Pressure-volume changes associated with changing atmospheric pressure precipitate acute inflammation of the sinus and middle ear cavities, known collectively as barotrauma. Barotitis occurs during descent from high altitudes. A partial vacuum develops, manifested by a retracted tympanic membrane. Hemorrhage may occur as a consequence of the vacuum. Similar pathophysiology causes barosinusitis. While the cause of aerodontalgia is not known, pain in the teeth does occur during ascent rather than descent.