Methods for measuring blood pressure using a wearable device

A method for processing a photoplethysmography signal, the method comprising the steps of:

• emitting light from a wearable device at a plurality of light-wavelengths for measuring a blood pressure of a wearer of the wearable device for at least one light-wavelength;
• creating a photoplethysmography segment by acquiring the photoplethysmography signal within a predefined time window, wherein the photoplethysmography signal comprises a plurality of pulses and wherein a pulse is the photoplethysmography signal between two consecutive valleys;
• collecting at least one biologically vital sign, such as a heart rate of the wearer, a respiration rate of the wearer, or an oxygen saturation rate of the wearer;
• collecting at least one waveform-based parameter proportional to a peak amplitude of the photoplethysmography segment;
• collecting at least one time-based parameter proportional to a peak time of the photoplethysmography signal or proportional to a peak width of the photoplethysmography segment;
• creating a cardiovascular profile vector of the wearer;
• calculating a mean squared error between components of the collected profile vector and components of a profile vector belonging to previously predicted cluster of profile vectors;
• and
• estimating a blood pressure of the wearer using the photoplethysmography segments comprised in the cardiovascular profile of the wearer when the mean squared error is smaller than a first threshold value.