The middle ear is a small cavity inside the skull on the other side of the eardrum. The eustachian tube is a passageway between the middle ear and the back of the throat.

A clear eustachian tube insures that the air pressure in the middle ear is the same as the air pressure on the outside of the ear. Sometimes, the eustachian tube becomes blocked when the body is subjected to changing air pressure, such as diving or flying.

Barotitis media is a common disorder experienced by scuba divers and skydivers.