Barosinusitis, also known as sinus barotrauma or aerosinusitis, refers to inflammatory changes that affect the paranasal sinuses due to alterations in atmosphere pressure, with uncompensated pressure changes within the sinonasal cavities.

Epidemiology

Barosinusitis is most common in aviation travelers, deep-sea divers, and patients after altitude chamber accidents ^1-4. The prevalence of sinus barotrauma ranges from 19.5% in pilots to 34% in divers ¹. Concomitant sinus inflammation increases the prevalence of barosinusitis in pilots, with rates of 34% in fighter pilots and 55% in commercial pilots ¹.

Risk factors

• acute sinusitis
• chronic sinusitis
• obstruction of sinus ostia with mucous or fungus ball
• acute or chronic upper respiratory tract infections
• allergic rhinitis
• sinonasal polyposis
• sinonasal neoplastic disease
• deviated nasal septum
• stenosis of sinus ostia
• sinonasal anatomic deformities

Clinical presentation

A history of exposure to atmospheric pressure variations provides fundamental data for diagnosis ^1,3. The symptoms of barosinusitis range from a slight sensation of congestion, pressure, or pain with facial tenderness on palpation over the involved area ^1-4 to headache, odontalgia, lacrimation, rhinorrhagia, epistaxis, fever ^1,2  and even symptoms of neurological involvement in some cases. Neurological manifestations can include cranial trigeminal nerve dysfunction or dysesthesias ^1-4

Sinus barotrauma most often affects the frontal sinuses, followed by the maxillary, ethmoid, and more rarely the sphenoid sinuses ^1,2.

Pathology

Etiology

• hyperbaric oxygen therapy
• submarine decompression
• prolonged high-altitude exposure
• vigorous Valsalva maneuver
• nasal blowing

The pathophysiological mechanism of the condition is explained by Boyle-Mariotte's law, which postulates that "if the temperature is constant, the volume of a gas varies inversely proportional to the pressure it supports"^1,2,4. Gases found in the various cavities of the human organism obey this law.

Sinus barotrauma is due to a pressure-related change in sinus cavities ^1-4. Air pressure in the paranasal sinuses normally remains balanced due to the surrounding nasal passages through openings in the sinuses i.e. the ostia ^1,3,4. These air passages between the central nasal cavity and the paranasal sinuses compensate for changes in the volume of gas inside the sinus cavities, which allows for pressure equalization ^1,2.

During an ascent on a flight or after diving, the ambient pressure decreases, and the air in paranasal sinuses increases in volume, exiting through the ostia until it reaches a balance at that certain altitude ^1,2. On the way down, the reverse occurs ². There is recompression of gases, and negative pressure is formed inside the sinuses, with the progressive movement of air into the paranasal cavities, until it establishes a new balance ². Usually, this movement of air entering and leaving the sinus cavities is asymptomatic ^1,2.

In abnormal conditions, the ostia are narrowed or obstructed due to either anatomic stenosis or reversible obstruction such as mucosal inflammatory thickening and nasal polyposis ^1-4. These abnormal conditions can impede the flow of air through the ostia, impairs the ability to equilibrate and provide adequate pressure exchange, resulting in mucosal damage with edema and the mucosal's rupture with transudation of serosanguinous fluid, submucosal hemorrhage, or hematoma formation ^1-4.

Differences in atmospheric pressure can trigger inflammatory changes within the sinus cavities, resulting in sinus barotrauma ^1-3. The phenomena of decompression are associated with descent and increase gravity, resulting in a vacuum effect known as the squeeze, which is the most common cause of sinus barotrauma ^1,3,4. Barosinusitis related to ascent with decreased ambient pressure and elevated intrasinus pressure is known as reverse squeeze, which occurs less frequently ^1,3.

Radiographic features

Plain radiograph

Plain radiographs are usually not indicated for the routine evaluation of sinus disease nowadays ¹. Mild cases may present with no changes on x-ray. In some cases, the findings might include complete or subtotal sinus opacification, generalized or localized mucosal thickening, and the formation of gas-fluid levels, which may represent fluid transudation or bleeding into the sinus ^2,3.

CT

The gold standard test for the condition is a CT scan, which may show inflammatory mucosa swelling, partial to complete opacification, which represents fluid transudation, or even bleeding into the sinus with or without the formation of air fluid levels ^1,4. Polypoid masses corresponding to submucosal hematoma may be seen ^1,4.

MRI

MRI may reveal mucosal thickening or a polypoid mass in the sinus, representing submucosal hematoma ^1,3,4.

• T1: submucosal hemorrhage, hyperintensity 
• T1 C+ (Gd): submucosal hemorrhage, without enhancement
• T2: submucosal hemorrhage, hyperintensity

Treatment and prognosis

Most sinus barotrauma injuries are self-limiting and resolve spontaneously within a few days ^1,2. Treatment should be directed towards pain relief, promotion of drainage of the paranasal sinuses' contents, and decreasing mucosal inflammation, usually through analgesics, topical and systemic decongestants, and sometimes oral corticosteroids, and nasal lavage ^1,2,4. Antibiotics may be indicated to offer protection against infection ^1,2.

Occasionally, surgery may be necessary for sinus decompression, with balloon sinuplasty or functional endoscopic sinus surgery ^1-4. Surgical procedures can open or dilate sinus ostia and remove abundant mucosal tissue overlying an outflow tract ^2-4.

For the fighter pilot, depending on operational conditions, relief of symptoms may be achieved at the first sign of barosinusitis and consists of returning to the altitude at which the symptoms occurred to balance intra and extra-sinus pressures, then reattempting a new descent very slowly ².

Avoidance of flying or diving during head colds, sinusitis, and allergic rhinitis episodes are preventive measures ^1-3.

History and etymology

The first reported case of barosinusitis occurred in 1919, during experiments in a decompression chamber, by Marchoux and Nepper ². In 1942, during World War Two, Campbell described the mechanism of the pathophysiology of barotrauma ^1,2,4. In divers, the first reported case occurred in 1965, by Flottes ¹.

Differential diagnosis

• acute sinusitis
• chronic sinusitis 
• fungal sinusitis
• allergic rhinosinusitis
• non-allergic rhinitis with eosinophilia syndrome (NARES)
• vasomotor rhinitis
• mucocele
• cholesterol granuloma