Intracranial catheter for measuring blood flow

Abstract

The present invention relates to an intracranial catheter (2) for measuring blood flow in body tissue, comprising a longitudinal body (4) adapted to be inserted into the cranial spinal cavity, the longitudinal body (4) having a tip element (6) forming the distal end of the longitudinal body (4), and a conduit preferably extending from the proximal end of the longitudinal body (4) to at least one opening (18) of the tip element (6), and a sensor (22) adapted to detect a pulse pressure curve that is analyzed via pulse pressure waveform analysis performed by a processing unit (44) coupled to the sensor (22).

Description

Technical Field

[0001] The present invention relates to an intracranial catheter for measuring blood flow through body tissue, the intracranial catheter comprising a longitudinal body adapted to be inserted into the cranial spinal cavity and having a tip element forming the distal end of the longitudinal body.

Background Art

[0002] Such intracranial catheters are known, for example, from Patent Document 1. Patent Document 1 relates to an intracranial catheter comprising a sensor for determining the oxygen utilization rate of tissue within the skull, the sensor being placed epidurally through the skull for measuring the oxygen utilization rate. During neurology and neurosurgery-related surgeries, it is generally desirable to continuously monitor the oxygenation of the blood supplied to the brain. Frequently, access to the brain is provided through a perforation in the skull, and a sensor for optically measuring oxygenation can be inserted through such a perforation. In that case, the optical sensor should meet a number of design and performance criteria in order to operate well in this environment. The sensor must be insertable through the perforation so as to contact the tissue where the oxygen utilization rate is measured. The sensor should be soft so as not to damage neural tissue, yet be sufficiently rigid at a certain size so that it can be operated from outside the skull. Also, it must be sized to fit within the perforation and at the location where the measurement is to be made. Furthermore, the sensor should be designed to avoid detecting ambient light that would interfere with the detection of the desired optical signal. The sensor must also prevent the detection of direct transmission light from the light source of the sensor.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] Patent Document 1 focuses on monitoring the oxygen utilization rate of cerebral blood flow by optical measurement, but the object of the present invention is to measure cerebral blood flow (CBF).

Means for Solving the Problems

[0005] As a solution to the above object, the present invention proposes an intracranial catheter for measuring the blood flow according to the features of claim 1.

[0006] This intracranial catheter is characterized by a sensor configured to detect a pulse pressure curve analyzed through pulse pressure waveform analysis performed by a processing unit coupled to the sensor, and the sensor preferably comprises a plurality of sensor devices. Since the blood volume is proportional to the area below the systolic part of the pressure curve, it is possible to determine the cerebral blood flow by analyzing the pulse pressure curve through pulse pressure waveform analysis.

[0007] The viscoelasticity of blood vessels also affects cerebral blood flow. The Moens-Korteweg equation models the relationship between the incremental elastic modulus of the arterial wall and the pulse wave velocity (PWV). By using the signal utilizing the distance between the sensor devices, the PWV in m / s can be measured.

[0008] For example, the pulse pressure waveform algorithm can be calibrated to calculate an absolute CBF value that is updated for each heartbeat, that is, continuous, using absolute CBF measurement performed by indocyanine green spectroscopy, or CT or MRI perfusion measurement, and the patient-specific viscoelasticity by calculation.

[0009] Preferably, the sensor comprises a pressure sensor device configured to detect a pulse pressure curve. Specifically, 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 pulse pressure curve. The operating 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, specifically by using a photoplethysmogram, a pulse pressure curve can be derived from the light absorption measurement.

[0010] The sensor can be a piezoresistive sensor that uses the piezoresistive effect, i.e., the change in electrical resistivity when pressure is applied, to detect the pulse pressure curve.

[0011] The sensor can be provided in or on the longitudinal body, while the processing unit can be provided at a certain distance from the longitudinal body. For example, the processing unit can be provided by an external device coupled to the sensor to receive the sensor signal via a cable or wirelessly. However, in one embodiment, the processing unit may be provided within the longitudinal body.

[0012] Preferably, a conduit is formed in the longitudinal body, and the conduit extends from the proximal end of the longitudinal body to at least one opening of the tip element. This conduit can be used as a drainage conduit 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 conduit. The longitudinal body can be formed in a manner similar to or the same as that disclosed in Patent Document 1 or Patent Document 2, and the contents of these documents are incorporated herein by reference.

[0013] In a preferred embodiment of the intracranial catheter, the sensor preferably comprises an optical sensor device including at least one emitter for emitting light in the near-infrared range into the body tissue, and at least one light receiver for receiving the light reflected by the body tissue and returning to the longitudinal body and generating a signal. It is preferred to use a source of coherent light in the near-infrared range capable of penetrating living tissue. It is highly preferred to specifically use wavelengths suitable for the selected measurement technique. Light having wavelengths of 690 nm, 760 nm, 808 nm, and 905 nm is preferably used.

[0014] Generally, indocyanine green is used in medical diagnosis as an indicator substance administered intravenously. The absorption and fluorescence spectra of indocyanine green are in the near-infrared region. Both are approximately concentration-dependent, and the concentration profile measured by the intracranial catheter depends greatly on blood flow.

[0015] The optical sensor device is preferably disposed in a recess formed in the longitudinal body and covered by a translucent window portion. The pressure sensor device can be disposed in a similar recess. The recess can be formed and the optical sensor device and the pressure sensor device can be disposed in a manner similar to or the same as that disclosed in Patent Document 2, which is incorporated herein by reference.

[0016] In a preferred embodiment of the intracranial catheter, the signal generated by the light receiver contains information about the difference between the oxyhemoglobin concentration and the deoxyhemoglobin concentration, and this signal is processed to monitor continuous cerebral blood flow.

[0017] In a more preferred embodiment, the intracranial catheter comprises a first set of at least two LEDs, the first LED of the first set emits light of a wavelength different from that of the second LED of the first set, the LEDs of the first set are adapted to emit light in the near-infrared range, a light receiver adapted to receive the reflected light of the first set generates a signal, and this signal is processed to monitor cerebral blood flow. Specifically, it is preferable that the first LED of the first set emits light having a wavelength of 808 nm, and the second LED of the first set emits light having a wavelength of 905 nm.

[0018] In a more preferred embodiment, the intracranial catheter comprises a second set of at least two LEDs, the first LED of the second set emits light having a wavelength different from that of the second LED of the second set, the LEDs of the second set are adapted to emit light in the near-infrared range, a light receiver adapted to receive the reflected light of the second set generates a signal, and this signal is processed to monitor cerebral oxygen saturation. Specifically, the first LED of the second set emits light having a wavelength of 690 nm, and the second LED of the second set emits light having a wavelength of 760 nm or 905 nm.

[0019] In a more preferred embodiment, the intracranial catheter comprises a third set of at least two LEDs, the first LED of the third set emits light of a wavelength different from that of the second LED of the third set, a light receiver adapted to receive the reflected light of the third set generates a signal, and this signal is processed to monitor cerebral cytochrome c oxidase and / or water content. Specifically, for monitoring cerebral cytochrome c oxidase, it is preferable that the first LED of the third set emits light having a wavelength of 520 nm, and the second LED of the third set emits light having a wavelength of 550 nm. Alternatively, for monitoring water content, the wavelength of the LEDs of the third set can be any of 740 nm, 840 nm, and 960 nm.

[0020] According to the present invention, any one of the first, second, and third sets can be provided without any other set. However, any combination of two sets may be provided. Most preferably, the intracranial catheter comprises all three sets. Further, one light receiver can be provided for each set or each LED, or one light receiver can be provided for all sets.

Brief Description of the Drawings

[0021] Further details and advantages of the present invention will be obtained from the following description of the embodiments and the accompanying drawings.

Figure 1

Figure 2

Figure 3

Mode for Carrying Out the Invention

[0022] As shown in FIG. 1, the intracranial catheter 2 comprises a longitudinal body 4 having a tip element 6 that forms the distal end of the longitudinal body 4. The proximal end of the longitudinal body 4 is provided with a connector 8 having a fluid port 10 and a data port 12. The fluid port 10 is connected to an opening of a discharge conduit (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 the processing unit. The fluid port 10 is closed via a cap 14 fixed to the connector 8 by a retaining band 16. The discharge conduit extends from the proximal end of the longitudinal body 4 to the opening 18 of the tip element 6 (see FIG. 2). Thus, discharge of the peripheral tissue through the intracranial catheter 2 becomes possible.

[0023] The pressure sensor device 20 of the sensor 22 is disposed near the opening 18 of the tip element 6. Further, the sensor 22 includes an optical sensor device 24, which includes a first set 26 of two LEDs 26a, 26b, a second set 28 of two LEDs 28a, 28b, a third set of two LEDs (not shown), and a photodetector as a light receiver 30. The sensor 22 of this embodiment includes a pressure sensor device and an optical sensor device, but 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 set, and / or more than one, two, or three sets of LEDs. In any case, the sensor 22 may additionally include a temperature sensor device. Further, more than one photodetector may be provided as a light receiver.

[0024] The pressure sensor device 20 and the optical sensor device 24 are disposed in a cavity formed in the tip element 6 and covered in a sealed manner by the window portions 32, 34, 36. The window portions 32, 34 are translucent. When the pressure sensor device 20 is not an optical sensor device, the window portion 36 may not be translucent. The portion of the tip element 6 that supports the optical sensor device 24 and the distal tip that supports the pressure sensor device 20 are typically rigid. The portion between the portion of the tip element 6 that supports the optical sensor device 24 and the distal tip that supports the pressure sensor device 20 may be flexible or may not exist.

[0025] Due to the absorption characteristics of indocyanine green and oxygenated and deoxygenated hemoglobin, it is preferable to use an LED that emits light in the near-infrared range. In this embodiment, the first LED 26a of the first set 26 emits light having a wavelength of 808 nm, the second LED 26b of the first set 26 emits light having a wavelength of 905 nm, the first LED 28a of the second set 28 emits light having a wavelength of 690 nm, the second LED 28b of the second set 28 emits light having a wavelength of 760 nm, the first LED of the third set emits light having a wavelength of 740 nm, and the second LED of the third set emits light having a wavelength of 840 nm.

[0026] Similar to non-invasive pulse oximetry, human cerebral oxygen saturation is monitored by measuring changes in absorbance, reflectance, and / or scattering at two different wavelengths of at least one set of LEDs. Also, cerebral blood flow is monitored by measuring the pulse pressure curve using the signal and / or optical signal generated by the pressure sensor device 20 and analyzing these signals using pulse pressure waveform analysis employed by the processing unit. By combining the analysis results of oxygen saturation measurement and pressure curve measurement, the monitoring of cerebral blood flow is improved, preferably with respect to the volume per unit time or the volume per unit time with respect to the amount of brain tissue, for example, in ml / min for 100 g of brain tissue.

[0027] As shown in FIG. 3, the intracranial catheter 2 can be inserted through the burr hole 38 in the skull 40 into the cranial spinal cavity disposed between the dura mater 42 and the skull 40 (epidural) or under 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 may be incorporated into the intracranial catheter 2.

[0028] For epidural or subdural applications, the intracranial catheter 2 can be formed without a drainage conduit. However, when the intracranial catheter 2 is inserted all the way through the burr hole 38 in the skull 40 into the ventricles of the brain, i.e., when the intracranial catheter 2 is used as a ventricular probe, the intracranial catheter 2 preferably has a drainage conduit.

Description of the Reference Numerals

[0029] 2 Intracranial catheter 4 Longitudinal body 6 Tip element 8 Connector 10 Fluid port 12 Data port 14 Cap 16 Retaining band 18 Opening 20 Pressure sensor device 22 Sensor 24 Optical sensor device 26a First LED of the first group 26b Second LED of the first group 28a First LED of the second group 28b Second LED of the second group 30 Light receiver 32, 34 Translucent window portions 36 Window portion 38 Through hole 40 Skull 42 Dura mater 44 Processing unit

Claims

1. An intracranial catheter (2) for measuring blood flow in body tissue, comprising a longitudinal body (43) adapted for insertion into the cranial spinal cavity, a tip element (6) forming the distal end of the longitudinal body (4), and preferably a conduit extending from the proximal end of the longitudinal body (4) to at least one opening (18) of the tip element (6), the longitudinal body (4) having a sensor (22) configured to detect a pulse pressure curve analyzed via pulse pressure waveform analysis performed by a processing unit (44) coupled to the sensor (22).

2. The intracranial catheter (2) according to claim 1, wherein the sensor (22) preferably comprises an optical sensor device (24) including at least one emitter for emitting light in the near-infrared range into the body tissue and at least one light receiver (30) for receiving and generating a signal from the light reflected by the body tissue back to the longitudinal body (4). The intracranial catheter (2) according to claim 1.

3. The intracranial catheter (2) according to claim 2, wherein the signal generated by the light receiver (30) contains information about the difference between the oxyhemoglobin concentration and the deoxyhemoglobin concentration, and the signal is processed to monitor continuous cerebral blood flow.

4. The intracranial catheter (2) according to any one of claims 1 to 3, characterized by a first set (26) of at least two LEDs (26a, 26b), wherein the first LED (26a) of the first set (26) emits light of a different wavelength from the second LED (26b) of the first set (26), the LEDs (26a, 26b) of the first set (26) being adapted to emit light in the near-infrared range, and a light receiver (30) adapted to receive the reflected light of the first set (26) generating a signal, the signal being processed to monitor cerebral blood flow.

5. Characterized by a second set (28) of at least two LEDs (28a, 28b), wherein a first LED (28a) of the second set (28) emits light of a wavelength different from that of a second LED (28b) of the second set (28), the LEDs (28a, 28b) of the second set (28) are adapted to emit light in the near-infrared range, a light receiver (30) adapted to receive the reflected light of the second set (28) generates a signal, and the signal is processed to monitor cerebral oxygen saturation, the intracranial catheter (2) according to any one of claims 1 to 4.

6. Characterized by a third set of at least two LEDs, wherein a first LED of the third set emits light of a wavelength different from that of a second LED of the third set, a light receiver (30) adapted to receive the reflected light of the third set generates a signal, and the signal is processed to monitor cerebral cytochrome c oxidase and / or water content, the intracranial catheter (2) according to any one of claims 1 to 5.

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