RU2772849C2 - Device for measuring physiological parameter using wearable sensor - Google Patents

Abstract

FIELD: medical equipment.

SUBSTANCE: invention relates to medical equipment, namely to a sensor device for measuring a physiological parameter of a subject, made with the possibility of being worn by a subject. The device contains case (14), support structure (16), motion sensor (22). The support structure is contained in the case, and it contains contact part (18). The contact part is made with the possibility of placement with the case opposite to the subject’s skin, and it is gas-permeable. The support structure and the case define air space (20) between the contact part and the case. The support structure contains conductive support mesh and non-conductive coating. At the same time, electrical connections to the motion sensor are made using conductive support mesh. The motion sensor is designed to percept the movement of the contact part of the support structure. In this case, the motion sensor is made with the possibility of movement relatively to the case.

EFFECT: due to features of the device design, the implementation of the wearable device for measuring a physiological parameter is provided with the possibility of provision of accurate data with less discomfort for a user.

14 cl, 7 dwg

Description

FIELD OF TECHNOLOGY

The present invention relates to sensors for measuring a physiological parameter of a subject, wherein the sensor can be worn by a user. Examples of wearable sensors include a photoplethysmographic (PPG) sensor, an electrocardiographic sensor, an ultrasound sensor, a heart rate sensor, and a skin monitoring sensor.

BACKGROUND OF THE INVENTION

Monitoring a physiological parameter of a subject using a device, including a wearable device, is becoming increasingly popular. Such devices are convenient to use as they offer increased freedom of movement for the user while monitoring a physiological parameter. Thus, it is possible to measure physiological parameters under a wide range of circumstances, for example, at different levels of physical activity of the subject.

The physiological parameter sensor can be installed on the user in various ways for various applications. The position of the installed physiological parameter sensor relative to the subject may vary depending on the parameter to be measured, the type of physiological parameter sensor, and/or the circumstances under which the physiological measurement occurs.

In many cases, the physiological parameter sensor must be in contact with the user's body. One problem with wearable sensors is the need to ensure that contact is maintained between the physiological parameter sensor and the wearer's body and that contact pressure is maintained at a comfortable level.

One example of a sensor that has become particularly common is a wrist-worn heart rate monitor. This type of sensor provides the user with the ability to monitor some of their vital signs in a simple, non-burdensome manner. Typically, these sensors use an optical PPG sensor that measures the volumetric pulse of the blood, or they use a bioimpedance sensor. Capacitive methods have also been explored to determine heart rate.

PPG-based sensors have the disadvantage that their power consumption is rather high due to the required LEDs. Thus, the disadvantage of these sensors is the low battery life.

Capacitance and bioimpedance based methods (as well as some PPG sensors) require reliable sensor contact with the skin. This can lead to skin irritation and wearing discomfort. One particular reason is the layer of sweat that forms between the sensor and the skin because the sweat cannot evaporate. In addition, it may be necessary for this layer of sweat to remain in order to provide the desired galvanic contact. Some sensors are also susceptible to motion artifacts, making them inaccurate if the subject makes strong or specific movements.

More recently, heart rate and respiration rate sensors have been proposed that use an accelerometer or gyroscope to measure subtle movements caused by arterial dilation and heartbeat. They can be described as movement-based methods. This approach is described, for example, in "Biological Clock: Assessing Heart Rate and Respiration Rate from Wrist Movements", J. Hernandez, D. McDuff, R.W. Richard, 9th International Conference on PervasiveHealth Technologies (“PervasiveHealth”) 2015, pp. 169-176 (“Biowatch: Estimation of heart and breathing rates from wrist motions”, J. Hernandez, D. McDuff, R.W. Picard , 9th International Conference on Pervasive Computing Technologies for Healthcare (PervasiveHealth)).

To improve the accuracy of the results, a combination of sensor functionality can be used, for example, using any combination of accelerometers, gyroscopes, and PPG sensors. The determination of individual blood pulses enables heart rate measurements as well as heart rate variability and heart rate measurements.

Motion Detection To detect the motion of an artery (or other blood vessel) requires contact with the skin, which can lead to discomfort, and the sensitivity must be high. Thus, there is a need for a wearable physiological parameter measurement device that can provide accurate data with less discomfort for the user.

DISCLOSURE OF THE INVENTION

The present invention is defined in the claims.

According to examples in accordance with an aspect of the invention, there is provided a sensory device for measuring a physiological parameter of a subject, configured to be worn by a subject and comprising:

frame;

a support structure mounted on the body, the support structure comprising a contact portion which is configured to be positioned by the body against the subject's skin, wherein at least the contact portion of the support structure is gas-permeable, the support structure and the body defining an air space between the contact part and the body, and

a motion sensor for sensing the movement of the contact portion of the support structure, the motion sensor being movable relative to the housing.

This design of the sensor provides a gas-permeable (and in particular permeable to sweat-induced water vapor) support structure when in contact with the subject. This breathable support structure reduces discomfort. The air space between the contact part and the housing allows the steam to escape so that an air flow can be present above the contact part. The movement of the contact part is determined, while it is separated from the movement of the entire body. For this, the support structure is flexible.

The sensitivity is thus improved in that the detected movement (eg arterial pulse) should only apply kinetic energy to the support structure (with relatively low inertia) and not to the body. Thus, the motion sensor is not in a fixed position in the body of the entire device.

The use of motion detection makes it possible to reduce power consumption compared to a PPG-based wearable system. The invention provides the motion detection system with increased accuracy, while also reducing skin irritation and hence increasing wearing comfort.

The body, for example, includes a bandage to be worn around a finger or wrist, or a patch to be worn on the skin. A wrist bandage can be used to monitor arterial pulse values at the wrist. The overlay can be used on the heart to monitor the movement of the pulse (local movements) as well as the movements of the chest (general movements of the trunk).

The bandage may include various elements such as a rigid containing part and a flexible bandage part. The flexible strapping portion is preferably adjustable so that the device can be adapted to different users.

The support structure, for example, includes a plate that is mounted on opposite edge portions on the housing, with the contact portion offset in the direction of the subject. This displacement maintains contact with the subject, so that the movements of the skin are translated into movements of the contact portion, which can then be detected by the motion sensor.

The motion sensor is, for example, attached to the support structure. It can be attached to:

edge part of the supporting structure,

contact part or

intermediate part between the contact part and the edge part.

When mounted on the edge portion, the motion sensor can detect a rotary motion rather than a linear motion, thus the movement of the contact portion results in a rotary motion on the edge portions.

The motion sensor, for example, contains an accelerometer and/or a gyroscope. One motion sensor or a plurality of motion sensors may be provided. The use of a plurality of motion sensors can provide more accurate measurements, for example by providing more accurate signal filtering to separate local movements of the contact portion.

The support structure may have one of a number of structures such as:

non-conductive mesh or

support mesh and non-conductive coating or

a conductive support grid; and a non-conductive coating, wherein electrical connections to the motion sensor are made using a conductive support grid.

The mesh (and cover, if any) may be supported in the outer frame.

In one example, the support structure comprises a perforated nylon mesh supported in an outer frame.

In all cases, mesh openings provide the desired permeability. The perforations may be large scale (ie as holes in an impermeable layer) or small scale (ie as a material that is inherently permeable).

The support structure or housing may contain one or more additional sensors. This makes the system more stable in the sense that sensors of various functionalities can be used.

The one or more additional sensors, for example, comprise one or more of a PPG sensor, a capacitive sensor, or a bioimpedance sensor.

Preferably, the device further comprises a controller that is configured to activate one or more of the additional sensors depending on the quality of the signal associated with the motion sensor.

Thus, the motion detection functionality can be used to ensure low power consumption. If the signal quality drops below a threshold value, then other detection functions can be used in addition to or instead of this to maintain reliable sensor performance despite the cost due to temporarily increased power consumption.

The controller may be configured to combine signals from multiple sensors with weighting factors to produce a combined sensor signal. This ensures that a reliable sensor signal can be output, which makes using sensors with different functionality the best option.

The controller may be configured to alert the subject that contact with the sensor has been lost, depending on the characteristics of the signal from the motion sensor. This alert can be used, for example, to advise the subject to tighten the case strap or re-attach the case strap (as applicable).

The device is intended, for example, to measure heart rate and/or respiratory rate and/or heart rate variability and/or heart rate.

BRIEF DESCRIPTION OF THE DRAWINGS

Examples of the present invention will now be described in detail with reference to the accompanying drawings, in which:

in fig. 1 depicts a wrist-worn sensor and the concept behind the invention,

in fig. 2 shows a first example of a wearable sensor,

in fig. 3 shows a second example of a wearable sensor,

in fig. 4 shows different possible motion sensor locations,

in fig. 5 shows a third example of a wearable sensor,

in fig. 6 shows a fourth example of a wearable sensor and

in fig. 7 shows the sensor system.

IMPLEMENTATION OF THE INVENTION

The invention provides a wearable physiological sensor that includes a housing and a gas-permeable support structure mounted on the housing that comes into contact with the skin of a subject. An air space is provided between the support structure and the housing. The movement of the support structure relative to the body is determined. This provides a sensor that is user-friendly and also provides good sensitivity in the sense that the detected motion (eg arterial pulse) only has to apply kinetic energy to the support structure with relatively low inertia.

In FIG. 1 shows a wrist-mounted sensor comprising a sensor portion 1 and a wrist strap 2. The sensor part 1 contains a motion sensor such as an accelerometer for detecting local movements caused by the artery. In the illustrated example, it is provided on the underside of the wrist. On the upper side of the wrist, a dispensing block 3 is provided. In the dispensing unit 3, all the usual functions of a watch or a smart watch can be combined together with a sensor output display function.

The touch portion 1 is configured to pass an air flow through the touch area, as shown by arrows 4. This air flow enhances the user's comfort. For this purpose, the sensory part 1, the strap 2 can also be porous, as shown schematically by the holes 6. The whole device forms a bandage, which in this example is intended to be worn around the wrist.

Figure 2 shows the touch device in more detail. The sensor device is designed to measure a physiological parameter of a subject. In this example, it also contains a wrist band located around the wrist 12 of the subject. For simplicity, only the touch portion is shown in detail, with the output device schematically shown as 10. In this example, the touch portion is intended to be located on the upper side of the wrist. Thus, in FIG. 1 and 2 show that, in the case of a wrist-mounted device, the sensor portion may be on the upper or lower side of the wrist, and a sensing portion (like a watch face) may also be provided in the same or different location as the sensor portion.

The sensor device includes a housing 14 and a flexible support structure 16 mounted on the housing. The support structure includes a contact portion 18 which comes into contact with the user's skin. In use, the contact part 18 is against the skin. This is the result of the execution of the support structure 16 and the housing 14.

For example, support structure 16 may be a non-planar plate that is offset in the direction of the subject. By this is meant that the natural shape of the support structure is such that the contact portion 18 is pressed against the wrist. As shown, it may have a bent shape. When the sensor is attached to the wrist with a suitable tightness, the contact part is pressed against the skin.

Alternatively, the support structure may be flat, such as a flat stretched mesh that extends in a plane that, in use, intersects with the subject's skin plane. The purpose is to maintain contact between the contact part 18 and the subject when the sensor device is worn.

At least the contact part 18 of the support structure is gas-permeable, in particular to steam. This can be achieved by providing the support structure 16 as an open mesh or lattice structure, or as a continuous layer with a series of holes. The support structure 16 may have a single design or it may have a different design of the contact part compared to other parts of the support structure with which the contact part is attached to the body 14. It has some flexibility and can be spring loaded to move to a specific shape.

An air space 20 is provided between the contact part 18 and the housing 14. This means that the sweat generated on the contact part 18 can penetrate through the support structure and then be dispersed to the environment.

To sense the movement of the contact part 18 of the support structure, a motion sensor 22 is provided. The motion sensor (in particular the movable part of the motion sensor) is movable relative to the housing 14. It is provided within the housing 14 and is therefore protected by it. It contains an accelerometer and/or a gyroscope, or a combination of a plurality of accelerometers and/or a plurality of gyroscopes.

The motion sensor 22 can be mounted on the contact part 18 itself in such a way that a direct detection of the movement to be detected (for example, arterial pulses at the contact part) takes place. However, the motion sensor can be removed from the contact part. In this case, the support structure acts as a motion transmission mechanism from the contact part to the motion sensor. Motion is applied to the support structure on the contact part, and this motion is defined elsewhere in the support structure.

For example, in FIG. 2 shows a motion sensor on the edge of the support structure 16. In this position, it detects the angular movement resulting from the change in the position of the contact part, and not the direct translation of the contact part 18.

To determine the angular position, there is a direct relationship between the linear transition on the contact part and the angle formed between the contact part and the housing. In this way, a certain angle can be converted into a translation level.

For the direct determination of translational motion, the offset versus time relationship provides a direct measure of pulse pressure as a function of time.

Slowly varying movements (outside the frequency range of interest) detected by the motion sensor can be filtered from the motion signals so that only arterial pulse movements are processed.

Certain motion (ie, arterial movements) is transmitted to the support structure 16 and not to the housing 14. For example, a motion sensor may be attached to the support structure only. This improves the accuracy of the determination, since the inertia of the part that is mechanically connected directly to the subject is reduced.

The electrical connection to the motion sensor can be made with wires that do not interfere with movement. However, as an alternative, the support structure 16 includes conductive lines, for example formed in the form of a conductive grid.

This transducer design uses a gas permeable support structure to reduce discomfort. The air space 20 provides an outlet for sweat. The motion sensor has low power consumption compared to a PPG-based wearable system.

The support structure may have a plurality of parts such as mesh and cover. The mesh may provide the desired mechanical and/or electrical properties of the support structure, and the cover may provide the desired skin contact properties. Instead, a single layer mesh can be used.

The support structure 16 is made, for example, in the form of a conductive mesh, for example with a biocompatible coating. It may have a total thickness in the range of 0.5 mm to 2 mm. The mesh is stiff enough to stay in contact with the skin, yet flexible enough to respond to arterial movements. The rigidity of the support structure may be a natural property of the material used, or a less rigid material may be provided in the framework that retains the resilience of the material.

Part of the conductive mesh can be used to transmit electrical signals from the motion sensor and to power the motion sensor from the built-in battery.

The support structure material must be strong enough for long-term operation and therefore there are limits to how thin it can be. The outer material will be biocompatible. The support structure may extend approximately the entire width of the dressing (by which is meant the width direction of the strap, ie from left to right in FIG. 1). The height of the airspace 20 is, for example, in the range of 0.5 mm to several mm.

The support structure may only come into contact with the skin at a local contact portion, or a large contact area may be provided. There may be only one large grid of the support structure, or a plurality of smaller grids of the support structure.

The support structure, for example, comprises a nylon mesh supported within a peripheral frame. An alternative is a rubber mesh or any other "breathable" material suspended from the frame. The mesh supported within the frame may comprise conductive lines or a conductive mesh as explained above to provide an electrical connection to the motion sensor.

The body 14 may also be gas-permeable where it comes into contact with the skin, such as in the strap portion 23. The wrist strap is made, for example, of an absorbent or permeable material, or has microscopic and/or macroscopic holes to allow sweat to escape.

In FIG. 2 shows the device worn around the wrist. Instead, it may be designed to be worn around the finger in the form of a ring, or attached to the phalanx of the finger, or attached to the earlobe.

In FIG. 3 shows a modification in which additional sensors are provided in the housing mounted on the support structure 16. In FIG. 2 shows a PPG sensor 24 mounted on the contact part 18, comprising two LEDs 24a, 24b and a photodiode sensor 24c. The PPG sensor provides an alternative mechanism for determining the pulse.

The components of the PPG sensor can be mounted on a support structure as shown. The LED and photodiode shown in Fig. 2 can instead be installed on the inside of the case. The LED light may pass through the holes of the support structure 16 and be appropriately received by the photodiode, or the material of the support structure may be transparent to the wavelength of the LED light. This has the advantage that the design can be made more robust and also that less heat will be dissipated by the skin due to the photodiode and LED.

Other sensors such as capacitive sensors and/or bioimpedance sensors may be provided to detect the pulse. Then, the system can use a combination of sensor readings to improve accuracy.

In FIG. 4 shows three possible locations for motion sensor 22. As explained above, one option is to place a motion sensor on the edge portion of the support structure 16 to detect angular movement. This has the advantage that the entire sensor assembly is mounted on housing 14, making the whole structure robust. It is shown as location 30. Another option is to place it on the contact part 18, shown as location 32. Another option is to place it at an intermediate location between the center of the contact part of the support structure and the edge. Thus, the sensor does not block the permeable support structure in the contact part, but can still be used to determine the linear transient displacement.

In all cases, the sensor itself, or the contact part of the sensor, can move relative to the housing 14. The sensor can transmit its sensory signals by wire within the device to a signal processing unit in the housing, or wirelessly to this signal processing unit or to remote signal processing unit.

A plurality of motion sensors may be provided at different locations. They can be used to make the pulse detection more sensitive, and motion sensors can also be used to correct for motion artifacts present in other additional sensor signals, such as a PPG sensor or a capacitive sensor and/or a bioimpedance sensor.

The motion sensor shown in Fig. 1-3 may be on the upper side of the wrist (on the side where the watch face would be) instead of on the lower side of the wrist as shown in FIG. one.

In FIG. 5 shows that the support structure 16 may be in the form of a flat tension mesh. Therefore, the support structure does not need to be a curved structure, and the position in which the support structure 16 is installed provides the necessary contact when the device is put on. Thus, the stack deforms to follow the shape of the wrist when the device is worn. The mesh has some bending resistance so that the contact part is against the skin. However, the mesh is quite flexible in the sense that it does not inhibit the movement of the artery, and movement can still be detected at the contact portion or away from the contact portion.

The above examples are based on a bandage type device worn around the wrist or finger, for example.

In FIG. 6 shows the execution in the form of an overlay.

The device comprises a rigid housing 40 on which is mounted a support structure 16 and a motion sensor 22, all of which function exactly as described above. The body 40 is attached to the skin by means of an adhesive patch 42. The airspace 20 is open to the environment. This can be achieved in a number of different ways. One option is to provide pad 42 on the sides only, leaving an open air passage to space 20. Another option is to provide holes 44 in housing 40 in combination with gas permeable pad 42. In this way, the entire structure can "breathe" and air space 20 can then be physically closed (on a more macroscopic level).

The overlay design can be applied to the chest over the heart. Thus, based on a motion sensor that directly measures the beats of the heart, a seismocardiogram can be obtained. The sensitivity may be sufficient to measure individual heartbeat cycles. By additionally turning on the PPG sensor, the pulse wave propagation time (PWT) can also be determined from the time difference between the (first) beat in the motion sensor signal and the pulse measured in the PPG signal.

The heart beat is determined based on local motion detection. More global motion detection can be used to determine respiration rate by functioning as a belt with a chest strap.

In addition, the device may contain ECG electrodes, in which case a pre-ejection phase (PEP) may be obtained.

In FIG. 7 depicts the entire system in which controller 60 receives sensor signals 62 from sensor hardware 64 and generates an output signal 66.

The controller 60 may reside in a device body and the device may include an output device such as a display. Thus, the system can be completely autonomous, for example in the form of a wrist band. Instead, controller 60 may be remote and provide wired or wireless communication from sensor hardware 64 to controller 60.

Controller 60 may perform various signal processing functions to improve measurement accuracy and/or to minimize power consumption, and some of these approaches are described below.

The first approach refers to the choice of sensor functionality to be used at any given time when there are multiple types of sensors. If the signal-to-noise ratio in motion-based heart rate detection is high, for example, due to the presence of weak motion artifacts, then other detection functions (PPG or capacitive or bioimpedance) can be disabled to save power. Then, only output data 66 is obtained from the motion sensor system, which is a function for which power consumption is very low. Other sensor functionality can be enabled as soon as the motion sensor system produces invalid signals. Thus, additional sensors can be used when increased accuracy is needed.

Another indication of poor signal quality may be when the heart rate detection of one of the functionals (eg, a motion sensor-based functional) differs from that of another functional (eg, a PPG-based functional).

Thus, one or more additional sensors may be activated depending on the quality of the signal associated with the motion sensor. Instead, the motion sensors may operate intermittently in order to reduce the frequency of other measurements.

The second approach refers to the use of motion detection to provide verification of the operation of other sensors. The accelerometer signals can be used, for example, to check if an optical sensor (eg PPG sensor) is in contact with the skin. If not, the user may be prompted to tighten the bandage or re-apply the bandage.

Thus, the subject may be warned that contact with the sensor has been lost, depending on the characteristics of the signal from the motion sensor. In particular, the absence of local acceleration signals (ie, the absence of a definite pulse signal) may be an indication that sensor contact has been lost.

The third approach refers to the combination of multiple motion sensors. The optical sensor system is sensitive to changes in blood volume in the superficial layers of the skin, while the motion sensor system is sensitive to changes in blood volume deep in the tissue.

The ratio of the two indicators is indicative of the structure and reaction of blood vessels. In addition, the average heart rate can be calculated as follows:

w*M1+(1-w)*M2.

Here, w is a weighting factor that can be determined based on the validity of the first functional M1 (ie based on motion) and the second functional M2 based on eg PPG, bioimpedance or capacitance. The reliability of M1 or M2 can be based on the level of signal distortion to determine the weighting factor w.

When PPG detection is enabled, signal distortion by ambient light can be compensated for by known techniques, for example by using a duty cycle in which the LEDs are turned on and off and in which the off state signal is subtracted from the on state signal. In addition, angle-selective filtering before the PPG photodetector or wavelength-selective filtering (eg, infrared blocking filter) can be used.

The invention is of primary interest for a wearable heart rate device for obtaining one or more of heart rate, heart rate variability, and heart rate (eg, detecting arterial fibrillation). In addition, the respiration rate can be obtained. Such a wearable device can be used in a general hospital room or at home.

As stated above, the main physiological parameter studied is heart rate or heart rate-related parameters. Other possible measurements include blood oxygen saturation (SpO2) using an SpO2 sensor, ECG measurements using ECG electrodes in contact with the skin, and ultrasound measurements using an ultrasonic transducer.

As described above, implementations use a controller. The controller may be implemented in numerous ways, in software and/or hardware, to perform various desired functions. A processor is one example of a controller that uses one or more microprocessors that can be programmed using software (eg, microcode) to perform the necessary functions. However, the controller may be implemented with or without a processor, and may be implemented as a combination of special purpose hardware to perform some functions and a processor (eg, one or more programmed microprocessors and associated circuitry) to perform other functions.

Examples of controller components that may be used in various embodiments of the present invention include, but are not limited to, conventional microprocessors, application specific integrated circuits (ASICs or ASICs), and field programmable gate arrays (FPGAs).

In various embodiments, the processor or controller may be associated with one or more storage such as volatile or non-volatile computer memory such as RAM, PROM, EPROM, and EEPROM. The store may be encoded by one or more programs that perform the necessary functions when executed on one or more processors and/or controllers. The various stores may reside within the processor or controller, or may be moved so that one or more programs stored therein may be downloaded to the processor or controller.

Other variations of the described examples can be understood and implemented by a person skilled in the art in the implementation of the present invention in practice after reading the drawings, description and appended claims. In the claims, the word "comprising" does not exclude the presence of other elements or steps, and singular grammatical indicators do not exclude the plural. The mere fact that certain measures are listed in mutually distinct dependent clauses does not in itself indicate that a combination of these measures cannot be used successfully. All references in the claims are not to be construed as limiting the scope of the claims.

Claims (20)

1. A sensory device for measuring a physiological parameter of a subject, configured to be worn by a subject and comprising: body (14); a support structure (16) contained in the body, wherein the support structure comprises a contact part (18) configured to be positioned by the body against the subject's skin, wherein at least the contact part (18) of the support structure is gas-permeable, and the support structure and the body define an air space (20) between the contact part and the housing, the support structure comprising a conductive support grid and a non-conductive coating, the electrical connections to the motion sensor being made using a conductive support grid; a motion sensor (22) for sensing the movement of the contact part of the support structure, the motion sensor being movable relative to the housing. 2. The device of claim. 1, in which the body contains a bandage to be worn around the finger or wrist or patch to be worn on the skin. 3. The device according to claim 1 or 2, in which the support structure (16) comprises a plate that is mounted on opposite edge parts on the housing, while the contact part (18) is located with the possibility of coming into contact with the skin of the subject. 4. Device according to claim 3, wherein the motion sensor (22) is attached to the support structure. 5. The device according to claim 4, in which the motion sensor (22) is attached to: edge part of the supporting structure, contact part (18) or intermediate part of the support structure between the contact part and the edge part. 6. Device according to claim 1, wherein the support structure (16) comprises a mesh supported in an outer frame. 7. A device according to any one of the preceding claims, wherein the motion sensor (22) comprises an accelerometer and/or a gyroscope. 8. The device according to any of the previous claims, which contains motion sensors. 9. The device according to any of the preceding claims, which also contains one or more additional sensors mounted on the support structure or housing. 10. The device of claim 9, wherein the one or more additional sensors comprise one or more of a PPG sensor, a capacitive sensor, or a bioimpedance sensor. 11. The device according to claim 9 or 10, which also contains a controller (60) configured to activate one or more of the additional sensors (24a, 24b, 24c) depending on the quality of the signal associated with the motion sensor. 12. The device according to any one of paragraphs. 9-11, which includes a controller (60) configured to combine sensor signals with weighting factors to obtain a combined sensor signal. 13. The device according to any of the preceding claims, comprising a controller (60) configured to issue a warning to the subject that contact with the sensor has been lost, depending on the characteristics of the signal from the motion sensor. 14. An apparatus according to any one of the preceding claims, which is capable of measuring heart rate and/or respiration rate and/or heart rate variability and/or heart rate.

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