Sedation Monitoring via Skin Conductance Derivative Analysis

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Solution Overview

Problem

Current methods for monitoring a patient's sedation level during surgery lack reliability, particularly in assessing a sufficiently deep sedation state to avoid excessive anesthesia administration, and rely on calculating skin conductance signal fluctuations and averages.

Innovation Solution

A method and apparatus using skin conductance measurements with alternating current and a control unit to analyze the signal, calculating the derivative of the conductance over a specific interval and applying a non-linear transformation to determine the sedation level based on the Observer's Assessment of Anaesthesia and Sedation (OAAS) scale, providing a more reliable indication of sedation without relying on fluctuation peaks or average values.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If skin conductance signal fluctuations and average values are calculated through measurement intervals, then sedation level monitoring is performed, but reliability of output indications is insufficient

Engineering Contradiction:

Improvereliability of sedation level indicationVSAvoidprecision of skin conductance measurement

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

The patent changes the measurement parameter from skin conductance magnitude to skin conductance slope (rate of change). This transformation converts a noisy magnitude measurement into a more reliable derivative measurement that directly correlates with sedation depth, resolving the contradiction between reliability and measurement precision.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent replaces the conventional analysis method (calculating fluctuation peaks and average values) with a derivative-based analysis method. This substitution of analytical approach transforms the measurement from static signal characteristics to dynamic rate-of-change characteristics, improving reliability.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Loss of information

If skin conductance measurements are used to monitor sedation level, then information about autonomous nervous system activity is obtained, but the measurement does not provide sufficient indication of sufficiently deep sedation

Engineering Contradiction:

Improveinformation about sedation depthVSAvoidreliability of deep sedation indication

Core Design Contradiction:

Loss of informationVSReliability

Solution Approach 1:

The patent transforms the skin conductance parameter from absolute conductance values to the slope (first derivative) of conductance change over time. This parameter transformation captures the dynamic aspect of sedation depth, providing more reliable information about whether sufficiently deep sedation has been achieved.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent establishes a feedback mechanism where the calculated slope of skin conductance is continuously monitored and compared against threshold values to determine sedation depth. This feedback loop provides continuous information about sedation status, reducing information loss about deep sedation achievement.

Inventive Principle:

Principle #23Feedback

3Reliability

If conventional skin conductance analysis methods are used, then sedation monitoring is performed, but excessive anesthesia may be administered due to unreliable measurements

Engineering Contradiction:

Improvereliability of sedation assessmentVSAvoidloss of anesthesia

Core Design Contradiction:

ReliabilityVSLoss of substance

Solution Approach 1:

The patent replaces unreliable conventional analysis methods with a derivative-based analysis system that calculates the slope of skin conductance change. This substitution provides more reliable sedation assessment, preventing both excessive and insufficient anesthesia administration.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

By changing from magnitude-based parameters to rate-of-change parameters, the system achieves more reliable sedation depth indication, directly addressing the issue of unreliable sedation assessment that leads to inappropriate anesthesia dosing.

Inventive Principle:

Principle #35Parameter changes

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

The solution provides a more reliable output for determining a sufficiently deep sedation level, reducing unnecessary anesthesia administration by accurately monitoring sedation through real-time analysis of skin conductance signals, ensuring patient safety during surgical procedures.

Implementation Method 1

a measurement converter (4) connected to said sensor means (3) and arranged for measuring the skin's conductance

Methodology Applied

Scientific EffectElectrical Conductivity: Conduction (electrical)

Data Source

PatentUS8027717B2Method and apparatus for monitoring the sedation level of a sedated patient

Publication Date: 2011.09.27 MED STORM INNOVATION

AI summary

A method and an apparatus for monitoring the sedation level of a sedated patient during anaesthesia, in particular during a pre-surgical phase. The method comprises the steps of providing a skin conductance signal measured at an area of the patient's skin, calculating a derivative signal of said conductance signal with respect to time, and establishing said sedation level based on said derivative signal.