A method for measuring respiration and physical activity in bed by optical flow analysis

A fully noncontact and unconstrained monitoring method, based on optical flow of movement of body surface that is developed by introducing image sequence analysis, is described. A spatiotemporal local optimization method is applied to determine optical flow in the image sequence. The optical flow visualizes the apparent velocity field of the entire body motion, including breast movement due to respiration and posture changes in a bed. A temporal increase in heart rate reflects the magnitude of physical activities. We propose two candidate parameters for evaluation of respiratory and physical activities based on comparison among experimental results. The average of squared motion velocities reflects the magnitude of physical activities. The representative field-averaged component shows a waveform with periodic fluctuation corresponding to that of respiration obtained with a nasal thermistor. This optical flow analysis is a promising new technique for evaluation of body motion for clinical use.