The performance of the elderly in the first three days of death: First, at first, they eat a small amount of liquid food, and slowly they cannot eat and need to rely on fluids to maintain nutrition. In terms of mental state, drowsiness starts to appear, then confusion, shallow coma and deep coma gradually progress. In terms of respiration, shortness of breath and dyspnea appear, followed by deep breathing, shallow and slow breathing, and finally respiratory arrest, and blood oxygen saturation gradually decreases from over 90%. In terms of heart rate, the heart rate increases compensatingly at the beginning, then gradually decreases, and finally the heart rate is zero. In terms of blood pressure, patients with previous hypertension may have normal blood pressure, followed by a gradual decrease in blood pressure.