Extraction of heart inter beat interval from multichannel measurements
A monitoring apparatus comprising a multichannel pressure sensing sensor for measuring a ballistocardiographic signal of a human body is provided. The monitoring apparatus comprises a manner for selecting a time window for heart inter beat interval including two consecutive heart beats to be estimated, defining a spectrum for the signal averaging between at least two measurement channels of the sensor, a cepstrum from the logarithm of the spectrum, and a heart inter beat interval. A method for defining a heart inter beat interval is also provided, where a ballistocardiographic signal of a body is measured with a multichannel pressure sensing sensor, a time window for heart inter beat interval including two consecutive heart beats to be estimated is selected, a spectrum for the signal averaging between at least two measurement channels of the sensor, a cepstrum from the logarithm of the spectrum, and a heart inter beat interval are defined.
1. A monitoring apparatus comprising:
a multichannel sensor for measuring a ballistocardiographic signal of a body, said multichannel sensor comprising at least two measurement channels;
a selector for selecting a time window for a heart inter beat interval including two consecutive heart beats to be estimated;
wherein the monitoring apparatus is configured for
defining a spectrum for the ballistocardiographic signal for each selected time window;
forming an average of the ballistocardiographic signal spectra of at least two measurement channels of the multichannel sensor;
defining a cepstrum from the logarithm of the spectrum; and
defining a heart inter beat interval on the basis of the cepstrum.
2. The monitoring apparatus according to claim 1 , wherein the selection of the time window is based on at least one of ballistocardiographic (BCG) signal heart beat analysis, or looping for a multitude of pre-selected window lengths and shifting in time.
3. The monitoring apparatus according to claim 1 , wherein the multichannel sensor is a multichannel pressure sensor.
4. The monitoring apparatus according to claim 3 , wherein the multichannel pressure sensor is integrated into a bed mattress or to a seat.
5. The monitoring apparatus according to claim 3 , wherein the multichannel pressure sensor is a matrix-type, row-type or column-type multi-electrode multichannel pressure sensor foil.
6. The monitoring apparatus according to the claim 3 , wherein the multichannel pressure sensor is configured to be laid under a body.
7. A method for defining a heart inter beat interval comprising:
measuring a ballistocardiographic signal of a body with a multichannel sensor comprising at least two measurement channels;
selecting a time window for a heart inter beat interval including two consecutive heart beats to be estimated;
defining a spectrum for the ballistocardiographic signal for each selected time window;
averaging between signal spectra of at least two measurement channels of the multichannel sensor;
defining a cepstrum from the logarithm of the spectrum; and
defining a heart inter beat interval on the basis of the cepstrum.
8. A method according to claim 7 , comprising selecting the time window on the basis of at least one of a ballistocardiographic (BCG) signal heart beat analysis, or looping for a multitude of pre-selected window lengths and shifting in time.
9. A method according to claim 7 , comprising using a multichannel pressure sensor as said multichannel sensor.
10. A method according to claim 9 , comprising using a matrix-type, a row-type or a column-type multi-electrode multichannel pressure sensor as said multichannel pressure sensor.
11. A method according to the claim 9 , comprising laying the multichannel pressure sensor under a body.
12. A method according to claim 7 , comprising using a multichannel pressure sensor integrated into a bed mattress or to a seat.