Shell Cuff Apparatus Tissue Property Calibration
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Solution Overview
Problem
Current shell cuff apparatuses fail to account for individual variations in tissue properties, leading to inaccurate blood pressure measurements, as they rely on average tissue properties expected for a particular size, which can result in significant differences between subjects with varying arm compositions such as obese or muscular individuals.
Innovation Solution
A method and system that use a shell cuff apparatus to apply multiple pressures to a body part, measuring changes in radius and pressure to determine tissue properties like elastic modulus, Poisson ratio, and fat-free mass, allowing for individual calibration of measurements to improve the accuracy of physiological characteristic estimates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If shell cuff apparatus uses average tissue properties for calibration, then device complexity is reduced, but measurement precision deteriorates for subjects with varying tissue compositions
Solution Approach 1:
The system performs preliminary measurement of tissue properties (such as tissue stiffness or compressibility) before conducting blood pressure measurement. This preliminary action allows the system to obtain subject-specific calibration parameters in advance, improving measurement precision without requiring complex pre-calibration procedures. The tissue property measurement is used to determine calibration parameters that are then applied during the actual blood pressure measurement process.
2Measurement precision
If shell cuff apparatus applies multiple different pressures to determine tissue properties, then measurement precision improves, but loss of time increases due to additional measurement steps
Solution Approach 1:
The system combines the tissue property measurement process with the blood pressure measurement process into a single integrated procedure. By merging these two functions, the system determines tissue properties during the same measurement session when blood pressure is being measured, eliminating the need for separate calibration steps. This reduces time loss while maintaining measurement precision through the use of subject-specific tissue property data.
3Ease of operation
If shell cuff apparatus uses simple calibration based on arm size, then ease of operation is improved, but reliability deteriorates for subjects with atypical tissue compositions
Solution Approach 1:
The system performs self-calibration by automatically measuring tissue properties directly from the subject's arm during the measurement process. Instead of requiring manual calibration procedures or pre-stored calibration data, the system autonomously determines subject-specific tissue properties and uses these to calibrate the blood pressure measurement. This self-service approach maintains ease of operation while significantly improving reliability for subjects with atypical tissue compositions such as obese or muscular individuals.
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
Enables precise determination of tissue properties, enabling accurate calibration of blood pressure measurements and reducing errors, especially for subjects with small or stiff arms, thereby improving the reliability of cardiac output and other physiological characteristic assessments.
Implementation Method 1
The pulse wave 8 causes a pressure wave in the tissue in the body part 4 and this is measured by the sensor pad 6
Implementation Method 2
The liquid in the sensor pad 6 can be, for example, a silicone oil such as AK10. The sensor pad 6 is connected via a flexible tube filled with a similar liquid filled to a pressure sensor
Implementation Method 3
Similar to a standard blood pressure cuff there is an actuator (e.g. an air pump) that can fill a cuff with air, to compress the hard shell and thus the arm tissue
Data Source
AI summary
According to an aspect, there is provided a computer-implemented method of determining a tissue property of a body part. The method comprises controlling (101) a shell cuff apparatus to apply a plurality of different pressures to the body part, wherein the shell cuff apparatus at least partially encloses the body part, and wherein the shell cuff apparatus comprises a hard shell portion placed at least partially around the body part and an inflatable cuff surrounding the hard shell portion that is inflated and/or deflated to apply the plurality of different pressures to the body part via the hard shell portion; obtaining (103) radius measurements of a radius of the body part, or changes in the radius of the body part, as the plurality of different pressures are applied to the body part; obtaining (105) pressure measurements of the different pressures applied to the body part; and determining (107) the tissue property of the body part from the radius measurements and the pressure measurements.