Stretchable blood pressure cuff

A wearable cuff, comprising:

• a measurement bladder configured to restrict blood flow through the limb of the user when measuring blood pressure of the user;
• a pump fluidly coupled to the measurement bladder and operable to inflate the measurement bladder when measuring the blood pressure of the user;
• a pressure sensor configured to measure pressure within the measurement bladder when measuring the blood pressure of the user;
• a bladder assembly configured to contain a fluid, and defined by:
• an outer component that is liquid impermeable and defines a series of expandable channels;
• and
• an inner component and formed from a fluid permeable material that has a lower compliance than the outer component;
• and
• a reservoir coupled with the bladder assembly and configured to exchange the fluid with the bladder assembly;
• wherein:
• the bladder assembly and the reservoir are isolated from the measurement bladder and the pump;
• the bladder assembly is configured to:
• increase in length when a volume of the fluid within the bladder assembly decreases;
• and
• decrease in length when the volume of the fluid within the bladder assembly increases.

A wearable blood pressure measuring device, comprising:

• a cuff defining an interior surface that at least partially wraps around a user's limb;
• a first bladder assembly coupled with the cuff and defining a chamber that is configured to:
• contain a fluid;
• and
• maintain a circumferential dimension when a volume of the fluid within the chamber is held constant;
• a reservoir configured to exchange the fluid with the first bladder assembly;
• a valve configured to control the exchange of the fluid between the first bladder assembly and the reservoir;
• a second bladder assembly positioned along a portion of the interior surface and configured to inflate and deflate to restrict blood flow through the user's limb when a user's blood pressure is measured;
• and
• a pump and fluidly coupled to the second bladder assembly;
• wherein:
• the first bladder assembly and the reservoir are isolated from the second bladder assembly and the pump;
• in response to measuring the user's blood pressure, the valve prevents movement of fluid between the first bladder assembly and the reservoir such that the volume of the fluid within the chamber is held constant and the pump is operated to inflate the second bladder assembly.