In the United States, 30,000–40,000 amputations are performed annually. An estimated 1.6 million individuals are living with the loss of a limb in 2005; these estimates are expected to more than double to 3.6 million such individuals by 2050.[15] Antibiotics alone are not effective because they may not penetrate infected tissues sufficiently.[16] Hyperbaric oxygen therapy (HBOT) treatment is used to treat gas gangrene. HBOT increases pressure and oxygen content to allow blood to carry more oxygen to inhibit anaerobic organism growth and reproduction.[17] A regenerative medicine therapy was developed by Dr. Peter DeMarco to treat diabetic gangrene to avoid amputations. Growth factors, hormones, and skin grafts have also been used to accelerate healing for gangrene and other chronic wounds.