Apparatus and method for estimating respiration rate
Inventors
MCCANN, Christopher Thomas • Whiting, Stewart William
Assignees
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Publication Number
US-12507908-B2
Publication Date
2025-12-30
Expiration Date
Abstract
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.
Core Innovation
A wearable monitoring apparatus for measuring the respiratory rate of a subject includes an upper arm unit configured for attachment to a subject’s upper arm while worn. The upper arm unit comprises at least one movement sensor and a photoplethysmograph (PPG) configured to monitor blood volume within the subject’s upper arm. A processor calculates and outputs an estimate of the rate of respiration of the subject by processing both the movement sensor output and the PPG output.
The respiratory-rate estimate is based on respiratory-cycle induced variations present in the PPG output and in the movement sensor output. The processing includes independent respiratory-cycle frequency analyses of a respiratory-induced amplitude/intensity waveform derived from the PPG and a respiratory-induced variation waveform derived from accelerometer/gyroscope movement sensing. The computed respiratory-cycle frequencies are validated using filtering and autocorrelation density/peak validation within eligible frequency ranges.
A confidence status is set based on PPG quality/accuracy, movement quality/accuracy, and agreement between the PPG-derived and movement-derived respiration-rate estimates. The output behavior includes displaying the respiration rate only when the confidence status meets confidence requirements, and otherwise suppressing the displayed estimate. The upper-arm unit structure is configured to improve contact and signal quality.
Claims Coverage
The document contains two independent claims: one directed to a monitoring apparatus and one directed to a method. Across these independent claims, the core coverage includes processing outputs from an upper-arm PPG and an upper-arm movement sensor to calculate and output an estimated respiratory rate.
Upper arm unit with PPG and movement sensor for respiration estimation
An upper arm unit configured for attachment to a subject’s upper arm, comprising at least one movement sensor and a photoplethysmograph (PPG) configured to monitor blood volume within the subject’s upper arm while the upper arm unit is worn on the subject’s upper arm, wherein at least one processor is programmed to process both the output of the at least one movement sensor and the output of the PPG to thereby calculate and output an estimate of the rate of respiration of the subject.
Processing movement sensor output and PPG output to estimate and output respiratory rate
A method using an upper arm unit attached to a subject’s upper arm, the upper arm unit comprising 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 method comprising processing both the output of the at least one movement sensor and the output of the PPG to thereby calculate an estimate of the rate of respiration of the subject, and then outputting the calculated estimate of the rate of respiration of the subject.
The independent claims cover both apparatus and method aspects of calculating an estimated respiratory rate using combined outputs from an upper-arm PPG and an upper-arm movement sensor, followed by outputting the estimated respiration rate.
Stated Advantages
Improved robustness during vasoconstriction compared with finger PPG.
Documented Applications
Wearable ambulatory monitoring using an upper-arm unit to estimate respiration rate while the subject is in motion.
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