Imaging Breathing Rate in the CO2Absorption Band

Area of Science:

• Biomedical Engineering
• Medical Imaging
• Physiological Monitoring

Background:

• Accurate measurement of human breathing rate is crucial for medical diagnosis and monitoring.
• Existing contact-based methods can be intrusive and uncomfortable for patients.
• Non-contact methods offer a promising alternative for continuous and unobtrusive vital sign assessment.

Purpose of the Study:

• To develop and validate a novel non-contact method for measuring human breathing rate.
• To utilize Mid-Wave Infra-Red (MWIR) imaging with a CO2 absorption band filter for enhanced contrast.
• To establish a Fourier analysis-based approach for breathing frequency computation from thermal signals.

Main Methods:

• Retrofitted an MWIR imaging system with a narrow band-pass filter at 4.3 µm (CO2 absorption band).
• Acquired dynamic thermal signals from expired air, capturing periodic variations in intensity.
• Employed Fourier analysis on sampled thermal signals to determine breathing frequency.
• Validated the method against a traditional contact-based device (PowerLab/4SP) across 9 subjects (6-8 ft distance).

Main Results:

• The MWIR imaging system demonstrated improved contrast between expired air and background.
• A quasi-periodic dynamic thermal signal was successfully extracted from the breath flow region.
• Fourier analysis of the thermal signal accurately computed breathing rate.
• High correlation was observed between the novel non-contact method and the ground-truth contact device.

Conclusions:

• A novel, non-contact breathing rate measurement method using MWIR imaging and CO2 absorption band filtering has been successfully developed.
• The Fourier-based analysis of thermal signals provides an accurate and reliable means for computing respiratory frequency.
• This technology enables unobtrusive, desktop monitoring of breathing rate, with potential applications in preventive medicine and chronic disease management.