The Eustachian tube is a small passageway that links the post-nasal space to the middle ear. It has many functions including draining fluid from the middle and equalising pressure in the ear. Typically, the Eustachian tube remains closed unless you’re yawning, sneezing, or swallowing. Eustachian tube dysfunction (ETD) is a condition that impairs the proper functioning of the Eustachian tube. Symptoms of ETD include a feeling of fullness, ringing in the ears, or popping sounds.