| CPC A61B 5/02116 (2013.01) [A61B 5/021 (2013.01); A61B 5/02125 (2013.01); A61B 5/681 (2013.01); A61B 5/7275 (2013.01); A61B 5/746 (2013.01); A61B 2560/0228 (2013.01)] | 9 Claims |
|
1. A wearable device comprising:
a main body comprising a memory, a photoplethysmogram (PPG) sensor, at least one processor, and a display; and
a strap that is filled with or has an air bag to have an elasticity according to a change in pressure applied to a wrist of a user, and that is configured to transmit the change in pressure to the main body;
wherein the PPG sensor comprises a light source configured to emit light to the user and a detector configured to obtain a PPG signal by detecting light scattered or reflected from the user;
wherein the at least one processor is configured to:
extract a first feature and a second feature from the PPG signal measured at an extraction time, by combining a plurality of characteristic points of the PPG signal, the plurality of characteristic points comprising peak times and peak amplitudes of constituent pulse waveforms of the PPG signal;
calculate a first difference between an initial value of the first feature at a calibration time before the extraction time and a changed value of the first feature at the extraction time;
calculate a second difference between an initial value of the second feature at the calibration time and a changed value of the second feature at the extraction time;
calculate a product of the first difference and the second difference;
normalize the first difference, the second difference, and the product of the first difference and the second difference, based on at least one of the initial value of the first feature and the initial value of the second feature at the calibration time, to obtain normalization results;
obtain a combined result of a weighted sum of the normalization results by applying a weight to each of the normalization results and applying a scaling factor to the weighted sum of the normalization results;
estimate a mean arterial pressure (MAP) of the user by adjusting at least one of the weight and the scaling factor;
obtain a pulse pressure from the PPG signal; and
estimate a diastolic blood pressure (DBP) and a systolic blood pressure (SBP) of the user based on the MAP, the pulse pressure, and at least one of the adjusted weight and the adjusted scaling factor,
wherein the display is configured to provide warning information when the estimated DBP or the estimated SBP falls outside a predetermined range.
|