Wearable Sleep Need Estimation Using Dual Sleep Debt Metrics

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Solution Overview

Problem

Wearable devices for physiological monitoring are susceptible to data quality variations due to positioning, activity, and other factors, necessitating real-time, data-driven assessments to improve accuracy.

Innovation Solution

A model is developed to derive data quality by comparing wearable device data with ground truth data from chest straps or electrocardiogram monitors, using machine learning to evaluate data quality based on contextual features, and providing feedback for adjustments.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If wearable photoplethysmography devices are used for physiological monitoring, then convenience and portability are improved, but data quality and measurement accuracy deteriorate due to positioning errors, motion artifacts, and insecure strapping

Engineering Contradiction:
ImproveconvenienceVSAvoiddata quality
Core Design Contradiction:
Ease of operationVSMeasurement precision

Solution Approach 1:

The patent implements a data quality metric system that continuously monitors wearable device measurements and provides feedback on measurement quality. The system calculates quality metrics based on multiple features (signal strength, heart rate variability, motion levels) and uses this feedback to identify when measurements are unreliable, allowing users to adjust positioning or discard poor quality data points.

Inventive Principle:
Principle #23Feedback

Solution Approach 2:

The patent changes the parameter of measurement quality assessment by introducing a composite quality metric that evaluates multiple signal characteristics simultaneously. Instead of relying on a single threshold, the system dynamically adjusts quality assessment based on varying parameters such as signal amplitude, frequency content, and motion artifacts, allowing adaptive evaluation of data quality across different wearing conditions.

Inventive Principle:
Principle #35Parameter changes

2Measurement precision

If ground truth devices like chest straps are used for accurate heart rate measurement, then measurement precision is improved, but device complexity and bulk increase

Engineering Contradiction:
Improveheart rate accuracyVSAvoidequipment bulk
Core Design Contradiction:
Measurement precisionVSDevice complexity

Solution Approach 1:

The patent introduces a data quality metric system as an intermediary layer between the wearable photoplethysmography sensor and the final measurement output. This intermediary evaluates signal quality using multiple features and provides a quality score without requiring the physical presence of bulky ground truth equipment, thus maintaining accuracy assessment capability while avoiding the bulk of chest straps.

Inventive Principle:
Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent replaces the mechanical chest strap system with a computational approach using photoplethysmography combined with quality metric evaluation. Instead of relying on mechanical compression and electrical contact of chest straps, the system uses optical sensing with algorithmic quality assessment to achieve accurate heart rate measurement without the bulk and discomfort of traditional ground truth devices.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

3Measurement precision

If multiple features are monitored to assess data quality, then measurement precision is improved, but computational complexity and processing time increase

Engineering Contradiction:
Improvedata quality assessment accuracyVSAvoidcomputational complexity
Core Design Contradiction:
Measurement precisionVSDevice complexity

Solution Approach 1:

The patent segments the data quality assessment into multiple independent feature evaluations (signal strength, heart rate consistency, motion levels, signal morphology) that can be computed separately and then combined. This segmentation allows each feature to be processed using optimized algorithms appropriate to its characteristics, reducing overall computational complexity while maintaining comprehensive quality assessment.

Inventive Principle:
Principle #1Segmentation

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

Enhances the accuracy of physiological data from wearable devices by continuously monitoring heart rate and other parameters, enabling reliable health and fitness tracking without bulky equipment.

Implementation Method 1

obtaining uncalibrated heart rate data from the number of subjects concurrently with the calibrated heart rate data using one or more physiological monitors of a wrist-worn photoplethysmography type

Methodology Applied
Scientific EffectPhotoplethysmography: Absorption (EM radiation)

Data Source

PatentUS20250288255A1Determining sleep need from physiological measurements
Publication Date: 2025.09.18 WHOOP INC
  • US20250288255A1 patent drawing
  • US20250288255A1 patent drawing
  • US20250288255A1 patent drawing

AI summary

Sleep need for a user is assessed using continuous physiological data from a wearable monitor. In particular, by calculating a first sleep debt metric based on user strain and a second sleep debt metric based on accumulated sleep debt, an objective metric can be obtained that estimates an amount of sleep needed by the user in a next sleep period. This approach takes advantage of multiple modes of information embedded in the physiological data, such as a sleep and exercise patterns for a user over one or more preceding days.