CEFID-I (CEra Flow Improves DVT-1)

Inclusion Criteria for all subjects; 1. Adult men and women over 19 years of age 2. Subjects who have not been diagnosed with deep vein thrombosis in the lower extremities through the following test results prior to the application of medical devices. 1. Subjects diagnosed by Doppler ultrasonography as having no blood clots in the femoral vein and the vena poplitea 2. D-dimer negative test result (Even if the D-dimer test is positive, the subject can be selected through the additional test at the discretion of investigator.) 3\. Subjects who fully understand the purpose and procedure of the study and wish to participate in clinical trials with voluntary consent Additional Inclusion Critetia for the DVT risk subjects; 1\. Subjects have two or more points of venous thromboembolism (hereinafter referred to as VTE) clinical prediction score (Two-level wells scroe) at the time of screening Exclusion Criteria: 1. Subjects who complain of a decrease in the sensation of the lower extremities or who is unable to feel the sensation of pain 2. Subjects who have inflammation or trauma on the skin that directly touches the device