Hyperbaric oxygenation (HBO) involves breathing of 100% oxygen under elevated ambient pressure. In correlation to the pressure level oxygen dissolves in the plasma resulting in an increase of total oxygen in the body. The elevated tissue levels of oxygen may persist for hours, instigating healing processes in wounds caused by disturbances in of perfusion in small vessels, a condition often found in patient with diabetes.

We plan a prospective, double-blind randomized clinical study in 80 patients with chronic diabetic ulcer. All will have optimum treatment of diabetes. The HBO group will be given HBO at 2.4 bar, 90 min., 30 sessions, controls will have sham HBO. Routine wound care will be identical in both groups. Before, during and after treatment (3, 6 and 12 months), a number of monitoring and imaging procedures will be done, cells in the bloodstream indicating improved healing will be determined.

Hypothesis: HBO will instigate the healing process in the majority of patients with chronic diabetic leg ulcer, provided the patency of the large vessels is given.

We plan a prospective, double-blind randomized clinical study (phase III) in 80 patients with diabetes mellitus. All of them will receive the optimum metabolic treatment for their underlying disease. The treatment group will be administered HBO according to the problem wound schedule, the controls will have sham treatment in the hyperbaric chamber. Routine wound care (dressings, physiotherapy, antibiotics if necessary) will be identical in both groups and according to its clinical needs.

Before treatment, indocyanine green videoangiography (ICG), transcutaneous (partial) oxygen pressure (TcPO2) and LifeViz 3D (three-dimensional medical imaging and reconstruction) documentation will be done and endothelial progenitor cells (EPC) as well as markers of bone metabolism will be determined in all patients.

The measurements will be repeated according to the schedule during the treatment period and at controls after 3, 6 and 12 months.

Inclusion Criteria:

• Diabetes mellitus
• Age between 18 and 80 years
• Chronic foot ulcer (up to Wagner scale III)
• Patency of large vessels tributary to region of wound
• Good outpatient diabetes management as verified by a specialized centre (HbA1c<8.5%; IFCC: 69mmol/mol).

Exclusion Criteria:

• Clinically relevant obstruction of large vessels tributary to region of wound
• Non-adherence to diabetes therapy
• Pregnancy
• Reactive airway disease
• Radiographic evidence of pulmonary blebs or bullae
• Untreated pneumothorax
• History of seizures except childhood febrile seizures
• Cardiovascular instability
• Mechanical ventilator support
• Treatment with Bleomycin or Anthracyclin in history
• Unable to perform the Valsalva-procedure
• Participation as a subject in any other medical or biomedical research project; if previously involved as a subject, sufficient time must have elapsed to permit "wash out" of any investigational agent.