Speckle Vibrometry for Instantaneous Heart Rate Monitoring.

Area of Science:

• Biomedical Engineering
• Physiological Monitoring
• Optical Sensing

Background:

• Instantaneous heart rate (IHR) monitoring is crucial for sleep applications like sleep apnea detection and staging.
• Current methods often require physical contact, impacting user comfort during sleep.
• Contact-free measurement is desirable for unobtrusive sleep monitoring.

Purpose of the Study:

• To evaluate the efficacy of speckle vibrometry (SV) for contact-free IHR monitoring in a sleep environment.
• To assess SV performance across different sleeping positions (supine, lateral, prone).
• To determine the feasibility of on-skin and on-textile IHR measurement using SV.

Main Methods:

• Utilized speckle vibrometry (SV) to capture subtle cardiac-induced motions on skin and textiles.
• Employed a defocused camera to detect these minute motions under laser illumination.
• Conducted Bland-Altman analysis comparing SV measurements with electrocardiogram (ECG) across various sleep positions.

Main Results:

• Achieved limits of agreement with ECG of [-8.65, 7.79] bpm (supine), [-9.79, 9.25] bpm (lateral), and [-10.81, 10.23] bpm (prone).
• Demonstrated successful IHR detection even when participants were covered by textile layers.
• Confirmed the capability of SV to measure cardiac motion through clothing.

Conclusions:

• Speckle vibrometry shows significant potential as a contact-free method for monitoring instantaneous heart rate during sleep.
• SV enables comfortable, non-invasive IHR assessment in spontaneous sleeping positions, even with textile coverings.
• This technology could advance unobtrusive sleep tracking and health monitoring systems.