# Implementation of Portable Automatic Tourniquet with High-Elasticity Biocompatible Strap
## 3 Experimental Results  
### Results of Blood Flow Control  
The blood flow control characteristics of the proposed automatic tourniquet are shown in Table 3 and Figure 7a. In particular, Table 3 shows the velocity of blood flow measured when applying latex tubing and the automatic tourniquet to each of the five members of the control group. For the conventional latex tube tourniquet, the compression level (1.5-2 N) for blood sampling was uniformly adjusted [24; 25]. Blood flow velocities in the normal state, measured on the subjects' median cubital vein, were measured to be 0.950 m/s on average. In addition, when the latex tubing was applied, the measured blood flow velocities averaged 0.760 m/s. In the control group, blood velocities were measured to be somewhat lower in female than male subjects. In the case of the automatic tourniquet, it was adjusted to tension steps 1 to 5. When the automatic tourniquet was used at tension steps 1 to 5, the means of the corresponding blood flow velocities were 0.806 m/s, 0.593 m/s, 0.533 m/s, 0.425 m/s, and 0.310 m/s, respectively. The experiment using the proposed system was measured repeatedly, five times for each step, and was performed after the subject took sufficient rest at 30 min intervals. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \multirow{2}{*}{**Control**} & \multirow{2}{*}{\
\begin{tabular}{c} **Normal (m/s),** \\ **Mean (N = 5)** \\ **(Min–Max)** \\ \end{tabular} } & \multirow{2}{*}{
\begin{tabular}{c} **Late Tubing** \\ **(m/s) (N = 1)** \\ **(Min–Max)** \\ \end{tabular} } & \multicolumn{4}{c}{**Proposed Automatic Tourniquet (m/s), Mean (N = 5)**} \\ \cline{3-8}  & & & **Step 1** & **Step 2** & **Step 3** & **Step 4** & **Step 5** \\  & & **(Min–Max)** & **(Min–Max)** & **(Min–Max)** & **(Min–Max)** & **(Min–Max)** & **(Min–Max)** \\ \hline \multirow{4}{*}{Male} & 0.946 & \multirow{4}{*}{0.760} & \multirow{4}{*}{0.845} & 0.764 & 0.590 & 0.557 & 0.454 & 0.316 \\  & (0.917–0.980) & & (0.717–0.896) & (0.567–0.610) & (0.522–0.600) & (0.420–0.489) & (0.293–0.377) \\  & 1.034 & & 0.884 & 0.579 & 0.523 & 0.468 & 0.334 \\  & (0.974–1.064) & & (0.738–0.940) & (0.560–0.602) & (0.501–0.581) & (0.430–0.482) & (0.310–0.380) \\  & 0.915 & & 0.773 & 0.789 & 0.597 & 0.559 & 0.447 & 0.320 \\  & (0.901–0.933) & & (0.721–0.850) & (0.564–0.622) & (0.510–0.596) & (0.404–0.490) & (0.286–0.361) \\ \hline \multirow{4}{*}{Female} & 0.967 & \multirow{4}{*}{0.710} & \multirow{4}{*}{0.854} & 0.712 & 0.612 & 0.521 & 0.405 & 0.324 \\  & (0.930–1.006) & & (0.672–0.830) & (0.592–0.624) & (0.490–0.587) & (0.384–0.477) & (0.294–0.350) \\  & 0.888 & & 0.854 & 0.595 & 0.504 & 0.354 & 0.257 \\  & (0.851–0.920) & & (0.658–0.896) & (0.565–0.618) & (0.480–0.556) & (0.320–0.457) & (0.210–0.328) \\ \hline \multirow{2}{*}{Mean} & 0.950 & \multirow{2}{*}{0.760} & \multirow{2}{*}{0.806} & 0.593 & 0.533 & 0.425 & 0.310 \\  & (0.851–1.064) & & (0.710–0.845) & (0.658–0.940) & (0.560–0.624) & (0.480–0.600) & (0.320–0.490) & (0.210–0.380) \\ \hline \end{tabular}
\end{table} 
Table 3: Results of blood flow velocity with the healthy control group according to the pressure method (the blood flow velocities were measured using the ultrasonic measurement system). Figure 7: Experimental results of (**a**) the velocity of blood flow and (**b**) tension force using the proposed tourniquet and the latex tubing. (The blue dot indicates blood velocity in normal state, the red dot indicates velocity of blood flow and tension force when the cephalic vein is compressed using the latex tube tourniquet). It was confirmed that blood flow was controlled quantitatively according to the pressure intensity, although there was some difference according to the physical characteristics and the experimental environment of the healthy control group. The results demonstrate that the velocities of blood flow were maintained at more than 6 dB higher at the maximum pressure state, compared with those of the conventional latex tube tourniquet.