bubble_chart Overview

When atmospheric pressure changes abruptly, the eustachian tube fails to open smoothly to regulate the pressure in the tympanic cavity, leading to tympanic injury, similar to sterile otitis media, known as barotrauma. Normally, the eustachian tube opens momentarily during swallowing, yawning, or nose blowing to balance the pressure between the tympanic cavity and the external environment. Pathological changes in the eustachian tube—such as those caused by the common cold, sinusitis, nasopharyngeal tumors, nasal polyps, deviated nasal septum, palatopharyngeal muscle paralysis, or malocclusion of the temporomandibular joint—or its dysfunction during sleep or unconsciousness can impair its ability to regulate pressure, constituting internal factors. External factors include sudden drastic changes in external pressure, such as those experienced during naval diving, air force ascents, or hyperbaric oxygen therapy, where inadequate protective measures can easily result in barotrauma of the tympanic cavity.

bubble_chart Etiology

As a normal aircraft ascends, the atmospheric pressure decreases while the pressure inside the tympanic cavity becomes relatively higher. When the pressure difference between the inside and outside of the tympanic cavity reaches 2 kPa (equivalent to an altitude of 152 meters), gas inside the tympanic cavity escapes through the Eustachian tube to maintain pressure balance. If the aircraft continues to climb higher, the Eustachian tube automatically opens for adjustment each time the pressure difference reaches 1.5 kPa. Therefore, ascending rarely causes tympanic trauma. Conversely, during descent from high altitude, the external air pressure increases while the pressure inside the tympanic cavity gradually decreases, making it difficult for external air to force open the Eustachian tube and enter the tympanic cavity. According to Armstrong's 1937 tests, even when the pressure difference reaches 12 kPa during descent, the Eustachian tube does not open automatically. McGibbon's 1947 research showed that the pressure differences in the tympanic cavity caused by rapid descents from high and low altitudes differ significantly. For example, descending from 9,144 meters to 6,096 meters (a drop of 3,048 meters) results in a pressure difference of 16.4 kPa, whereas descending from 3,657.6 meters to 609.6 meters (also a drop of 3,048 meters) produces a pressure difference of 29.7 kPa—nearly double. This demonstrates that low-altitude dive flights generate greater pressure differences than high-altitude dives, leading to a higher incidence of tympanic trauma, which commonly occurs between 1,000 and 4,000 meters. For divers, every 10 meters of descent increases the pressure by one atmosphere, and without breathing compressed air, tympanic trauma can also occur. Once negative pressure forms in the tympanic cavity, the tympanic membrane invades inward, the mucosal blood vessels dilate and become edematous, and even hemorrhage may occur.

bubble_chart Diagnosis

As the flight gradually ascends or a diver slowly rises to the surface, the pressure in the middle ear transitions from high to low. The Eustachian tube can open periodically to regulate this pressure, so symptoms are rare, though occasional stuffiness or tinnitus may occur. Conversely, during a sudden dive or rapid descent, the Eustachian tube loses its ability to adjust, especially under pathological conditions, making middle ear trauma highly likely. The first symptoms include severe tinnitus, deafness, a sensation of water in the ear, and ear pain that may radiate to the temple and cheek. When the pressure exceeds 14 kPa, the eardrum ruptures, leading to intense ear pain, worsened tinnitus and deafness, as well as vertigo, nausea, and vomiting. These symptoms generally last from half a day to two days before gradually subsiding. Initially, the eardrum shows signs of congestion inward, with hyperemia around the handle of the malleus and scattered bleeding points. Sometimes, a fluid level or air bubbles can be seen through the eardrum, which may develop a linear perforation.

bubble_chart Treatment Measures

1. Pilots and divers with upper respiratory tract infections are prohibited from working. Those with diseases in the nasal, sinus, or nasopharyngeal areas should undergo active treatment.

2. During flights, civil aviation passengers should periodically consume fruits and beverages, chewing and swallowing to promote the opening of the eustachian tube and regulate air pressure. Sleeping during aircraft descent is prohibited. If ear discomfort occurs, actively perform nose-blowing to equalize pressure. If unsuccessful, ephedrine drops can be used before repeating the maneuver. For children, encourage blowing toys or breastfeeding.

3. For those who fail eustachian tube inflation, treatment can be administered in a pressure chamber after aircraft landing or diver surfacing. Alternatively, inhale a helium-oxygen mixture (4:1 ratio) for 4–10 minutes at a flow rate of 8L/min and pressure of 1.6kPa. Due to helium's lighter molecular weight and 2.5 times greater diffusivity than nitrogen, inhalation accelerates gas diffusion and increases middle ear pressure.

4. If eustachian tube ventilation fails or significant middle ear effusion is present, a tympanic membrane incision may be performed, followed by tube placement for long-term drainage. Antibiotics should be administered to prevent infection. {|103|}