Blood Pressure Measurement Device with Dynamic Fluid Control
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Solution Overview
Problem
Existing blood pressure measurement devices using oscillometric methods face accuracy issues due to variations in fluid density and discharge/inflow rates, leading to errors in detecting volume changes of blood vessels, especially when the pressure of the fluid bladder changes.
Innovation Solution
A blood pressure measurement device with a control unit that regulates the pressurizing and depressurizing processes to maintain a proportional relationship between fluid change and pressure change, using a sensor to calculate systolic and diastolic blood pressure values based on internal pressure changes, and adjusting valve gaps or pump drive voltages to achieve consistent measurement accuracy regardless of the measurement perimeter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the pressure of the fluid bladder is increased to improve detection sensitivity, then the detection accuracy of blood pressure increases, but the fluid density increases causing non-linear volume-pressure relationship and measurement errors
Solution Approach 1:
The patent applies dynamics by making the pressurizing rate variable rather than constant. The control unit adjusts the pressurizing rate dynamically based on the current pressure level in the fluid bladder, ensuring that the product of pressurizing rate and fluid compressibility remains constant across different pressure ranges. This resolves the contradiction by adapting the system behavior to maintain measurement accuracy despite changes in fluid density.
Solution Approach 2:
The patent changes the parameter of pressurizing rate according to pressure level. By modifying the pressurizing rate as a variable parameter that decreases as pressure increases (to compensate for increased fluid compressibility), the system maintains a constant relationship between volume change and pressure change, thereby preserving measurement accuracy across the entire pressure range.
2Productivity
If the discharge rate of fluid from the fluid bladder is increased to reduce measurement time, then productivity improves, but the volume change of the fluid bladder decreases reducing detection accuracy
Solution Approach 1:
The patent applies dynamics by making the depressurizing rate variable rather than constant. The control unit adjusts the depressurizing rate dynamically based on the current pressure level, ensuring that the product of depressurizing rate and fluid compressibility remains constant. This allows faster discharge at lower pressures while maintaining adequate volume changes at higher pressures, thus improving overall measurement speed without sacrificing accuracy.
Solution Approach 2:
The patent changes the depressurizing rate parameter according to pressure level. By increasing the depressurizing rate as pressure decreases (where fluid compressibility is lower), the system achieves faster overall measurement cycles while maintaining sufficient volume changes for accurate detection throughout the depressurization process.
3Adaptability or versatility
If the volume of the fluid bladder is increased to improve comfort and adaptability to different perimeters, then ease of operation improves, but the density change of fluid caused by blood vessel volume change decreases reducing detection accuracy
Solution Approach 1:
The patent applies dynamics by adjusting the pressurizing and depressurizing rates dynamically based on the fluid bladder volume and current pressure level. For larger fluid bladders, the system uses higher pressurizing/depressurizing rates to compensate for the smaller density changes, thereby maintaining detection accuracy across different bladder sizes and measurement perimeters.
Solution Approach 2:
The patent changes the operational parameters (pressurizing rate and depressurizing rate) according to the fluid bladder volume. By scaling these parameters proportionally with bladder volume, the system maintains a constant product of rate and compressibility, ensuring consistent detection accuracy whether using a small or large fluid bladder.
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
This approach improves the detection accuracy of blood pressure measurements by maintaining a constant rate of fluid change relative to pressure changes, reducing errors caused by fluid density and perimeter variations, and eliminating the need for complex corrections based on wrapping conditions or body softness.
Implementation Method 1
A volume change of the fluid bladder transmitted by a volume change of a pressurized blood vessel is recognized as a pressure change of the fluid bladder (pressurized pulse wave amplitude)
Implementation Method 2
a pump for pressurizing the fluid bladder by injecting a fluid into the fluid bladder
Implementation Method 3
a valve for depressurizing the fluid bladder by discharging a fluid from the fluid bladder
Implementation Method 4
a sensor for measuring an internal pressure change of the fluid bladder
Data Source
AI summary
In a sphygmomanometer, a value representing a perimeter of a measuring portion is obtained. A parameter for controlling a drive voltage of a pump is determined based on the value. The drive voltage is determined based on the parameter and an internal pressure of a fluid bladder to pressurize the fluid bladder. In pressurizing process, a diastolic blood pressure value is calculated. A systolic blood pressure value is estimated, and when the internal pressure of the fluid bladder reaches the pressure, the pressurizing is stopped. A gap of a valve for discharging the fluid from the fluid bladder is determined based on a perimeter of a measuring portion, and the fluid bladder is depressurized with the gap constant. In the depressurizing process, the systolic blood pressure value is calculated. When the systolic blood pressure value is calculated, the fluid is discharged from the fluid bladder, and the measurement is terminated.