Computer-implemented method for synchronizing a photoplethysmography (ppg) signal with an electrocardiogram (ecg) signal

A computer-implemented method for synchronizing a photoplethysmography signal, abbreviated PPG signal, with an electrocardiogram signal, abbreviated ECG signal, said method comprising:

• recording said ECG signal using an ECG monitoring system;
• recording said PPG signal, semi-synchronously with said recording of said ECG signal, using a contact PPG sensor;
• cutting said PPG signal into PPG signal pieces;
• for a PPG signal piece out of said PPG signal pieces:
• generating a vector of PPG peak times for peaks in said PPG signal piece;
• selecting different offsets o;
• cutting different ECG signal pieces out of said ECG signal by applying said different offsets o in said ECG signal;
• generating respective vectors of ECG peak times for said ECG signal pieces;
• computing distances d between said vector of PPG peak times and said respective vectors of ECG peak times;
• determining a best matching ECG signal piece with minimal distance do amongst said distances d;
• and
• registering a start time x of said PPG signal piece in said PPG signal, a start time yo of said best matching ECG signal piece in said ECG signal, and said minimal distance do;
• determining an offset between said PPG signal and ECG signal as the offset of a regression model modelling the relation between said start time x and said start time yo, inverse weighted by said minimal distance do;
• determining a drift between said PPG signal and ECG signal as the slope of said regression model;
• and
• applying said offset and said drift to said PPG signal to synchronize said PPG signal with said ECG signal.

A controller comprising at least one processor and at least one memory including computer program code, the at least one memory and computer program code being configured to, with the at least one processor, cause the controller to perform:

• recording said ECG signal using an ECG monitoring system;
• recording said PPG signal, semi-synchronously with said recording of said ECG signal, using a contact PPG sensor;
• cutting said PPG signal into PPG signal pieces;
• for a PPG signal piece out of said PPG signal pieces:
• generating a vector of PPG peak times for peaks in said PPG signal piece;
• selecting different offsets o;
• cutting different ECG signal pieces out of said ECG signal by applying said different offsets o in said ECG signal;
• generating respective vectors of ECG peak times for said ECG signal pieces;
• computing distances d between said vector of PPG peak times and said respective vectors of ECG peak times;
• determining a best matching ECG signal piece with minimal distance do amongst said distances d;
• and
• registering a start time x of said PPG signal piece in said PPG signal, a start time yo of said best matching ECG signal piece in said ECG signal, and said minimal distance do;
• determining an offset between said PPG signal and ECG signal as the offset of a regression model modelling the relation between said start time x and said start time yo, inverse weighted by said minimal distance do;
• determining a drift between said PPG signal and ECG signal as the slope of said regression model;
• and
• applying said offset and said drift to said PPG signal to synchronize said PPG signal with said ECG signal.

A computer readable storage medium comprising computer-executable instructions of a program for performing the following steps when the program is run on a computer:

• recording said ECG signal using an ECG monitoring system;
• recording said PPG signal, semi-synchronously with said recording of said ECG signal, using a contact PPG sensor;
• cutting said PPG signal into PPG signal pieces;
• for a PPG signal piece out of said PPG signal pieces:
• generating a vector of PPG peak times for peaks in said PPG signal piece;
• selecting different offsets o;
• cutting different ECG signal pieces out of said ECG signal by applying said different offsets o in said ECG signal;
• generating respective vectors of ECG peak times for said ECG signal pieces;
• computing distances d between said vector of PPG peak times and said respective vectors of ECG peak times;
• determining a best matching ECG signal piece with minimal distance do amongst said distances d;
• and
• registering a start time x of said PPG signal piece in said PPG signal, a start time yo of said best matching ECG signal piece in said ECG signal, and said minimal distance do;
• determining an offset between said PPG signal and ECG signal as the offset of a regression model modelling the relation between said start time x and said start time yo, inverse weighted by said minimal distance do;
• determining a drift between said PPG signal and ECG signal as the slope of said regression model;
• and
• applying said offset and said drift to said PPG signal to synchronize said PPG signal with said ECG signal.