Background: A pressure ulcer is a complication related to the need for the care and treatment of primarily disabled and elderly people. With the decrease of the blood flow caused by the pressure loaded, ulcers are formed and the tissue will be wasted with the passage of time.Objective the aim of this study was to construct blood flow monitoring system on the heel tissue which was under external pressure in order to evaluate the tissue treatment in the ulcer.Methods: To measure the blood flow changes, three infrared optical transmitters were used at the distances of 5, 10, and 15 mm to the receiver. Blood flow changes in heels were assessed in pressures 0, 30, and 60 mmHg. The time features were extracted for analysis from the recorded signal by MATLAB software.Changes of the time features under different pressures were evaluated at the three distances by ANOVA in SPSS software. The level of significance was considered at 0.05.Results:In this study, 15 subjects, including both male and female, with the mean age of 54±7 participated.The results showed that the signal amplitude, power and absolute signal decreased significantly when pressure on the tissue increased in different layers (p<0.05). Heart rate only decreased significantly in pressures more than 30 mmHg (p=0.02). In pressures more than 30 mmHg, in addition to a decrease in the time features, the pattern of blood flow signal changed and it wasn't the same as no-load signal. Conclusions: By detecting the time features, we can reach an early diagnosis to prognosticate the degeneration of the tissue under pressure and it can be recommended as a method to predict bedsores in the heel.