bubble_chart Overview

When atmospheric pressure changes abruptly, the Eustachian tube orifice fails to open smoothly to regulate middle ear pressure, leading to tympanic injury, similar to sterile otitis media, known as barotrauma. Under normal circumstances, the Eustachian tube opens momentarily during swallowing, yawning, and nose blowing to maintain pressure balance between the middle ear and the external environment. Pathological changes in the Eustachian tube, such as common cold, sinusitis, nasopharyngeal tumors, nasal polyps, deviated nasal septum, palatopharyngeal muscle paralysis, and malocclusion of the maxillary joint, or during sleep and unconsciousness, can impair its normal pressure-regulating function—these are intrinsic factors. Sudden drastic changes in external pressure, such as naval diving, air force ascent, and hyperbaric oxygen chamber therapy, can easily cause barotraumatic tympanic injury without proper protective measures—these are extrinsic factors.

bubble_chart Pathological Changes

During normal flight, as an aircraft ascends higher, 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), the gas inside the tympanic cavity escapes through the Eustachian tube to maintain pressure balance. If the aircraft continues to climb, the Eustachian tube automatically opens once every time the pressure difference reaches 1.5 kPa for adjustment. Therefore, ascending does not easily cause 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. In 1947, McGibbon's research showed that the tympanic pressure differences caused by rapid descents from high and low altitudes are entirely different. 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) results in a tympanic pressure difference of 29.7 kPa—nearly double. This indicates that low-altitude dive flights create larger pressure differences than high-altitude dives, leading to a higher incidence of tympanic trauma, which often occurs at altitudes between 1,000 and 4,000 meters. For divers, every 10 meters of descent increases the pressure by one atmosphere. Without inhaling compressed air, this can also cause tympanic trauma. Once negative pressure forms in the tympanic cavity, the tympanic membrane undergoes inward invasion, and the mucosal blood vessels dilate, leading to edema or even hemorrhage (Figure 1).

Figure 1: The response of the Eustachian tube and tympanic cavity during aircraft ascent and descent.

bubble_chart Clinical Manifestations

As the aircraft gradually ascends or a diver slowly rises to the surface, the middle ear transitions from high pressure to low pressure. The Eustachian tube can periodically open to regulate pressure, so symptoms are less common, though occasional stuffiness and 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 severe ear pain, worsened tinnitus and deafness, along with 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 with inward bulging, hyperemia around the handle of the malleus, and scattered bleeding spots. 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 actively undergo 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 the Valsalva maneuver. If the tube still fails to open, ephedrine drops can be applied before attempting the maneuver again. For children, blowing toys or breastfeeding can be encouraged.

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

4. If eustachian tube ventilation fails or there is significant tympanic effusion, a tympanotomy may be performed, with a tube inserted for long-term drainage, and antibiotics administered to prevent infection.