DE102008002747A1 - Ear sensor for monitoring physiological measured variable by non-invasive measurement in ear canal of patient, has detectors for detecting radiation reflected by tissue layers, where detectors are arranged offset to respective emitters - Google Patents

Abstract

The ear sensor has multiple sensors arranged in a distributed manner at a circumference of a housing, which is insertable in an ear canal of a patient. The sensors include two radiation-emitting emitters i.e. LEDs, and two detectors i.e. pin diodes, for detecting radiation reflected by tissue layers, where the detectors are arranged 90 degree to 180 degree offset to the respective emitters. The ear sensor is designed in a rotationally symmetric manner.

Description

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

No later than since the 30s of the last century is known that the dynamics of blood volume fluctuations in close - up vascular networks Human body already under physiological conditions strong in their course and frequency-selective composition subject to individual variations. The blood volume of the human is too small with about 5 liters (1/15 of body weight), at the same time all organs and tissue sections with the same intensity to perfuse. Especially the perfusion in capillary areas (vascular end stream) The individual body areas can therefore be autonomous at times reduced in favor of other areas due to the current Life situation and, from the point of view of life support, more important functions have to fulfill. Most researched are the heart-synchronous ones and the respiratory rhythms in the perfusion of the skin, much less so are the slower rhythms, which are often about range from 0.1 to 0.2 Hz and their genesis and diagnostic Relevance ultimately is not yet known in every detail. For example, in the literature, rhythmic fluctuations of organ perfusion with periods of 5-10 s as a result of the fact described that at rest of humans only 30% of the capillaries are hemodynamically effective. In pathophysiological vessel conditions, z. B. Oncological diseases (Neuvascula tion in the tumor area), these differences are even clearer intra- and interindividually 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 to explain all not described here in detail.

Most of these devices are methodically based on that of AB Hertzman in "The blond supply of various skin areas as estimated by the photoelectric plethysmograph" (Amer J. Physiol., 124 (1938)) First described principle of photoplethysmography (PPG for short).

Of the PPG technique is based on the fact that the light in the near Infrared region and large part of the visible of hemoglobin or from blood is absorbed much more than by tissue. Because a vascular dilatation always with an increase the blood volume in the measurement scenario is increased inevitably also the absorption volume. You send now selective light of low intensity into the tissue, so a detector near the light coupling with Increase in blood volume in the measurement area receiving less light. Also It is known that the photoplethysmographic signals in the Usually from a relatively large nichtpulsatilen Signalan part (i.e., DC), which is an amplitude-wise much smaller perfusion signal (a.c., alternating signal), which in turn is composed of different frequency components, superimposed is.

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 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.

One inventive ear sensor for solution This object is specified in claim 1.

Of the Ear sensor according to the invention allows with the used Sensor arrangement 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 is a so-called one-fits-all (UFO) design possible, d. H. one and the same ear sensor can be used by different patients be without any custom shape and size adjustments are necessary. In this way, the inventive Ear sensor can be manufactured as a low-cost mass product.

• – das UFO-Konzept benötigt ein nachgiebiges und/oder selbstanpassendes Material;
• – ohne ausreichenden Anpressdruck können 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 initially starts from the recognition that the following main problems are unresolved in ear sensors according to the prior art and are to be overcome by the invention:

• The UFO concept requires a compliant and / or self-adapting material;
• - without adequate contact pressure signal quality and Bewegungsartefakteresistenz 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 Bioverträglichkeit 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 with regard to biocompatibility and hygiene

Further Details of the ear sensor according to the invention will follow with general reference to the attached Drawing explained. 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 bananenfönnigen trajectories from the LED cluster to those at 90 ° or 180 ° tangentially twisted 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 stands out the advantage that the photon paths are maximum. So will too the pulsatile modulation by the arterial perfusion maximum. This arrangement creates a sensor with virtual 360 ° aperture. This is the motion artifact vulnerability of the sensor reduced, because varying contact forces than for responsible main cause at least partially by the rotational symmetry the photon paths are averaged.

The 90 ° arrangements (2 emitters and 2 detectors are in the grid rotated by 90 ° alternately arranged on the perimeter) 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)

Optionally, radially distributed reflectance sensors (eg VIP, PDX) can be used, which work 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 advantageous in combination used with short emitter wavelengths to detect motion artifacts become.

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 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, can an "anchor screen" medial (after the first Bend of the ear canal) are attached.

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 will result in both improved artifact resistance and better signal-to-noise ratio (SNR).

The final and permanent anchoring of the SF-LP and the Surface sealing of the ear sensor by means of Silicone or latex coating in the dipping process. It will a thin, optically transparent, tear-resistant and biocompatible coating. If necessary for a smooth surface relief, the SF-LP be sunk into suitable channels.

For the production of foam cores comes in small quantities Subsequent surface treatment (if necessary by laser) commercially available ear plugs in question. For large numbers should the shaping done via an injection molding tool.

The electrical contacting of the sensors is a back-ear electronics out, at least the signal pre-processing, better still a WLAN interface should realize. 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.

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 3100610 [0003]
• - DE 3609075 [0003]
• - DE 4226973 [0003]
• US 5830137 [0006]
• - DE 102005029355 A1 [0007, 0008]

Cited non-patent literature

• AB Hertzman in "The blond supply of various skin areas as estimated by the photoelectric plethysmograph" (Amer J. Physiol., 124 (1938)) [0004]

Claims (1)

Ear sensor for monitoring at least one physiological measurement by means of a non-invasive measurement in the ear canal, comprising a plurality of sensors, which are arranged in a housing, which is insertable into the ear canal, wherein the plurality of sensors are arranged distributed on the housing circumference, characterized in that the sensors at least two emitters emitting radiation and at least two detectors detecting radiation reflected by layers of tissue, which are arranged at 90 ° to 180 ° offset from the associated emitters.