Barostriction

Barostriction refers to a restriction of pressure equalization ventilation that should normally be present. Sealed containers, such as Pelican cases and SKB cases, often have a pressure release vent that can become blocked and cause rupture of the container during change in elevation. Similarly, acoustic suspension speakers have such need for ventilation.
In human hearing.
Most notably, human hearing involves an equalization of air pressure inside and outside the ear.
An ear is said to be barostricted if there are problems with this pressure equalization. Barostriction may arise from the common cold, or it may be chronic in certain individuals who have constant blockage.
Intermittent nature.
Barostriction is often intermittent, e.g. on some days a person may be able to enter a pool from a 5m diving platform without pain, and other days, even entering from a 1m board may be quite painful. Sometimes only one ear is barostricted. For example, sleeping with the left ear against the pillow, one may wake up with a blocked left nostril and left ear, so that, when swallowing, only the right ear "pops". Since the two ears are vented separately, the right Eustachian tube cannot alleviate pressure in the left ear. Therefore, it is advisable to make sure that both ears are free of barostriction prior to putting the head underwater, or engaging in other activity that might cause barotrauma.
Temporary mitigation.
Chronic barostriction may be partially mitigated with antihistamines, nasal decongestants, and the like, but these often have undesirable side-effects from prolonged use. A product known as Flonase may also be useful for chronic barostriction, and may be used either continually, or just prior to swims. Additionally, a "slow" performance of the Valsalva maneuver may resolve an acute incidence of barostriction.
Activities likely to cause barotrauma in barostricted individuals.
Barostriction leads to ear barotrauma, that may be associated with chronic clogging of the Eustachian tubes (e.g. catarrh), manifesting itself when: