Patent ID: 11918324
Assignee: APPLE INC.
Field: Medical technology (Instruments)
Classification: CPC A | IPC A

Claim 0:
1. A method of determining one or more blood pressure values of a subject, the method comprising:
propagating an alternating drive current through the subject between a first drive current electrode and a second drive current electrode, wherein the second drive current electrode is externally located on a wrist-worn device worn on a wrist of the subject and engaged with the subject so that a portion of the alternating drive current travels through a thorax of the subject, and wherein the first drive current electrode is non-invasively engaged with the subject's skin at the wrist;
sensing voltage levels of the subject resulting from the alternating drive current via a first sense electrode and a second sense electrode, wherein the second sense electrode is externally located on the wrist-worn device and engaged with the subject so as to sense a voltage level induced by the alternating drive current, and wherein the first sense electrode is non-invasively engaged with the subject's skin at the wrist;
processing the voltage levels to detect when a volume of blood is ejected from the left ventricle;
processing output from a pulse arrival sensor coupled to the wrist-worn device to detect when a blood pressure pulse generated by ejection of the volume of blood from the left ventricle arrives at the wrist;
calculating a pulse transit time (PTT) for transit of the blood pressure pulse from the left ventricle to the wrist; and
determining one or more blood pressure values for the subject based on the PTT.