WO1996020639A1

WO1996020639A1 - A device for indication and behaviour medical control of states of stress

Info

Publication number: WO1996020639A1
Application number: PCT/SE1995/001597
Authority: WO
Inventors: Bo Von Scheele
Original assignee: Bo Von Scheele
Priority date: 1994-12-29
Filing date: 1995-12-29
Publication date: 1996-07-11
Also published as: SE9404553D0; AU4362296A

Abstract

A device for indication of states of stress of an individual comprises members (1) arranged to detect the heart beats of the individual, means (5) arranged to calculate the heart rate of the individual from this detection, members (2) arranged to detect the breathing direction, in or out, of the individual, and an arrangement (6) arranged to work out data that are indicative of the state of the stress of the individual on the basis of the heart rate and breathing direction information delivered by said members and means.

Description

A DEVICE FOR INDICATION AND BEHAVIOUR MEDICAL CONTROL OF STATES OF STRESS

FIELD OF THE INVENTION AND PRIOR ART

The present invention refers to the problem of, in an individual, particularly a human being, detecting and indicating states of stress, which in medically physiological terms means state and changes in the balance and levels of the autonomic nervous system, that is of the sympathetic and parasympathetic nervous system, especially to be able to determine whether the body condition of the individual is effected by stress, but also to study how this state of stress can be changed by different types of training, the object of which is to improve the capability of the individual to master situations that cause stress. No device is yet known which tries to solve this problem, and even if the biological oscillator, named respiratory sinus arrhythmia, is a phe¬ nomenon known per se since approximately 100 years and known since 1983 in the psycho-physiology, its use as training and bio- feedback implement has not been applicated in any device designed for this purpose.

BRIEF SUMMARY OF THE INVENTION

The object of the present invention is to provide a device which makes it possible to solve the abovementioned problem in a satisfying way.

According to the invention, this object is reached by provision of a de¬ vice for indication of states of stress of an individual, comprising members arranged to detect the heart beats of the individual, means arranged to calculate the heart rate of the individual from this detec- tion, members arranged to detect the breathing direction, in or out, of the individual, and an arrangement arranged to work out data that are indicative for the state of stress of the individual from the heart rate and breathing direction information delivered by said members and means. Accordingly, the invention is based upon use of the so called respiratory sinus arrhythmia which describes the connection between heart rate and the breathing of an individual. When an individual inhales an inhibition of the relaxation system of the body (parasympaticus) takes place, which means a release of the activating system of the body (sympaticus). This is functional for the inhalation, which is an active process. On the other hand, when the individual ex¬ hales, an inhibition of sympaticus takes place, which means that parasympaticus is released, which is functional for the exhalation, which is a passive process. In this way the oscillatory function operates to facilitate the respiratory behaviour and the transportation of the oxygen in the blood as well as the retransportation of carbon di¬ oxide from the cells for the exhalation thereof. The oxygen is to be brought to the cells and carbon dioxide is to be aired, eliminated. This is a biological, basal function in the so called cell metabolism, the cell breathing. Small changes of this function indicates changes in the re¬ lation between sympaticus and parasympaticus, such changes being an indication of a changed and/or disturbed co-ordination between the circulatory and respiratory system of the body and that the individual is in a state of stress, that is the organism is biologically set for struggle or flight, a state which is adequate for evolutionary related survival but in general not adequate in a modern, social life pattern. This relation is used by the device according to the invention to give an indication of states of stress of an individual, which indication then can be inter¬ preted as functional or dysfunctional by means of the specific analysis criteria which have been worked out by the applicant through digital as well as analogous treatment of received information.

By means of the device according to the invention data which are indicative of the state of stress of a person is accordingly obtained and are worked out from the basis of information as to the development of the heart rate of the individual along with her or his breathing, which not only makes it possible to state if a person is in a state of stress, but also makes it possible to use the device according to the invention as a training instrument for determining whether an individual becomes dysfunctionaliy "stressed" in certain situations and to measure the re- suits of tries to control stress. The device can also do well as a diagnostic implement to determine a risk for heart attacks or for prognoses and follow-up during bio-feedback treatment of heart attacks. Thereby, bio-feedback is defined as physiological feedback of information directly from the parameter which one seeks to effect in a predicted direction through execution of tested, individually "tailored" behaviour medical strategies, e.g. the execution of any breathing strategy.

By a device according to a preferred embodiment of the invention, said arrangement is designed to provide a stress dependent parameter for detection of stress symptoms of the individual by comparing heart rates with each other during different phases of the breathing of the individual, and calculate the dimension of a parameter which forms a measure of the relation between the heart rate and the breathing of the individual and such a relation of an individual in an ideal state. Thereby, the ideal state is a state in which no negative state of stress is present and thereby the co-ordination between the circulatory and respiratory system is perfect and the relaxation system and the activating system of the body harmonize in a desired way during inhalation and exhalation. As the device is designed to deliver such a parameter, an excellent measure of the degree of stress, that is the disturbance of the body functions of the individual, is obtained. Hereby, the device can immediately measure the result of training so as to control and try to get rid of a state of stress.

A device according to yet a preferred embodiment of the invention comprises means arranged to display the value of said parameter that has most recently been calculated by the arrangement. Through this feature, the device can be used by that individual onto whom it executes its functions so that he or her visually can determine what is the state of stress and how it is changed at different attempts to control stress during the training for obtaining such a control.

By a device according to yet a preferred embodiment of the invention, the arrangement comprises means arranged to continuously display the present heart rate of the individual and his or her position in the in- halation and exhalation cycle which is just being executed, by means of information from said means and members as to heart rate and breathing direction. Hereby, during on-going measurements, the individual in question or another person can control the relation between the heart rate and the breathing by watching how the heart rate develops during different parts of an inhalation and exhalation cycle and comparing this with the ideal development of the heart rate during a breathing cycle, i.e. an increase of the heart rate during the inhalation and a decrease thereof during the exhalation.

By a device according to another preferred embodiment of the inven¬ tion, said means of the arrangement are arranged to display the present heart rate in the shape of a vertical or fully or partly horizontal pile, the height or length of which increases with the increasing heart rate and vice versa, and the position of the individual in the breathing cycle by means of a similar pile, the height and length of which increases continuously during the inhalation of the individual and decreases continuously during his or her exhalation, these means be¬ ing arranged to show the two piles so that they can be regarded simultaneously for an optical determination of the relation between heart rate and the breathing of the individual. By visualising the connection between heart rate and the breathing of an individual in this way, the individual or another person can, without greater difficulties, obtain a very good apprehension of how well this connection is in accordance with the ideal state, as it is easy for the eye to note that, suddenly, one pile decreases while the other one increases and, thereby, a disturbance is present in the relation between breathing and heart function.

Further advantages and advantageous features of the invention will be shown in the following description and in the remaining, dependent patent claims. BRIEF DESCRIPTION OF THE DRAWINGS

Hereinbelow a device according to a preferred embodiment, referred to by way of example, is described with reference to the disclosed drawings, in which:

Fig 1 is a schematic block diagram which illustrates the function of the device according to a preferred embodiment of the invention, and

Fig 2 shows a circuit diagram for the device according to this preferred embodiment.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION

In Fig 1 , by means of a block diagram, the function of a device according to a preferred embodiment of the invention is illustrated. The device comprises members 1 arranged to detect the heart beats or pulse of the individual, different designs of these members being possible, and, by way of example, by transillumination of blood¬ vessels, for instance in the ear of a human being, they can produce a signal which is sinusoidally varying with the beat rate of the heart. Furthermore, the device comprises members 2 arranged to detect the breathing direction of the individual, and such a member can, by way of example, be formed by a thermistor arranged at the nostril of the individual or an exhalation carbon dioxide measuring hose, which member also provides a sinusoidal signal. The signals from the members 1 and 2 are forwarded to a unit 3 where adaption of the amplitudes thereof is executed, as different instruments like the members 1 and 2 can provide totally different signal amplitudes, and it is desirable that the rest of the device can function also when the in¬ struments acting as the members 1 and 2 are substituted by other in¬ struments. The unit 3 is arranged to forward the signals adapted to the amplitude to a transforming unit 4 for transformation of the analogous signals to digital signals. The signal referring to the function of the heart is forwarded to a means 5 which is arranged to calculate the heart rate of the individual by means of said signal, said calculation being intended to take place continuously through measurement of dis¬ tance and time between, preferably, 3-4 subsequent signal peaks or bottoms.

The heart rate signal accordingly worked out by the means 5, and the breathing signal from the transforming unit 4 are forwarded to an arrangement 6 which is designed to compare heart rates during different phases of the breathing of the individual and calculate the dimension of a parameter which forms a measure of the correlation be- tween a relation between the heart rate and the breathing of the individual and such a relation of an individual in an ideal state. Thereby the so called respiratory sinus arrhythmia parameter or RSA is calculated. This parameter is preferably calculated by forming a difference between the top and bottom heart rate during a breathing cycle, and the dimension of the parameter is made proportional to the dimension of this difference, while at the same time consideration is taken to at which level the heart rate is during said breathing cycle. The difference between the top and bottom heart rate during a breath¬ ing cycle is very individual and it can easily vary between 5 and 10 beats/minute for different persons in a resting state. This difference is also dependent on under which strain the body of the individual is, that is what base heart rate the person has, and therefore the arrangement 6 is preferably arranged to consider the absolute level of the heart rate of the individual during a breathing cycle while calculating said parameter. Even if the value itself is very individual, it is desirable that said difference is clear, but a small difference at a higher heart rate level can indicate a state of the individual in question which is as good as for a larger difference at a lower heart rate level. To determine whether the co-ordination between the relaxation system and the activating system of the body functions satisfactorily it is also of importance to make clear where in a breathing cycle said top and bot¬ tom heart rate exists and how the heart rate develops during a breathing cycle. The heart rate shall increase all time during the inhalation and continuously decrease during the exhalation, and the development of the heart rate over time shall generally describe a sinus curve. It is namely possible that the difference between the top and bottom heart rate is relatively large, but that a serious state of stress is yet present, as, during stress, the relation between heart rate and breathing can be inverted, which makes the heart rate decrease during the inhalation and increase during the exhalation.

It also happens that stress produces displacements of the develop¬ ment of the heart rate in relation to the breathing with less than half a phase, so that for instance the heart rate is delayed in relation to the breathing, that is the heart rate begins to increase after the inhalation has started and reaches its maximum as the exhalation has already begun. During states of stress it sometimes also exists "extra humps" at the heart rate curve, that is intermediate maxima and minima. Therefore, the arrangement is preferably arranged to make the value of the parameter dependent on in which position in the breathing cycle the top and bottom heart rates are registered, and it preferably comprises means arranged to continuously register or calculate in which direction the heart rate is changed, upwards or downwards, to make the arrangement able to compare this change of direction to the respective position in the breathing cycle and make the value of said parameter dependent on this comparison. The means in question can thereby, by way of example, be formed by suitable components for continuous calculation of the time derivative of the heart rate. Thereby it is possible to make different disturbances in the relation between heart rate and breathing render a direct influence upon the parameter which is calculated by the arrangement, or that at such malfunctions, this is indicated through any type of alarm, for instance by emission of sound or light signals which tell that said relation is disturbed and ac¬ cordingly the individual is in a state of stress. Principally it would thus be possible that the parameter is presented as a measure of the difference between top and bottom heart rate within a breathing cycle, possibly made dependent on the absolute level of the heart rate, and that it in a suitable way is separately stated that a disturbance is pre¬ sent in the connection between heart rate and breathing, without the value of the parameter for that reason being effected of this distur¬ bance, that is the information as to disturbance broadly tells that the value of the parameter does not give any indication of in which state the individual finds himself. It would therefore be better if possible dis¬ turbances in said relation are included directly in the parameter, so that the latter forms a measure of the correlation between the present relation and such a relation of the individual in an ideal state. In such a case, the parameter then can show directly if the person is in a state of stress and in that case provide a measure of the degree of the state of stress.

The arrangement 6 is arranged to forward information concerning said parameter, the heart rate and the position of the individual in the breathing cycle to a unit 7 for continuous display of this information. Thereby, the unit 7 is arranged to display the present heart rate in the shape of a vertical or fully or partly horizontal pile, the height or length of which increases with increasing heart rate and vice versa, the pile preferably being horizontal, which makes it increase to the right at the display unit regarded by the individual or another person. The position of the individual in the breathing cycle is displayed by means of a similar pile, the height or length of which increases continuously during the inhalation of the individual and decreases continuously during her or his exhalation. Thereby, the two piles are presented beside each other, which makes it possible to observe them at the same time for an optical determination of the relation between heart rate and the breathing of the individual. The information is used as feedback while at the same time information as to suitable behaviour medical strate¬ gies is executed, that is bio-feedback, to normalize the obtained infor¬ mation about actual balance and position in the above described parameters. The display arrangement continuously also shows said parameter, that is RSA, in the shape of a numerical value calculated during the most previously finished breathing cycle. Thereby, prefer¬ ably, a breathing cycle is defined as the time which passes between the start of an inhalation and the subsequent start of the next inhala- tion, but it is of course fully possible to define a breathing cycle in a different way, so that it by way of exemple begins with an exhalation and is ended by the subsequent inhalation.

Furthermore, the device comprises a memory unit 8 to which the information displayed via the displaying unit 7 is sent and stored for later evaluations and the like. The memory unit 8 is connected to a communication unit 9, which makes real time communication between the device and a computer unit 10 possible for the immediate treat¬ ment of the information delivered by the device and concerning the state of the individual, i.e. also sorting, interpretation and feedback as to suitable behaviour medical strategies and methods for tests and revision of negative states of stress immediately during the measure¬ ments of the device upon the individual can be accomplished at the same time as continuously the result of these interventions can be seen, and alternatively the information can be presented at a later stage as communication with another computer unit 11 takes place to treat and analyse said information later on. The component present within the broken line frame in Fig 1 are preferably accommodated in a common housing.

In Fig 2, by means of a circuit diagram, it is finally shown how the de- vice described with reference to Fig 1 can be constructed, the addi¬ tional reference number 12 indicating a central processor unit which principally corresponds to the blocks 4-6 and 8 in Fig 1.

The device according to the invention can thus in a well functioning way momentarily indicate how well the relaxation system and the acti¬ vating system of the body interacts and thereby indicate the state of stress of the individual. Through the parameter RSA, the function of the organism can be monitored with considerable sensibility. Thereby the parameter can be used both as result variable, that is read the effect of changes to, by way of example, be able to increase stress checking, but it can also be used as a diagnostic implement to determine the risk for heart attacks or prediction of treatment of heart attacks. It can also be used as a guide line for treatment processes di¬ rected towards the malfunctions of the autonomous nerve system. Fi- nally, the parameter can be used as a treatment implement, that is one can train behaviour medical strategies while at the same time watching the changes of the parameter. However, as mentioned above, also through observations of the change of the heart rate in connection to the breathing direction at the displaying unit 7, indications of whether a state of stress is present or not can be obtained. The information regarding tailoring of behaviour medical strategies are supplied to the individual through detailed, written information included as a disclo- sure to the device. Accordingly, the device is intended for bio-feed¬ back, that is direct feedback for the training person while executing his or her "tailored" strategies, as well as feedback for the instructor about his or her instruction for effect ion, and data storage and automatic in- terpretation of data in so called expert systems (computer based decision support systems).

Of course, the invention is in no way delimited to the above described, preferred embodiment, but a plurality of possibilities of modifications thereof should be obvious for a man skilled in the art without departing from the scope of the invention.

Claims

1. A device for indication of a state of stress of an individual, compris¬ ing members (1) arranged to detect the heart beats of the individual, means (5) arranged to calculate the heart rate of the individual from this detection, members (2) arranged to detect the breathing direction, in or out, of the individual, and an arrangement (6) arranged to work out data that are indicative for the state of stress of the individual from the heart rate and breathing direction information delivered by said members and means.

2. A device according to claim 1 , characterized in that said arrange¬ ment (6) is arranged to deliver data, the object of which is to be the basis of a determination as to whether the body condition of the individual is effected by stress and for studying how a determined state of stress changes by different types of training that aims at improving the capability of the individual to master situations causing stress.

3. A device according to claim 2, characterized in that said arrange¬ ment (6) is arranged to deliver data, the object of which is to be the basis of such mastering by means of bio-feedback, i.e. physiological feedback of information directly from the parameter which one intends to effect in a predicted direction by means of tested, individually "tailored" behaviour medical strategies, e.g. the execution of any breathing strategy.

4. A device according to any of claims 1-3, characterized in that the arrangement (6) is designed to present a stress dependent parameter for detecting stress symptoms of the individual by comparison of hart rates with each other during different phases of the breathing of the individual, and calculate the dimension of a parameter that forms a measure of the correlation between a relation between the heart rate and the breathing of the individual and such a relation of an individual in an ideal state.

5. A device according to claim 4, characterized in that said arrange¬ ment (6) is arranged to continuously calculate the dimension of said parameter on the basis of the heart rate and breathing direction information delivered by said members and means during the most re- cently finished in and out breathing cycle, to deliver a parameter value which is a measure of said correlation during said cycle.

6. A device according to claim 4 or 5, characterized in that it comprises means (7) arranged to display the value of said parameter most recently calculated by the arrangement.

7. A device according to any of claims 4-6, characterized in that the arrangement (6) is arranged to calculate said parameter by forming a difference between the top and bottom heart rate during a breathing cycle and make the value of the delivered parameter dependent of the dimension of this difference and increasing therewith.

8. A device according to claim 7, characterized in that the arrange¬ ment (6) is arranged to make the value of the parameter dependent on the absolute level of the heart rate of the individual during a breathing cycle.

9. A device according to claim 7, characterized in that the arrange¬ ment (6) is arranged to make the value of the parameter dependent on where in the breathing cycle the top and bottom heart rates are registered.

10. A device according to any of claims 4-9, characterized in that the arrangement (6) comprises means arranged to continuously register or calculate in which direction the heart rate changes, upwards or downwards, and that the arrangement is arranged to compare this change of direction with the respective position in the breathing cycle and make the value of said parameter dependent on this comparison.

11. A device according to claim 7, characterized in that the arrange¬ ment (6) is arranged to indicate, by means of memory storage, emission of a light signal or the like, every appearance, within a breathing cycle, of a top heart rate during exhalation and a bottom heart rate during inhalation.

12. A device according to claim 10, characterized in that the ar- rangement (6) is arranged to indicate, by means of memory storage, emission of a light signal or the like, every appearance within a breathing cycle of a decrease in heart rate during inhalation and an in¬ crease of the heart rate during exhalation.

13. A device according to any of the preceding claims, characterized in that the arrangement (6) comprises means (7) arranged to continu¬ ously display the present heart rate of the individual and his or her position in the inhalation and exhalation cycle which is just being exe¬ cuted, by means of information from said means and members as to heart rate and breathing direction.

14. A device according to claim 13, characterized in that said means (7) of the arrangement are arranged to display the present heart rate in the shape of a vertical or fully or partly horizontal pile, the height or length of which increases with increasing heart rate and vice versa, and the position of the individual in the breathing cycle by means of a similar pile, the height or length of which increases continuously during the inhalation of the individual and decreases continuously during her or his exhalation, and that these means (7) are arranged to present both piles so that they can be simultaneously regarded for an optical determination of the relation between heart rate and the breathing of the individual.

15. A device according to any of the preceding claims, characterized in that it comprises a unit (9) which is connected to the arrangement

(6) and arranged to make the communication between the device and a computer (10, 11) for treatment of the data delivered by the device possible immediately during the device's measurements upon the individual or at a later time.

16. A device according to claim 15, characterized in that the com¬ puter (11 , 12) is designed for sorting, interpretation and feedback as to suitable behaviour medical strategies.