WO1998049932A1

WO1998049932A1 - Diagnosis based on phasic sinus arrhythmia

Info

Publication number: WO1998049932A1
Application number: PCT/DE1998/001194
Authority: WO
Inventors: Friedhelm R. Drepper; Michael Schiek; Hans-Henning Abel; Katrin Suder
Original assignee: Forschungszentrum Jülich GmbH
Priority date: 1997-05-03
Filing date: 1998-04-30
Publication date: 1998-11-12
Also published as: DE19718806A1

Abstract

Disclosed is a device comprising a pacemaker for setting the inhale-to-exhale-ratio, a sensor enabling the rate of heart beat to be measured, a storage unit for storing master data, and a assessement unit for providing a value derived from both the measured rate of heart beat and the stored master data. Said device is used for arriving at a diagnosis based on values such as the rate of heart beat, which is a function of the breathing rate.

Description

Diagnosis using respiratory sinus arrhythmia

The invention relates to a device with a clock generator for specifying a breathing rhythm and with a detector for measuring the heart rate.

According to the publication “Hirsch J.A, and B. Bishop. Respiratory sinus arrhythmia in humans: how breathing pattern modulates heart rate, Am. J. Physiol. 241: H620-H629, 1981 "using the aforementioned device, it was found that the fluctuations in the heart rate in the frequency range of breathing generally have the same frequency as breathing. The amplitude of this so-called respiratory sinus arrhythmia (RSA) generally decreases with physical and psychological stress as well as with age. According to the publication "Angelone A., and NA Coulter. Respiratory sinus arrhythmia: a frequency dependent phenomenon. J. Appl. Physiol. 19: 479-482, 1964" the amplitude of the RSA also increases if the breathing rhythm slows down. According to the publication "Schiek M., F.R. Drepper, R. Engbert, H.-H. Abel, and K. Suder, Cardiorespiratory Synchronization, in: K. Kantz,

Kurths, and G. Mayer-Kress (eds.) Nonlinear Analysis of Physiological Data, Springer, Berlin, 1997 "also found that the amplitude of the RSA is subject to strong fluctuations. Even when breathing in a relaxed, stress-free state, there are strong fluctuations in the amplitude on. Since the heartbeat dependent on the breathing rhythm correlates with the physical and / or psychological state of a person, the heartbeat rate could be used for diagnostic purposes. The object of the invention is to provide a device in which a diagnosis can be made based on the heart rate dependent on the respiration.

The object is achieved by a device with the features of the main claim. Advantageous embodiments result from the related claims.

According to the claim, the device has a clock for setting a respiratory rate. A clock generator in the sense of the claim is present, in particular, if it is able to convey a uniform rhythm to the subject, so that the predetermined breathing profile, that is to say the ratio of inhalation time to exhalation time, corresponds to spontaneous breathing. The ratio of inhalation time to exhalation time for spontaneous breathing is regularly 2: 3 to 3: 4.

In particular, an optical clock is suitable for generating phase-correct periodic breathing.

Experience has shown that particularly reliable results can be achieved if the test subjects can freely identify and predict the times of the change between inhalation and exhalation. Recognizability and predictability is ensured by an optical clock generator, which conveys the clock by means of a growing and then shrinking optical display. For example, it is a growing and then shrinking surface or line that is displayed on a monitor or LED odenfeld can be seen. The growth of the surface or line then signals inhalation, for example. Exhale with a shrinking surface or line. With such an optical clock, the respective reversal point can be reliably recognized and predicted by the test subject.

Furthermore, the device according to the claims has a detector for measuring the heart rate such as e.g. B. an EKG measuring device. Every measuring device with which the pulse of a person and thus the heartbeat rate can be determined has proven to be sufficient.

The reliability of a diagnosis using the device according to the claims increases with the accuracy with which the heartbeat length is determined. A heartbeat length can e.g. B. can be determined by determining the time between adjacent maxima of the R peaks within the QRS complex known in specialist circles. The heartbeat length should be determined with an accuracy of at least ± 5o, preferably with an accuracy of U ». The measuring device must be selected accordingly.

Furthermore, the device according to the claims comprises a memory in which reference data are stored. For the purposes of the invention, reference data are data of heartbeat speeds or heartbeat patterns as a function of the respiratory rate or data derived therefrom before the device is completed. In particular, the stored reference data are heart rate data which, before being stored, transforms into polar coordinates in the manner described below and in which only the angles of the positions thus determined are bar coordinates have been stored as reference data.

It has been found that in the case of uniform breathing, the profile of which is adapted to spontaneous breathing, the heart rate follows a pattern. The frequency of rhythmic breathing should be slightly below that of spontaneous breathing, since with a frequency below the spontaneous breathing frequency the amplitude of the respiratory sinus arrhythmia is comparatively large. More precise results are then achieved.

If the measured data is transformed into polar coordinates and only the coordinate angles are taken into account, this schematic dependency between two successive angles of the polar coordinate system can be visualized. Typical patterns result in healthy subjects in a stress-free state. A deviation from the typical pattern can indicate physical or psychological changes. Conclusions about the existence of pathological conditions are therefore possible.

The sophisticated evaluation means compares the measured data with the stored reference data and provides deviations between the determined data and reference data. The deviations indicate that a change has occurred from the state on which the reference data was based.

A PC with an analog-digital converter interface for recording the ECG, respiratory flow and clock signals as well as with software for signal analysis and visualization is e.g. B. used as an evaluation means. In order to achieve the desired measuring accuracy, the analog-digital converter interface should be designed that the analog-digital conversion can be carried out with at least 200 Hz, preferably with 1000 Hz.

The reference data can represent mean values from the results of many test subjects and thus "normal" values. Alternatively, the values of a single test subject can be used as reference data. This test subject, by means of which the reference data was determined, is then expedient with the currently diagnosed test subject In the first case, a statement can be made about deviations from "normal" values. In the latter case, relative statements, in particular statements about changing psychological or physical conditions of a test person, are possible. In an advantageous embodiment, the device according to the invention comprises a conventional respiratory flow or a tidal volume measuring device. The measurement of breathing is used for online monitoring whether breathing is suitable or for offline checking whether breathing is suitable.

In particular in the case of online measurement and evaluation, the measuring device should visually indicate the respiratory flow or the respiratory volume, since an acoustic display can then put the test subject into an undesirable stress state. The optical display makes it possible for the person who is carrying out the examination to register when the specified respiratory rate is being observed and which measurement data are consequently relevant.

In a further advantageous embodiment of the invention, the device according to the invention has a high-pass filter which detects the relatively short-term fluctuations in the heartbeat lengths in the frequency range separates breathing from long-term fluctuations or trends.

A preferred embodiment of the high-pass filter results if a centered moving average value is subtracted from the measured heartbeat lengths, which is formed with a weight function whose argument contains heartbeat lengths. The Gaussian distribution with the respective (non-equidistant) time differences to the center of the mean as an argument represents a possible function type of the weight function. The half-value width of the weight function should correspond to the breath length. In the case of high-pass filtering, the respiratory rate in particular is selected as the cutoff frequency. The teaching of the invention has been preceded by the knowledge that with tactical breathing, i.e. H. when breathing according to a predetermined rhythm, the variation of the heartbeat lengths can be described by a relatively simple law of motion. The regularity refers to the relationship of successive ones

Heartbeat lengths. This regularity can be represented by a law of motion of successive angles, ie by a so-called circular image. With slow cycle breathing (for cardio-pulmonary healthy subjects in a rested state) the motion law can be represented as a curve with high significance. In contrast to, for example, artificial ventilation under anesthesia, there was no fundamental difference in the function of the control mechanisms compared to spontaneous breathing during tactical breathing during waking. The shape of the curve, which is dependent on the subject and his condition, is typical. Both the shape of this curve and the deviations from of the curve are of interest, inter alia, for cardiology, anesthesiology, sports medicine, neurology and psychology.

The expediency of the devices results from the fact that, in the case of clock breathing, the strong irregularity of the amplitude fluctuations is countered by an unexpected regularity in the form of the heartbeat length fluctuations.

FIG. 1: QRS complex

Figure 2: Heartbeat lengths as a function of time,

FIG. 3: plot of the heartbeat lengths at time “n + 1” against those at time “n”,

Figure: Two-dimensional embedding of the angle Φ taken from FIG. 3.

The signal analysis is explained in more detail using the following exemplary embodiment:

Figure 1 shows the electrocardiogram of a subject. The voltage U is plotted against the time t. As shown in FIG. 1, an electrocardiogram is identified by the points labeled P, Q, R, S and T. The QRS complex is particularly characteristic.

The time between two successive R-peaks and thus the heartbeat length of a subject is determined using a device according to the claims. High-pass filtering with a cutoff frequency that corresponds to the respiratory rate is carried out. For this purpose, a centered moving average is subtracted, which is formed with a Gaussian-shaped weight function, the argument of which is the respective time difference from Center of the mean. The half-value width of the weight function is equal to the breath length, ie approximately equal to 9 s.

The resultant course of the heartbeat lengths is shown in FIG. 2. The vertical, dashed lines mark the beginning of an inspiration. The course shown is typical for a cardiopulmonary healthy test subject who is in a stress-free state. The heartbeats numbered 1 to 9 in FIG. 2 or the associated heartbeat lengths are now taken out by way of example and converted into a two-dimensional representation according to FIG. 3.

The heartbeat length of the heartbeat 1 is plotted against the heartbeat length of the heartbeat 0 in the manner shown in FIG. 3. The heartbeat length of the heartbeat 2 is plotted against the heartbeat length of the heartbeat 1. In general, the heartbeat length of the heartbeat n is plotted against the heartbeat length of the heartbeat n-1, and consequently an embedding is carried out. This typically results in an ellipse according to FIG. 3.

These so-called “delayed” coordinates shown in FIG. 3 are then transformed into polar coordinates (angles and radii). The mean heartbeat length of approximately 1050 ms serves as the center C. Starting from this center C, the angles Φ become the heartbeats 1 to 9. Figure 3 shows how the angle Φ for the heartbeat 1 is determined.

The time sequence of the angles is then embedded in successive angles in the figure 4 clearly shown (circle illustration). The result is a typical heartbeat pattern that resembles the profile of a two-step staircase.

In the next step, the regularity of the respiratory sinus arrhythmia visible in this representation is B. shown on the screen of a personal computer using a diagram.

The regularity is quantified in a particularly descriptive manner by characteristic parameters. A first characteristic parameter, referred to below as asymmetry index 1, is formed by the relative difference in the number of heartbeat intervals that are greater than the mean, minus the number less than the mean. A second characteristic parameter, referred to below as asymmetry index 2, represents the relative difference between the number of increasing heartbeat intervals minus the number of decreasing intervals. The first number corresponds to the number of points in the angular range from 0.25 π to 1.25 π, the second to the remaining angular range.

A third characteristic parameter, referred to below as the degree of clumping, is quantified as a negative logarithm of the mean value of the respective minimum angle change in the angle range 0.75 π to 1.75 π. This first degree of clumping is a measure of the degree of clumping or, in other words, the clustering of the angles in the region of the maximum of the heartbeat lengths. A second degree of clumping is a measure of the degree of clumping in the remaining angular range. This corresponds to the lumping in the area of the minimum heartbeat lengths. The associated clumping angles each indicate the mean value of the angle for which the minimum angle change is assumed. The deviations of 0.25 π and 1.25 π respectively indicate to what extent the clumping of the angles coincides with the maximum or with the minimum of the heartbeat lengths.

Then this data is compared with already classified parameters from a reference database. The comparison enables conclusions to be drawn about deviations from a normal state or changes that have occurred.

The more precise properties of the relevant devices and algorithms are defined from the intended use above.

Claims

Patent claims

1.Device with a clock generator for specifying an inhalation and / or exhalation frequency, with a detector for measuring the heart rate, with a memory in which reference data are stored, with an evaluation means for generating a value which is derived from the measured heart rate and from the stored reference data depends.

2.Device with the features of the preceding claim with a measuring device for monitoring breathing.

3.Device with the features according to one of the preceding claims, in which the clock of the clock generator is conveyed by means of a growing and then shrinking optical display.

4.Device with the features according to one of the preceding claims, in which a respiratory flow or a tidal volume measuring device is provided as a measuring device for monitoring breathing.

5.Device with the features according to one of the preceding claims, in which an optical display is provided which optically displays the respiratory flow or the respiratory volume.

6.Device with the features according to one of the preceding claims, is provided in the high-pass filter, which separates the fluctuations in the heartbeat lengths in the frequency range of breathing from longer-term fluctuations or trends.