What does low ear canal volume in a Type B tympanogram imply?

Low ear canal volume in a Type B tympanogram typically indicates the presence of fluid behind the eardrum, which can be a sign of otitis media or other middle ear issues. In a healthy ear, a normal tympanogram would show a certain volume of air in the ear canal, signifying proper functioning of the tympanic membrane and middle ear structures. When fluid accumulates in the middle ear space, it can dampen the movement of the tympanic membrane and significantly alter the compliance observed in tympanometry.

The low volume reading suggests that the tympanic membrane is not able to move freely due to the presence of fluid, rather than being inflated by air like it would be in a typical situation. This fluid creates a barrier to pressure equalization, resulting in the characteristic Type B tympanogram, which reflects immobility rather than normal vibratory motion. Thus, a low ear canal volume in this context is an important diagnostic indicator of middle ear pathology, particularly fluid presence.