Device and Method for Detecting and Reporting a Stress Condition of a Person

Abstract

The invention relates to a device for determining the current stress state of a person in a simple manner, which device measures the pulse rate and based on that additionally determines the heart rate variability. In addition, at least one parameter should be used for the history of one of the two above-mentioned values. The deviation of the pulse rate and the heart rate variability from a normal variable is preferably integrated and used as an additional stress indicator. The device preferably includes a wearable electrocardiography device.

Claims

1. A method for detecting and reporting of a stress condition of a person, wherein the method comprises the following steps: continuously acquiring data of a current pulse frequency P and of a current heart rate variability HRV of said person by means of a wearable electrocardiography device, continuously processing the data of the current pulse frequency P and of the current heart rate variability HRV, determining a stress index and comparing the stress index with an alarm value indicative of an occurrence of said stress condition, characterized in that said determining of the stress index comprises: within a first time interval T.sub.1, or across a predetermined number of pulse beats, a first value SI.sub.1 for the stress index is determined by adding a value SI.sub.P, which is obtained from a normalized average value P.sub.d1 of the pulse frequency in said first time interval T.sub.1 or across said predetermined number of pulse beats, plus a value SI.sub.HRV, which is obtained from a normalized average value HRV.sub.d1 of the heart rate variability HRV within said first time interval T.sub.1 or across said predetermined number of pulse beats according to:
SI.sub.1=c*SI.sub.P+d*SI.sub.HRV wherein normalization is carried out by means of tabulated values P.sub.max, P.sub.min, HRV.sub.max and HRV.sub.min obtained from age dependent minimum and maximum pulse frequency values and HRV values, and, furthermore, the maximum and minimum values of the measured pulse frequency values and HRV values within the time interval T.sub.1 or across the predetermined number of pulse beats are determined, wherein T.sub.1 lies between 100 s and 1000 s, or the predetermined number of pulse beats lies between 50 and 500, in at least one further time interval T.sub.x (x=2 . . . n), or across a further predetermined number of pulse beats, determining a further value SI.sub.x for the stress index by adding a value SI.sub.P which is obtained from a normalized average value P.sub.d1 of the pulse frequency in said further time interval T.sub.x or across said further predetermined number of pulse beats, plus a value SI.sub.HRV, which is obtained from a normalized average value HRV.sub.d1 of the heart rate variability HRV within said further time interval T.sub.x or across said further predetermined number of pulse beats according to:
SI.sub.x=c*SI.sub.P+d*SI.sub.HRV wherein said further time interval T.sub.x has the same length as said first time interval T.sub.1 and wherein said further predetermined number of pulse beats is the same as that predetermined number of pulse beats, wherein normalization is carried out by means of values P.sub.max, P.sub.min, HRV.sub.max and HRV.sub.min, wherein P.sub.max and HRV.sub.max are selected from the larger value between P.sub.max and HRV.sub.max determined in the previous time interval T.sub.x?1 or across the predetermined number of pulse beats, respectively, and the values of P.sub.max and HRV.sub.max used in the previous time interval T.sub.x?1 or across the predetermined number of pulse beats, respectively, and wherein P.sub.min and HRV.sub.min are selected from the smaller value between P.sub.min and HRV.sub.min determined in the previous time interval T.sub.x?1 or across the predetermined number of pulse beats, respectively, and the values of P.sub.min and HRV.sub.min used in the previous time interval T.sub.x?1 or across the predetermined number of pulse beats, respectively. thereby obtaining said stress index as being equal to said further value SI.sub.x.

2. The method according to claim 1, wherein normalization is each carried out by means of a normalization value
P.sub.z=P.sub.min+a*(P.sub.max?P.sub.min)
HRV.sub.z=HRV.sub.min+b*(HRV.sub.max?HRV.sub.min) and the calculation of the stress index is carried out with
SI.sub.P=(P.sub.d1?P.sub.z)/(P.sub.max?P.sub.z) if P.sub.d1>P.sub.z
SI.sub.P=(P.sub.d1?P.sub.z)/(P.sub.z?P.sub.min) if P.sub.d1<P.sub.z
SI.sub.HRV=?(HRV.sub.d1?HRV.sub.z)/(HRV.sub.max?HRV.sub.z) if HRV.sub.d1>HRV.sub.z
SI.sub.HRV=?(HRV.sub.d1?HRV.sub.z)/(HRV.sub.z?HRV.sub.min) if HRV.sub.d1<HRV.sub.z
and
SI.sub.P=(P.sub.dx?P.sub.z)/(P.sub.max?P.sub.z) if P.sub.dx>P.sub.z
SI.sub.P=(P.sub.dx?P.sub.z)/(P.sub.z?P.sub.min) if P.sub.dx<P.sub.z
SI.sub.HRV=?(HRV.sub.dx?HRV.sub.z)/(HRV.sub.max?HRV.sub.z) if HRV.sub.dx>HRV.sub.z
SI.sub.HRV=?(HRV.sub.dx?HRV.sub.z)/(HRV.sub.z?HRV.sub.min) if HRV.sub.dx<HRV.sub.z.

3. The method according to claim 2, wherein a is selected as 0.25 and b as 0.5.

4. The method according to claim 1, wherein c and d are selected as 1.

5. The method according to claim 1, wherein said stress index is selected after said further time interval T.sub.x or after said further predetermined number of pulse beats by means of a digital low-pass filter according to SI=f*SI.sub.x+(1?f)*SI.sub.x?1 with f between 0.05 and 0.5.

6. The method according to claim 1, wherein time intervals or times during which whichsaid predetermined number of pulse beats are measured, overlap.

7. The method according to claim 1, wherein time intervals or times in which said predetermined number of pulse beats are measured, have a fixed distance between each other.

8. A device for detecting and reporting of a stress condition of a person, comprising: an acquisition device for continuously acquiring data of a current pulse frequency and of the current heart rate variability, said acquisition device being a wearable electrocardiography device, a processing device for continuously processing the data of a current pulse frequency and of the current heart rate variability of said person, and a comparator device for determining a stress index and comparing the stress index with an alarm value indicative of an occurrence of said stress condition characterized in that the processing device is configured in such manner that, within a first time interval T.sub.1 or across a predetermined number of pulse beats, a first value SI.sub.1 for the stress index is determined by adding a value SI.sub.P, which is obtained from a normalized average value P.sub.d1 of the pulse frequency in said first time interval T.sub.1 or across said predetermined number of pulse beats, plus a value SI.sub.HRV, which is obtained from a normalized average value HRV.sub.d1 of the heart rate variability HRV within said first time interval T.sub.1 or across the predetermined number of pulse beats according to:
SI.sub.1=c*SI.sub.P+d*SI.sub.HRV wherein normalization is carried out by means of tabulated values P.sub.max, P.sub.min, HRV.sub.max and HRV.sub.min obtained from age dependent minimum and maximum pulse frequency values and HRV values, and, furthermore, the maximum and minimum values of the measured pulse frequency values and HRV values within the time interval T.sub.1 or across the predetermined number of pulse beats are determined, wherein T.sub.1 lies between 100 s and 1000 s, or the predetermined number of pulse beats lies between 50 and 500, in at least one further time interval T.sub.x (x=2 . . . n) or across a further predetermined number of pulse beats, a further value SI.sub.x for the stress index is determined by adding a value SI.sub.P for the stress index, which is obtained from a normalized average value P.sub.d1 of the pulse frequency in said further time interval T.sub.x or across said further predetermined number of pulse beats, plus a value SI.sub.HRV, which is obtained from a normalized average value HRV.sub.d1 of the heart rate variability HRV within said further time interval T.sub.x or across said further predetermined number of pulse beats according to:
SI.sub.x=c*SI.sub.P+d*SI.sub.HRV wherein said further time interval T.sub.x has the same length as said first time interval T.sub.1 and wherein said further predetermined number of pulse beats is the same as that predetermined number of pulse beats, wherein normalization is carried out by means of values P.sub.max, P.sub.min, HRV.sub.max and HRV.sub.min, wherein P.sub.max and HRV.sub.max are selected from the larger value between P.sub.max and HRV.sub.max determined in the previous time interval T.sub.x?1 or across the predetermined number of pulse beats, respectively, and the values of P.sub.max and HRV.sub.max used in the previous time interval T.sub.x?1 or across the predetermined number of pulse beats, respectively, and wherein P.sub.min and HRV.sub.min are selected from the smaller value between P.sub.min and HRV.sub.min determined in the previous time interval T.sub.x?1 or across the predetermined number of pulse beats, respectively, and the values of P.sub.min and HRV.sub.min used in the previous time interval T.sub.x?1 or across the predetermined number of pulse beats, respectively, thereby obtaining said stress index as being equal to said further value SI.sub.x.

9. The device according to claim 8, wherein the device is configured in such manner that the method can be carried out according to claim 2.

10. The device according to claim 8, wherein a is selected as 0.25 and b as 0.5 and/or wherein c and d are selected as 1, and/or wherein the current stress index is selected after said further time interval T.sub.x or after said further predetermined number of pulse beats by means of a digital low-pass filter according to: SI=f*SI.sub.x+(1?F)*SI.sub.x?1 with f between 0.05 and 0.5.

11. The device according to claim 9, wherein a is selected as 0.25 and b as 0.5 and/or wherein c and d are selected as 1, and/or wherein the current stress index is selected after said further time interval T.sub.x or after said further predetermined number of pulse beats by means of a digital low-pass filter according to SI=f*SI.sub.x+(1?f)*SI.sub.x?1 with f between 0.05 and 0.5.

12. The method according to claim 2, wherein c and d are selected as 1.

13. The method according to claim 3, wherein c and d are selected as 1.

14. The method according to claim 2, wherein the current stress index SI is selected after said further time interval T.sub.x or after said further predetermined number of pulse beats by means of a digital low-pass filter according to SI=f*SI.sub.x+(1?f)*SI.sub.x?1 with f between 0.05 and 0.5.

15. The method according to claim 3, wherein the current stress index SI is selected after said further time interval T.sub.x or after said further predetermined number of pulse beats by means of a digital low-pass filter according to SI=f*SI.sub.x+(1?f)*SI.sub.x?1 with f between 0.05 and 0.5.

16. The method according to claim 4, wherein the current stress index SI is selected after said further time interval T.sub.x or after said further predetermined number of pulse beats by means of a digital low-pass filter SI=f*SI.sub.x+(1?f)*SI.sub.x?1 with f between 0.05 and 0.5.

17. The method according to claim 2, wherein time intervals or times during which said predetermined number of pulse beats are measured, overlap.

18. The method according to claim 3, wherein time intervals or times during which said predetermined number of pulse beats are measured, overlap.

19. The method according to claim 4, wherein said time intervals or said times during which said predetermined number of pulse beats are measured, overlap.

20. The method according to claim 5, wherein said time intervals or said times during which said predetermined number of pulse beats are measured, overlap.

21. The method according to claim 2, wherein said time intervals or said times in which said predetermined number of pulse beats are measured, have a fixed or variable distance between each other.

22. The method according to claim 3, wherein said time intervals or said times in which said predetermined number of pulse beats are measured, have a fixed or variable distance between each other.

23. The method according to claim 4, wherein said time intervals or said times in which said predetermined number of pulse beats are measured, have a fixed or variable distance between each other.

24. The method according to claim 5, wherein said time intervals or said times in which said predetermined number of pulse beats are measured, have a fixed or variable distance between each other.

Description

DETAILED DESCRIPTION OF AND MODES FOR CARRYING OUT THE INVENTION

[0039] The device of the present invention comprises, according to a preferred exemplary embodiment of the invention, a measuring device for detecting the pulse rate and the values that are necessary for calculating heart rate variability. In the present case this is a pulse measuring sensor, but alternatively it can also be an electrical sensor for measuring electrical cardiographic measurement values, as well as a display device. Moreover, the device comprises an interface for the input of person-related parameters, which are particularly needed for determining the history to be used according to the invention. A key component of the device is a computing device that controls the necessary acquisition of the measurement data, processes the measurement data in the digital form needed, executes the data processing and controls the display.

[0040] In the present exemplary embodiment the heart rate variability HRV is determined by means of the RMSSD method (Root mean square of successive differences), but also by other methods, such as e.g. the method SIR based on standard deviations, the method pRR50, in which the number of consecutive RR intervals that are larger than 50 ms is determined and the value thus obtained is divided by the total number of consecutive RR intervals, or frequency-oriented methods such as, for example, the calculation via the quotient LF.sub.tot/HF.sub.tot of the low-frequency frequency components divided by the higher-frequency frequency components. The HRV value obtained by means of RMSSD is calculated as the square root of the sum of the squared differences between neighboring RR intervals. In this context it should be noted that for the selection of the calculation method one may use, on the one hand, pertinent recent findings of the respective technical field and of the respective application range of the method according to the present invention or of the device according to the present invention, but on the other hand it is conceivable to simply take into account practical aspects of the respective selection. In the case where the HRV values are determined by means of the RMSSD method, in the present exemplary embodiment 0 is used as tabulated value for HRV.sub.min for all ages. The other minimum values used in the exemplary embodiment shown here, which refer to the pulse and to the HRV, are selected according to the following table:

[0041] Age dependent resting heart rate values

TABLE-US-00001 Youths: 14 . . . 18 Resting heart rate: 85 beats/minute Adults: 19 . . . 65 Resting heart rate: 70 beats/minute Seniors: 65+ Resting heart rate: 90 beats/minute

[0042] Age dependent HRV.sub.max values (RMSSD)

TABLE-US-00002 15 . . . 20 47 ms 21 . . . 30 46 ms 31 . . . 40 40 ms 41 . . . 50 35 ms 51 . . . 60 30 ms 61 . . . 70 24 ms
according to Angelink et al: Innovationstagung FH Rapperswil 4.5.2011

[0043] In this context it should be noted thatwithout departing from the sense of the method of the present inventionrather different parameters of the subjects such as e.g. the gender etc. can be incorporated into the table.

[0044] According to the exemplary embodiment the normalizations are each carried out by means of a normalization value

P.sub.z=P.sub.min+a*(P.sub.max?P.sub.min)

HRV.sub.z=HRV.sub.min+b*(HRV.sub.max?HRV.sub.min)

and the calculation of the summands of the stress value SI is each carried out according to

SI.sub.P=(P.sub.d1?P.sub.z)/(P.sub.max?P.sub.z) if P.sub.d1>P.sub.z

SI.sub.P=(P.sub.d1?P.sub.z)/(P.sub.z?P.sub.min) if P.sub.d1<P.sub.z

SI.sub.HRV=?(HRV.sub.d1?HRV.sub.z)/(HRV.sub.max?HRV.sub.2) if HRV.sub.d1>HRV.sub.z

SI.sub.HRV=?(HRV.sub.d1?HRV.sub.z)/(HRV.sub.z?HRV.sub.min) if HRV.sub.d1<HRV.sub.z

and

SI.sub.P=(P.sub.dx?P.sub.z)/(P.sub.max?P.sub.z) if P.sub.dx>P.sub.z

SI.sub.P=(P.sub.dx?P.sub.z)/(P.sub.z?P.sub.min) if P.sub.dx<P.sub.z

SI.sub.HRV=?(HRV.sub.dx?HRV.sub.z)/(HRV.sub.max?HRV.sub.z) if HRV.sub.dx>HRV.sub.z

SI.sub.HRV=?(HRV.sub.dx?HRV.sub.z)/(HRV.sub.z?HRV.sub.min) if HRV.sub.dx<HRV.sub.z,

wherein a was selected as 0.25 and b as 0.5 and c and d were selected as 1. In the exemplary embodiment the current values of the stress index SI are selected after the predetermined number of pulse beats by means of a digital low-pass filter SI=f*SI.sub.x+(1?f)*SI.sub.x?1 calculated with f of 0.1. The device has been set up acordingly.

[0045] It should be still noted that the individual windows in which the stress index values are determined advantageously include various states of the subjects, such as e.g. lying, standing, movingin the sense of the Conconi testetc.

[0046] Moreover, it should be noted that even if test intervals are very widely separated in time, the adoption of the last test interval leads to a better result or more quickly to a good result than starting out with tabulated values. On the other hand, it may of course be appropriate to revert using tabulated values if the status of the subject has significantly changed in a fundamental manner.