Upper Arm PPG Respiration Monitoring for Ambulatory Accuracy
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing respiratory rate monitoring devices are not practical for long-term use with moving subjects, particularly outside clinical settings, due to inaccuracy and detachment issues, especially when vasoconstriction occurs.
Innovation Solution
A wearable upper arm unit equipped with both a photoplethysmograph and movement sensors, such as accelerometers and gyroscopes, processes combined signals to estimate respiratory rate, enhancing signal quality and reliability in various postures and conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a photoplethysmograph is attached to a patient's digit for respiratory rate monitoring, then the device can be worn ambulatorily, but the signal quality deteriorates when the subject moves or experiences vasoconstriction
Solution Approach 1:
The patent uses the upper arm as an intermediary location between the finger (original measurement site) and the thorax (respiratory movement source). The upper arm provides a stable platform closer to the respiratory mechanics while maintaining ambulatory capability, serving as a mediator that improves signal quality without sacrificing portability
Solution Approach 2:
The patent changes the measurement location parameter from the digit to the upper arm. This spatial parameter change positions the photoplethysmograph closer to the thoracic cavity where respiratory movements generate stronger physiological signals, thereby improving measurement precision while maintaining ambulatory use
2Measurement precision
If a monitoring device is designed for clinical setting use, then measurement accuracy is maintained, but the device is readily detached and not practical for moving patients
Solution Approach 1:
The patent designs the upper arm unit to serve multiple functions: it provides accurate respiratory monitoring for stationary patients while simultaneously enabling ambulatory monitoring for moving patients. The device becomes universal across different patient mobility states and care settings, eliminating the need for separate clinical and ambulatory devices
3Quantity of substance
If the photoplethysmograph signal is measured at the finger, then the signal is strong in stationary conditions, but the signal becomes unreliable during movement or vasoconstriction
Solution Approach 1:
The patent transitions the measurement from the peripheral digital dimension to the proximal upper arm dimension, which is spatially closer to the thoracic respiratory mechanics. This dimensional change in measurement location captures stronger respiratory-induced photoplethysmographic signals while maintaining signal reliability during movement and vasoconstriction events
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 reliable and accurate respiratory rate monitoring for ambulatory subjects by leveraging cleaner and more robust signals from the upper arm, even in the presence of vasoconstriction, with confidence indicators to ensure accuracy.
Implementation Method 1
a photoplethysmograph configured to monitor blood volume within the subject's upper arm
Implementation Method 2
at least one movement sensor... can, in at least some body postures, directly detect respiratory movement of the thorax
Data Source
AI summary
Monitoring apparatus for measuring the respiratory rate of a subject comprises an upper arm unit attached to a subject's upper arm in use and containing at least one movement sensor and a photoplethysmograph configured to monitor blood volume within the subject's upper arm while the upper arm unit is worn on the subject's upper arm. The output from the photoplethysmograph and movement sensor(s) are processed to calculate and output an estimate of the rate of respiration of the subject. Respiratory cycle induced variations in the photoplethysmograph signal and movement sensor signals can be independently determined and there is a greater confidence in the calculated respiratory rate when these independent calculations give consistent readings. If there is insufficient confidence, no rate of respiration is displayed.