Wearable device and method of detecting atrial fibrillation

A method of detecting atrial fibrillation, the method comprising:

• obtaining a photoplethysmogram (PPG) signal from a first sensor of a wearable device;
• obtaining a motion detection signal from a second sensor of the wearable device;
• determining whether there is motion exceeding a reference value, based on the motion detection signal;
• detecting a heart rate from the PPG signal based on a peak-peak interval (PPI) of the PPG signal when the motion does not exceed the reference value and based on power spectrum analysis in a frequency domain of the PPG signal when the motion exceeds the reference value;
• detecting atrial fibrillation based on the heart rate;
• identifying, using a finite state machine including a stable state, a recovery state, a pulse state, and an atrial fibrillation state, a state in which the heart rate is calculated;
• when the state is the stable state or the atrial fibrillation state, outputting the heart rate to be used in detecting the atrial fibrillation;
• and
• when the state is the recovery state or the pulse state, not outputting the heart rate and discarding the heart rate.

A wearable device comprising:

• a first sensor configured to sense a pulse wave of a user and generate a photoplethysmogram (PPG) signal based on the pulse wave;
• a second sensor configured to sense motion of the user and generate a motion detection signal;
• a memory storing program code;
• and
• at least one processor configured to access the memory to execute the program code,
• wherein the program code causes at least one of the at least one processor to detect a heart rate based on a peak-peak interval (PPI) of the PPG signal when the second sensor senses no motion and based on power spectrum analysis of the PPG signal in a frequency domain when the second sensor senses the motion, and
• wherein the program code causes at least one of the at least one processor to detect atrial fibrillation based on the heart rate, and
• wherein:
• the program code causes at least one of the at least one processor to identify, using a finite state machine including a stable state, a recovery state, a pulse state, and an atrial fibrillation state, a state in which the heart rate is calculated,
• when the state is the stable state or the atrial fibrillation state, the program code causes at least one of the at least one processor to output the heart rate to be used in detecting the atrial fibrillation;
• and
• when the state is the recovery state or the pulse state, the program code causes at least one of the at least one processor to not output the heart rate and discard the heart rate.