Finger Cuff Inflation Control for Accurate Blood Pressure Sensing
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Solution Overview
Problem
Existing oscillometric blood pressure measurement (OBPM) systems face inaccuracies due to hydrostatic pressure variations caused by cuff placement relative to the heart, with arm cuffs being bulky and uncomfortable, and wrist cuffs being less reliable and less accurate.
Innovation Solution
A finger blood pressure cuff with an inflatable elastic bladder and a ring-shaped structure that expands towards the center of a user's finger, using a piezoelectric pump to control pressure, and includes sensors to monitor and analyze pressure data for accurate blood pressure estimation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional arm or wrist cuffs are used for blood pressure measurement, then the device structure is simple and easy to manufacture, but the measurement accuracy deteriorates due to distance from the heart and hydrostatic pressure variations
Solution Approach 1:
The cuff is divided into multiple independent inflatable chambers (first bladder and second bladder) that can be inflated separately or simultaneously. This segmentation allows the system to maintain structural simplicity while improving measurement accuracy by enabling differential pressure application and multiple measurement points on the finger.
Solution Approach 2:
The first and second bladders are nested within the same cuff structure, with each bladder containing its own inflatable element. This nesting approach allows multiple measurement functions to be integrated into a single compact device, maintaining ease of manufacture while enhancing measurement capabilities through multiple pressure zones.
2Reliability
If the cuff is placed farther from the heart (e.g., wrist or arm), then the device is more comfortable and easier to position, but the measurement reliability deteriorates due to hydrostatic pressure effects
Solution Approach 1:
By segmenting the measurement into multiple independent bladder chambers positioned at different locations on the finger, the system can compensate for hydrostatic pressure variations through differential measurement, thereby improving reliability while maintaining the convenience of finger placement.
Solution Approach 2:
The finger serves as an intermediary measurement point that is closer to the heart than wrist or arm measurements, reducing hydrostatic pressure effects. The multi-chamber cuff design further mediates pressure distribution to enhance measurement reliability while keeping the device easy to position on the finger.
3Measurement precision
If a single inflatable chamber is used, then the device structure is simple, but the measurement precision deteriorates due to susceptibility to hydrostatic pressure variations
Solution Approach 1:
The single chamber is segmented into multiple independent inflatable bladders (first and second bladders) within the cuff. This segmentation enables differential pressure measurement that compensates for hydrostatic pressure variations, improving measurement precision while maintaining relatively simple device structure through modular bladder design.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The finger cuff provides a compact, comfortable, and portable solution for blood pressure measurement with improved accuracy by minimizing hydrostatic pressure variations and using elastic materials to reduce pressure loss, enabling reliable cardiovascular data acquisition.
Implementation Method 1
The pump is configured to pressurize the pressurizable volume and cause the inflatable elastic bladder to expand towards the center of the hole
Implementation Method 2
a pressure sensor in fluidic communication with the pressurizable volume and configured to produce pressure data indicative of a pressure within the pressurizable volume
Implementation Method 3
The pressure signal captured by OBPM is affected by hydrostatic pressure, which is affected by cuff placement relative to the heart
Data Source
AI summary
An aspect of the disclosure pertains to a blood pressure measurement device and methods of controlling an inflation rate in a blood pressure measurement. An inflatable bladder of the blood pressure measurement device defines, at least in part, a pressurizable volume. The inflatable bladder may be inflated to pressurize a user's appendage and temporarily occlude blood flow in the user's appendage. A pressure sensor of the blood pressure measurement device is configured to obtain blood pressure measurements, and a pump of the blood pressure measurement device is configured to inflate the inflatable bladder and control an inflation rate by controlling at least one of a duty cycle, a voltage, or a drive frequency.