Effects of hyperbaric oxygen treatment in post-ischemic muscle. A quantitative morphological study.

In the post-ischemic muscle, hyperbaric oxygen (HBO) treatments have been shown to reduce post-ischemic edema and enhance aerobic metabolism. In the present paper histological, histochemical and ultrastructural methods were used to study the influences of HBO treatment on the morphology of post-ischemic skeletal muscle. The changes were also quantified using morphometry. The circulation of the rat hindlimb was interrupted for 3 hours and muscle biopsies were taken 5 and 12 hours post-ischemia. Light microscopy showed signs of ischemic changes in the muscle. Morphometrically, the area with activity of the muscle enzyme phosphorylase was greatly reduced post-ischemia. HBO treatment at 2.5 atmospheres of absolute pressure (ATA) for 45 min significantly increased muscle cross sectional area with a positive phosphorylase reaction 5 hours post-ischemia. Three HBO treatments were necessary to maintain this effect, 12 hours post-ischemia. Ultrastructurally, the ischemic changes seen using light microscopy were confirmed. Morphometrically, there was a significant increase of mitochondrial size in the ischemic muscle compared with the control uninjured muscle but HBO did not markedly reduce these ultrastructural changes. It was concluded that the reduction of phosphorylase activity, a sensitive marker for muscle cell damage, is to a great extent prevented by HBO treatment in the post-ischemic phase.