Non-invasive Blood Pressure Monitor Using Inflation Phase Detection
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Solution Overview
Problem
Conventional non-invasive blood pressure (NIBP) monitors are uncomfortable for subjects due to prolonged measurement times, high maximum cuff pressures, and skin irritation, which can lead to non-compliance and inaccurate measurements, especially when used in home settings.
Innovation Solution
A method and NIBP monitor that measures blood pressure during cuff inflation, utilizing a separate pulse rate sensor to continuously obtain heart rate information, allowing for real-time filtering and processing of pressure signals to determine blood pressure quickly and accurately, thereby reducing discomfort and measurement time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional oscillometric method is used with cuff deflation, then blood pressure can be measured accurately, but measurement time is prolonged and causes discomfort
Solution Approach 1:
The patent inverts the conventional approach by measuring blood pressure during cuff inflation rather than during deflation. The control unit determines blood pressure parameters (systolic, diastolic, mean pressure) by analyzing pressure oscillations detected during the inflation phase, which significantly reduces measurement time while maintaining accuracy.
Solution Approach 2:
The patent implements continuous pressure signal acquisition and processing throughout the cuff inflation process. The control unit continuously monitors pressure oscillations and determines blood pressure parameters in real-time during inflation, eliminating the need for separate deflation phase measurements and reducing total measurement time.
2Measurement precision
If high cuff pressure is applied to ensure accurate measurement, then measurement precision improves, but subject comfort deteriorates and skin irritation increases
Solution Approach 1:
The patent changes the pressure parameter profile by inflating the cuff to a controlled maximum pressure (e.g., 180 mmHg) and maintaining it briefly, then rapidly deflating to measure blood pressure during the rapid deflation phase. This parameter change allows accurate measurement at lower sustained pressures, reducing skin irritation and discomfort while maintaining measurement precision.
3Productivity
If cuff inflation rate is increased to reduce measurement time, then productivity improves, but measurement accuracy may deteriorate
Solution Approach 1:
The patent employs feedback control where the control unit continuously monitors pressure oscillations during cuff inflation and adjusts the inflation rate and maximum pressure based on real-time signal characteristics. This feedback mechanism ensures that the cuff inflation rate is optimized to maintain accurate blood pressure measurement while minimizing total measurement time.
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 enables faster and more comfortable blood pressure measurements by allowing the cuff to be inflated at a controlled rate based on heart rate, reducing the peak pressure and total measurement time while maintaining accuracy, thus improving user compliance and comfort.
Implementation Method 1
The pressure sensor 24 measures the gas pressure in the system (and therefore the pressure of the gas in the cuff 28) and outputs a signal representing the pressure in the cuff 28
Implementation Method 2
the pump 22 blows air into the cuff 28, thereby inflating it
Implementation Method 3
the valve 26 is opened and slow (or step wise) deflation occurs
Implementation Method 4
The measured cuff pressure 10 is high pass filtered, and the resulting trace 12 shows the cuff pressure oscillations due to volume changes in the brachial artery
Implementation Method 5
An envelope 14 of the oscillation amplitudes is determined. The maximum A max of this pulse envelope 14 is taken as a reference point for determining the systolic 16 and diastolic pressure 15
Data Source
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AI summary
According to an aspect there is provided a method of obtaining a measurement of the blood pressure of a subject using a non-invasive blood pressure, NIBP, monitor and including using a pulse rate sensor and a cuff that is to be placed around a limb of the subject, the method comprising using the pulse rate sensor to obtain information on the pulse rate of the subject; adapting a pressure signal filter according to the obtained information on the pulse rate of the subject; starting inflation of the cuff; obtaining a pressure signal representing the pressure in the cuff as the cuff is inflated; filtering the pressure signal using the adapted pressure signal filter during inflation of the cuff; and processing the filtered pressure signal to obtain a blood pressure measurement for the subject during inflation of the cuff.