Stethoscope-Based Pulse Transit Time Measurement
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Solution Overview
Problem
Existing methods for determining blood pulse characteristics, such as pulse transit time (PTT) and blood pressure (BP), are inaccurate in cases where the delay between the R peak of ECG data and aortic valve opening is inconsistent, particularly in conditions like aortic regurgitation, leading to unreliable BP measurements.
Innovation Solution
A system that uses stethoscope data to determine the closure of the tricuspid valve, assuming it coincides with the opening of the aortic valve, in conjunction with photoplethysmography (PPG) data to calculate PTT, allowing for more accurate BP measurements by bypassing the reliance on consistent ECG-based delays.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If ECG-based methods are used to determine pulse transit time, then the measurement process is simple, but the measurement precision deteriorates in cases where the delay between R peak and aortic valve opening is inconsistent
Solution Approach 1:
The patent introduces an acoustic signal detector (stethoscope) as an intermediary to detect the actual aortic valve opening time. This mediator provides a direct acoustic measurement of valve opening, which serves as a reference point to correct the ECG-based time delay, thereby resolving the inconsistency between ECG R peak and actual valve opening timing
Solution Approach 2:
The patent replaces the purely electrical ECG-based timing method with a hybrid approach that incorporates acoustic detection. The acoustic signal detection substitutes for the unreliable electrical signal timing, providing a more accurate mechanical/physical reference point for valve opening that can be used to correct the ECG-based measurements
2Measurement precision
If stethoscope data and PPG data are integrated to determine PTT, then the measurement precision improves, but the device complexity increases
Solution Approach 1:
The patent divides the measurement system into distinct functional segments: an acoustic signal detector for valve opening detection, a PPG sensor for pulse wave detection, and a processor that integrates these separate data streams. This segmentation allows each component to specialize in one measurement task while the processor combines them, improving precision without creating unmanageable complexity
Solution Approach 2:
The processor is designed to handle multiple data types (acoustic signals and PPG signals) and perform multiple functions (detecting valve opening, detecting pulse waves, calculating PTT, and determining blood pressure). This multi-functionality consolidates the complexity into a single universal component rather than requiring separate specialized devices for each function
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 provides persistent and accurate estimation of PTT and BP, even in conditions where ECG data is unreliable, enabling continuous and precise monitoring of blood pressure.
Implementation Method 1
a stethoscope component that monitors a heart and generates stethoscope data representative of a sound wave generated by the heart
Implementation Method 2
PPG data representative of a pulse wave at the extremity that is determined based on PPG data
Data Source
AI summary
Techniques for determining pulse transit time (PTT) and blood pressure measurements based on stethoscope data are provided. In one example, a system comprises a stethoscope component that monitors a heart and generates stethoscope data representative of a sound wave generated by the heart. The system can further comprise an analysis component that receives the stethoscope data and receives, from a photoplethysmography (PPG) component that monitors an extremity, PPG data representative of a pulse wave at the extremity. The analysis component can determine, based on the stethoscope data, a first time corresponding to closure of a tricuspid valve of the heart and can determine a PTT as a function of the first time and a second time corresponding to the pulse wave at the extremity that is determined based on the PPG data. Blood pressure measurements can be obtained from algorithms with the inputs of PTT or times determined based on the PPG data.