Cerebrovascular Autoregulation Monitoring via Respiratory Wave Phase Shift
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Solution Overview
Problem
Current methods for monitoring cerebrovascular autoregulation state are inadequate due to their inability to provide continuous real-time data, as they rely on invasive or non-invasive methods that are inaccurate, time-consuming, and unsuitable for clinical practice, especially in intensive care unit (ICU) settings where rapid assessment is critical.
Innovation Solution
A non-invasive method involving simultaneous monitoring of intracranial blood volume and lung volume respiratory waves, with real-time decomposition into narrowband sinewave first harmonic components, and derivation of cerebrovascular autoregulation state from the phase shift between these waves, allowing for accurate and immediate assessment of cerebrovascular autoregulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If slow wave correlation monitoring methods are used to assess cerebrovascular autoregulation, then continuous monitoring capability is provided, but measurement precision is insufficient due to low amplitude of slow ICP waves and time delay in data appearance
Solution Approach 1:
The patent utilizes respiratory waves as a periodic physiological phenomenon to drive intracranial blood volume changes. By synchronizing measurement with the respiratory cycle, the system achieves both continuous monitoring and high measurement precision through the regular, predictable nature of respiratory movements that generate measurable intracranial pressure variations.
Solution Approach 2:
The patent transitions from measuring slow ICP waves with low amplitude to measuring respiratory-related intracranial blood volume waves with higher amplitude. This parameter change involves shifting the frequency range and amplitude characteristics of the measured signal, thereby improving measurement precision while maintaining continuous monitoring capability.
2Object-affected harmful factors
If non-invasive transcranial Doppler CBFV measurement is used to replace invasive slow ICP wave measurement, then patient safety is improved, but measurement precision deteriorates due to additional errors and distortions
Solution Approach 1:
The patent uses respiratory waves as a reference signal that copies or mirrors the intracranial blood volume changes. By comparing the respiratory wave pattern with the intracranial pressure wave pattern, the system can accurately assess cerebrovascular autoregulation without requiring direct invasive ICP measurement, thus maintaining patient safety while improving measurement precision.
Solution Approach 2:
The patent introduces respiratory waves as an intermediary medium to indirectly measure intracranial blood volume changes. Instead of directly measuring ICP or using TCD with its inherent errors, the system uses respiratory movements as a mediator that transmits information about intracranial hemodynamics in a more accurate and non-invasive manner.
3Duration of action of stationary object
If slow wave monitoring method is used to evaluate cerebrovascular autoregulation, then continuous assessment is provided, but response time is too slow due to accumulation of data during 4.0 minutes or longer
Solution Approach 1:
The patent performs preliminary action by using respiratory waves as a continuous reference signal that is already present and measurable. Instead of waiting to accumulate slow wave data over 4 minutes or longer, the system continuously captures respiratory-related intracranial blood volume changes, enabling immediate real-time assessment of cerebrovascular autoregulation without delayed data accumulation.
Solution Approach 2:
The patent ensures continuity of useful action by utilizing the ongoing respiratory cycle as a continuous source of measurement data. Since respiration is a continuous physiological process, the system can continuously extract cerebrovascular autoregulation information in real-time, eliminating the need for intermittent slow wave accumulation and providing immediate clinical feedback.
4Adaptability or versatility
If correlation factor between ABP and ICP slow waves is used to indicate cerebrovascular autoregulation state, then assessment capability is provided, but reliability is reduced due to nonlinearity of cerebrovascular autoregulation system
Solution Approach 1:
The patent changes the parameter being measured from the correlation factor between ABP and ICP slow waves to the phase relationship between respiratory waves and intracranial blood volume waves. This parameter transformation addresses the nonlinearity issue because phase relationship analysis is more robust to nonlinear system behavior, thereby improving the reliability of cerebrovascular autoregulation assessment while maintaining assessment capability.
Data Source
AI summary
A non-invasive method for continuous real-time monitoring of cerebrovascular blood flow autoregulation state includes simultaneous non-invasive monitoring of intracranial blood volume respiratory waves and lung volume respiratory waves, real-time decomposition of intracranial blood volume respiratory waves and lung volume respiratory waves into narrowband sinewave first harmonic components, determination therefrom of the phase shift between intracranial blood volume respiratory wave and lung volume respiratory wave first harmonics' and derivation of cerebrovascular autoregulation state from that phase shift value.