Multi-sensor Volume Index for Heart Failure Monitoring
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Solution Overview
Problem
Current methods for monitoring fluid volume status in patients, particularly those with heart failure, are invasive, unreliable, and require frequent clinical visits, leading to suboptimal therapy and increased morbidity and mortality.
Innovation Solution
An ambulatory medical device system that combines heart sound and impedance sensors to calculate a volume index, comparing it to threshold values to generate an indication of fluid volume status, allowing for continuous monitoring and adjustment of therapy to maintain an optimal volume range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If radioisotope indicator dilution is used for volume measurement, then measurement precision is improved, but device complexity and ease of operation worsen due to invasiveness and infeasibility for routine monitoring
Solution Approach 1:
The patent replaces the mechanical/invasive radioisotope indicator dilution method with an electrical impedance-based measurement system. The impedance sensor detects changes in electrical impedance across body tissues to infer fluid volume status, eliminating the need for invasive radioisotope injection while providing continuous, routine-monitoring-capable measurements.
Solution Approach 2:
The patent introduces electrical impedance as an intermediary measurement parameter. Instead of directly measuring fluid volume with invasive methods, the system measures electrical impedance (which changes with fluid volume) and uses this as a proxy indicator, enabling non-invasive volume status assessment.
2Reliability
If multiple sensor measurements are combined to derive volume index, then reliability is improved, but device complexity increases
Solution Approach 1:
The patent merges measurements from multiple sensor types (impedance sensor, heart sound sensor, and other available sensors) into a single integrated volume index calculation. The processor combines these diverse measurements using algorithms that account for individual sensor limitations, producing a more reliable composite indicator than any single sensor could provide alone.
Solution Approach 2:
The patent makes existing multi-functional ambulatory medical devices (already containing various sensors for other purposes) capable of volume status monitoring by adding volume index calculation algorithms. This allows the same device to serve multiple functions including cardiac monitoring, rhythm detection, and now fluid volume assessment, avoiding the need for dedicated single-function devices.
3Productivity
If continuous monitoring is implemented, then productivity is improved through timely therapy adjustment, but use of energy increases
Solution Approach 1:
The patent implements continuous volume status monitoring by continuously measuring impedance and heart sound parameters and continuously updating the volume index calculation. This uninterrupted monitoring enables real-time detection of volume status changes, allowing timely therapy adjustments that improve patient outcomes, while the device is designed to manage the associated energy consumption.
Solution Approach 2:
The patent enables the device to automatically monitor volume status and generate volume index calculations without requiring external intervention or frequent clinical visits. The embedded algorithms continuously process sensor data and provide self-service monitoring, reducing the need for manual assessments and enabling proactive therapy management.
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 continuous, non-invasive monitoring of fluid volume status, reducing hospitalizations and improving patient outcomes by enabling timely adjustments to therapy and maintaining patients within an optimal volume range.
Implementation Method 1
an impedance sensor configured to generate an impedance signal representative of physiological impedance of the subject
Implementation Method 2
a heart sound sensor configured to generate a heart sound signal representative of mechanical cardiac activation of a subject
Data Source
AI summary
An apparatus comprises plurality of physiologic sensors and a processor circuit. The sensors provide sensor signals having physiological information and include a heart sound sensor and an impedance sensor. The processor circuit includes a volume index module configured to determine a value of at least one heart sound parameter using the heart sound signal and determine a value of at least one physiological impedance parameter value using the impedance signal, calculate a volume index representative of fluid volume status of the subject using the at least one heart sound parameter value and the at least one physiological impedance parameter value, compare a determined metric of the calculated volume index to one or more high threshold metric values and one or more low threshold metric values, and generate an indication of a fluid volume status of the subject according to the comparison.