Apple Inc.
Electrical Coupling of Pulse Transit Time (PTT) Measurement System to Heart for Blood Pressure Measurement

Abstract:

A pulse transit time is measured non-invasively and used to calculate a blood pressure value. A method of determining one or more blood pressure values includes propagating an alternating drive current through a thorax of a subject via electrodes located on a wrist-worn device. Resulting voltage levels of the subject are sensed by the wrist-worn device. The voltage levels are processed to detect when a volume of blood is ejected from the left ventricle. Output from a pulse arrival sensor coupled to the wrist-worn device is processed to detect when a blood pressure pulse generated by ejection of the volume of blood from the left ventricle arrives at the wrist. A pulse transit time (PTT) for transit of the blood pressure pulse from the left ventricle to the wrist is calculated. One or more blood pressure values for the subject are determined based on the PTT.