Today the U.S. Patent and Trademark Office officially granted Apple a patent that relates to a possible future Apple Watch with blood pressure measurement devices that includes a liquid filled sensor.

In Apple's patent background they note that a user may monitor one or more of their physiological parameters by attaching a monitoring device such as a blood pressure monitor to one of their limbs. The blood pressure monitor may include a cuff that secures an inflatable bladder against a limb of the user. The bladder can be inflated to compress the limb, thereby compressing one or more blood vessels in the limb and restricting and/or stopping blood flow through the vessels. The various pressures in the inflated bladder that restrict and/or stop blood flow through the vessels in the limb may be measured and used to determine one or more physiological parameters of a user such as blood pressure of the user. The accuracy of correlating changes in air pressure within the bladder to blood pressures in the arm may vary based on a variety of factors including inflation and deflation rates, the volume of the cuff, and/or the material of the cuff among others.

It may be desirable to reduce some of these variations and/or increase the sensitivity of the pressure measurements to help increase the accuracy or precision of measurements taken by blood pressure monitors. This what Apple's new granted patent covers .

Apple Watch: A Liquid Filed Sensor for Bloom Pressure Monitoring

Apple's granted patent is a new patent that relates to a blood pressure measurement device that uses a liquid filled pressure sensing chamber to measure blood pressure of a user.

The blood pressure measurement device can include a compression system that is separate from the liquid filled pressure sensing chamber and is used to compress the liquid filled pressure sensing chamber against the skin of the user to measure the user's blood pressure. The liquid filled pressure sensing chamber may be more sensitive to pressure changes in the blood vessel as compared to conventional air filled pressure sensing chambers due to the incompressible nature of liquid.

Further, having the pressure sensing system separated from the inflation system may help reduce noise and/or increase accuracy of blood pressure measurements as compared to typical blood pressure measurement systems in which a single inflatable cuff is used to both compress a user's arm and measure air pressure in the cuff to estimate blood pressure.

In some embodiments, the blood pressure measurement device is implemented as a pressure sensing stack that includes a liquid filled pressure sensing chamber positioned on an inflatable chamber. A strap can secure the stack against a skin surface of a user such that the pressure sensing chamber is positioned between the inflatable chamber and the user.

The inflatable chamber can be inflated to expand towards the user thereby pressing the pressure sensing chamber against the user's skin surface. The pressure sensing chamber can measure blood pressure of the user during the inflation and/or deflation of the inflatable chamber. The pressure sensor can include a flexible housing that contains a volume of liquid, and a pressure sensor that is configured to detect a pressure of the liquid volume.

In some cases, the stack structure of the pressure sensing device can help decrease the size of the blood pressure measurement device such that it can be integrated into smaller devices while achieving desirable accuracy and reliability.

The blood pressure measurement device can also include an air pump that is configured to inflate the inflatable chamber. The air pump can be integrated into the pressure sensing stack structure of the pressure sensing device.

For example, the inflatable chamber can be positioned on an upper surface of the air pump such that when the blood pressure measurement device is worn by the user the stack includes the air pump positioned furthers from the user, the inflatable chamber positioned between the air pump and the user, and the pressure sensing chamber positioned between the inflatable chamber and the user. The strap can secure the pressure sensing stack to the user such that as the inflatable chamber is inflated it expands primarily towards the user.

In some implementations, the blood pressure measurement device includes a support plate that is positioned between the expansion chamber and the pressure sensing chamber. The support plate can be a rigid or semi-rigid structure that helps distribute the force generated by the inflatable chamber across the pressure sensing chamber and can prevent blood pressure pulse signal loss that may occur between the pressure sensing chamber and the inflatable chamber.

In some cases, the expansion chamber, the support plate and the pressure sensing chamber can all have similar profiles such that the support plate and/or expansion chamber extend across substantially the entire bottom surface of the pressure sensing chamber.

The blood pressure measurement device can be an independent device that includes a display, dedicated processor, battery, and so on, which can be mounted to or otherwise integrated into the strap.

In other cases, the blood pressure measurement device can be integrated to function with a wearable device such as a smartwatch. For example, the pressure sensing stack can be mounted to a smartwatch band and be electrically coupled with the smartwatch. In these cases, the pressure sensing stack could send pressure measurements to the smartwatch and the smartwatch can analyze, display or combine the pressure data with other data that was collected by the smartwatch, which could include ambient pressure, other physiological measurements of a user such as electrocardiograms, temperatures, oxygen saturation, and so on. In some cases, the blood pressure measurement device could utilize components of the smartwatch such as a power sources.

The example of a smartwatch is given as one example of a device that the blood pressure measurement device can be integrated with. However, the blood pressure measurement device can also be configured to detect blood pressure at locations other than the wrist and/or integrated with other devices such as a dedicated display and processing system, a smartphone, other wearable health monitors, portable music players, and the like.

For example, the blood pressure measurement device could be mounted to a strap that is configured to wrap around the upper arm, the wrist, and/or other portions of a user to estimate a blood pressure using measurements from one or more of these locations.

In some cases, the blood pressure measurement device can wirelessly communicate with one or more other devices. For example the pressure sensing device could send blood pressure measurement data to a smartphone, tablet, computer, or other connected devices where it can be viewed, analyzed, stored or otherwise accessed by the user or other authorized party.

The blood pressure measurement device could also be integrated into clothing, belts, hats or other items worn by a user. In some cases, the blood pressure measurement device could be placed on a surface and the user could check their blood pressure by pressing a portion of their body against the device to measure their blood pressure.

Apple has filed for other patents on this subject matter as noted below:

• 01: Apple wins an extremely detailed Hypertension (Blood Pressure) Monitoring System patent that pertains to a future Apple Watch+
• 02: Apple Wins Second Major Blood Pressure Monitoring Patent that's part of a larger Project
• 03:  Apple Files Major Updates to Two of their Blood Pressure inventions for Apple Watch

On the rumor front, Mark Gurman has reported in the past that the "next Apple Watch, likely Series 11 and Ultra 3 will feature blood pressure monitoring capability, potentially arriving in the fall of 2025."