Abstract： Objective To investigate the conditions for the establishment of the model of middle ear barotrauma induced by rapid air compression in rabbits and the pathological processes involved.Methods Used in the study were 22 male New Zealand rabbits,of which 18 were exposed to rapid air compression and were assigned as the exposure group,and the remaining 4 rabbits were assigned as the control group.The rabbits in the control group were just placed in the chamber for the same length of time as the exposure group,but without pressure exposure.The rabbits in the exposure group were pressurized with air to a pressure of 0.8 MPa at an exponential rate of 21/3 and stayed at the said pressure for 5 seconds,and were then decompressed to atmosphere pressure at a linear rate of 3 n/s.Bilateral tympanic membrane samples were harvested at 0,3 and 7 d after exposure,and 10,4 and 4 animals were respectively used for the study.The pathological processes of tympanic membrane were investigated by macroanatomy,light microscopy and transmission electron microscopy.Results The rate of tympanic membrane perforation induced by rapid air compression was 2.8％ (1/36).O'neill pathological grade evaluation at day 0 after exposure indicated that Grade Ⅰ and Grade Ⅱ middle ear barotrauma accounted for 80％ (16/20) and 20％ (4/20) respectively.Initial pathological changes in tympanic membrane was mainly featured by tissue damage,hemorrhage and apoptosis of epithelial cells and fibroblasts at day 0,by epithelial edema at day 3,and near recovery of tissue morphology at day 7,except for irreversible disordered arrangement of elastic fibers in middle layer.Conclusion Following exposure of rapid air compression,rabbit tympanic membrane undergoes a damage-repair process of about 7 days and this process appears to be reversible.Consequently,the animal model could partially reflect pathological features of middle ear barotrauma experienced in diving.