Applanation Apparatus for Non-Invasive Hemodynamic Monitoring
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Solution Overview
Problem
Current non-invasive methods for monitoring arterial blood pressure are limited by their inability to provide continuous, accurate measurements due to anatomical incompatibility, tissue injury, nerve damage, incomplete pressure pulse transfer, and sensitivity to transducer orientation, leading to inaccuracies and variability in readings.
Innovation Solution
The method involves using parametric scaling and an applanation apparatus with a pressure transducer to minimize errors by correlating tissue compression with maximum pulse pressure amplitude, adjusting for body mass index and pulse pressure, and optimizing applanation levels through iterative analysis and servoing to achieve accurate, continuous blood pressure monitoring.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a rigid array of miniature pressure transducers is applied against the tissue to applanate the artery, then pressure pulses can be recorded, but anatomical incompatibility with tissue contours causes measurement inaccuracies and potential tissue injury
Solution Approach 1:
The rigid array of discrete transducers is divided into multiple independent sensing elements distributed across a flexible surface. Each transducer operates independently, allowing the array to conform to curved tissue surfaces while maintaining measurement capability at multiple points simultaneously.
Solution Approach 2:
The transducer array is mounted on a flexible substrate that can conform to the contours of the tissue and artery. This flexible mounting eliminates the anatomical incompatibility of rigid arrays while maintaining the ability to applanate the artery and record pressure pulses accurately.
2Measurement precision
If the transducer array is urged against the tissue to achieve applanation, then pressure variations can be sensed, but the rigid structure restricts blood flow to distal tissue
Solution Approach 1:
The system transitions from a static rigid array to a dynamic flexible array that can adapt its configuration. The flexible substrate allows the transducer array to apply minimal necessary force for applanation while conforming to tissue movement and physiological changes, reducing restriction of blood flow to distal tissue.
3Measurement precision
If a single tonometric sensor is placed laterally above the artery, then signal coupling may be improved, but frequent re-calibration or repositioning is required due to subject movement
Solution Approach 1:
Instead of a single sensor, multiple transducers are distributed across the measurement area. This segmentation provides redundancy and allows the system to maintain continuous measurement even when subject movement changes the optimal positioning, eliminating the need for frequent repositioning.
Solution Approach 2:
The flexible transducer array serves multiple functions simultaneously: it maintains signal coupling through conformal contact, provides redundant measurement points, and adapts to subject movement without requiring repositioning or recalibration.
4Productivity
If tonometry is used to achieve beat-to-beat pressure monitoring, then continuous measurement is possible, but sensitivity to transducer orientation causes variability in readings
Solution Approach 1:
Multiple transducers are arranged in an array across the measurement area, providing multiple orientation references. This allows the system to identify and compensate for orientation sensitivity by comparing signals from transducers at different angles and positions.
Solution Approach 2:
The system uses signal processing to identify the optimal orientation and amplitude parameters from the array of transducers. By analyzing parameters such as pulse amplitude and waveform characteristics across multiple sensors, the system can determine the best measurement orientation and compensate for variability caused by subject movement or positioning changes.
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 allows for highly accurate, continuous, and non-invasive blood pressure monitoring that closely reflects true intra-arterial pressure, reducing errors and improving repeatability under varying conditions, making it suitable for both medical professionals and self-monitoring.
Implementation Method 1
The transducers each directly sense the mechanical forces in the underlying subject tissue, and each is sized to cover only a fraction of the underlying artery
Implementation Method 2
At the onset of a decreasing applanation sweep, the artery is overcompressed into a 'dog bone' shape, so that pressure pulses are not recorded. At the end of the sweep, the artery is undercompressed, so that minimum amplitude pressure pulses are recorded
Data Source
AI summary
An improved method and apparatus for non-invasively assessing one or more hemodynamic parameters associated with the circulatory system of a living organism. In one aspect, the invention comprises a method of measuring a hemodynamic parameter (e.g., arterial blood pressure) by applanating or compressing portions of tissue proximate to the blood vessel of concern until a desired condition is achieved, and then measuring the hemodynamic parameter. Such applanation effectively mitigates transfer and other losses created by the tissue proximate to the blood vessel, thereby facilitating accurate and robust tonometric measurement. An algorithm adapted to maintain optimal levels of applanation is also described. Methods and apparatus for scaling such hemodynamic parameter measurements based on subject physiology, and providing treatment to the subject based on the measured parameters, are also disclosed.