WO1999022641A1

WO1999022641A1 - Device and method for determining physiological data, and corresponding use

Info

Publication number: WO1999022641A1
Application number: PCT/FR1998/002335
Authority: WO
Inventors: Claude Gagnadre; Sandrine Thuillier; Michel Valette; Henry Lher; Olivier Sentieys; Michel Billon
Original assignee: Universite De Rennes I; Universite De Bretagne Sud
Priority date: 1997-11-03
Filing date: 1998-10-30
Publication date: 1999-05-14
Also published as: EP1035798A1; AU1038499A; FR2770390A1; FR2770390B1

Abstract

The invention concerns a device and a method for determining physiological data, using: at least one sensor placed in contact with a subject's skin, reacting in particular to variations in the subject's instantaneous blood pressure, and delivering a signal (151) representing said instantaneous blood pressure; and means (19) for processing and analysing said signal representing the instantaneous blood pressure, delivering at least a physiological information (192); said sensor comprising at least an optical fibre portion (11) subjected to deformations based in particular on said variations in the instantaneous blood pressure, a source of light (14) being disposed at one first end (111) of said optical fibre portion (11), and a photodiode (15) being disposed at the second end (112) of said optical fibre portion (11), and powering both said processing and analysing means (19).

Description

Device and method for determining physiological information, and use thereof.

The field of the invention is that of determining one or more physiological information representative of the state of a human or animal subject. More specifically, the invention relates to an autonomous device, at least as far as the measurement reading is concerned, and capable of providing physiological information continuously.

A particular field of the invention is that of sleep analysis, and in particular of the recognition and quantification of the different phases of sleep in a subject. In this case, the invention relates to an autonomous and portable device for recognizing sleep phases.

The applications of recognition and quantification of sleep phases are numerous. They range from the medical field (aid in the diagnosis of sleep apnea in pulmonology, sleep disorders, etc.) to the "general public" field (evaluation of the quality and quantity of a person's sleep, awakening in a preselected phase).

In the medical field, recognition of sleep phases is generally obtained using polysomnographs, complex and expensive systems, the use of which is reserved for specialized hospital services. These systems analyze in deferred time a plurality of biological signals corresponding to a night's sleep. They can reach a good phase recognition score of around 90%.

However, the technology for acquiring biological signals in these systems is complex and uncomfortable for the patient. It is based on the use of a series of electrodes fixed on the patient's body, and connected to a treatment unit. The mere presence of these electrodes and their connecting cables can disturb the patient's sleep, especially if it is a person suffering from sleep disorders. This therefore introduces a bias into the measurements made. This bias is generally further aggravated by the fact that the patient is in a particular environment (hospital room) which is not usually his own.

In the general public domain, there is currently no affordable and comfortable device for regular monitoring of sleep phases. Recognition of the sleep phases can also make it possible to control the awakening of a subject, according to these phases. We know indeed that the awakening must take place, to be pleasant, during a period of light slow sleep. We may also want to wake up in a REM sleep phase, to remember your dreams, or even after one or two periods of deep sleep, which is the most restorative.

Known devices having this objective are for example described in patent FR 86 06241 and the certificate of addition FR 88 10126. The device of the first document is not effective, because it is based on a simple calculation of sleep cycles, without involving any physiological data specific to the subject. The second document presents a device limited to the recognition of REM sleep, and seems particularly uncomfortable, since it requires the presence of electrodes at the corner of the eyelids.

Another wake-up device is described in patent application FR 91 09702.

This device is based on the use, in a portable box, of a cardiac activity sensor making it possible to follow the pulse of the subject. Knowing that the heart rate varies according to the different phases of sleep, their recognition is then, in principle, easy.

In practice, the inventors have however observed that taking into account the heart rate information alone does not make it possible to obtain satisfactory results. The success rate of recognition by this system remains indeed less than 70%, which is insufficient to consider its use, in particular in the medical field.

More generally, knowledge of physiological data presents many advantages, whether for diagnostic assistance in a medical environment, long-term monitoring of patients, detection of abnormal situations, ...

In practice, the reliable devices offering these possibilities are reserved for the medical field. It requires the presence of a dedicated machine connected to the patient by a plurality of sensors, with all the drawbacks already described above.

Most of the known devices intended for the general public are limited to the detection of the pulse. While this is important information, it is generally insufficient to draw a reliable conclusion. There are also known devices capable of determining blood pressure, but these are complex systems requiring impractical handling and not being able to deliver continuous measurements, but only on demand (like conventional polysomnographs).

PCT patent application WO-94/16610 describes a device which overcomes most of these drawbacks. This device makes it possible to determine at least one datum representative of the pulse, of the blood pressure or of the respiration, in a simple manner.

These data are obtained from a suitable analysis of the instantaneous blood pressure signal.

To obtain this result, the device comprises a piezoelectric sensor placed in contact with the skin of a subject, and reacting to variations in instantaneous blood pressure. However, this technique cannot be implemented in such a simple manner, the signal detected by the piezoelectric sensor being of course very disturbed by the movements of the subject.

A second similar sensor, isolated from the subject's skin is therefore necessary, to detect the only movements. Then, a specific processing is carried out, to obtain a corrected signal, exploitable by processing means.

The presence of this double sensor has various drawbacks, in particular as regards the cost price, the size, in particular when it is desired to integrate the device in a small case such as a watch case, the precision required for assembly, ...

In addition, in particular when the system is placed in a watch, an additional sensor is still necessary, to determine the stress induced by the tightening of the bracelet (it is indeed clear that the amplitude of the measured signal varies as a function of this tightening) .

Furthermore, the precision obtained by this system may prove to be insufficient in certain fields.

The invention particularly aims to overcome the various drawbacks of this state of the art. More specifically, an object of the invention is to provide a device for determining physiological information, and a corresponding method, which has increased precision compared to known techniques.

Another objective of the invention is to provide such a device, which is of reduced production cost both with regard to the elements used and their assembly.

The invention also aims to provide such a device, which is compact, can be easily placed, for example, inside a watch case.

An additional objective of the invention is also to provide such a device, which makes it possible to detect certain extraordinary events, such as a fall.

These objectives, as well as others which will appear subsequently, are achieved according to the invention using a device for determining physiological information, comprising: - at least one sensor placed in contact with the skin of a subject, reacting in particular to variations in the instantaneous blood pressure of said subject, and delivering a signal representative of said instantaneous blood pressure; and means for processing and analyzing said signal representative of instantaneous blood pressure, delivering at least physiological information, said sensor comprising at least one portion of optical fiber undergoing deformations depending in particular on said variations in instant blood pressure, a source of light being placed at a first end of said portion of optical fiber, and a photodiode being placed at the second end of said portion of optical fiber, and supplying said processing and analysis means.

Thus, the invention is based on the analysis of micro-deformations of one (or more) optical fibers. It is possible, with this technique, to obtain very high precision, for a reasonable cost price. The resulting size can be greatly limited, and assembly is easy. This is all the more true since the same assembly also makes it possible to obtain information on the tightening force of the support strap (in the event of the use of a strap). The analysis of micro-deformations is known in certain fields very far from the invention. However, these known methods (see for example "fiber optic sensors and associated networks", pr P. Ferdinand) apply to long optical fibers, and requires bulky equipment. No one has ever considered using a very small optical fiber, and even less in the field of determining physiological information.

Furthermore, known techniques propose measurements by reflectometry. The technique of the invention, however, is based on the use of a photodiode at the end of the fiber opposite to that through which the light is introduced.

Advantageously, said sensor comprises a plate in contact with the skin of said subject, the displacements of which are passed on to clamping means comprising a first and a second jaw enclosing said portion of optical fiber over part of its length.

According to a preferred embodiment of the invention, said means of tightening comprise a first planar jaw, and a second jaw having a series of grooves perpendicular to the axis of said portion of optical fiber.

This structure is simple to implement (one of the parts being flat) and proves to be effective, in particular if the number of streaks and the pitch between them are well chosen.

Thus, good results are obtained when said second jaw has between 8 and 12 streaks. More generally, according to the invention, the number of streaks representing a compromise between the sensitivity and the width of the resonance peak is sought to ensure sufficient stability, by promoting the first resonance. Advantageously, said plate and said clamping means are interconnected by means of a ball. This improves the quality of the repercussions of movements due to blood pressure, regardless of the movements and position of the arm.

According to a particular characteristic of the invention, the device further comprises at least one accelerometer, and preferably two accelerometers, corresponding respectively to two perpendicular directions.

These are used to detect falls and sudden movements in particular.

Said processing and analysis means advantageously comprise means for frequency decomposition (by filtering or Fourier transform) of said signal representative of instantaneous blood pressure, so as to distinguish at least two pieces of information belonging to the group comprising: piece of information representative of the force of clamping of said sensor against the skin of said subject; - information representative of the respiratory rate of said subject; one or more pieces of information representative of the blood pressure of said subject. According to one embodiment, the device of the invention comprises means for transmitting data signals to a remote unit for processing and / or restoring physiological information.

The invention also relates to a method for determining physiological information, comprising in particular the following steps: - application of a sensor in contact with the skin of a subject, said sensor comprising at least one portion of optical fiber undergoing functional deformations in particular variations in the instantaneous blood pressure of said subject; emitting light at a first end of said portion of optical fiber; processing and analysis of said light signal, so as to determine at least one physiological item of information, as a function of the disturbances of said signal. Advantageously, said processing and / or analysis step comprises at least one of the steps belonging to the group comprising the steps of: determining information representative of the tightening force of said sensor against the skin of said subject; amplification and bandpass filtering of the electrical signal corresponding to said light signal; - analog / digital conversion of measured values; separation of at least two distinct pieces of information, by filtering or Fourier transform; data processing, by statistical decision, forecast decision and / or fuzzy logic; - transmission of at least one of said pieces of information and / or at least one result of said data processing to a remote station. Said information may in particular belong to the group comprising: information representative of the amplitude and / or respiratory rate; information representative of the heart rate and / or variance; - information representative of the blood pressure wave and / or its variance. Advantageously, the method also comprises a step of detecting an abnormal situation in said subject, as a function of a signal delivered by at least one accelerometer. The device and method described above can be used for many applications, such as: monitoring people at risk; recognition of sleep phases; awakening of the subject in a predetermined sleep phase and / or in a determined time interval; drowsiness detection; sleep quantification; sleep disorder detection; sleep apnea detection; - help in monitoring cardiovascular diseases; programming of devices according to sleep phases; assists in the analysis of Parkinson's disease; helps in the prevention of cerebral ischemia; respiratory monitoring; - infant monitoring; polyphasic sleep analysis; observation of recovery after exercise; monitoring of a level of vigilance; helps in the detection of stress; applications to livestock. Other characteristics and advantages of the invention will appear more clearly on reading the description of a preferred embodiment, given by way of simple illustrative and nonlimiting example, and of the appended drawings, among which: FIG. 1 is a block diagram of a device according to the invention; FIG. 2 shows an example of a signal that can be detected at the output of the optical fiber of the device of FIG. 1; FIG. 3 shows the signal of FIG. 2, transformed in the frequency space; Figure 4 is a simplified block diagram of the method of the invention; FIG. 5 illustrates a method of mounting the light source and the optical fiber of FIG. 1; FIG. 6 is an electrical diagram of the amplification means of FIG. 1.

As indicated above, the invention relates to a device for determining portable and autonomous physiological information.

In the embodiment described below, it is inserted in a watch case, and can therefore be worn on the wrist. Many other arrangements can of course be envisaged, depending on the needs and applications (the elderly, athletes, infants, animals, etc.). Different means other than a bracelet can be used to maintain a sensor such as that described below in contact with the subject's skin.

The invention is based on the use of an optical micro-deformation sensor. An optical fiber is sandwiched between two jaws, forcing it to micro-deformation. Light power is injected into the fiber, and the resulting illumination is analyzed.

A variation in the force applied to the jaw creates local deformations which generate a variation of the local index, due to the photoelastic effect of the fiber. This influences the modal balance, and therefore on the output intensity.

An embodiment of the invention is illustrated in FIG. 1.

A portion of optical fiber 11, with a length of the order of 2 cm (for example), is placed between two jaws 12 and 13. The fiber 11 is for example a 50/125 silica fiber with an acrylate coating of 250 μm in diameter.

The optical fiber 11 comprises an optically transparent central core with zero applied stress, a layer forming an optical sheath, concentrically surrounding the core and having a refractive index lower than the core, and possibly one or two protective layers more elastic than the first two materials are brought together concentrically.

When a microdeformation is applied to the fiber, part of the light which propagates in the central core in the vicinity of the microdeformation is directed into the sheath layer. This then reduces the intensity of the light propagating over the entire length of the optical fiber. The sensitivity of the phenomenon is amplified when the microdeformations are distributed along the fiber by a distance depending on the numerical aperture of the fiber and the diameter of the core.

It is of course possible to provide several optical fibers mounted in a similar manner, to obtain several readings, and to refine the treatments and analyzes. Advantageously, one of the constraint parts, or jaws, (12) is flat.

The other jaw 13 is a serrated part, having several ridges 131, on which the fiber 11 is supported.

The number of streaks 131 may be of the order of 8 to 12, and for example of 10. The pitch between two consecutive streaks is preferably 1.1 mm, for the fiber considered.

More precisely, the number of streaks and the pitch between them are chosen so as to offer the best compromise between the sensitivity and the width of the peak of the first resonance to obtain sufficient stability. Ferdinand, in the work already cited, evaluated the sensitivity of stress detection by a fiber subjected to micro deformations.

The latter determined the resonance steps and observed the very high sensitivity of a fiber optic sensor compared to that obtained with a point contact (equivalent to a streak) (1.6 dB) for a force of 9 N. measurements have also shown that the width of the resonance peak is a function of the number of streaks and that, for a given number of streaks, the widest peak is not obtained at the first resonance.

These known results were obtained by reflectometry techniques, therefore using bulky means. To minimize the size of the sensor, the inventors favor the first resonance, and have determined a number of streaks representing a compromise between the sensitivity and the width of the resonance peak to ensure sufficient stability. They found that, with 10 streaks, one obtains, under a static stress of 10 N, a resonance pitch of 1.10 mm, 30% of leakage measured at the end of the fiber. A light source 14, for example of power 1 mW, with pulse or continuous excitation, is placed at one of the ends 111 of the fiber 11. It is for example a laser diode, a light-emitting diode ( LED) or a surface emission laser diode (which has the advantage of higher efficiency).

At the other end 112 of the optical fiber is placed a photodiode detector 15 (for example of the BPW 34 type distributed by SIEMENS (registered trademarks)). This detector 15 delivers an electrical signal 151, representative of the light signal received, carrying information representative of the micro-deformations undergone by the fiber 11.

These micro-deformations are due to the stresses transmitted to the jaws 12 and 13. These stresses correspond to the displacements of a plate 16, integral with the jaw 12 via a ball 17.

The plate 16 is intended to come into contact with the skin of a subject. It reflects the movements existing on the surface of the skin and in its vicinity, and in particular those due to variations in instantaneous blood pressure. The presence of a ball 17 between the jaw 12 and the plate 16 makes it possible to obtain flexibility in mounting, so that the plate 16 remains as fully as possible applied against the subject's skin.

It will be noted that the mounting and assembly are very simple, in particular as regards the optical part. In particular, no additional optical component to ensure the injection is necessary. The optical fiber is positioned for example using a positioning and holding element in the shape of a "V". The light source 14 is placed in the axis, using a preformed part 51 receiving on the one hand the source 14 and on the other hand the end 111 of the optical fiber, according to the assembly illustrated in FIG. 5. The device of the invention also comprises means for processing and analyzing the signal 151.

These means advantageously include a first low-pass amplifier

181, which delivers a continuous component 182 representative of the tightening of the bracelet (in the event that the device described above is placed in a watch case conventionally held by a bracelet). This amplifier supplies a voltage of 1 volt for a photodiode current of 0.5 mA.

A second bandpass amplifier 183 delivers a blood pressure signal 184, having a gain of 50 in the bandwidth 0.1 - 10 Hz.

An embodiment of these amplification means is illustrated in FIG. 6. The amplification chain comprises two stages 61 and 62 supplied with monotension and with very low consumption. The output 63 of the first stage 61 is a function of the tightening of the bracelet. This one, of standard type, must have an elasticity of 1 mm / N and be tightened in a comfortable way, that is to say approximately with a tightening force ranging between 5 and 10 N. For a zero tightening the tension output voltage is around 1 V. For maximum tightening, the output voltage is around 2 V, ensuring very good dynamics for measuring bracelet tightness.

Indeed, the measurement of this quantity is very important since the amplitude of the second stage output signal is a function of the tightening of the bracelet. The more the bracelet is the better the cardiac impulse is transmitted, through the muscle and the skin via the bracelet, to the serrated moving part compressing the fiber.

The second stage 62 has the function of amplifying the cardiac pulse in the passband 0.1 Hz-10 Hz. This composite signal 64 includes information on the heart rate, an image of the difference in blood pressure, respiratory parameters and possibly a disturbance as a function of movement or of nerve sources exciting the bracelet.

These different variables are separated by the processing means.

Figure 6 is not described in detail, the montags used being conventional in themselves. As an indication the components can be the following:

D: DEL;

RI: 200 kΩ;

R2: 150 kΩ;

R3: 1 MΩ

R4: 20 kΩ

R5: 40 kΩ

R6: 51 kΩ

R7: 47 kΩ

R8: 1.8 MΩ;

Cl: 47 μF;

C2: 8.2 nF;

U1, U2: LM 6142

The processing means 19 format and analyze the signals 182 and 184. In particular, they extract the various information representative of respiration and the heart rate, and perform various calculations on this information, such as those described below in relation with figure 4.

An example of signal 184 is presented in FIG. 2. FIG. 3 presents the same signal, transformed in the frequency space. We can easily distinguish: a respiratory component 31; the fundamental 32 of the heart rate; the 2nd (33) and 3rd harmonics of the heart rate. Advantageously, the processing means 19 take account of actimetric information delivered by two accelerometers 201 and 202, which supply two conditioners 203 and 204. This information is particularly relevant at the time of certain transitions during sleep or in the event of a fall.

The accelerations are measured in the following directions, defined by the resting forearm lying horizontally: direction parallel to F forearm; vertical direction. The accelerometers are, for example, piezoelectric cells. The processing means 19 still manage 191 the laser emission. The information obtained 192 feeds transmission means 21 to a remote station 22, such as a microcomputer. Of course, this information can also be reproduced, by a screen and / or a speaker, directly on the housing.

We will now describe the process of the invention, implemented by the device described above, and illustrated by FIG. 4. The optical fiber is therefore subjected to micro-deformations, which plays on the light signal transmitted by the fiber. optical. This light signal 41 is detected (42) by a photodiode, and amplified (transfer coefficient: 2 V / 20 μW).

The electrical signal thus obtained is separated into two elements: a continuous component 43, representative of the tightening of the bracelet; - a composite signal 44.

This composite signal 44 is amplified (by 50) and undergoes bandpass filtering (0.1 Hz-10 Hz) 45.

At the same time, movements are detected (46) by the accelerometers perpendicular and transverse.

The different information obtained is converted (47) from analog to digital and stored in memory, under the control of a sequencer 413 (64 measurements / channel / s). Then, we separate (48) the different variables forming the composite signal

(Figure 3), by filtering or by Fourier transform. The tightening of the bracelet is taken into account, knowing that the tighter the bracelet, the higher the amplitude of the heart wave.

The separation 48 makes it possible in particular to extract the following information: - respiratory amplitude and frequency 49 (around 0.3 Hz); heart rate and variance 410; 411 heart rate harmonics; amplitude of the pressure wave and variance 412. With the aid of this information and the actimetric data, the application-specific processing 415 is carried out. These may notably be statistical, forecasting or fuzzy logic decisions.

We can in particular verify that the variance of the pulse (equal to the heart rate multiplied by 60) corresponds substantially to the width at half-height of the main line. Depending on the situation, this line can be very resonant (deep sleep) or very wide (awakening).

Similarly, the relationship between the amplitude of the second harmonic and the amplitude of the fundamental is an objective indication of the purity of the tensor wave, and therefore a function of the state of the subject.

After the separation step 48 (which can be carried out in the watch case or in a delocalized case), one can envisage a transmission 414, for example via the telephone network, to a monitoring station. This provides a remote monitoring service for people at risk. In the event of a fall or significant and / or abnormal variations in certain physiological parameters, detected from a algorithm implemented locally, an alarm is automatically emitted by the box, and transmitted to the monitoring station. To confirm the urgency of the call, a telephone connection is established from this station. In other words, it is telesurveillance (and not telemedicine). The decision to generate an alarm partly takes into account the past. This calls for fuzzy logic techniques (associations of objective and subjective information).

As already indicated, the invention has many other applications. As an indication, we can recall: assistance in the detection of apneas (the device emitting an alarm in the event of a risky situation, or generating an unlocking action); helps in the detection of drowsiness, for example for shift work, tiring and / or dangerous; applications to breeding, for example to check that pigs have not had any disease (by monitoring the sleep and temperature of the animal), or for behavioral monitoring (in particular for breeding animals);

Claims

1. Device for determining physiological information, comprising: at least one sensor placed in contact with the skin of a subject, reacting in particular to variations in the instantaneous blood pressure of said subject, and delivering a signal (151) representative of said instantaneous blood pressure ; and means (19) for processing and analyzing said signal representative of instantaneous blood pressure, delivering at least physiological information (192), characterized in that said sensor comprises at least one portion of optical fiber (11) undergoing deformations which are a function in particular of said variations in instantaneous blood pressure, a light source (14) being placed at a first end (111) of said portion of optical fiber (11), and a photodiode (15) being placed at the second end ( 112) of said portion of optical fiber (11), and supplying said processing and analysis means (19).

2. Physiological information determination device according to claim 1, characterized in that said sensor comprises a plate (16) in contact with the skin of said subject, whose movements are reflected on clamping means (12, 13) comprising a first (12) and a second (13) jaws enclosing said portion of optical fiber (11) over part of its length.

3. Physiological information determination device according to claim 2, characterized in that said clamping means comprise a first planar jaw (12), and a second jaw (13) having a series of grooves (131) perpendicular to the axis of said portion of optical fiber (11).

4. Physiological information determination device according to claim 3, characterized in that said second jaw (13) has between 8 and 12 ridges (131).

5. Device for determining physiological information according to any one of claims 2 to 4, characterized in that said plate (16) and said clamping means (12) are interconnected by means of a ball (17).

6. Device for determining physiological information according to any one of claims 1 to 5, characterized in that it comprises at least one accelerometer (201, 202).

7. Device for determining physiological information according to claim 6, characterized in that it comprises two accelerometers (201, 202), corresponding respectively to two perpendicular directions.

8. Device for determining physiological information according to any one of claims 1 to 7, characterized in that said means (19) for processing and analysis comprise means for frequency decomposition (48) of said signal representative of instantaneous blood pressure , so as to distinguish at least two pieces of information belonging to the group comprising: - information representative of the tightening force of said sensor against the skin of said subject (43); information representative of the rhythm and / or the respiratory amplitude of said subject (49); one or more pieces of information representative of the heart rate of said subject (410, 411); one or more pieces of information representative of the blood pressure of said subject (412).

9. Device for determining physiological information according to any one of claims 1 to 8, characterized in that it comprises means (21) for transmitting data signals to a remote unit (22) for processing and / or restitution of physiological information.

10. Method for determining physiological information, characterized in that it comprises the following steps: application of a sensor in contact with the skin of a subject, said sensor comprising at least one portion of optical fiber (11) undergoing deformations depending in particular on variations in the instantaneous blood pressure of said subject; - emission of light at a first end of said portion of optical fiber; processing and analysis of said light signal (42, 45, 47, 48, 415), so as to determine at least one physiological item of information, as a function of the disturbances of said signal.

11. Method for determining physiological information according to claim

10, characterized in that said processing and / or analysis step comprises at least one of the steps belonging to the group comprising the steps of: determining information representative of the tightening force of said sensor against the skin of said subject (43 ); - amplification and bandpass filtering (45) of the electrical signal corresponding to said light signal; analog / digital conversion of measured values (47); separation (48) of at least two distinct pieces of information, by filtering or Fourier transform; - data processing (415), by statistical decision, forecast decision and / or fuzzy logic; transmission (414) of at least one of said pieces of information and / or of at least one result of said data processing to a remote station.

12. Method for determining physiological information according to claim

11, characterized in that said pieces of information belong to the group comprising: information representative of the amplitude and / or of the frequency respiratory (49); information representative of the heart rate and / or variance (410, 411); information representative of the blood pressure wave and / or its variance (412).

13. Method according to any one of claims 10 to 12, characterized in that it comprises a step of detecting a fall, a transition during sleep and / or a significant and / or abnormal variation certain physiological parameters in said subject, as a function of a signal delivered by at least one accelerometer.

14. Use of the device according to any one of claims 1 to 9 and / or of the method according to any one of claims 10 to 12, for at least one of the applications belonging to the group comprising: monitoring of people at risk; - recognition of sleep phases; awakening of the subject in a predetermined sleep phase and / or in a determined time interval; drowsiness detection; sleep quantification; - helps in the detection of sleep disorders; assists in the detection of sleep apnea; help in monitoring cardiovascular diseases; programming of devices according to sleep phases; assists in the analysis of Parkinson's disease; - help in the prevention of cerebral ischemia; respiratory monitoring; infant monitoring; polyphasic sleep analysis; observation of recovery after exercise; monitoring of a level of vigilance; helps in the detection of stress; applications to livestock.