Method and device for quantifying a respiratory sinus arrhythmia and use of said type of method or said type of device

Abstract

In a method and a device for quantification of a respiratory sinus arrhythmia, a heart-rate curve is measured first and then the time elapsed between two heartbeats is determined and quantified by an analysis in the phase domain. A more informative quantification is obtained when suitable coefficients are used or the heart-rate curve is interpolated and/or detrended for the quantification.

Claims

1. A quantification method for quantification of a respiratory sinus arrhythmia, in which firstly a heart-rate curve is measured and then a time elapsed RR.sub.n between two heartbeats is determined and, by an analysis of the time elapsed RR.sub.n between the heartbeats, the respiratory sinus arrhythmia is quantified from a ratio containing SD1 and SD2, wherein $\mathrm{SD}1=\frac{\mathrm{RMSSD}}{\sqrt{2}},\mathrm{SD}2=\sqrt{2\times {\mathrm{SDNN}}^2-\mathrm{SD}{1}^2},\mathrm{SDNN}=\sqrt{\frac{\underset{n=1}{\overset{N}{.Math.}}{\left({\mathrm{RR}}_n-{\mathrm{RR}}_{\mathrm{mean}}\right)}^2}{N-1}},\mathrm{RMSSD}=\sqrt{\frac{\underset{n=1}{\overset{N-1}{.Math.}}{\left({\mathrm{RR}}_{n+1}-{\mathrm{RR}}_n\right)}^2}{N-1}}\mathrm{and}$ ${\mathrm{RR}}_{\mathrm{mean}}=\frac{\underset{n=1}{\overset{N}{.Math.}}{\mathrm{RR}}_n}{N},$ wherein a value G′, where $G^{\prime }=a\frac{\mathrm{SD}{2}^b}{{\left(\mathrm{SD}1+c\right)}^d}$ is the quantification of the respiratory sinus arrhythmia; wherein “a” lies between 0.5 and 1.5; wherein “b” lies between 2.4 and 3.3; wherein “c” lies between 4.0 and 10.0; wherein “d” lies between 2.8 and 4.2; wherein SD1 is a measure for the distribution of the measured points transverse to the identity line; and wherein SD2 is a measure for the distribution of the measurement points along the identity line.

2. The quantification method according to claim 1, wherein the heart-rate curve is interpolated before the calculation of the ratio containing SD1 and SD2.

3. The quantification method according to claim 2, wherein the heart-rate curve is interpolated to a heart-rate curve recorded with regular time intervals.

4. The quantification method according to claim 1, wherein the heart-rate curve is detrended before the calculation of the ratio containing SD1 and SD2.

5. The quantification method according to claim 4, wherein the heart-rate curve is detrended by determination of a linear tendency of the heart-rate curve by calculation of a linear regression line and subtraction of the linear regression line from a linear interpolation of the heart-rate curve recorded with regular time intervals.

6. A method using the quantification method according to claim 1 for biofeedback, comprising: undertaking a plurality of measurements and a plurality of evaluations of the the measurements; and displaying results of the evaluations.

7. The quantification method according to claim 1, wherein “a” is 1.

8. The quantification method according to claim 1, wherein “b” lies between 2.5 and 3.2.

9. The quantification method according to claim 1, wherein “c” lies between 5.0 and 9.0.

10. The quantification method according to claim 1, wherein “d” lies between 2.9 and 4.1.

Description

(1) Further advantages, objectives and properties of the present invention will be explained on the basis of following description of exemplary embodiments, which in particular are also illustrated in the attached drawing. In the drawing:

(2) Table 1 shows an actual measurement of the RR intervals and the heart rate derived from them;

(3) Table 2 shows an interpolation of the measurement according to Table 1 to a regular measurement;

(4) Table 3 shows a set of coefficients applicable in practice;

(5) FIG. 1 shows a typical EKG with 4 heartbeats;

(6) FIG. 2 shows a heart-rate curve before and after a detrending;

(7) FIG. 3 shows a second heart-rate curve with its fast Fourier transform and an associated Poincaré diagram;

(8) FIG. 4 shows a third heart-rate curve with its fast Fourier transform;

(9) FIG. 5 shows two further heart-rate curves, which were measured on two different subjects; and

(10) FIG. 6 shows the Poincaré diagrams associated with FIG. 5.

(11) In the interpolation according to Table 2, a specifically 5-Hz linear interpolation is employed. Alternatively, for example, a 4-Hz cubic spline interpolation may also be used.

(12) In practice, it is possible, by linear interpolation of an actually recorded heart-rate curve, as is illustrated by way of example in Table 1, for example, as an actual measurement of the RR intervals and of the heart rate derived from them, to simulate a measurement that is made every 200 msec, as is then illustrated in Table 2.

(13) Starting from this Table 2, a detrending may first be undertaken, in which, as illustrated by way of example in FIG. 2, determines a basic tendency—here a downward path of the curve—by calculation of a linear regression line and is then subtracted from the values of Table 2, in order that an analysis process, which in particular may result in the values G or G′ as quantification, is then undertaken with these data in the phase domain. For the quantification, the coefficients indicated in Table 3 are suitable in particular for measurement intervals or for time windows, in which SD1 and SD2 are summed, of less than one minute. For other measurement intervals or time windows, other coefficients, which may be experimentally determined without difficulty, however, could be more advantageous as the case may be.

(14) These values may then be defined and used as quantification of the respiratory sinus arrhythmia.

(15) Such a quantification may take place in particular for a biofeedback, for example, in which corresponding measurements and evaluations are undertaken in real time and the result of the evaluation is correspondingly displayed in real time. Thus, for example, the values G and G′ may be reinterpreted in a display as “good” or “bad”. If necessary, a finer reinterpretation is obviously conceivable here.

(16) Supplementarily to the undertaken interpolation, it is of advantage when the values G′ are respectively used for the quantification.

(17) In an experimental comparison, it has been proved that known quantification devices or methods as are described, for example, in DE 10 2006 039 957 A1, are simulated with the coefficients listed in Table 3, wherein the calculations of the values G or G′ to be undertaken, including the interpolation and also the adjustment if necessary of the coefficients a, b, c and d, need substantially less energy and computing time, and so an implementation is possible without difficulty with smaller appliances or with appliances to which little computer power or little energy is available, or else with powerful instruments, which operate correspondingly faster.

(18) TABLE-US-00001 TABLES Time [sec] RR interval [ms] Heart rate [bpm] 0 822 72.99 848 848 70.75 1754 906 66.23 2670 916 65.50 3618 948 63.29 4572 954 62.89 5490 918 65.36 6378 888 67.57 7240 862 69.61 8076 836 71.77 8888 812 73.89 9684 796 75.38 10492 808 74.26 11336 844 71.09 12222 886 67.72 13120 898 66.82 14042 922 65.08 14960 918 65.36 15856 896 66.96 16718 862 69.61 17562 844 71.09 18382 820 73.17 19184 802 74.81 19976 792 75.76 20784 808 74.26 21634 850 70.59 22524 890 67.42 23438 914 65.65 24366 928 64.66 25286 920 65.22 26184 898 66.82 27058 874 68.65

(19) TABLE-US-00002 TABLE 2 Time [sec] RR interval [ms] Heart rate [bpm] 0 822 72.99 200 828 72.46 400 834 71.94 600 840 71.43 800 847 70.84 1000 858 69.93 1200 871 68.89 1400 883 67.95 1600 896 66.96 1800 907 66.15 2000 909 66.01 2200 911 65.86 2400 913 65.72 2600 915 65.57 2800 920 65.22 3000 927 64.72 3200 934 64.24 3400 941 63.76 3600 947 63.36 3800 949 63.22 4000 950 63.16 4200 952 63.03 4400 953 62.96 4600 953 62.96 4800 945 63.49 5000 937 64.03 5200 929 64.59 5400 922 65.08 5600 914 65.65 5800 908 66.08 6000 901 66.59 6200 894 67.11

(20) TABLE-US-00003 TABLE 3 a b c d 1 3.0640933514 6.1416416168 3.8932845592 1 2.9336259365 5.8386063576 3.705612421 1 2.9868226051 7.0778589249 3.6734967232 1 3.0965418816 8.7936115265 3.7033727169 1 2.8916110992 5.5824341774 3.6648161411 1 3.0149903297 5.5045495033 3.9051029682 1 3.0251405239 5.3571920395 3.9388401508 1 3.0995018482 5.3888492584 4.0623898506 1 3.1028745174 5.3845295906 4.0731034279 1 2.5600000000 6.2700000000 2.9600000000