The tube behind the ears is called the Eustachian tube, also known as the auditory tube or pharyngotympanic tube. It is made of bone and cartilage and connects the middle ear to the back of the throat and nose. The Eustachian tube has several functions, including:
Balancing pressure: Helps to balance pressure in the middle ear, which can be felt as popping ears
Draining fluid: Helps to drain fluid from the middle ear
Protecting the ear: Protects the ear from hearing sounds caused by the body and nasal drainage
Aerating the middle ear: Aerates the middle ear system
Clearing mucus: Clears mucus from the middle ear into the nasopharynx

I've read into it, but as of now insurance doesn't cover the treatments and it can be quite expensive. If you give it a shot I'd love to hear how it goes.

I believe it's called a hyperbaric chamber. At least that's what I've heard it called over here . They have soft ones and they have hard ones. They use it for emergencies when divers have the bends as well as therapy. Just a heads up if you have issues with ears . The audiologist told me it's not good idea for me because I have some issue possibly with my eustachian tube which I still have to have checked out. My eardrum's been broken several times in the past.

I’ve never heard of oxygen chamber therapy