When applying the CAT tourniquet, when is the friction adaptor buckle not necessary?

The friction adaptor buckle is not necessary when applying the CAT tourniquet to the arm (upper extremity) because the anatomy of the arm allows for effective compression without it. In upper extremity applications, the tourniquet can be secured tightly enough through the natural resistance offered by the arm itself, thus eliminating the need for the friction adaptor buckle to prevent loosening.

In contrast, for areas like the thigh or lower leg, additional support and stability are required due to the larger diameter of these limbs, which is where the friction adaptor proves valuable. It enhances the effectiveness of the tourniquet by keeping it secure during movement or in high-stress situations. The abdomen is not applicable for standard tourniquet use since it doesn't feature a limb structure that the tourniquet is designed to fit or compress in the same manner. Therefore, the unique structural considerations of the upper extremity make the friction adaptor buckle unnecessary in such applications.