CNAP Mouse Blood Pressure Sensor Housing Design
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Solution Overview
Problem
Current methods for continuous non-invasive measurement of intra-arterial blood pressure using the Vascular Unloading Technique face challenges in maintaining accurate cuff pressure synchronization with intra-arterial pressure changes, particularly due to the need for the pressure generating system to be located near the cuff, which can obstruct access points and lead to positioning issues and motion artifacts.
Innovation Solution
A measuring system with a housing that serves as a supporting surface for the hand and fingers, integrating the pressure generating system beneath the hand, allowing the fingers to rest on a surface with the sensors, thus keeping the pressure generating system close to the cuff and preventing motion artifacts while maintaining access points on the forearm and back of the hand.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the pressure generating system is located on the distal forearm next to the wrist, then the cuff pressure can be varied fast enough to mirror intra-arterial pressure changes, but access points for intravenous and intra-arterial access are blocked and the system may slip or tilt during operation
Solution Approach 1:
The patent combines the pressure generating system with the finger sensor assembly, merging two previously separate components into a single integrated unit. This allows the pressure generating system to be positioned at the finger (distal end) while maintaining access points on the forearm and back of the hand, resolving the contradiction between fast pressure variation capability and access point availability.
Solution Approach 2:
The patent repositions the pressure generating system from the forearm (proximal location) to the finger assembly (distal location), changing the spatial dimension of placement. This dimensional relocation allows the system to achieve fast pressure response at the measurement site while preserving access points on the forearm and hand.
2Speed
If the pressure generating system is located on the distal forearm, then fast pressure response is achieved, but the system may slip or tilt during operation affecting sensor positioning
Solution Approach 1:
By merging the pressure generating system with the finger sensor assembly, the patent eliminates the risk of slipping or tilting that occurs when the system is placed on the forearm. The integrated design ensures stable positioning of both the pressure sensor and the measurement site, while maintaining fast pressure response capability.
3Adaptability or versatility
If long air tubes are used to connect the pressure generating system to the cuff, then the system can be positioned remotely, but the frequency limit condition cannot be met due to the low-pass characteristic of the tubes
Solution Approach 1:
The patent extracts the pressure generating system from the remote forearm location and integrates it directly with the finger sensor assembly. This eliminates the need for long air tubes and their associated low-pass characteristics, allowing the system to meet the frequency response requirements while maintaining positioning flexibility.
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 configuration enhances patient comfort by reducing hand tension and preventing sensor tilting, ensuring accurate and stable blood pressure measurement over extended periods without obstructing access points, and allows for longer measurement durations by alternating finger roles.
Implementation Method 1
This technique is based on a publication by Penáz (Digest of the 10th International Conference on Medical and Biological Engineering, 1973 Dresden) and has been improved by diverse enhancements. The Vascular Unloading Technique begins with shining light through a finger, thus determining the pulsatile (pulse-shaped) blood flow in the finger. This method is called photo-plethysmography (PPG)
Implementation Method 2
A control system keeps the registered flow and thus the resulting PPG signal (volume signal v(t)) constant by applying counter pressure in a cuff (cuff pressure pc(t)) around the finger
Implementation Method 3
Further there is provided a pressure generating system with at least one valve, which is controlled in real time by the plethysmographic system for generating pressure in the cuff, the pressure essentially corresponding to the intra-arterial blood pressure in the finger
Data Source
AI summary
The invention describes a measuring system for the continuous non-invasive determination of blood pressure at one or more fingers. The fingers chosen for measurement and the adjacent parts of the palm rest on a supporting surface of a housing, which has the shape of a computer mouse. Inside the housing of the “CNAP Mouse”, i.e. underneath the supporting surface for the hand, the pressure generating system is located. The finger sensors are mounted on the supporting surface for the hand. The forearm and the back of the hand are left free and may be used to place intra-venous or intra-arterial access elements. Since the hand will rest on the supporting surface motion artefacts are largely avoided. Tilting or turning of the sensors is hardly possible since the fit of the sensors and thus the coupling of light and pressure are optimized.