DE102008002747B4 - ear sensor - Google Patents

Abstract

Ear sensor for monitoring at least one physiological measured variable by means of a non-invasive measurement in the ear canal, comprising a plurality of optoelectronic components which are arranged in a housing which can be inserted into the ear canal, the plurality of optoelectronic components being arranged distributed around the circumference of the housing, at least two of the optoelectronic components are formed by detectors detecting radiation reflected from tissue layers, characterized in that the core of the ear sensor consists of a cone-shaped, plastically deformable self-relaxing foam; - at least two of the optoelectronic components are formed by radiation-emitting clusters; the detectors are each offset by 90 ° or 180 ° to the associated emitter clusters; and - the optoelectronic components are attached to a cross-shaped, rigid-flexible printed circuit board.

Description

The invention relates to an ear sensor according to the preamble of claim 1. Such an ear sensor is particularly suitable for use in humans for the selective detection and visualization of the dermal arterial perfusion rhythm of the human.

It has been known since the 1930s at the latest that the dynamics of blood volume fluctuations in close-up vascular networks on the human body are subject to strong individual variations even under physiological conditions in their course and frequency-selective composition. The blood volume of humans is about 5 liters (1/15 of body weight) too small to simultaneously perfuse all organs and tissue sections with the same intensity. In particular, the perfusion in capillary areas (vascular end stream) of the individual body areas can therefore be autonomously reduced temporarily in favor of other areas that have to fulfill more important functions due to the current life situation and from the point of view of life support. Heart-synchronous and respiratory-induced rhythms are the most perfused in skin perfusion, but less so are slower rhythms, which often range from 0.1 to 0.2 Hz, and their genesis and diagnostic relevance are not fully understood is known. For example, in the literature rhythmic fluctuations of organ perfusion are described with periods of 5-10 s as a consequence of the fact that only 30% of the capillaries are haemodynamically effective when the human is at rest. In pathophysiological vessel conditions, eg. As oncological diseases (Neuvascularisierung in the tumor area), these differences are intra- and interindividual even more pronounced.

In recent decades, a whole range of devices for noninvasive optoelectronic detection of dermal hemodynamics has been developed. Devices which are assumed in the formulation of the preamble of claim 1 are, for example, from the patents DE 3100610.8 (Blazek and Wienert, 1981), DE 3609075.1 (Schmitt and Blazek, 1986) and DE 4226973.3 (Blazek and Schmitt, 1992). All of these devices have an optoelectronic sensor that includes at least one light source and a light detector. Incidentally, these documents are expressly referenced for explanation of all not described here in more detail.

Most of these devices are methodologically based on the principle of photoplethysmography (PPG for short) first described by A.B. Hertzman in "The Blood Supply of Various Skin Areas as Estimated by the Photochemical Plethysmograph" (Amer J. Physiol., 124 (1938)).

The PPG technique is based on the fact that the light in the near infrared range and much of the visible of hemoglobin or blood is absorbed much more than tissue. Since a vascular dilatation is always associated with an increase in the blood volume in the measurement scenario, inevitably increases the absorption volume. If selective low-intensity light is then emitted into the tissue, a detector in the vicinity of the light coupling will receive less light as the blood volume in the measurement area increases. It is also known that the photoplethysmographic signals generally consist of a relatively large non-pulsatile signal component (d.c., d.c. signal) which is superposed by an amplitude-wise much smaller perfusion signal (a.c., alternating signal), which in turn is composed of different frequency components.

Optoelectronic sensors are known which use a plurality of wavelengths in the red and infrared regions of the spectrum, for example for determining dermal oxygen saturation (pulse oximetry). Other sensor versions, described for example in the U.S. Patent No. 5,830,137 (Scharf, 1996), use two slightly different wavelengths of green light for the same application. However, none of these publications uses widely spaced measurement wavelengths.

The WO 2007/004083 A1 shows an ear sensor with one or more sensors, which are arranged distributed on the housing circumference. The sensors may be optoelectronic sensors which emit radiation or detect radiation. The sensors are arranged on an inflatable balloon device. This solution is intended above all the arterial blood pressure measurement in the ear canal by the physiological blood flow parameters are set in correlation with the contact pressure of the sensor in the ear canal and from this the blood pressure value is determined.

From the WO 1997/36538 A1 is a pulse oxymetric sensor with two or more photodiodes for measuring the light intensities known. As a preferred embodiment, a clamp-shaped finger sensor is described.

The DE 10 2005 029 355 A1 shows an arrangement for monitoring at least one physiological measure by means of a non-invasive measurement on a body surface, comprising one or more sensors, which are surrounded by a housing which is insertable into a body opening. In this case, the sensor or sensors are arranged in the housing such that the transmission path between the body surface in the body opening and the respective sensor is approximately constant under the conditions of use of the arrangement. The problem with this solution is that the housing must be adapted for useful measurements especially to the respective patient. In addition, movements, for example, have a negative effect on the measurement result.

The main object of the invention is based on the DE 10 2005 029 355 A1 It is to provide an improved ear sensor that allows improved blood flow measurement using low cost optrodes.

An inventive ear sensor to solve this problem is specified in claim 1.

The ear sensor according to the invention allows with the sensor arrangement used an in-ear measurement based on a vital parameter measurement at two different wavelengths. The ear sensor is suitable for permanent use on the patient (24/7 application). Due to the special housing design and material selection, a so-called one-fits-all (UFO) design is possible, ie. H. one and the same ear sensor can be used by different patients without the need for individual shape and size adjustments. In this way, the ear sensor according to the invention can be manufactured as a cost-effective mass product.

• – das UFO-Konzept benötigt ein nachgiebiges und/oder selbstanpassendes Material;
• – ohne ausreichenden Anpressdruck konnen Signalqualität und Bewegungsartefakteresistenz nicht erreicht werden;
• – die seismische Masse des Sensors und der Krafteintrag vom Kabel müssen so klein wie möglich gehalten werden;
• – die wirksame Apertur des Sensors (der von Photonen durchdrungene Volumenanteil des perfundierten Ohrkanals) muss gegenüber bisherigen Anordnungen größer werden, um einen höheren Integrationseffekt und damit reproduzierbare und artefakteresistente Messergebnisse zu bekommen;
• – die Herstelltechnologie muss potentiell für große Stückzahlen geeignet sein;
• – das Einsetzen und Entfernen des Sensors muss unkompliziert, schmerzfrei und ohne Sichtkontrolle möglich sein;
• – der Sensor darf auch durch robustes Handling (Kneten, Biegen, Stauchen, Ziehen) nicht in seiner Funktion beeinträchtigt werden.

The invention is initially based on the recognition that the following main problems with ear sensors according to the prior art are unsolved and must be overcome by the invention:

• The UFO concept requires a compliant and / or self-adapting material;
• - without adequate contact pressure signal quality and movement cardiac resistance can not be achieved;
• - The seismic mass of the sensor and the force input from the cable must be kept as small as possible;
• - The effective aperture of the sensor (the volume fraction of the perfused ear canal penetrated by photons) must be greater than previous arrangements in order to obtain a higher integration effect and thus reproducible and artifact-resistant measurement results;
• - The manufacturing technology must potentially be suitable for large quantities;
• - The insertion and removal of the sensor must be uncomplicated, painless and without visual inspection possible;
• - The sensor must not be impaired by robust handling (kneading, bending, upsetting, pulling) in its function.

• – selbstjustierendes „all-fits”-Konzept,
• – hohe Flexibilität beim Sensordesign und der Parameteroptimierung,
• – einfache Größenabstufung („Konfektionsgrößen” möglich)
• – kostengünstige Herstellung
• – sehr gute optische Voraussetzungen für SNR und Bewegungsartefaktetoleranz durch verteilte bilaterale Sensoren,
• – sehr geringe seismische Masse,
• – geringe Krafteinkopplung vom Verbindungskabel zum Sensor,
• – erfüllt hohe Anforderungen hinsichtlich Biovertraglichkeit und Hygiene

The ear sensor according to the invention offers the following advantages:

• - self-adjusting "all-fits" concept,
• - high flexibility in sensor design and parameter optimization,
• - simple size graduation ("clothing sizes" possible)
• - cost-effective production
• - very good optical requirements for SNR and motion artifact tolerance due to distributed bilateral sensors,
• Very low seismic mass,
• - low power input from the connection cable to the sensor,
• - meets high requirements in terms of biocompatibility and hygiene

Further details of the ear sensor according to the invention are explained below with general reference to the accompanying drawings. Show it:

1 a basic layout of an inventive ear sensor;

2 a cross-sectional view of the ear sensor used in the ear canal.

The ear sensor according to the invention is rotationally symmetrical and consists of the hybrid mounted components LED cluster, pin diode 1, pin diode 2. The optical interaction with the ear canal tissue runs on banana-shaped trajectories from the LED cluster to the tangentially twisted by 90 or 180 degrees pin diodes ( 2 ). The detectors (pin diode) generate usable signals even if the associated emitter (LED) faces diametrically (180 °). Any other angular arrangement will provide even higher detector currents.

The diametrical arrangement of emitter and detector is characterized by the advantage that the photon paths are maximal. This also maximizes pulsatile modulation by arterial perfusion. This arrangement creates a sensor with virtual 360 ° aperture. As a result, the movement artifact susceptibility of the sensor is reduced because varying contact forces as the main cause responsible for it are at least partially averaged by the rotational symmetry of the photon paths.

The 90 ° arrangements (2 emitters and 2 detectors are arranged in a grid of 90 ° rotated alternately on the circumference) represent a development of the 180 ° variant, with the advantage of higher detector currents.

• a) sensor-intern (mit kurzer Reichweite ins Gewebe)
• b) von Sensor zu Sensor (mit sehr großer Reichweite)

Die unterschiedliche Reichweite kann z. B. vorteilhaft in Kombination mit kurzen Wellenlängen der Emitter zur Erkennung von Bewegungsartefakten genutzt werden.Optionally, radially distributed reflectance sensors (eg VIP, POX) can be used, which operate in 2 different operating modes:

• a) sensor-internal (with short reach into the tissue)
• b) from sensor to sensor (with very long range)

The different range can z. B. are advantageously used in combination with short wavelengths of the emitter for the detection of motion artifacts.

The core of the ear sensor consists of a cone-shaped, plastically deformable, self-relaxing foam (SMP foam) with sufficient restoring force for the fixation of the sensor to the ear canal wall. To control the compliance or the contact pressure and for ventilation of the ear canal bores / channels are provided with a suitable cross-section. To improve the sensor range, the core material can be made white reflective or with reflective surface coating.

If required for better fixation of the ear sensor in the ear, an "anchor shade" can be attached medially (after the first bend of the ear canal).

The optoelectronic components (LED chips and pin diodes) are mounted on a cross-shaped rigid-flex printed circuit board (SF-LP) in fine pitch technology ( 1 ) pre-assembled and tested. Then the SF-LP is fixed on the foam core (eg by self-adhesive back or "buttoning" in prefabricated channels), that LEDs and pin diodes are in optimum remission position (distance and direction of radiation). The paired arrangement of LED chips (2 × 660/880 nm or 760/880 nm) and pin diodes (2 × 10 mm ² ) drastically increases the irradiated solid angle (effective aperture) and the effective detector area. This results in improved artefact resistance as well as better signal-to-noise ratio (SNR).

The final and permanent anchoring of the SF-LP and the surface sealing of the ear sensor is done by means of silicone or latex coating in the dipping process. In this case, a thin, optically transparent, tear-resistant and biocompatible coating is formed. If necessary for a smooth surface relief, the SF-LP can be recessed into suitable channels.

For the production of the foam cores, the subsequent surface treatment (possibly by laser) commercially available ear plugs comes in small numbers in question. For large numbers of the shaping should be done via an injection molding tool.

The electrical contacting of the sensors is based on a behind-the-ear electronics, which should realize at least the signal preprocessing, better still a WLAN interface. The one-sided extended arm of the SF-LP serves as a low-mass, 4-pin connection cable (width 2.5 mm) via zero-force connector to the HOE.

Claims (8)

An ear sensor for monitoring at least one physiological measured quantity by means of a non-invasive measurement in the ear canal, comprising a plurality of optoelectronic components, which are arranged in a housing, which is insertable into the ear canal, wherein the plurality of optoelectronic components are distributed on the housing circumference, wherein at least two of optoelectronic components are formed by detected by tissue layers reflected radiation detectors, characterized in that - the core of the ear sensor consists of a cone-shaped, plastically deformable self-relaxing foam; - At least two of the optoelectronic components are formed by radiation emitting emitter cluster - the detectors are each arranged at 90 ° or 180 ° offset from the associated emitter clusters; and - the optoelectronic components are mounted on a cross-shaped rigidly flexible printed circuit board. Ear sensor according to claim 1, characterized in that the emitter clusters are each formed by two LEDs. Ear sensor according to claim 2, characterized in that light can be emitted in different wavelength ranges by the two LEDs of each of the emitter clusters. Ear sensor according to claim 3, characterized in that by the one LED of each of the emitter cluster light having a wavelength of 660 nm or 760 nm is emitted and that by the other of the two LEDs of each of the emitter cluster light with a Wavelength of 880 nm is emissive. Ear sensor according to one of claims 1 to 4, characterized in that in each case one of the emitter clusters and in each case one of the detectors are integrated in a remission sensor. Ear sensor according to claim 5, characterized in that the remission sensors are both sensor-internal and cross-sensor operable. Ear sensor according to one of claims 1 to 6, characterized in that it comprises a core material which is executed white reflective. Ear sensor according to one of claims 1 to 7, characterized in that a core material of the ear sensor is designed with a reflective surface coating.

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