Capacitive Arterial Pressure Waveform Sensor
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Solution Overview
Problem
Conventional methods for continuously measuring arterial pressure waveforms are either inconvenient, such as cuff-based systems, or highly invasive, like internal sensors, which can be painful and have physical drawbacks.
Innovation Solution
A biophysical sensor system with electrodes positioned over a body surface proximate an artery, using capacitance, resistance, or inductance sensing to detect displacement caused by arterial pressure waves, enabling non-invasive and continuous measurement of arterial pressure waveforms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If cuff-based tonometer/sphygmomanometer is used, then arterial pressure waveform measurement is achieved, but continuous measurement convenience is poor
Solution Approach 1:
The patent replaces the mechanical cuff-based measurement system with a capacitive sensing system that uses electrical fields to detect skin displacement. The capacitive sensor measures changes in capacitance caused by arterial pressure-induced skin movement, eliminating the need for mechanical inflation and deflation cycles, thereby enabling continuous convenient measurement while maintaining measurement capability.
Solution Approach 2:
The patent introduces skin displacement as an intermediary parameter that mediates between the arterial pressure wave and the capacitive sensor. The arterial pressure wave causes skin displacement, which in turn causes capacitance changes in the sensor. This intermediary mechanism allows indirect measurement of arterial pressure in a non-invasive, continuous manner.
2Reliability
If invasive internal arterial pressure sensors are used, then continuous arterial pressure readings are obtained, but invasiveness and physical effects increase
Solution Approach 1:
The patent uses skin displacement as an intermediary that allows measurement of arterial pressure without direct contact with the artery. The capacitive sensor placed on the skin surface detects displacement caused by the underlying arterial pressure wave, providing continuous readings while avoiding the harmful effects of invasive cannulation.
Solution Approach 2:
The patent replaces the invasive mechanical sensor that would directly contact the artery with a non-contact capacitive sensor that measures electrical field changes. This substitution eliminates physical invasion while maintaining the ability to detect continuous arterial pressure variations through the intermediary of skin displacement.
3Ease of operation
If capacitive sensing is used to detect skin displacement, then non-invasive continuous sensing is enabled, but sensitivity to distance changes must be maintained
Solution Approach 1:
The patent exploits the parameter relationship between distance and capacitance, where capacitance is inversely proportional to the square of the distance between the sensor and skin. By carefully controlling and maintaining a specific distance between the capacitive sensor and skin surface, the system achieves high sensitivity to the small capacitance changes caused by arterial pressure-induced skin displacement.
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 system allows for continuous, non-invasive monitoring of arterial pressure waveforms, providing vital signs like heart rate and blood pressure without the pain or invasiveness of traditional methods.
Implementation Method 1
electrodes can be capacitive sensors. Changes in distance between the electrode and skin surface can result in capacitance changes, which can be used to generate an APW and/or related data
Data Source
AI summary
A system can include one or more electrodes; a sensor structure configured to position electrodes over a surface of a body that includes an artery. A capacitance sensing circuit can be coupled to the electrodes and configured to acquire capacitance values of the electrodes over a predetermined time period. The capacitance values can correspond to a distance between the body surface and the at least one electrode. Processor circuits can be configured to generate APW data from the capacitance values. Corresponding methods and devices are also disclosed.