In accordance with the law of physics, a gas will expand when the pressure around that gas is reduced. This occurs anytime we fly. It will occur in each part of the body containing gas. It is of no consequence unless the gas becomes trapped in those areas. This video details the areas of the body where gas can be trapped. It also addresses the conditions (such as flying with head colds) that make an aviator more prone. Finally, it provides advice and procedures for in-flight treatment.