DE102009017797A1 - Implantable device i.e. reflective photoplethysmograph sensor, for extravascular detection of blood pressure of patient, has light absorbing optical barrier provided between solid body light source and solid body photodetector - Google Patents

Abstract

The device has a light absorbing optical barrier (5) provided between a light emitting unit i.e. solid body light source (2) e.g. LED or semiconductor diode, and a light receiving unit i.e. solid body photodetector (4), where the device is in the form of a surface element. An electrode surface is provided at a surface element and is brought in contact with a vessel. The surface element comprises a surface substrate (1), which consists of a biocompatible material and is made of polyimide. A surface upper side of the substrate is sealed with a light-transparent sealing compound i.e. silicone.

Description

Technical area

The This invention relates to an implantable extravascular device Detecting at least one vital parameter, preferably blood pressure, in the form of a surface element, the at least one light emitting means and at least one light receiving means provides as well as with a surface element fixing Precaution suitable for extravascular attachment to an intracorporeal, preferably blood leading vessel.

State of the art

A continuous monitoring of blood pressure over a longer period in hypertensive patients is of great interest to medicine. In particular for therapy monitoring and optimization, as well as in the future for autonomous blood pressure regulation, For example, with the help of drug pumps, it is desirable To measure the blood pressure as accurately as possible.

For some time, the recognized functional relationship between blood pressure and pulse wave transit time, or pulse transit time (PTZ), forms the basis for device developments for measuring the blood pressure. For example, is from the DE 44 27 991 C2 a method for measuring the blood pressure change of a person can be removed, in which the pulse transit time is detected as a measured variable, which denotes the time interval between the "R wave" of an ECG signal and a characteristic point of the peripheral pulse wave.

From the DE 699 30 113 T2 is an implantable medical device for measuring the absolute blood pressure and the barometric pressure, which includes an extravascular implantable electronic module with power supply and transponder unit, to which a blood vessel in the right ventricle of the heart running cable is connected, to which a physiological sensor for absolute blood pressure and temperature detection is appropriate. Due to the principle of such use of vascular-invasive sensors due to the influence of blood flow is always associated with an increased patient risk due to a high risk of resulting thrombus formation.

To avoid this risk associated with intravascular sensors is in the WO 2006/122 750 describes an implantable blood pressure sensor which can be applied as an elastic ring around an arterial blood vessel and thereby detects the blood pressure-induced change in shape of the vessel and is able to determine blood pressure values on the basis of a calibration curve. Although the possibility of carrying out the so-called Riva-Rocci method also described in this document avoids the above-mentioned calibration effort, on the other hand, by means of an actuator, it appreciably intervenes in the vascular mechanics of the blood-carrying vessel.

Further is in the above document another embodiment for an implantable blood pressure sensor, in addition to an optical sensor for detecting the Oxygen saturation of the blood within a blood vessel is detectable. The additional sensor has two light emitting Diodes on, whose light passes through the vessel wall coupled into the blood vessel to be examined becomes. An arranged on the blood vessel, the diodes in transmission opposite light detector is able to detect transmitted light components and the won Detector signals for evaluation to a likewise implantable evaluation transferred to.

An optical sensor for blood oxygen detection can from the US 6,106,477 are taken, which is part of an implantable blood pressure sensor and clamped to collect blood pressure around a blood vessel to be examined vascular line. The rigid embodiment of the sensor sleeve prevents the blood-carrying vessel from deforming in a natural manner, as a result of which disadvantageous physiological influences act on the vessel. The integrated in the sensor sleeve optical sensor can be configured either for reflective or transmitiven measurement, as in the in 14 The printed example shown embodiment can be removed.

Another implantable optical sensor for deep-resolution, light spectroscopic and spectrometric investigations is the EP 1 139 683 B1 refer to. The sensor head described consists of a plurality within a transparent potting compound, arranged side by side, end-side terminating light-conducting fibers, all of which is arranged downstream in the beam exit direction a deflecting approximately 90 ° reflection surface. The potting compound forms with the fiber ends and the corresponding reflector surfaces a surface element which rests largely flat on a tissue surface to be examined, in which perpendicular to the tissue surface light can be coupled. Reflected light components likewise pass through the corresponding reflector surfaces into the optical fibers for further evaluation. The sensor system described in the document sees extracorporeally proximal to the implantable sensor head extending optical fibers, which are connected to extracorporeal light sources and detector units.

Presentation of the invention

Starting from the above-described prior art, the object is a device for extravascular detection of at least one vital parameter, preferably for detecting the blood pressure, in the form of a surface element having at least one light-emitting means and at least one light-receiving means and one fixing the surface element Provision that is suitable for extravascular fixation relative to an intracorporeal vessel, to develop such that a continuous blood pressure monitoring of a patient over a long period of time with a much better measurement accuracy than is possible with the previously known systems to realize. The measures required for this purpose should not affect the patient in his daily life, as is often the case with extracorporeal monitor systems or with implanted sensor systems with extracorporeal cable guides, as for example in the EP 1 139 683 B1 described is the case.

The Solution of the problem underlying the invention is specified in claim 1. The concept of the invention advantageously further Features are the subject of the dependent claims and the other Description in particular with reference to the embodiment refer to.

Drawing according to the solution an implantable device according to the features of the preamble of claim 1, characterized in that the at least one light emitting Means is a solid state light source and that at least a light receiving means a solid state photodetector is and that between the at least one solid-state light source and the solid state photodetector is a light absorbing Barrier is provided.

With Help of the optical implantable according to the invention Sensors, to operate all the necessary additional components, such as power supply unit, control and evaluation unit for the at least one solid-state light source as well as the solid state photodetector, also in implantable Are formed, it is possible the pulse transit time (PTZ) and this with unprecedented accuracy. This is realized by the at least one light source is provided immediately at the place of measurement, so that no Light losses, for example, by way of light transmissions or by spatial light steering, as in the state of Technique is the case, occur. In addition, any interference excluded in the light detection, since measures taken be, such as the provision of an optical barrier between the location of the light source and the photodetector to direct stray light components exclude the signal to noise ratio to optimize.

The Determination of the time interval called the pulse transit time (PTZ) requires the detection of two temporal reference points, which are the temporal course of the pulse wave in the arterial vascular system assigned. The first reference point is usually used the "R-wave" of the ECG signal, as a second reference point serves a characteristic point of intrathoracic or intra-abdominal recorded plethysmogram showing a recorded volume change an arterial bloodstream at a localized Measuring point corresponds. Usually becomes the Inclusion of a plethysmogram of an arterial blood vessel Transmitted light, which transmitted through the tissue layer Light is detected by means of a photoreceiver. Of the the tissue penetrating light part experiences inside of the body a damping, the u. a. dependent is of the wavelength of the light source, the type and the Concentration of the substances in the irradiated tissue and of the Pulsation of the blood. The thus obtained signal of the photoreceptor is in the form of a photocurrent, and corresponds to a first approximation the blood volume changes caused by myocardial contraction arterial vessels.

alternative to use the "R-wave" of the ECG signal as well as the first reference point also the foot point of an the aorta ascendenz recorded plethysmogram be used which offers the advantage that the determined pulse transit time (PTZ) of physiological fluctuations, for example in the form of temporal deviations between the occurrence of the "R wave" and the actual blood ejection at the heart, is decoupled.

The implantable device according to the invention, which enables a purely optical detection of the vessel in its simplest embodiment, can thus be implanted in duplicate on the one hand as close to the heart as possible, preferably on the ascending aorta and on the other at a location spaced from the heart, for example within the thorax. preferably within the intercostal tissue located between the ribs and / or in the abdomen (abdomen), whereby fluctuations in the hydrostatic pressure due to temperature and position, strong movement artefacts, alignment inaccuracies during repositioning of the sensor unit according to the invention, skin irritation or high absorption due to strong pigmentation of the skin are completely avoided or at least avoided strong re all advantages which are not to be mentioned in extracorporeal measuring methods as well as in intravascular measuring methods.

Furthermore restricts the implantable design of the entire To be implanted measuring system to the patient in everyday life Living by no means and also allows the use the determined measurement data for the regulation of physiological variables for example by means of active implants, such as medicament pump, Pacemaker, etc., without the expense of telemetric transmissions in and out of the body and without increased risk of infection in percutaneous cable guides.

in the Contrary to known intravascular measuring methods comes it with the implantable according to the solution Sensor system to no blood contact, so that the natural Blood flow is not affected.

In a supplemented embodiment sees the solution-based optical sensor in addition at least one electrode surface in front in the same How the optical measuring sensor components on a vessel or Tissue area zuwendbaren surface substrate surface is positioned. The electrode surface gets device this in direct physical contact with the vessel or to the adjacent tissue and can with appropriate positioning the ECG signal and thus the "R-wave" explained above detect. Such a trained sensor head is thus in the Able to detect both ECG signals as well as plethysmographic Perform measurements. Only the completeness It should be noted that for ECG signal acquisition a second electrode is provided on another area of the implantable device is to install.

to Control or for the operation provided on the sensor head optical sensor components, d. H. Solid state light sources and photodetector, and optionally the electrode surface, requires a control, energy supply and signal evaluation unit, either together with the sensor components in the form of a single Surface element are integrated or in the form of a separate accommodated to the sensor head formed implantable unit are and the corresponding electrical connection structures is connected to the sensor head in a suitable manner. On more Statements in particular with regard to actual Implementation forms that also meet the medical requirements, such as biocompatibility etc., be on the in the figures referenced embodiments.

Brief description of the invention

The Invention will hereinafter be understood without limitation of the general Erfindungsgedankenens with reference to embodiments below Reference to the drawings described by way of example. Show it:

1 Top view of the implantable device (detail),

2 Top view of a complete implantable device,

3 schematic representation for illustrating the optical measuring method,

4 implantable device with ECG electrode as well

5 Representation for fixing the solution according implantable device to a vessel.

Ways of carrying out the invention, commercial usability

In 1 is a detailed view of a solution designed according to implantable device for extravascular detection of a vital parameter, preferably the blood pressure within a blood-perfused vessel shown. In its simplest embodiment, the implantable device is limited to a reflective photoplethysmographic sensor, ie a sensor device with which it is possible purely optically to detect the temporal reference points characteristic for the determination of the pulse transit time (PTZ) based on the blood pressure-related vascular volume change , For this purpose, the implantable device according to the invention has on the surface of a surface substrate consisting of biocompatible, flexible, preferably polyimide 1 at least one, preferably a plurality of solid-state light sources 2 on. The solid-state light sources are preferably in the form of LEDs or semiconductor laser diodes and capable of emitting light of suitable wavelengths. When providing multiple solid-state light sources 2 For example, each individual light source preferably emits light in a different wavelength range to allow spectroscopic examinations in this manner. The solid-state light sources 2 are on the surface substrate top via electrical interconnects 3 contacted accordingly and with a not in 1 connected electrical power source and a drive unit connected. Further, on the same surface substrate upper side is a solid state photodetector 4 , preferably in the form of a photodiode, which, as will be described hereinafter, is applied by the solid-state light sources 2 emitted light that is reflected or reemitiert on the tissue or vessel is able to receive. To direct light transfer from the solid state light sources 2 to the solid-state photodetector 4 To avoid this is also an optical barrier 5 provided, which has an absorbance at least in that spectral wavelength range in which the individual solid-state light sources 2 to emit assets. The optical barrier 5 preferably consists of a filled with light-absorbing pigments silicone, which is like the material of the surface substrate 1 has biocompatible properties.

Optionally, on the surface substrate 1 additionally an electrical IC component 6 be provided with the at the photodetector 4 obtained signals amplified and can be fed to a further signal processing, the in 1 not further illustrated. In addition to a signal amplification can be part of the IC component 6 Signal filtering of the signals detected by the photodetector also takes place, which has the advantage of reducing the proportion of coupled disturbance variables in relation to the useful signal of the overall signal.

All on the surface substrate 1 Processed optical and electronic components 2 . 4 . 6 are via appropriate ladder structures 3 with a not in 1 connected control and evaluation unit, which is also on the surface substrate 1 applied or in a separate module to the surface substrate 1 can be accommodated.

The area size of the implantable surface element formed in accordance with the invention preferably measures a few mm ² to 60 mm ² and adheres to a local surface of a preferably blood-carrying tissue, for example by means of a suitable adhesive bond or by means of mechanical fixations, for example by sewing or tying.

In 2 is a preferred embodiment of an implantable device that in detail in 1 is shown, whose processed surface substrate top almost completely with a biocompatible potting compound 7 which is designed to be light-transparent at least in that spectral wavelength range in which the solid-state light sources 2 to emit assets. For purposes of attachment of the sensor head formed as a surface element at a not in 2 represented vessel are through holes 8th provided that both the surface substrate 1 as well as the biocompatible potting compound 7 enforce, can be threaded through the optionally thread or band-shaped fixative. Both the solid-state light sources 2 as well as the solid state photodetector 4 is completely from the preferably made of light transparent silicone potting compound 7 encapsulated.

The potting compound 7 , which serves as an encapsulation, ends in a connection area 9 at which the electrical conductors 3 open for electrical contact, for example, at a likewise implantable unit free. About the connection area 9 can be a contact, for example, to an implantable power supply unit and a control and evaluation unit for the technical operation of all on the surface substrate 1 applied electrical components are produced.

In 3 is a schematic diagram for explaining the technical operation of the sensor according to the invention illustrated. It is assumed that the optical sensor head rests flat and local on a surface of a fabric G. The light of the solid-state light sources 2 is thereby emitted into the underlying, traversed by blood vessels B tissue G, wherein a portion of the light in the direction of the photodetector 4 is backscattered and recorded by it. The optical barrier explained in the introduction 5 prevents an immediate transfer of light from the solid state light sources 2 to the photodetector 4 , As a result, error signals can be significantly reduced.

By positioning the light sources 2 Immediately at the location of the sensor head and an associated direct illumination of the vessel G to be examined, high light intensities can be deposited into the tissue area to be examined largely loss-free, of which a considerable part is due to backward scattering on the part of the photodetector 4 can be received. With the help of the sensor head according to the invention meaningful and with a large signal to noise ratio evaluable measurement signals can be obtained with which an accurate and largely error-free determination of vital signs is possible. In addition, all those areas of the potting compound can advantageously be used 7 in which light transparency is not required, as it were mixed with light-absorbing pigment materials, in order in this way the introduction of scattered light, for example by the surface substrate 1 through.

A further advantageous embodiment of a sensor head according to the invention is shown in FIG 4 shown next to the solid state light sources 2 , the optical barrier 5 and the solid state photodetector 4 on the surface of the surface substrate 1 an electrode surface 11 provides via which a tap of ECG signals is possible, wherein the freely accessible electrode surface 11 also out biocompatible material. In the case shown the 4 is within the solidified, light-transparent potting compound 7 a recess 7 ' around the electrode surface 11 have been left free, so that in the recess 7 ' Press in the tissue and make intimate contact with the electrode surface. Alternatively, the recess could 7 ' filled with electrical contact material and form a flush electrode with the upper Vergussmassenoberfläche.

With the help of the ECG electrode 11 it is possible to capture the first temporal reference point for determining the pulse transit time.

For protection against moisture, all on the surface substrate 1 applied conductor tracks 3 and the electronic and optoelectronic components are coated with a diffusion-inhibiting material as a diffusion barrier.

For the intracorporeal extravascular application of the surface element according to the invention on a perfusing tissue or vessel to be examined, the surface element according to the method described in US Pat 5 illustrated arrangement on a fabric surface on one side. For fixing both an adhesive method can be used as well as sewing or stapling come as a mounting method used. A possible variant for fixing the sensor head designed in accordance with the invention along a blood-carrying vascular line G is shown in FIG 5 illustrated. For this serve band-shaped fastening means 10 which comprise the vessel G at least in a half-loop and the area sensor in the in 5 illustrated manner relative to the vessel fix. The band-shaped fastening means 8th are so elastic that they do not affect the natural vessel wall change.

Preferably is the solution according to sensor to design, that he subcutaneously implanted with the least possible effort can be, for example in the field of intercostal tissue. The elastic configuration of the sensor should have a total thickness of Do not exceed 2 mm, allowing subcutaneous placement of the sensor with minimal mechanical stress in relation to the surrounding tissues, even in cases of movement or local extracorporeal mechanical stress of the tissue with as possible low irritation is associated. Of particular importance is the Inherent elasticity or flexibility of the surface sensor, not by the surrounding tissue or the contacted vessel or as little as possible in the natural expansion behavior gets irritated.

Further It is possible, with a suitable choice in different Wavelength ranges emitting solid state light sources Pulse oximetry for the determination of blood oxygen saturation perform, for example, using at least two solid-state light sources in the range of 660 nm or emit 940 nm. Using other light sources in other suitable wavelength ranges in the visible and near-infrared spectrum can complement hemoglobin derivatives like methemoglobin or carboxyhemoglobin as well diagnostic dyes are detected. Further, when using of suitable wavelengths (for example at the isosbestic point at 800 nm) a measure of relative change in perfusion of the tissue to which the sensor is attached possible.

Under Use of wavelengths corresponding to the absorption spectrum of glucose for the differentiation of glucose to other blood components are suitable, a pulsglucometric determination of the glucose concentration be performed.

1

surface substrate

2

Solid state light source

3

conductor tracks

4

Solid-state photodetector

5

optical barrier

6

IC amplifier component

7

potting compound encapsulation

7 '

recess

8th

Through openings

9

terminal area

10

band-shaped fixer

11

ECG electrode surface

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - DE 4427991 C2 [0003]
• - DE 69930113 T2 [0004]
• WO 2006/122750 [0005]
• - US 6106477 [0007]
• - EP 1139683 B1 [0008, 0009]

Claims (13)

An implantable device for extravascular detection of at least one vital parameter, in the form of a surface element comprising at least one light-emitting means and at least one light-receiving means and a surface element fixing provision, which is suitable for extravascular fixation relative to an intracorporeal vessel, characterized in that the at least one light-emitting means is a solid-state light source, wherein the at least one light-receiving means is a solid-state photodetector, and that a light-absorbing barrier is provided between the at least one solid-state light source and the solid-state photodetector. Device according to claim 1, characterized in that that on the surface element one with the vessel in Contactable electrode surface is provided. Apparatus according to claim 1 or 2, thereby characterized in that in the surface element one with the at least one solid-state light source electrically connected Drive unit is provided, and that in the surface element one with the electrode surface and / or the solid state photodetector electrically connected signal evaluation unit is provided. Device according to one of claims 1 to 3, characterized in that the at least one solid-state light source an LED or a semiconductor diode. Device according to one of claims 1 to 4, characterized in that a plurality of solid-state light sources are provided, which differ in each case in the emission spectrum. Device according to one of claims 1 to 5, characterized in that the surface element a made of biocompatible material existing surface substrate provides, on the one surface top which at least a solid state light source and the at least one solid state photodetector applied are, between which the light-absorbing barrier in the form of a the surface substrate web-like overhanging backdrop is formed, and that the at least one surface top of the surface substrate with a biocompatible, light transparent Potting compound is shed. Device according to claims 3 and 6, characterized in that that the electrical connection lines, the drive unit as well as the signal evaluation unit on the one surface upper side of the surface substrate are applied and of the potting compound are shed. Device according to Claims 2, 3 and 6, characterized that the electrode surface has a free surface, d. H. not covered by the potting compound represents. Device according to one of claims 6 to 8, characterized in that the surface substrate of Polyimide and the potting compound consists of a silicone. Device according to one of claims 1 to 9, characterized in that the light-absorbing barrier from a pigmented biocompatible material consists. Device according to one of claims 1 to 9, characterized in that the surface element over has such surface elastic properties, so that vessel deformations by the surface element not be affected. Device according to one of claims 1 to 11, characterized in that the fixing provision in Form formed at least one band-shaped loop is with which the surface element can be attached to the vessel is. Device according to one of claims 1 to 12, characterized in that the surface element has an area size that is one Rectangular size with a width of 3 to 5 mm and a length of 7 to 12 mm.