Frequency processing of an rr series in an analogue cardiac signal

• US 20060155199A1
• Filed: 04/16/2003
• Published: 07/13/2006
• Est. Priority Date: 05/31/2002
• Status: Active Grant

• Current Assignee: Centre Hospitalier Régional Universitaire de Lille
• Original Assignee: Centre Hospitalier Régional Universitaire de Lille
• Inventors: Logier, Regis, Dassonneville, Alain
• Granted Patent: US 7,899,523 B2
• Time in Patent Office: Days
• US Class Current: 600/509
• CPC Class Codes: A61B 5/316 Modalities, i.e. specific diagnostic methods
• CPC Class Codes: A61B 5/347 Detecting the frequency distribution of signals
• CPC Class Codes: A61B 5/352 Detecting R peaks, e.g. for synchronising diagnostic apparatus; Estimating R-R interval
• CPC Class Codes: A61B 5/364 Detecting abnormal ECG interval, e.g. extrasystoles, ectopic heartbeats
• CPC Class Codes: A61B 5/4035 Evaluating the autonomic nervous system

Abstract

The RR series, which is constituted by a plurality of samples respectively defining the time intervals between pairs of successive heart beats, is filtered by means of a digital bandpass filter (F_k) presenting a predefined bandwidth [fc, f′c], and preferably by means of an IIR recursive selective filter, and a variability index (I_k) is computed which is a function of the instantaneous amplitude [vs(n)] of the discrete signal (S_k) from said bandwidth filter. The variability index (I_k) is preferably a function of, and in particular equal to, the effective value of the discrete signal (S_k) from the bandpass filter.

Claims

1. A method of frequency processing an RR series, the method being characterized by filtering the RR series by means of at least one digital bandpass filter (F_k) presenting a predefined bandwidth [fc, f′

c], and computing a variability index (I_k) that is a function of the instantaneous amplitude [vs(n)] of the discrete signal (S_k) from said bandpass filter.

2. A method according to claim 1, characterized in that an infinite impulse response recursive selective filter is used.

3. A method according to claim 1, characterized in that the variability index (I_k) is a function of and is preferably equal to the effective value of the discrete signal (S_k) from the bandpass filter.

4. A method according to claim 1, characterized in that a digital filter is used of bandwidth lying in the frequency range [0, 2 Hz].

5. A method according to claim 4, characterized in that a digital filter is used of bandwidth lying in one of the frequency bands:

[0.04 Hz, 0.1 5 Hz];

[0.1 5 Hz, 2 Hz] and preferably [0.15 Hz, 0.5 Hz];

[0.05 Hz, 0.07 Hz];

[0.04 Hz, 2 Hz] and preferably [0.04 Hz, 0.5 Hz];

[0.03 Hz, 0.15 Hz] and preferably [0.031 Hz, 0.102 Hz];

[0.1 Hz, 2 Hz] and preferably [0.102 Hz, 0.5 Hz].

6. A method according to claim 1, characterized in that the RR series is filtered by means of a plurality of filters (F₁, F₂, . . . ), and in that a frequency variability index is computed that is a function of a plurality of variability indices (I₁, I₂, . . . ) that are computed in parallel.

7. A method according to claim 6, characterized in that the RR series is filtered by means of at least two filters (F₁, F₂) of bandwidth lying respectively in the following frequency bands:

F₁;

[0.04 Hz, 0.15 Hz];

F₂;

[0.15 Hz, 2 Hz] and preferably [0.15 Hz, 0.5 Hz];

and in that a frequency variability index is computed as a function of the variability indices I₁ and I₂.

8. A method according to claim 6, characterized in that the RR series is filtered by means of at least two filters (F₁, F₂) of bandwidth lying respectively in the following frequency bands:

F₁;

[0.03 Hz, 0.15 Hz] and preferably [0.031 Hz, 0.102 Hz];

F₂;

[0.1 Hz, 2 Hz] and preferably [0.102 Hz, 0.5 Hz];

and in that a frequency variability index is computed as a function of the variability indices I₁ and I₂.

9. A process for acquiring and electronically processing an analog cardiac signal characteristic of cardiac rhythm, in which the cardiac signal is recorded, said signal is digitized, and an RR series is constructed, the process being characterized in that the RR series is processed automatically in real time, as said series is constructed, by implementing the frequency processing method specified in claim 1.

10. A process according to claim 9, characterized in that the analog cardiac signal is a fetal cardiac signal.

11. A system for acquiring and processing in real time a cardiac signal, which system comprises acquisition means (1;

11) enabling a cardiac signal to be acquired, first electronic means (2, 4;

12) enabling an RR series to be constructed automatically, said series being made up of a plurality of samples (RR_i) respectively defining time intervals between successive pairs of heart beats, the system being characterized in that it further comprises second electronic means (5;

15) designed to process the RR series delivered by the first electronic means in accordance with the frequency processing method specified in claim 1.

12. A system according to claim 11, characterized in that the acquisition means (11) are designed to enable the cardiac signal of a fetus to be acquired, and in that the second electronic means (15) are designed to process the RR series delivered by the first electronic means in accordance with a frequency processing method wherein the RR series is filtered by means of a plurality of filters (F₁, F₂, . . . ), and in that a frequency variability index is computed that is a function of a plurality of variability indices (I₁, I₂, . . . ) that are computed in parallel.

13. A system according to claim 12, characterized in that it constitutes a cardiotocograph including a function of measuring fetal suffering.