Effects of hyperbaric oxygenation and prolonged hypoxia on the healing of open wounds

In a study on rats, long-tern intermittent hyperbaric oxygenation at 2 ATA had no effect on the healing rate of open wounds in which the circulation was left intact. When the wound edges were devascularized, however, hyperbaric oxygen enhanced the wound closure rate in the final stages of healing, thus counteracting the delay caused by disturbed blood supply. During the hyperbaric exposure, tissue pO-2 increased considerably in both normal and devascularized skin, whereas tissue pCO-2 increased only slightly. Combined systemic and local hypoxia--12% oxygen at 1 atm--retarded the closure rate of full-thickness skin wounds. This was noted both in acclimatized and in unacclimatized rats. Thirteen-day adaptation to hypoxia increased the healing rate and subcutaneous tissue pO-2 to normal levels, but when hypoxia was continued, tissue pO-2 and the wound closure rate decreased markedly. This was probably due to a decreased blood flow induced by secondary erythrocytosis and an elevated blood viscosity.