A new patent published by U.S Patent and Trademark Office reveals that Apple might be testing a new blood pressure measurement technology for Apple Watch. The patent titled “electrical coupling of pulse transit time (PTT) measure system to heart for blood pressure measurement” describes the measurement system to calculate blood pressure via pulse transit time. If developed, the new technology will allow users to monitor their blood pressure on Apple Watch without the use of a wrist cuff.
To distinguished its smartwatch from others, Apple has always promoted Apple Watch as a health and fitness device, and not just a smartwatch. Therefore, the company integrated health-related features on the smartwatch, like Workout, Health, Activity, ECG, blood-oxygen level, sleep tracking, hand-wash detection, and other apps. The discovered patent shows the company’s focus on bringing more health features to the device.
Apple Watch Could Measure Blood Pressure
According to the filing, the company will develop a system which will process voltage levels to determine the volume of blood ejected and arriving at the wrist. Apple explains that,
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.
The document mentions that a pulse arrival sensor comprising of PPG (photoplethysmogram) sensor will determine a tone of the users’ blood vessels and two light detectors in the PPG sensor will detect “when blood pressure pulse arrives at the wrist at a deeper of the different mean penetration depths.” PPG is used to detect blood volume changes in the microvascular bed of tissue of the skin.
Apple Watch’s health features have proven to be life-saving, especially its fall detection, SOS, and irregular heartbeat alerts. The data recorded on the smartwatch, such as ECG, is reliable enough to share with doctors for consultation. Therefore, a new blood pressure measurement feature will be the next big step for the smartwatch. Having said that, the company files for several patents in a year, and not all of the proposed technology gets developed, so it is likely that blood pressure monitoring will not come to Apple Watch users.