Surgery – Diagnostic testing – Cardiovascular
Reexamination Certificate
1999-10-05
2001-08-28
Lacyk, John P. (Department: 3736)
Surgery
Diagnostic testing
Cardiovascular
C600S516000, C600S300000
Reexamination Certificate
active
06282439
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to measuring a vital function, and particularly to measuring the heart rate.
BACKGROUND OF THE INVENTION
Prior art solutions utilize filtering and a detection threshold for detecting the heart rate. In filtering the frequency band of the received signal is limited so that preferably only the heart rate signal passes through the filter. Furthermore, when the heart rate is calculated, only pulses which have a sufficiently high amplitude and exceed (or are below) the detection threshold are taken into account.
The disadvantages of the prior art solutions include the fact that they do not take the different forms of the QRS complex the heart rate into account, even though different persons may have very different QRS complex widths and wave forms. This can also easily lead to incorrect heart rate detection especially if there is interference in the environment. By adapting the detection method and measuring device to each person's own QRS signal, heart rate detection and wave form recognition can be improved and made more reliable.
BRIEF DESCRIPTION OF THE INVENTION
The object of the invention is to provide a method and a measuring device implementing the method to solve the above-mentioned problems. The invention relates to a method of measuring a recurrent signal episode of a vital function, the method employing an adapted filter for detecting the signal episode. The method of the invention comprises calculating a coherent average of single signal episodes to determine the wave form of the signal episode. The invention also relates to a method of determining the impulse response of a recurrent signal episode of a vital function in a detector based on an adapted filter. The method of the invention comprises calculating a coherent average of single signal episodes and employing the coherent average of the signal episode for forming the impulse response of the adapted filter.
The invention also relates to a measuring device for measuring a recurrent signal episode of a vital function, the measuring device comprising electrodes for receiving signal episodes generated by the vital function and an adapted filter for detecting the signal episodes received by the electrodes. The measuring device of the invention comprises a coherent averaging unit which is arranged to determine the wave form of the signal episode received by the electrodes. The invention also relates to a measuring device for measuring a recurrent signal episode of a vital function, the measuring device comprising electrodes for receiving the signal episodes generated by the vital function. The measuring device according to the invention comprises a coherent averaging unit which is arranged to calculate the coherent average of the signal episodes received by the electrodes, and an adapted filter the impulse response of which is based on the coherent average of the signal episode.
The method and measuring device of the invention offer several advantages. The measuring device is capable of adapting to changing wave forms. One important feature of the solution is that it combines good noise tolerance with quick learning and adaptation to changing wave forms. This is a significant feature in the measurement of the heart rate and the exercise-electrocardiogram (EKG), for example, where the form of the QRS complex may change due to exertion or displacement of the electrodes.
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Rhyhe, V. Thomas, “A Comparison of Coherent Averaging Techniques for Repetitive Biological Signals”, Medicl Research Engineering, Aug.-Sep., 1969, vol. 8, pp. 22-26.
Hoffman & Baron LLP
Lacyk John P.
Natnithithadha Navin
Polar Electro OY
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