TAILIEUCHUNG - Recent Advances in Biomedical Engineering 2011 Part 13

Tham khảo tài liệu 'recent advances in biomedical engineering 2011 part 13', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Discovery of Biorhythmic Stories behind Daily Vital Signs and Its Application 469 respiration heart rate blood pressure and body temperature. These features are clinically discernible in a polysomnogram measured by attaching more than 10 sensors to a subject. This section describes a method for estimating the cyclic property of sleep based on HR only. Because variation in HR in the REM state is much larger than that in the NREM state variance of the HR was used as a criterion to distinguish between REM and NREM sleep states. The windowed local variance WLV method is used extensively in image processing for edge detection and pattern segmentation Bocher McCloy 2006a 2006b Law Chung 2007 . It is defined as the variance computed for pixel values within a window of size w X w from aggregated pixel data. This study deals with one-dimensional HR data sequences and defines the WLVi at data point i as shown in Equation 9 . WLV w 2 ẻs Xj w w j i 7 1 1 w where w is the window length and X is the input data within the window. Figure 5 shows the noise-suppressed HR data in the red trace and the estimated result of a biphasic sleep cycle in the blue trace. The low-level phase indicates the period with lower HR perturbation and the high-level phase corresponds to a period with increased HR fluctuation. Although it is not yet a conclusion that there is a relationship between the REM-NREM cycle and the estimated biphasic cycle because no concomitant EEG was recorded it is inferred that the low-level phase may imply the NREM state while the high-level phase refers to the REM state. As shown in Figure 5 the period length of the high-level phase gradually increased during the course of sleep . it was short at the beginning of the sleep period and longer towards the end of the sleep period a behaviour similar to the REM state although confirmation of this is required from an EEG. 470 Recent Advances in Biomedical Engineering 90 85 80 75 70 65 60 55 50 45 40 0 00 00 1 00 00 2 00 00

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