Barotrauma is physical damage to body tissues caused by a difference in pressure between a gas space inside, or in contact with, the body, and the surrounding gas or fluid. The initial damage is usually due to over-stretching the tissues in tension or shear, either directly by expansion of the gas in the closed space or by pressure difference hydrostatically transmitted through the tissue. Tissue rupture may be complicated by the introduction of gas into the local tissue or circulation through the initial trauma site, which can cause blockage of circulation at distant sites or interfere with normal function of an organ by its presence.