Cyclical Topical Wound Oxygen Therapy (TWO2) in the Treatment of Chronic Wounds

Inclusion Criteria: ①18 years old or older, regardless of gender; ②It was clinically diagnosed as chronic lower limb wound, which was located below the thigh. Patients who received mainly etiological treatment, wet dressing change and necessary decompression for more than 2 weeks had no obvious wound healing tendency; ③Understanding the experimental conditions, Patients are willing to participate in and cooperate with the experimental treatment, and sign the informed consent. Exclusion Criteria: 1. Edema of lower extremity caused by cardiac insufficiency; 2. patients with venous thrombosis of lower extremity; 3. Diabetics with poor blood glucose control: FBS\>=8mmol/L; Blood glucose 2h after meal\>=10.0mmol/L; HbA1c \>= 9% 4. Participated in similar clinical trials in the last three months; Patients with lower extremity arterial occlusion requiring lower extremity vascular surgery; 5. Patients with wound infection requiring systemic antibiotic therapy; 6. Dry scab or necrotic tissue covered more than 50% of the wound, and was not suitable or refused to accept debridement treatment. 7. Immunodeficiency patients 8. Patients with malignant change of wound or with malignant lesions 9. Patients with wound area greater than 10 cm\*10 cm; 10. the wound is deep into sclerotin,articular cavity and body cavity; 11. The wound with sinus tract; 12. patients with serious hepatic dysfunction and malnutrition; 13. Patients with mental or other problems and unable to self-manage equipment 14. Treatment of patients with poor compliance. 15. The researchers think there are other reasons which the patients cannot participate in this clinical trial.