Soft Sternal PPG Patch for Vasoconstriction Monitoring
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Solution Overview
Problem
Conventional blood oxygen oximeters using optical-based PPG measurements struggle to detect vasoconstriction effectively due to venous pooling at traditional measurement locations like the finger and toe, which limits their ability to monitor blood pressure and other health conditions in real-time.
Innovation Solution
A flexible sternal photoplethysmographic patch sensor is developed, which can be placed on the sternum to provide robust vasoconstrictive response measurements by using a flexible printed circuit board with elastomer layers to ensure conformal contact with the skin, allowing for the integration of additional sensors like ECG and seismocardiography for comprehensive health monitoring.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a clip-based PPG device is used on the finger, then reliable measurements can be obtained, but it disrupts daily activities and cannot be placed on flat surfaces like the sternum
Solution Approach 1:
The patent employs a flexible printed circuit board (FPC) as the substrate for the PPG sensor, replacing the rigid clip structure. This flexible substrate can be conformally attached to flat surfaces like the sternum, enabling reliable PPG measurements without disrupting hand usage or daily activities. The flexible nature of the FPC allows it to maintain intimate contact with the skin surface while being comfortable for continuous wear.
2Measurement precision
If near diastolic pressure is applied to the finger to address venous pooling, then vasoconstriction can be detected, but it causes disruptions during daily activities
Solution Approach 1:
The patent applies a lightweight adhesive patch that provides sufficient compression force to overcome venous pooling effects without requiring near-diastolic pressure levels. The flexible substrate and adhesive backing deliver just enough pressure to ensure conformal contact and accurate PPG signal acquisition, enabling vasoconstriction detection while maintaining comfort and allowing normal daily activities.
3Stability of the object's composition
If a rigid PPG sensor is used, then stable contact can be maintained, but it cannot conform to the skin surface at the sternum
Solution Approach 1:
The patent utilizes a flexible printed circuit board substrate that can conform to the skin surface at the sternum while maintaining stable contact. The flexibility of the FPC allows it to adapt to slight variations in skin topography, and the adhesive backing ensures stable attachment during normal movement and daily activities, achieving both conformability and contact stability.
4Ease of operation
If air gaps are present between the PPG sensor and skin, then the device can be comfortably worn, but optical contact is insufficient for reliable measurements
Solution Approach 1:
The flexible substrate with adhesive backing creates intimate conformal contact between the PPG sensor and skin surface, eliminating air gaps that would interfere with optical measurements. This conformal contact is achieved without rigid compression, maintaining comfort during continuous wear while ensuring reliable optical signal acquisition for accurate PPG measurements.
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 device effectively detects vasoconstriction and sleep apnea with high agreement compared to commercial systems, demonstrating its potential for continuous, long-term vasoconstriction monitoring without disrupting daily activities.
Implementation Method 1
One or more elastomer layers couple to the printed circuit board and dispose over the PPG sensor to generate a compression force around the PPG sensor and urge the PPG sensor toward the tissue to make conformal contact with the skin without any air gap
Implementation Method 2
Conventional blood oxygen oximeters employ optical-based PPG measurements
Data Source
AI summary
An exemplary system and method are disclosed that employ a wireless, fully integrated, soft sternal patch to capture PPG signals from the sternum, an anatomical region that exhibits a robust vasoconstrictive response while also providing a convenient sternal location for the integration of electrocardiography and seismocardiography sensors in a single, all-in-one device capable of multifaceted human health monitoring. With healthy control subjects, the device is is configured to detect vasoconstriction induced endogenously through controlled breathing exercises and exogenously through changes in ambient temperature. Furthermore, in overnight trials with sleep apnea patients, the device shows a high agreement in vasoconstriction detection with a commercial system, demonstrating its potential use in continuous, long-term vasoconstriction monitoring.