WO2008139380A2

WO2008139380A2 - System and method for guiding breathing exercises

Info

Publication number: WO2008139380A2
Application number: PCT/IB2008/051797
Authority: WO
Inventors: Andreas Brauers
Original assignee: Koninklijke Philips Electronics N.V.; Philips Intellectual Property & Standards Gmbh
Priority date: 2007-05-14
Filing date: 2008-05-08
Publication date: 2008-11-20
Also published as: WO2008139380A3

Abstract

System and method for guiding breathing exercises, a method of processing a sensor signal related to breathing and a use thereof. The application describes a system that allows a guided breathing exercise, where the intensity, frequency and duration of exercises can be adapted to the actual performance of the exercising user. This is obtained a sensing unit (1) monitoring throughout the exercise the process of in- and exhalation and bated breath. A controller (3) uses this information to adapt the actual timing of each of these phases to the desired rhythm of the specific exercise. Also the intensity of inhalation and exhalation can be monitored and adjusted. An instruction device (2) instructs the user with the adjusted exercise, preferably by feedback in audible, visual or tactile manner.

Description

System and method for guiding breathing exercises

The present invention refers to a system and method for guiding breathing exercises, a method of processing a sensor signal related to breathing and a use thereof.

Breathing exercises are typically part of health and wellness related techniques, like Yoga and stress relaxation exercises, but are also used as supportive measures in the treatment of diseases like asthma and chronic obstructive pulmonary disease (COPD). A breathing exercise usually consists of a repeated sequence of inhalation, exhalation and retention of breath at different intensities, where the relative timing of inhalation, exhalation and bated breath is important. Additionally, the location of breathing (thoracic vs. abdominal) may play a role. A comprehensive system of such breathing techniques is found, for example, in yoga. Yoga is practiced by approximately 15 million people in the United States. While yoga addresses an all-embracing family of spiritual practices, into which physical exercises (asanas) and breathing exercises

(pranayama) are integrated, these ancient techniques or similar exercises have entered into modern practices of physiotherapy and relaxation exercises. Qigong as a Traditional Chinese Medicine includes similar breathing exercises. So the number of people practicing breathing exercises will significantly exceed those doing Yoga. Positive effects are documented for these techniques in terms of a basic sense of well-being, but it is also known that these techniques support stress relaxation, can help improve sleep and problem solving capabilities as well as the cardiopulmonary performance. Breathing exercises are also known as supportive measures during asthma and COPD therapy (Buteyko technique). Usually, all of these techniques should be learned from an instructor and practiced (at home) on a regular basis, preferably daily. It is common to practice at home self-directedly or with the use of an audio tape or CD, where an instructor guides through the different exercises. The exercises are to be done in a relaxed position, preferably sitting or lying, and in a concentrated state of mind, which means with a minimum of distraction.

Audible instructions (as in classes or from a CD) appear to be not disturbing. From the patent application publication US 2002/0024888 Al, a visual guidance, using a light projecting sphere, to breathing exercises and a timing device for guiding the exercises are known. It is a drawback of the systems according to the state of the art that the pre-recorded sequence of exercises is not suitable for certain users, For example, if the user is not able to keep the breath as long as required by the prerecorded sequence, the inhaling and exhaling times are also not matched to the user requirements.

It is therefore an objective of the present invention to provide a system for guiding breathing exercises that provides exercises which match the individual and actual user requirements.

The above object is achieved by a system for guiding breathing exercises, comprising a sensing unit, an instruction device and a controller, the controller being adapted to process a data signal from the sensing unit, the controller further being adapted to adjust the breathing exercise according to the data signal from the sensing unit. The sensing unit is used to monitor the breathing of a user who is instructed via the instruction device to execute the exercise. It is an advantage of the system according to the invention that overstressing the user by the instructions is avoided by adjusting the breathing exercise, the adjustment taking the data retrieved from the sensing unit into account. The instructions then instruct the user to execute the adapted breathing exercise. For example, if the user is not able to keep the breath as long as required by the exercise, the time is adapted to match to the user requirements. With the same line of thought the exercises may advantageously be intensified if the instructions did not challenge the user.

According to a preferred embodiment of the invention, the controller is further adapted to detect and distinguish respiratory phases in the data signal. The respiratory phases are generally inhaling, exhaling and breath retention, where deep inhaling and exhaling may further be distinguished from normal inhaling and exhaling. It is an advantage of this embodiment that the performance of the user can be evaluated more accurately by the system if the respiratory phases are analyzed and not only, for example, the breathing rate.

According to another preferred embodiment of the invention, the sensing unit comprises at least one force sensor or pressure sensor. Generally, any sensor for force or pressure measurement of suitable sensitivity may be used. In particular, however, the sensor is an electret foil or piezoelectric element. In another preferred embodiment, the sensing unit comprises a respiration belt. In yet another preferred embodiment, the sensing unit comprises a textile sensor, i.e. a sensor which is integrated in a textile fabric of any kind. The textile fabric may further advantageously comprise a conductive shielding for suppressing electromagnetic interference with the sensor. According to a preferred embodiment of the invention, the conductive shielding is connected to a potential equalization. The potential equalization may, in the sense of the embodiment, be an electric potential at which the conductive shielding is actively driven or a grounding. It is an advantage of the sensor arrangement according to this embodiment that static charges or dynamic charges which would disturb capacitive or inductive measurements, may be discharged via the textile fabric. The conductive shielding need not be a closed area, but is preferably composed of a net of conductive elements. A textile sensor may advantageously be integrated into garment, like a shirt or into a pillowcase. The sensor is to be linked to a power supply when necessary and to a data acquisition and processing equipment.

An integration of the textile sensor into wearable textiles or covers advantageously allows to measure a pressure or force exerted by a body portion of a person. The scope of applications of textile sensors advantageously covers, for example, T-shirts, underwear, pajamas, pillowcases or yoga-mats. According to another preferred embodiment of the invention, the force sensor or pressure sensor is capacitance sensor which is also referred to as a capacitive sensor which, in the sense of the invention, comprises a capacitor which is an electrical device that can store energy in the electric field between a pair of closely-spaced flat electrodes or conductors. According to a preferred embodiment of the invention, the capacitance sensors comprise two capacitor electrodes isolated by a dielectric, wherein the dielectric is preferably compressibly elastic for allowing an alteration of a distance between the two electrodes.

Advantageously, the capacitance sensor may be used for measuring a shear force as well as for measuring pressure. The pressure is measurable as a force acting in a normal direction onto the plane of the electrodes, by which force the dielectric is compressed and the distance between the electrodes is reduced. A resulting increase in capacitance of the sensor is measurable, preferably using suitable electronics as, for example, a bridge type circuit.

A shear force acting on the capacitance sensor displaces the electrodes in a direction parallel to a plane of the electrode which is a plane defined by the extension of the flat electrode. Thus, an overlap of the electrodes, the so-called effective area of the capacitor is reduced which results in a measurable reduction of capacitance of the sensor. According to the invention, one part of the capacitance sensors may be used for pressure measurement and another part for shear force measurement. However, it is also within the scope of the invention, that one or more capacitance sensor may be adapted to measure both pressure and shear force which requires a discrimination of the described effects.

According to a further preferred embodiment of the invention, the system further comprises a packaged sensor pad, the sensor pad comprising the sensing unit and electronics for streaming the data signal from the sensing unit to a data processing equipment. For example, the packaged sensor pad comprises an electret foil of suitable size, coated with a textile or other comfortable material. Connected to this sensor is electronics that reads in the data and streams the data to the data processing equipment, for example wired or via a wireless connection according to the bluetooth or zigbee standard. Furthermore preferred, the data processing equipment is a personal computer, the personal computer being used as the controller, a software running on the personal computer for processing the data signal from the sensing unit. Advantageously, the software running on the personal computer can also include an interface by which the user composes a desired sequence of exercises according to his own desires and aims prior to performing them. Alternately, programs can be run that have been composed by instructors (e.g. yoga teachers). For use, the person starts the program on the personal computer, establishes a connection between the electronics and the personal computer and sits or lies on the sensor pad. Relying on the user having a personal computer and being capable of using it, this embodiment has the advantage that it requires a minimum of additional hardware. Preferably, at least one output means of the personal computer is used as the instruction device, in particular a monitor and/or loudspeakers.

According to a further preferred embodiment of the invention, the system further comprises a support, the sensing unit being integrated in or on the support. The support, for example, may be any kind of meditation cushion, a pad that can be placed on a chair or on a yoga mat or some other surface, that the user chooses for the breathing exercises. Usually, such meditation cushions or pads are bulky and filled with removable material, so advantageously, not too large electronic devices are easily integrated. More preferably, the controller and/or the instruction device are as well integrated in the support. Advantageously, the user only needs one device to do the exercise. Of course there is a link for a power supply, for example a plug for recharging or wireless charging modules. The flexibility of this embodiment is advantageously enhanced by providing a possibility to upload different exercise schemes, for example using a bluetooth link to a personal computer.

According to a further preferred embodiment of the invention, the instruction device is a consumer electronics device. For example, standard audio equipment advantageously can be used as instruction device. Also, variety of lighting applications are possible as instruction devices. TV or projection devices can be used as instruction devices.

According to a further preferred embodiment of the invention, the instruction device is adapted to provide an optical feedback, wherein respiratory phases are represented by geometrical figures. More preferable, the geometrical figure alters in dimension during the respiratory phase. The geometrical figures advantageously indicate the reference state in the breathing phase and the actually measured state in the breathing phase. For example, the process of the respiratory phase of inhalation is represented by a circle, the radius of which grows during inhalation, has a maximum, when after inhalation breath is retained, and shrinks during exhalation. This can be done both for the reference breathing process and for the actually measured breathing process. The task of the user then would be to align the phases of both circles, and to keep them lie on top of each other during the exercise. The calculation of the radius of the circles can be related to the representation of the sensor signal. The circles can be displayed on a screen, by LED arrays or can be projected to walls or ceiling (e.g. in a vehicle or a sleeping room).

According to a further preferred embodiment of the invention, the sensing unit is integrated in an interior part of a vehicle, in particular of a motor vehicle. The sensing unit may advantageously be integrated in a driver seat or passenger seat, and can be used during driving breaks. Here the guidance can again be done via audio equipment, usually available in a vehicle (e.g. mp3-player) or via optical feedback, e.g. in a cockpit display or in a projection or other display integrated in the car ceiling.

A further object of the present invention is a method of processing a sensor signal related to breathing, comprising the steps of: detecting and distinguishing respiratory phases and determining a pattern of the respiratory phases, determining a deviation of the pattern from a reference pattern of a breathing exercise, and - adjusting the reference pattern according to the deviation.

Advantageously, by analysing the sensor signal regarding respiratory phases, the performance of a user executing a breathing exercise can be evaluated accurately, thus allowing adjustment of the breathing exercise according to the individual and actual performance. The reference pattern is preferably adjusted to facilitate the breathing exercise if the deviation exceeds a predetermined threshold. On the other hand, the reference pattern is adjusted to intensify the breathing exercise if the deviation falls below another, predetermined threshold. Advantageously, the user is not unnecessarily stressed by breathing exercise which are improperly hard and the user is not bored by too easy exercises.

According to a preferred embodiment, the step of detecting and distinguishing respiratory phases comprises a removal of high frequencies from the signal. Noise interference in the signal can thus advantageously be reduced, for example signals induced by slight movements of the user or the user's heartbeat. This is achieved, for example by integrating the signal or by suitable band-pass filtering. Furthermore preferable, the step of detecting and distinguishing respiratory phases comprises determination of minima, maxima and substantially constant phases of the signal. Any local minimum advantageously designates a change from exhalation to inhalation, whereas any local maximum corresponds to a change from inhalation to exhalation. Substantially constant signals refer to a phase of breath retention. Preferably, the duration of each respiratory phase is determined. The respiratory pattern is thus given as a sequence of distinguished respiratory phases and the related time information. The deviation from a reference pattern, i.e. the breathing excursion, is advantageously easily determined by comparing the patterns.

A further object of the present invention is a use of the method according to the invention as described in here before, for guiding a breathing exercise. Yet a further object of the invention is a method of guiding a breathing exercise, using a system according to the invention and processing the data signal according to the invention as described in here before.

The invention describes a system that allows a guided breathing exercise, where the intensity, frequency and duration of exercises can be adapted to the actual performance of the exercising user. This is obtained by monitoring throughout the exercise the process of in- and exhalation and bated breath. This information is used to adapt the actual timing of each of these phases to the desired rhythm of the specific exercise. Also the intensity of inhalation and exhalation can be monitored and adjusted. The user is instructed with the adjusted exercise, preferably by feedback in audible, visual or tactile manner.

These and other characteristics, features and advantages of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the invention. The description is given for the sake of example only, without limiting the scope of the invention. The reference Figures quoted below refer to the attached drawings.

Figure Ia illustrates schematically a first embodiment of the system according to the present invention

Figure Ib illustrates schematically a second embodiment of the system according to the present invention Figure 2 illustrates schematically examples of body- wearable textile sensors

Figure 3 illustrates schematically a third embodiment of the system according to the present invention

Figure 4 illustrates schematically a fourth embodiment of the system according to the present invention

Figure 5 illustrates a data signal related to breathing in a diagram

Figure 6 illustrates the data signal of Figure 5, processed according to an embodiment of the method of the invention

Figure 7 illustrates another data signal related to breathing in a diagram

Figures 8a and 8b illustrate different breathing patterns in a diagram

The present invention will be described with respect to particular embodiments and with reference to certain drawings but the invention is not limited thereto but only by the claims. The drawings described are only schematic and are non- limiting. In the drawings, the size of some of the elements may be exaggerated and not drawn on scale for illustrative purposes.

Where an indefinite or definite article is used when referring to a singular noun, e.g. "a", "an", "the", this includes a plural of that noun unless something else is specifically stated.

Furthermore, the terms first, second, third and the like in the description and in the claims are used for distinguishing between similar elements and not necessarily for describing a sequential or chronological order. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other sequences than described or illustrated herein.

Moreover, the terms top, bottom, over, under and the like in the description and the claims are used for descriptive purposes and not necessarily for describing relative positions. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other orientations than described or illustrated herein.

It is to be noticed that the term "comprising", used in the present description and claims, should not be interpreted as being restricted to the means listed thereafter; it does not exclude other elements or steps. Thus, the scope of the expression "a device comprising means A and B" should not be limited to devices consisting only of components A and B. It means that with respect to the present invention, the only relevant components of the device are A and B.

Figure Ia refers to a first embodiment of the system according to the present invention. A person (not depicted) doing breathing exercises sits on a support 5. This support 5 is equipped with a sensing unit or sensor 1 that is capable of monitoring the breathing activity. A preferred sensor 1 would be an electret foil, piezoelectric element or another force or pressure sensor with suitable sensitivity. Alternatively, the sensor 1 can be textile and integrated into a shirt or the like. A respiration belt would be another possible sensor 1. Breathing in, breathing out and holding breath results in distinguishable signals. The data are evaluated by suitable algorithms of a controller 3. A typical result of the data processing is the duration of inhalation, exhalation, breath retention. These data are used to adapt the instructions for the next sequence of exercises. Finally, the system contains an instruction device 2 which feeds back the adapted instructions to the user. The sensing unit 1, the controller and the instruction device 2 are connected via communication lines 7 which may be wired or wireless.

Figure Ib refers to a second embodiment of the system according to the present invention. The support 5 can be, for example, a meditation cushion 5. In this embodiment, the sensing unit 1 is integrated in the support 5. The sensor 1 is to be linked to a power supply (not depicted) when necessary and to a data acquisition unit 6. The embodiment comprises a packaged sensor pad 1, 5, 6, for example an electret foil of suitable size, coated with a textile or other comfortable material. Connected to the sensor 1 is the electronic data acquisition unit 6 that reads in the data and streams the data to a personal computer 4, via communication line 7 which may be a wired line or a wireless connection according to bluetooth or zigbee standard. According to the embodiment, the personal computer 4 is the controller 3, a software being installed and running on the personal computer 4 that controls the data processing sequence adaptation and sequence control. An output device 2 of the personal computer 4 is used for the user instruction, e.g. the display of the personal computer 4 or the audio output.

The software running on the personal computer 4 can also include an interface by which the user composes the desired sequence of exercises according to his own desires and aims prior to performing them. Alternately, programs can be run that have been composed by instructors (e.g. yoga teachers).

For using the system according to the embodiment, the person exercising has to start the program on the personal computer 4, a connection 7 between electronics 6 and personal computer 4 must be established and the person has to sit or lie on the sensor pad 5. Characteristic for this embodiment is that it relies on the user having a personal computer 4 and being capable of using it. Advantageously, it requires a minimum of additional hardware.

Figure 2 illustrates schematically an example of a textile sensors 1 integrated in a wearable piece of clothing 9. Sensors 1, like for example, capacitive or inductive or direct contact electrodes are shown which are integrated in garment. The sensors 1 may, for example, be integrated into a shirt 9. Depending on the geometry of the sensors 1 different shielding options apply. Further features of the system according to the invention are similar to those depicted in Figures Ia and Ib. Figure 3 refers to a third embodiment of the system according to the present invention. According to this preferable embodiment, all required hardware 1, 2, 3 is integrated into a meditation cushion 5 or any other support 5. The sensor 1, the controller 3, the instruction device 2, here, for example, a speaker of an mp3 player, are integrated into the meditation cushion 5. Usually meditation cushions 5 are bulky and filled with removable material, so an integration of not too large electronic devices can be easy. Of course there is a link for a power supply, for example a plug for recharging or wireless charging modules, which is not depicted.

Figure 4 refers to a fourth embodiment of the system according to the present invention. According to this preferable embodiment, the same level of integration as in Figure 3 is achieved with a pad 5 with an integrated sensor 1 that can be placed on a chair 8 or some other surface, that the user chooses for the breathing exercises. The controller 3, data acquisition electronics 6 and audio instruction device 2 are connected to the pad 5, but in this case not integrated.

For the embodiments in Figures 3 and 4, it is characteristic that the user only needs one device to do the exercise. The advantageous flexibility of these solutions can be enhanced by the possibility to upload different exercise schemes, e.g. using a bluetooth link to a personal computer. It can bee seen, that also different embodiments are possible, where different functions are realized in separate devices. For example, standard audio equipment can be used as instruction device 2. A variety of lighting applications are possible as instruction devices 2. TV or projection devices can be used as instruction devices 2.

Figure 5 shows a plot of a raw data signal 10 of a typical episode of 40 seconds taken from a breathing exercise. The signal amplitude is given on axis 20, the time on axis 21. The first twenty seconds the subject breaths in and out in its natural rhythm (about four cycles) and amplitude, followed by another twenty seconds of deep breathing (about four cycles). The signal 10 was obtained with a electret foil. When evaluating the signal 10, the differentiating nature of the electret foil has to be taken into account. This means that the signal 10 is maximal when the changes of feree acting on the foil are maximal.

When the signal 10 is integrated, a more intuitive representation of the signal 10 is given, as shown in Figure 6. Here inhalation corresponds to a signal increase, exhalation to a signal decrease. High frequency components in the original signal 10 are due to small movement and in particular the heartbeat of the user. They are removed by the integration step. Maxima in the signal 10 clearly correspond to a change from inspiration to expiration in this mode, and minima correspond to a change from expiration to inspiration. Thus, this signal 10 is well suited to distinguish inhalation and exhalation and to measure the duration of each of these respiratory phases. Suitable band pass filtering results in similar curves. This example is representative for the signal obtained from an electret foil sensor. Other sensors will have different response characteristics, e.g. non-differentiating, and thus require an adapted signal processing method, e.g. without integration.

The amplitude of the processed signal in Fig. 6 may advantageously be used for the calculation of the dimension of geometrical figures which represent the respiratory phases in the instruction device.

In Figure 7, the signal 10 of the following sequence is shown:

Deeply inhale 11, deeply exhale 12, normal breathing 13, 14 (2 cycles), breath retention 15. These different respiratory phases can clearly be distinguished. After proper band pass filtering the phase of breath retention 15 is virtually a flat line. Again begin and end of the different respiratory phases can be identified. Other phases of breathing exercises may comprise for example fast breathing with a high intensity (as in Kaphalabati), which can also be identified in the signal 10. Other exercises may include alternate breathing through left and right nostril with intermediate breath retention (Nadi-Shodhana Pranayama). In summary, different sequences of the most common breathing exercises can be monitored.

Referring now to Figures 8a and 8b, an example of a breathing exercise could be: four seconds breathing in (13) - eight seconds keeping breath (15) - eight seconds breathing out (14) - four seconds breathing in (13) - eight seconds keeping breath (15) - eight seconds breathing out (14). This sequence is to be done eight times. The (audio) instruction sequence for such an exercise would be for example: Breath in - Pause (131, total time four seconds); Hold your breath - Pause (151, total time eight seconds); Breath out (141, total time eight seconds); Breath in - Pause (131, total time four seconds); Hold your breath - Pause (151, total time eight seconds); Breath out (141, total time eight seconds). A representation of the subsequent instructions (131, 151, 141) are marked on the time axis 21 and the recorded signal 10 is schematically shown in Figures 8a and 8b. Figure 8a shows a signal 10 of a correctly performed exercise. In Figure 8b, the same sequence is shown for incorrect performance. Here the user is not holding breath as long as instructed.

From the signal 10, the different durations of the respiratory phases 13, 14, 15 can be extracted and can be compared to the requested values according to the instructions 131, 141, 151. As long as the deviation between requested values and the determined values is within a predefined threshold, for example below 20% deviation, the sequence will be repeated without adaptation. As in Figure 8b, the deviation of the breath retention time 15 derived from the signal 10 and the requested breath retention time (from 151 to 141) in this case exceeds the threshold of maximum allowed deviation. Here, the controller 3 would adapt the parameters and reduce the time for holding breath accordingly.

Instead of calculating the duration of the single respiratory phases, the time of transition from one respiratory phase to another may be monitored. After having performed the sequence the actual valid parameters (131, 141, 151) of the last successful exercise can be stored for future exercises. Depending on the nature of the exercise, also macro cycles can be introduced into the control software: For the example given above, a general target for the exercises would be to increase the period of holding breath, for example to 32 seconds. If the above exercise has been performed correctly for three subsequent times, for example, the time for breath retention can be increased according to a training plan, for example by 10%. This avoids, that the user is unchallenged and that practicing the exercises becomes boring. For the same reason different exercises should be combined differently in different sessions.

Having completed a session the user can be informed about the achievements of his practice, by providing appropriate feedback, for example about key parameters of the actually performed breathing exercise, like the duration of breath retention. Also trends over several sessions can show the progress the user makes. This should of course be done according to the rules of the methods that are used and will be different for Yoga than for autogeneous training or Buteyko breathing. It goes without saying that the setups described here can easily be combined with other aspects of Yoga or autogeneous training, like deep relaxation or physical exercises (asanas). During these phases of the training, the system can be used for instruction, for example as a simple audio device.

Claims

CLAIMS:

1. System for guiding breathing exercises, comprising a sensing unit (1), an instruction device (2) and a controller (3), the controller being adapted to process a data signal (10) from the sensing unit (1), the controller further being adapted to adjust the breathing exercise according to the data signal (10) from the sensing unit (1).

2. System according to claim 1, wherein the controller (3) is further adapted to detect and distinguish respiratory phases (11, 12, 13, 14, 15) in the data signal (10).

3. System according to claim 1, wherein the sensing unit (1) comprises at least one force sensor or pressure sensor, preferably a capacitance sensor.

4. System according to claim 1, wherein the sensing unit (1) comprises a respiration belt.

5. System according to claim 1, wherein the sensing unit (1) comprises a textile sensor.

6. System according to claim 5, wherein the textile sensor is integrated in a textile fabric, the textile fabric comprising a conductive shielding for suppressing electromagnetic interference with the sensor.

7. System according to claim 5, wherein the textile sensor is integrated in a wearable piece of clothing, such as a shirt, a pajama or underwear.

8. System according to claim 1, further comprising a sensor pad, the sensor pad comprising the sensing unit (1) and electronics for streaming the data signal (10) from the sensing unit to a data processing (4) equipment.

9. System according to claim 8, wherein the data processing equipment (4) is a personal computer, the personal computer being used as the controller (3), a software running on the personal computer for processing the data signal (10) from the sensing unit (1).

10. System according to claim 9, wherein at least one output means of the personal computer is used as the instruction device (2).

11. System according to claim 1 , further comprising a support (5), the sensing unit (1) being integrated in or on the support.

12. System according to claim 11, wherein the controller (3) and/or the instruction device (2) is integrated in the support (5).

13. System according to claim 1, wherein the instruction device (2) is a consumer electronics device.

14. System according to claim 1, wherein the instruction device (2) is adapted to provide an optical feedback, wherein respiratory phases are represented by geometrical figures.

15. System according to claim 14, wherein the geometrical figure alters in dimension during the respiratory phase.

16. System according to claim 1, wherein the sensing unit (1) is integrated in an interior part of a vehicle.

17. Method of processing a sensor signal (10) related to breathing, comprising the steps of: - detecting and distinguishing respiratory phases (11, 12, 13, 14, 15) and determining a pattern (16) of the respiratory phases, determining a deviation of the pattern (16) from a reference pattern (17) of a breathing exercise, and adjusting the reference pattern (17) according to the deviation.

18. Method according to claim 17, wherein the reference pattern (17) is adjusted to facilitate the breathing exercise if the deviation exceeds a predetermined threshold.

19. Method according to claim 17, wherein the reference pattern (17) is adjusted to intensify the breathing exercise if the deviation falls below a predetermined threshold.

20. Method according to claim 17, wherein the step of detecting and distinguishing respiratory phases comprises a removal of high frequencies from the signal (10).

21. Method according to claim 17, wherein the step of detecting and distinguishing respiratory phases comprises determination of minima, maxima and substantially constant phases of the signal (10).

22. Method according to claim 17, wherein the step of detecting and distinguishing respiratory phases comprises determination of a duration of each respiratory phase (11, 12, 13, 14, 15).

23. Use of a method according to claim 17 for guiding a breathing exercise.

24. Method of guiding a breathing exercise using a system according to claim

1 and processing the data signal (10) according to the method of claim 17.