Changes of histopathology and blood viscosity in mini pigs with dysbaric osteonecrosis

Abstract

Objective To develop the dysharie osteonecrosis (DON) model in mini pigs induced by rapid decompression, following repeated hyperbaric exposures and observe changes in blood rheology in DON. Methods Twelve male mini pigs were exposed to compressed air of 0.45 MPa for 6 hours twice to three times a week and were then brought to the surface with linear decompression at a rate of 0.35 MPa/min. Blood viscosity was measured with cone-plate type viscosimeter, platelet count was made under the light microscope. Emission of computed tomography (ECT) and pathologic examination were performed for the evaluation of accumulated rate of 99Tc in the femur, following 3 months of repeated compression and decompression. Results ECT showed an increased accumulation of isotope in the femur, when a comparison was made between the experimental animals and the control. Osteopatholngy revealed changes of osteonecrosis in the femur. Platelet count decreased progressively with frequencies of pressure exposures, and meanwhile blood viscosity also increased progressively at a low shear rate. Conclusions Dysharie osteronecrosis was usually accompanied with bone ischemia. Platelet consumption and increased blood viscosity induced by decompression bubbles could be attributed to decreased blood flow in the bone, resulting in osteonecrosis. Key words: Mini pig; Dysbaric osteonecrosis; Platelet; Blood viscosity