Optical Hydration Estimation via Capillary Refill Time

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Solution Overview

Problem

Current methods for assessing pediatric dehydration, such as parent reports and lab blood tests, are either subjective and inaccurate or expensive and time-consuming, respectively.

Innovation Solution

A medical device that estimates hydration levels using capillary refill time, which involves applying mechanical pressure to a body part to empty the capillary bed and then measuring the time it takes for the capillary bed to refill with blood using an optical sensor.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If lab blood tests are used to assess dehydration, then measurement precision is improved, but cost and time consumption increase

Engineering Contradiction:

Improvedehydration assessment accuracyVSAvoidtime consumption

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The patent replaces the mechanical/lab-based blood test system with an optical measurement system. An optical sensor measures capillary refill time by detecting light absorption changes in the capillary bed, eliminating the need for invasive blood draws and laboratory processing while providing rapid dehydration assessment.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent extracts the essential dehydration assessment function from the complex blood test system. By measuring only the capillary refill time parameter through optical means, the system isolates the key diagnostic information needed for dehydration assessment without requiring the full spectrum of blood laboratory tests.

Inventive Principle:

Principle #2Taking out (Extraction)

2Ease of operation

If parent report methods are used to assess dehydration, then ease of operation is improved, but measurement precision deteriorates

Engineering Contradiction:

Improveassessment simplicityVSAvoiddehydration assessment accuracy

Core Design Contradiction:

Ease of operationVSMeasurement precision

Solution Approach 1:

The patent implements a self-service assessment method where the optical sensor automatically measures capillary refill time without requiring parent involvement or subjective reporting. The device performs the measurement autonomously, combining ease of operation with objective, precise data collection.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The patent replaces the subjective human reporting mechanism with an objective optical measurement system. The optical sensor directly measures physiological parameters (capillary refill time) without relying on parent memory or perception, thereby improving precision while maintaining ease of use.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Productivity

If capillary refill time measurement is used to estimate hydration, then speed of assessment is improved, but measurement precision may deteriorate

Engineering Contradiction:

Improveassessment speedVSAvoidhydration estimation accuracy

Core Design Contradiction:

ProductivityVSMeasurement precision

Solution Approach 1:

The patent uses optical measurement to assess capillary refill time, which provides rapid and objective data. The optical sensor detects light absorption changes in real-time, enabling fast assessment while maintaining precision through quantitative optical data rather than subjective estimation.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent incorporates feedback mechanisms where the optical sensor continuously monitors capillary refill time and provides real-time hydration status information. This feedback loop enables rapid assessment while maintaining accuracy through continuous, objective measurement and comparison against reference values.

Inventive Principle:

Principle #23Feedback

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

Provides an objective and accurate estimation of hydration levels, reducing the need for expensive lab tests and improving the speed and reliability of dehydration assessment in pediatric patients.

Implementation Method 1

measuring the time it takes for the capillary bed to refill with blood using an optical sensor

Methodology Applied

Scientific EffectLight absorption: Absorption (EM radiation)

Data Source

PatentUS12220254B2Estimating hydration using capillary refill time

Publication Date: 2025.02.11 WELCH ALLYN INC

AI summary

An example system for estimating a hydration level of an individual can include: a mechanism configured to apply mechanical pressure to a digit of the individual; an light detector configured to sense the light from the digit; and a controller programmed to perform functions including: send a first signal to the mechanism to apply the mechanical pressure to the digit; send a second signal to the mechanism to release the mechanical pressure on the digit; determine a capillary refill time based upon a third signal from the light detector indicating an amount of time for capillaries of the individual to refill with blood; and estimate the hydration level of the individual based upon the capillary refill time and one or more additional parameters.