Our previous study revealed that the coefficient of variation of harmonic magnitude (HCV) of radial arterial pulse was significantly raised before the death of cancer patients. In this study, we recorded the caudate arterial pulse of 24 Sprague-Dawley rats that had a fatal dose of urethane injected into their abdomens. Twenty rats were dead within 3 hours after the injection and four survived. We defined the last 100 minutes of each rat's life as the dying process. During the dying process, we found that both the systolic blood pressure and diastolic blood pressure dropped steeply during the last 5 minutes. However, all HCVs, except HCV1, climbed steeply before the last 5 minutes. The HCV1 of the dying rats was significantly higher than that of rats that survived, starting from the first minute (P < 0.01). The HCV2 of the dying rats was significantly higher than that of the survived rats starting from the 52nd minute (P < 0.05). The HCV3 and HCV4 of the dying rats were significantly higher than those of the survived rats until the 70th minute and the 80th minute, respectively (P < 0.05). Furthermore, HCV2-HCV4 proceeded with the dying process and increased gradually. We concluded that HCVs, which failed first in the high-frequency components and then in the low-frequency components, could provide physicians with earlier information to prevent the coming failure of circulatory system, and could reflect quantitatively pathological severity and predict patient outcome. The specific Fourier components in the pulse provide more physiological information than systolic and diastolic blood pressures.

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Abstract-"Death" is often the largest issue people must face, but it is even more so in the medical field. Accurate forecasting of death not only has positive significance in treatment but also great help the doctor-patient relationship and the economics of medical treatment. However, accurate forecasting is not easy, so many studies to generate forecasting systems have been conducted. In this experiment, a fatal dose anesthetics, urethane, was injected into the abdomen of rats. Blood pressure waves in the rats' caudate arteries were then recorded during the dying process, and an analysis was conducted on the harmonics of the Fourier's transform obtained. Of the 24 rats used in the experiment, 18 died and 6 survived. When a Kappa test was performed on the coefficient variation of the fourth harmonic magnitude(C.V.4) for the two groups of rats, it was found that when C.V.4 exceeded 1.7, the Kappa value was 0.75. This shows that during the death process the coefficience variation of the fourth harmonic magnitude clearly increases.

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