 nm for monitoring water content.

[0018] According to the present invention, any one of the first, second and third groups may be provided without providing any of the other groups. However, a combination of any two groups may be provided. Most preferably, the intracranial catheter includes all three groups. In addition, one light receiver may be provided for each group or each LED, or one light receiver may be provided for all groups.

[0019] Further details and advantages of the invention will be gathered from the following description of an embodiment and the accompanying drawings, in which:

[0020] Figure 1 is a side view of an embodiment of an intracranial catheter,

[0021] Figure 2 is an enlarged view of the tip element ( Figure 1 Details in X), and

[0022] Figure 3 is a partial cross-sectional view of an intracranial catheter inserted into the skull chamber and connected to a processing unit.

[0023] like Figure 1 As shown in , the intracranial catheter 2 comprises a longitudinal body 4 having a tip element 6 forming the distal end of the longitudinal body 4. The proximal end of the longitudinal body 4 is provided with a connector 8 comprising a fluid port 10 and a data port 12, wherein the fluid port 10 is connected to the opening of a drainage channel (not shown) formed in the longitudinal body 4, and the data port 12 is configured as an interface for transmitting sensor signals generated by the intracranial catheter 2 to a processing unit. The fluid port 10 is closed via a cover 14, which is fixed to the connector 8 by a retaining band 16. The drainage channel extends from the proximal end of the longitudinal body 4 to a plurality of openings 18 (see Figure 2 ). It allows drainage of surrounding tissues through the intracranial catheter 2.

[0024] The pressure sensor device 20 of the sensor 22 is arranged near the opening 18 of the tip element 6. In addition, the sensor 22 includes an optical sensor device 24, which is: two LEDs 26a, 26b of a first group 26, two LEDs 28a, 28b of a second group 28, two LEDs of a third group (not shown) and a photodetector as a light receiver 30. Although in this embodiment the sensor 22 includes a pressure sensor device and an optical sensor device, in another embodiment the sensor 22 may include only a pressure sensor device or only an optical sensor device and / or more than two LEDs per group and / or one, two or more than three groups of LEDs. In any case, the sensor 22 may additionally include a temperature sensor device. In addition, more than one photodetector may be provided as a light receiver.

[0025] The pressure sensor device 20 and the optical sensor device 24 are arranged in cavities which are formed in the tip element 6 and which are covered in a sealed manner by windows 32, 34, 36. The windows 32, 34 are translucent. If the pressure sensor device 20 is not an optical sensor device, the window 36 does not have to be translucent. The portion of the tip element 6 supporting the optical sensor device 24 and the distal tip supporting the pressure sensor device 20 are generally rigid. The portion of the tip element 6 between the portion supporting the optical sensor device 24 and the distal tip supporting the pressure sensor device 20 may be flexible or non-existent.

[0026] Due to the absorption characteristics of indocyanine green and oxygenated and deoxygenated hemoglobin, it is preferred to use LEDs that emit light in the near infrared range. In this embodiment, the first LED 26a of the first group 26 emits light with a wavelength of 808nm, the second LED 26b of the first group 26 emits light with a wavelength of 905nm, the first LED 28a of the second group 28 emits light with a wavelength of 690nm, the second LED 28b of the second group 28 emits light with a wavelength of 760nm, the first LED of the third group emits light with a wavelength of 740nm, and the second LED of the third group emits light with a wavelength of 840nm.

[0027] Similar to non-invasive pulse oximetry, the oxygen saturation of the brain of a person is monitored by measuring the absorbance, reflectivity and / or scattering of changes at two different wavelengths of at least one set of LEDs. In addition, the cerebral blood flow is monitored by measuring the pulsating pressure curve using the signal generated by the pressure sensor device 20 and / or the optical signal and analyzing the signal using a pulse profile analysis employed by the processing unit. By combining the analysis results of the oxygen saturation measurement and the pressure curve measurement, the monitoring of the cerebral blood flow is improved, preferably in terms of volume per unit time or in terms of volume per unit time per brain tissue amount, for example in ml / min / 100 g brain tissue.

[0028] like Figure 3 As shown in , the intracranial catheter 2 can be inserted through a burr hole 38 in the skull 40 and enter the skull chamber located between the dura mater 42 and the skull 40 (extradural) or below the dura mater 42 (subdural). An external processing unit 44 is connected to the data port 12 of the intracranial catheter 2. In another embodiment, the processing unit can be integrated into the intracranial catheter 2.

[0029] For epidural or subdural applications, the intracranial catheter 2 can be formed without a drainage channel. However, when the intracranial catheter 2 is inserted through the burr hole 38 in the skull 40 and inserted into the ventricle in the brain, that is, the intracranial catheter 2 is used as a ventricular probe, the intracranial catheter 2 preferably has a drainage channel.

[0030] Reference numerals list

[0031] 2Intracranial catheter

[0032] 4 Vertical body

[0033] 6 cutting-edge components

[0034] 8 Connectors

[0035] 10 fluid ports

[0036] 12 Data Ports

[0037] 14 Cover

[0038] 16. Retention belt

[0039] 18 Opening

[0040] 20Pressure sensor equipment

[0041] 22 Sensors

[0042] 24 Optical sensor equipment

[0043] 26a The first LED of the first group

[0044] 26b The second LED of the first group

[0045] 28a The first LED of the second group

[0046] 28b The second LED of the second group

[0047] 30 optical receivers

[0048] 32,34 Translucent window

[0049] 36 windows

[0050] 38 Drilling

[0051] 40 Skull

[0052] 42 Dura mater

[0053] 44 processing units

Claims

1. An intracranial catheter (2) for measuring blood flow through body tissue, comprising a longitudinal body (4) adapted to be inserted into a skull chamber, said longitudinal body (4) having a tip element (6) forming the distal end of said longitudinal body (4) and preferably having a channel extending from the proximal end of said longitudinal body (4) to at least one opening (18) of said tip element (6), characterized by A sensor (22) is characterized in that the sensor is configured to detect a pulsating pressure curve, the pulsating pressure curve being analyzed via a pulse profile analysis performed by a processing unit (44) coupled to the sensor (22).

2. The intracranial catheter (2) according to claim 1, It is characterized in that The sensor (22) comprises an optical sensor device (24) comprising at least one light emitter for emitting light, preferably in the near infrared range, into the body tissue and at least one light receiver (30) for receiving light reflected in the body tissue and returning to the longitudinal body (4) and for generating a signal.

3. The intracranial catheter (2) according to claim 2, characterized in that: The signal generated by the optical receiver (30) contains information about the difference between the oxygenated and deoxygenated hemoglobin concentrations, and is processed to monitor continuous cerebral blood flow.

4. An intracranial catheter (2) as claimed in any one of the preceding claims, characterized by The invention relates to a method for monitoring cerebral blood flow in an optical system comprising: a first group (26) of at least two LEDs (26a, 26b), wherein a first LED (26a) of the first group (26) emits light of a different wavelength than a second LED (26b) of the first group (26), and wherein the LEDs (26a, 26b) of the first group (26) are adapted to emit light in a near infrared range, and wherein a light receiver (30) adapted to receive reflected light of the first group (26) generates a signal, which is processed to monitor cerebral blood flow.

5. An intracranial catheter (2) as claimed in any one of the preceding claims, characterized by A second group (28) is characterized by at least two LEDs (28a, 28b), wherein a first LED (28a) of the second group (28) emits light of a different wavelength than a second LED (28b) of the second group (28), and wherein the LEDs (28a, 26b) of the second group (28) are adapted to emit light in the near infrared range, and wherein a light receiver (30) adapted to receive reflected light of the second group (28) generates a signal that is processed to monitor cerebral blood oxygen saturation.

6. An intracranial catheter (2) as claimed in any one of the preceding claims, characterized by A third group is characterized by at least two LEDs, wherein a first LED of the third group emits light of a different wavelength than a second LED of the third group, and wherein a light receiver (30) adapted to receive reflected light of the third group generates a signal that is processed to monitor brain cytochrome-c-oxidase and / or water content.

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