Cuff-less Blood Pressure Measurement Using Reflectance PPG
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Solution Overview
Problem
Current methods for blood pressure measurement, such as oscillometry and pulse transit time, require invasive or costly equipment and suffer from accuracy issues due to confounding physiology, limiting their effectiveness for ubiquitous and reliable monitoring, especially in low-resource settings.
Innovation Solution
A handheld mobile device with a reflectance-mode photo-plethysmography sensor and pressure sensor allows users to measure blood pressure by applying pressure with their fingertip, generating an oscillogram to calculate and display blood pressure values, providing a cuff-less and cost-effective solution for ubiquitous monitoring.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If catheterization is used to measure blood pressure, then measurement accuracy is improved, but the method becomes invasive and requires medical personnel
Solution Approach 1:
The patent replaces the mechanical catheter-based measurement system with an optical sensing system using photoplethysmography (PPG). The PPG sensor detects blood volume changes optically through the fingertip, eliminating the need for invasive catheter insertion while providing continuous blood pressure monitoring capability
Solution Approach 2:
The patent introduces an intermediary relationship between the PPG sensor and blood pressure measurement. Instead of directly measuring pressure like catheterization, the system uses blood volume oscillations detected by PPG as an intermediary parameter to infer blood pressure values through algorithmic processing
2Extent of automation
If oscillometry with inflatable cuff is used, then automatic measurement is achieved, but device portability and accessibility are reduced
Solution Approach 1:
The patent extracts the essential measurement function from the bulky inflatable cuff system and implements it in a compact mobile device. The PPG sensor and processing algorithms are integrated into a portable form factor that fits in a smartphone, eliminating the need for large cuff mechanisms while maintaining automated measurement capability
Solution Approach 2:
The patent makes the blood pressure monitoring device universal by integrating it into a mobile device that everyone already possesses (smartphone). This multi-functional approach allows the device to serve both as a communication tool and a medical monitoring device, greatly enhancing accessibility without requiring specialized equipment
3Ease of operation
If pulse transit time method is used, then cuff-less measurement is achieved, but accuracy deteriorates due to confounding physiology
Solution Approach 1:
The patent employs continuous PPG monitoring to track blood volume oscillations over time, allowing the system to capture multiple cardiac cycles and compute more reliable blood pressure values. This continuous measurement approach reduces the impact of transient physiological variations that affect single-point pulse transit time measurements
Solution Approach 2:
The system uses feedback from continuous PPG signal analysis to adjust and refine blood pressure calculations. By monitoring changes in pulse wave characteristics over time and comparing them against reference values, the system compensates for confounding physiological factors and improves measurement accuracy
4Reliability
If traditional blood pressure monitoring methods are used, then measurement capability is achieved, but cost and resource requirements increase
Solution Approach 1:
The patent leverages the fact that mobile devices are already widely possessed by the population, eliminating the need to manufacture and distribute expensive dedicated medical devices. By utilizing existing smartphones and their processors, the system achieves widespread deployment at minimal marginal cost
Solution Approach 2:
The patent replaces expensive mechanical blood pressure measurement systems with software-based processing of optical signals from inexpensive PPG sensors. This substitution dramatically reduces hardware costs while maintaining monitoring reliability through sophisticated algorithmic analysis
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 mobile device enables reliable, non-invasive, and cost-effective cuff-less blood pressure monitoring, improving hypertension management by providing continuous feedback and accessibility, even in low-resource settings, with accuracy comparable to traditional methods.
Implementation Method 1
a reflectance-mode photo-plethysmography sensor configured to measure blood volume oscillations
Data Source
AI summary
A system and method is presented for cuff-less blood pressure measurement in a mobile device. A key aspect of this disclosure is the discovery of a new location for blood pressure measurement at the fingertip of a subject and that reflectance-mode photoplethysmography can be used to help make this measurement. Through experiments in human subjects, it was discovered that it is indeed possible to measure systemic blood pressure by having a subject press the fingertip against a reflectance-mode photo-plethysmography-force sensor unit under visual guidance and then compute blood pressure from the resulting variable-amplitude blood volume oscillations and applied pressure via an oscillometric algorithm.