A monitor for posture changes and respiration in bed using real time image sequence analysis

The authors developed a real time system of image sequence analysis to evaluate both a subject´s posture changes and respiration in bed. The system consists of a CCD video camera (used as the sensor), an image processing board and a PC. An image processing board that includes 256 CPUs detects optical flow (apparent velocity) of 256×240 pixels within 150 ms. The representative field-averaged velocity shows a waveform including two components with large peaks and a periodic fluctuation. The large peaks occur during posture change, and the periodic fluctuation corresponds to that of respiration obtained with a nasal thermistor. The system was tested in a nursing home, where it worked for 56 hours in total without any trouble. The authors found two sleep apnea syndrome patients who had not been diagnosed before the test