Ventricular Impedance Monitoring for Sleep Apnea Detection
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Solution Overview
Problem
Current monitoring systems for sleep disordered breathing (SDB) are inadequate as they often fail to detect obstructive apnea and provide only inferred information about cardiovascular impact, lacking specificity and timeliness in assessing SDB burden, which is crucial for managing cardiac disease.
Innovation Solution
A heart monitoring system that includes a ventricular sensing stage, activity sensor, impedance measuring module, signal generator, filter, memory, and control unit to derive and log impedance or conductance changes, differentiate obstructive apnea from successful ventilation, and report SDB episodes, providing direct cardiac function measurements and remote monitoring capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If intra-thoracic impedance measurement is used as a proxy for ventilation, then respiratory frequency and tidal volume can be monitored, but the clinical impact on the cardiovascular system cannot be directly measured
Solution Approach 1:
The patent combines intra-thoracic impedance measurement with direct ventricular electrical potential sensing to create a hybrid monitoring system. The ventricular sensing stage detects cardiac electrical signals while the impedance measurement continues to monitor ventilation, merging two previously separate measurement approaches into a single integrated device that provides both respiratory and cardiovascular information.
Solution Approach 2:
The patent uses ventricular impedance or conductance measurement as an intermediary parameter that bridges respiratory and cardiovascular systems. By measuring impedance changes in the ventricular region, the system can infer both ventilation status and cardiac function, serving as a mediator that translates respiratory mechanical changes into electrical signal variations that reflect cardiovascular impact.
2Quantity of substance
If three or four intra-thoracic electrode measurements are used, then thoracic information including breathing effort and minute ventilation can be obtained, but heart specific information cannot be reliably isolated
Solution Approach 1:
The patent transitions from measuring impedance in the general thoracic region to measuring impedance specifically in the ventricular region. By placing electrodes and sensing stages at the ventricular level, the system achieves local quality measurement that isolates cardiac-specific information from general thoracic signals, enabling precise detection of ventricular function changes during breathing maneuvers.
Solution Approach 2:
The patent segments the thoracic impedance measurement into separate components: ventricular impedance measurement for cardiac function and residual thoracic impedance for respiratory effort. This segmentation allows the system to independently analyze cardiac electrical properties from respiratory mechanical properties, preventing contamination of heart-specific information by general thoracic movements.
3Reliability
If intra-thoracic impedance measurement is used to monitor ventilation, then respiratory effort can be detected, but obstructive apnea cannot be detected due to persistence of thoracic and abdominal breathing effort
Solution Approach 1:
The patent replaces mechanical respiratory effort detection with electrical cardiac signal detection. Instead of relying on mechanical impedance changes in the thorax that persist during obstructive apnea, the system uses ventricular electrical potential sensing to detect cardiac electrical activity. This substitution allows detection of apnea by identifying the absence or abnormality of cardiac electrical signals during respiratory events.
Solution Approach 2:
The patent uses ventricular impedance or conductance measurement as an intermediary that is sensitive to both respiratory and cardiac factors. This intermediary measurement can differentiate between obstructive apnea (where cardiac function is compromised despite respiratory effort) and successful ventilation by analyzing the relationship between impedance changes and cardiac electrical signals, allowing precise detection of apneic episodes.
4Measurement precision
If apnea and hypopnea episodes are monitored at night out of the clinical setting, then SDB burden can be quantified, but the monitoring requires complex external equipment and continuous clinical observation
Solution Approach 1:
The patent implements a self-service monitoring system where the implantable device automatically performs all necessary measurements and analysis without external intervention. The device continuously monitors ventricular electrical potentials and impedance changes, processes the data to detect SDB episodes, and stores results in memory. This self-service capability eliminates the need for complex external monitoring equipment and continuous clinical observation while maintaining precise SDB burden quantification.
Solution Approach 2:
The patent merges multiple monitoring functions into a single implantable device: ventricular electrical potential sensing, impedance measurement, signal processing, data storage, and communication capabilities are all integrated into one unit. This consolidation reduces the overall system complexity compared to separate external monitoring devices while enabling comprehensive SDB monitoring that can be performed continuously without clinical setting intervention.
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 system offers a more specific, timely, and cost-effective indication of SDB severity, improving patient management, reducing hospitalizations, and extending life quality and duration while decreasing disease management costs.
Implementation Method 1
a ventricular sensing stage connected or being connectable to an electrode for picking up electric potentials inside at least a ventricle of a heart, said sensing stage being adapted to sense an excitation or a contraction of ventricular myocardium
Implementation Method 2
a ventricular impedance or conductance measuring module connected or being connectable to an electrode measuring the resistance of at least a ventricle of a heart, said impedance or conductance measuring module comprising a current source unit adapted to provide a sub-threshold excitation current to the myocardium and comprising an impedance or conductance measurement unit adapted to measure the resulting voltage on said electrode at the myocardium
Implementation Method 3
an activity sensor unit inside a lead or the device which is capable of determining an activity signal reflecting a patient's physical activity
Data Source
AI summary
A heart monitoring system comprises a ventricular sensing stage sensing excitation or contraction of ventricular myocardium, an activity sensor unit determining a signal reflecting a patient's physical activity, a ventricular impedance or conductance measuring module, said modules comprising a current source unit adapted to provide a sub-threshold excitation current to the myocardium and comprising an impedance or conductance measurement unit for measuring the resulting voltage on said electrode at the myocardium, a signal generator module, a filter module, a memory, a control unit adapted to derive single measures |ΣZ| of magnitude of impedance or conductance change over a preset sample time interval, determine the variability TARVI in the impedance or conductance change, compare this variability and the activity sensor output signal with a threshold and recent history, determine if sleep disturbed breathing (SDB) is present, and log the SDB episode in the memory device.