Cardiac Pacing Control Using Core Temperature Sleep Detection
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Solution Overview
Problem
Existing implantable medical devices (IMDs) struggle to accurately detect sleep and wake states in patients, leading to inappropriate diurnal and nocturnal pacing rates due to reliance on time-of-day algorithms that fail to adapt to changes in circadian rhythm and patient activity levels.
Innovation Solution
The IMD utilizes a temperature sensor to generate moving composite temperature (MCT) signals over varying periods, comparing them to control pacing rates, allowing for automatic adjustment between diurnal and nocturnal pacing based on core body temperature changes, independent of time-of-day.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If time-of-day algorithms are used to control pacing rates, then the device can provide programmable diurnal and nocturnal pacing rates, but the algorithm fails to adapt to changes in circadian rhythm and patient activity levels
Solution Approach 1:
The patent replaces the mechanical/time-based algorithm (time-of-day dependent pacing) with a physiological sensor-based system (core body temperature sensing). The temperature sensor continuously monitors core body temperature, and the control circuit uses this physiological data to detect sleep and wake states, thereby adapting pacing rates to the patient's actual circadian rhythm rather than relying on fixed time schedules.
2Measurement precision
If accelerometer sensors are used to detect patient motion, then the device can identify sleep periods, but it cannot distinguish between being asleep and being inactive while awake
Solution Approach 1:
The patent introduces core body temperature as an intermediary physiological parameter to detect sleep states. Instead of directly interpreting accelerometer data (which is ambiguous), the system uses temperature changes as a more reliable mediator - core body temperature naturally decreases during sleep and increases during wakefulness, providing a clear physiological marker that resolves the ambiguity of motion-based detection.
3Ease of operation
If the pacing rate is lowered based on lack of motion detection, then nocturnal pacing can be provided, but the pacing rate may be inappropriately lowered when the patient is awake and inactive
Solution Approach 1:
The patent implements a feedback mechanism where the control circuit continuously monitors core body temperature and uses this information to feedback-adjust the pacing rate. When temperature decreases indicating sleep onset, the system feedbacks by lowering the pacing rate to nocturnal levels. When temperature increases indicating wakefulness, the system feedbacks by raising the pacing rate to diurnal levels, ensuring appropriate pacing rate selection based on actual physiological state rather than just motion absence.
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 accurately determines sleep and wake states by measuring core body temperature, ensuring appropriate pacing rates without relying on patient movement or time-of-day information, thereby improving patient outcomes.
Implementation Method 1
a temperature sensor configured to sense a temperature signal indicative of a core body temperature of a patient
Data Source
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AI summary
Diurnal and nocturnal pacing for an implantable medical device (IMD) (100) that includes a temperature sensor (154), one or more electrodes (104, 106), one or more pulse generators (116) a control circuit (156) is managed. A temperature signal indicative of a core body temperature is sensed at the temperature sensor (154). The control circuit (156) produces first and second moving composite temperature (MCT) signals based on the temperature signal sensed over first and second periods of time, respectively, wherein the second period of time is longer than the first period of time. A current temperature signal is compared to the first and second MCT signals, and a pacing rate for pacing pulses, generated by the one or more pulse generators (116) and delivered to the one or more electrodes (104, 106), is controlled based on one or more relations between the current temperature signal, the first MCT signal and the second MCT signal.