How TWO2/O3 Works? A major issue fir healing wounds is that the hypoxic conditions caused by vascular complications inhibit healing. Molecular oxygen is essential during the inflammatory phase of wound healing and during collagen synthesis. Wound treatment with oxygen increases vascular endothelial growth factor (VEGF) expression at wound edges and increases angiogenesis. chronic wounds have lower tissue oxygen tensions than contro, tissue, predictor of extremity chronic wound healing.