# US 11,026,592 B2 · Finger blood pressure cuff

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- Number: US 11,026,592 B2
- Document ID: US11026592B2
- Status: Granted
- Kind: B2
- Application number: 15/855,932
- Filed: 2017-12-27
- Published: 2019-04-04
- Granted: 2021-06-08
- Earliest claimed: 2017-09-29
- Assignees: Fitbit, Inc.
- Applicants: Fitbit, Inc.
- Inventors: Xi Zhang; Keith Adam Wong; Andrew Larsen Axley; Dan Stefan Tudose; Conor Joseph Heneghan
- Web page: https://patentgrep.com/patent/US11026592B2

## CPC

- A61B 5/02241: {of small dimensions, e.g. adapted to fingers}
- A61B 5/02141: {Details of apparatus construction, e.g. pump units or housings therefor, cuff pressurising systems, arrangements of fluid conduits or circuits (A61B5/02233, A61B5/0235 take precedence)}
- A61B 5/6826: {Finger}
- A61B 5/7278: {Artificial waveform generation or derivation, e.g. synthesizing signals from measured signals}
- A61B 5/02116: {of pulse wave amplitude (A61B5/02225 takes precedence)}
- A61B 5/02225: {using the oscillometric method}
- A61B 5/1121: {Determining geometric values, e.g. centre of rotation or angular range of movement}
- A61B: DIAGNOSIS; SURGERY; IDENTIFICATION (usefulness limited to only animals A61D)

## Abstract

An aspect of the disclosure pertains to finger blood pressure cuff. The finger blood pressure cuff may include a housing having an opening sized to receive a human finger and an inflatable elastic bladder disposed about an inward-facing surface of the opening. The inflatable elastic bladder may be inflated to pressurize a user's finger and temporarily occlude blood flow in the user's finger. The finger blood pressure cuff may include a pressure sensor for obtaining blood pressure measurements.

## Claims

### Claim 1

A device for estimating a user's blood pressure, the device comprising:
a housing having a hole sized to receive a human finger;
a pump;
an inflatable elastic bladder disposed about an inward-facing surface of the hole and defining, at least in part, a pressurizable volume in fluidic communication with the pump, wherein the pump is configured to pressurize the pressurizable volume and cause the inflatable elastic bladder to expand towards the center of the hole and contact a user's finger when the user's finger is positioned in the opening of the device and the pump is activated;
a pressure sensor in fluidic communication with the pressurizable volume and configured to produce pressure data indicative of a pressure within the pressurizable volume as a function of time; and
a controller that is configured with instructions to cause the pump to pre-inflate the inflatable elastic bladder from a first pressure to a second pressure prior to user insertion of their finger into the hole, and configured with instructions to cause the pump to further increase the pressure in the pressurizable volume beyond the second pressure to a third pressure upon determining that the user's finger is inserted into the hole, the third pressure being a pressure at which pulsatile variations are detectable in the pressure data.

### Claim 2 (depends on 1)

The device of claim 1, further comprising:
a ring-shaped structure disposed within the hole and encircling the inflatable elastic bladder, the ring-shaped structure further defining, at least in part, the pressurizable volume.

### Claim 3 (depends on 2)

The device of claim 2, wherein:
the ring-shaped structure has a first end and a second end with a cylindrical inner surface spanning between the first end and the second end,
the inflatable elastic bladder including a first seal bead and a second seal bead with a membrane structurally interposed between the first seal bead and the second seal bead,
the first seal bead being sealed against the first end of the ring-shaped structure and the second seal bead being sealed against the second end of the ring-shaped structure, and
the ring-shaped structure including one or more ports that fluidically connect the pressurizable volume with the pump.

### Claim 4 (depends on 3)

The device of claim 3, wherein the one or more ports pass through the ring-shaped structure and are configured to fluidically connect the pressurizable volume with an annular passage encircling the ring-shaped structure and are in fluidic communication with the pump.

### Claim 5 (depends on 1)

The device of claim 1, wherein the pressurizable volume has a continuous annular shape.

### Claim 6 (depends on 5)

The device of claim 5, wherein the inflatable elastic bladder has an overall shape that is axially symmetric about a center axis of the hole.

### Claim 7 (depends on 6)

The device of claim 6, wherein the inflatable elastic bladder includes a plurality of longitudinal ribs that extend along directions parallel to the center axis and that are arranged in a circular array centered on the center axis.

### Claim 8 (depends on 1)

The device of claim 1, wherein:
the inflatable elastic bladder includes two or more lobes symmetrically distributed about a center axis of the hole,
each lobe including a middle portion bracketed between two end portions,
the middle portion of each lobe extending closer to the center axis than the corresponding end portions of that lobe when the pressurizable volume is at zero gauge pressure.

### Claim 9 (depends on 8)

The device of claim 8, wherein the inflatable elastic bladder has three lobes symmetrically distributed about the center axis.

### Claim 10 (depends on 8)

The device of claim 8, wherein the controller is configured with instructions to:
control the pump to further increase the pressure in the pressurizable volume to a fourth pressure at which pulsatile variations in the pressure data indicative of the pressure within the pressurizable volume decrease to a first predetermined level,
control the pump to deflate the pressure in the pressurizable volume, and
control the pump to re-inflate or maintain the pressure in the pressurizable volume at a target pressure, wherein the target pressure is less than the fourth pressure, wherein the pressure is held at the target pressure for a duration between about 3 seconds and about 10 seconds.

### Claim 11 (depends on 8)

The device of claim 8, wherein the inflatable elastic bladder has a helical twist about the center axis of the hole.

### Claim 12 (depends on 1)

The device of claim 1, wherein the inflatable elastic bladder is made of silicone or other elastomer having a Young's modulus selected from the group consisting of: between about 0.001 GPa to about 0.1 GPa and between about 0.003 GPa to about 0.05 GPa.

### Claim 13 (depends on 12)

The device of claim 12, wherein an external surface of the inflatable elastic bladder is oxidized through exposure to ultraviolet radiation to reduce a tackiness of the inflatable elastic bladder.

### Claim 14 (depends on 1)

The device of claim 1, wherein:
the inflatable elastic bladder includes a membrane section that transitions to a bellows section at opposing ends,
each bellows section extending back towards the other bellows section from where that bellows section transitioned to the membrane section,
each bellows section terminating in a seal bead that encircles the membrane section.

### Claim 15 (depends on 14)

The device of claim 14, wherein:
the membrane section has a first length along a center axis of the hole,
the bellows sections both have a second length along the center axis of the hole, and
the second lengths are each between 15% and 35% of the first length.

### Claim 16 (depends on 14)

The device of claim 14, wherein: the membrane section and the bellows sections have nominal thicknesses selected from the group consisting of: between about 0.1 mm and about 0.75 mm and between about 0.25 mm and about 0.5 mm.

### Claim 17 (depends on 1)

The device of claim 1, wherein the inflatable elastic bladder has a length along a center axis of the hole that is selected from the group consisting of: between about 0.5 inches and about 1.5 inches and between about 0.75 inches and 1.25 inches.

### Claim 18 (depends on 1)

The device of claim 1, further comprising one or more proximity sensors.

### Claim 19 (depends on 1)

The device of claim 1, wherein the inflatable elastic bladder is configured to be inflated to a volume between about 3 cubic centimeters and about 10 cubic centimeters.

### Claim 20 (depends on 1)

The device of claim 1, wherein the housing includes a circumferential lip that:
extends around the hole,
forms an aperture smaller than the hole when viewed along a center axis of the hole, and
obscures a portion of the inflatable elastic bladder from view when viewed along the center axis with the device oriented such that the inflatable elastic bladder is behind the circumferential lip.