Why Do Your Ears Feel Pressure in a Hyperbaric Chamber?

Some people notice ear fullness, a blocked feeling or a mild popping sensation after entering a hyperbaric chamber. This feeling is mainly related to a change in ambient pressure, not to oxygen itself. The principle is similar to the ear pressure experienced during an aircraft ascent or descent.

Why can pressure changes affect the ears?

The outer side of the eardrum is exposed to the surrounding environment, while the inner side borders the air-filled middle ear. The middle ear connects to the back of the nose and throat through the Eustachian tube, which helps equalize pressure.

As a chamber begins to pressurize, the pressure outside the eardrum gradually rises. If the middle-ear pressure does not equalize at the same time, a temporary pressure difference can produce fullness or a blocked sensation. Johns Hopkins Medicine notes that the ears may feel plugged as chamber pressure rises, similar to the sensation during air travel or at high altitude.

How does Boyle’s law explain the sensation?

When temperature remains approximately constant, the volume of a gas tends to decrease as pressure increases and to expand as pressure decreases. This relationship is known as Boyle’s law.

Air-filled spaces such as the middle ear and sinuses are therefore affected by changes in ambient pressure. According to the NCBI Bookshelf overview of hyperbaric physics, a middle ear that cannot equalize with the surrounding environment can develop a sensation of pressure or pain.

Ear pressure cannot be used to estimate oxygen concentration or replace a chamber pressure reading. ATA means absolute pressure. For a related explanation, see our previous article: What Does ATA Mean? What Happens at 2.0 ATA?

Why should pressurization and decompression be controlled?

A controlled pressure change gives the middle ear and other gas-filled spaces time to adapt. The actual pressurization rate, target pressure and operating sequence should follow the equipment documentation and the procedure established by the responsible facility.

Mild fullness or popping may occur during a pressure change, but persistent pain, marked dizziness or a change in hearing should not be ignored. These symptoms should be reported to the qualified person responsible for the session so they can be assessed under the facility’s procedure.

In its safety communication for hyperbaric oxygen devices, the U.S. Food and Drug Administration emphasizes following the manufacturer’s instructions and maintaining training, monitoring and safety checks.

Frequently asked questions

Is ear pressure caused by a higher oxygen concentration?

Usually not. Ear pressure is mainly related to ambient pressure and middle-ear equalization. Oxygen concentration and chamber pressure are separate parameters.

Is it the same as ear pressure on an airplane?

The basic principle is similar: an external pressure change can temporarily create a difference across the eardrum. The pressure range, direction and control method are different in each environment.

Can ear sensation show how many ATA the chamber has reached?

No. Sensation and equalization ability vary between individuals. Chamber pressure must be confirmed with calibrated instruments and the control system rather than by subjective feeling.

References

1. NCBI Bookshelf: Hyperbaric Physics
2. Johns Hopkins Medicine: Hyperbaric Oxygen Therapy
3. FDA: Follow Instructions for Safe Use of Hyperbaric Oxygen Therapy Devices