Sinus Squeeze

Etiology

Most underwater injuries are due to barotrauma. Barosinusitis occurs during rapid descent or increases in pressure twice as often as during ascent. Although descent barotrauma is more common, ascent barotrauma causes more severe consequences. Barotrauma occurs more readily in individuals with preexisting upper respiratory pathology, infections, or allergies. Individuals with a history of middle ear or sinus barotrauma are more likely to experience recurrent episodes and symptoms. Common risk factors for barosinusitis include allergic rhinitis, bacterial sinusitis, viral upper respiratory infections, nasal polyps, and idiopathic sinus congestion. No proven correlation exists between sinus squeeze and septal deviation, alcohol, or tobacco use.[5][6][7]

Epidemiology

The prevalence of sinus squeeze is roughly 34% in divers and 20% to 25% in pilots. High-performance pilots, such as fighter pilots, experience barosinusitis less often than commercial pilots. A concurrent upper respiratory infection increases the prevalence in commercial pilots to 55%. Hyperbaric oxygen treatments account for 3% of barosinusitis cases annually. Concomitant sinusitis of any etiology increases the incidence of barosinusitis.

Pathophysiology

The air within the paranasal sinuses is subject to Boyle's law (P₁ x V₁ = P₂ x V₂), which states at a constant temperature, the volume of gas is inversely proportional to the pressure of the gas. When an individual ascends at a constant temperature, the atmospheric pressure is reduced, and the air within the nasal passage and paranasal sinuses wants to expand. In the case of a blocked ostium, however, this sinus air is not allowed to expand, leading to pain and mucosal damage. Conversely, when a patient descends at a constant temperature, the atmospheric pressure increases, and the volume in the paranasal sinuses creates a relatively negative pressure environment. This leads to 2 possible types of sinus barotrauma: squeeze and reverse squeeze.

These changes in sinus pressure and volume are compensated for with the nasal passage via small openings termed ostia. Should these ostia and the sinus outlet be blocked due to any reason (anatomical abnormalities, polyps, inflammation), an equilibrium will not occur, and sinus mucosal damage and symptoms will ensue.

During ascent, the volume of air in the sinus expands against the containing tissues, compressing the sinus mucosa painfully. This may lead to pain or epistaxis, which is termed "reverse squeeze."

During descent, the relative negative pressure environment in the center of the sinus draws fluid from the mucosal capillaries, resulting in mucosal edema and pain. This is termed "sinus squeeze" and may result in mucosal edema, transudation, or a hematoma. This may manifest as a bloody nose due to pressure-induced vascular damage.[8]

Histopathology

The nasal mucosa is usually edematous and inflammatory, sometimes accompanying bloody discharge. Microscopically, mucosal layer thickening is the most common microscopic pathological change noted. Polyps and vesicles can also be seen on histology.

History and Physical

Patients with sinus squeeze often have a history of air travel or diving. Along with the history, there may be a history of recent upper respiratory infection.

Localized frontal pain is the most common chief complaint in patients with sinus squeeze. Symptoms from the maxillary and ethmoid sinuses are less significant and infrequent. The pain can radiate up the crown of the head and behind the orbits. Lacrimation frequently accompanies these cases. Epistaxis is the second most common patient concern and is more common after rapid ascent than descent as the pressure in the sinuses increases and damages the mucosal walls. Referred pain may also occur in the maxilla from the maxillary sinus (barodontalgia). Paresthesias may also be noted, which may become permanent due to nerve damage.[9]

Physical examination of the nasal mucosa may be normal or abnormal during an episode of sinus squeeze. Serous or bloody discharge can be observed up to a week after an inciting event. Discharge is commonly seen from the middle meatus between the middle and inferior conchae.

Evaluation

Imaging studies are unnecessary unless a complication is suspected, such as a ruptured sinus or pneumocephalus, or if the condition is recurrent. The preferred imaging study is a sinus CT with contrast, although x-ray imaging may also be used. Evaluation by an otolaryngologist with nasal endoscopy can also be diagnostic. Evaluation and imaging studies can reveal causative abnormal anatomies, such as polyps, air-fluid levels, septal deviations, or fractures.

Treatment / Management

Nasal decongestants, which help equalize the pressure, are the mainstay of treatment for barosinusitis. Painkillers such as NSAIDs usually adequately control pain. Nasal lavage can also be used for symptom management. Due to the damaged mucosa and concern for infection, prophylactic oral antibiotics may be indicated. The first-line treatment is amoxicillin. If allergic to penicillin, trimethoprim/sulfamethoxazole is recommended. Cephalosporins are also an option if penicillin allergy is not anaphylaxis.

In cases resistant to medical management, endoscopic sinus surgery is an option to re-establish sinus drainage and ventilation. This may be particularly helpful in cases of recurrent barosinusitis.

Preventative actions include avoiding diving in patients with concurrent upper respiratory infections or active allergic rhinitis. In patients predisposed to these conditions, prophylactic oral decongestants such as oxymetazoline spray, pseudoephedrine, and topical intranasal glucocorticoids can also be used before air travel or diving.

Differential Diagnosis

Differential diagnosis for sinus squeeze or barosinusitis include the following:

• Acute sinusitis
• Chronic sinusitis
• Fungal sinusitis
• Deviated nasal septum
• Nasal polyps
• Allergic rhinitis
• Toothache
• Vasomotor rhinitis
• Malignant tumors of the nasal cavity
• Malignant tumors of sinuses

Surgical Oncology

In cases of recurrent and chronic barosinusitis, referral to an otolaryngologist is useful to assess for anatomically correctable causes. Surgical treatments such as osteotomy, nasal polypectomy, septoplasty, turbinate reduction, uncinectomy, concha bullosa reduction, or sinus surgery may be indicated.

Isolated, acute barosinusitis requires surgery only for complications such as pneumocephalus and orbital fractures. If a sinus ostium is blocked during descent, a relative negative pressure environment is created in the sinus. If the subsequent ascent occurs too quickly, that negative pressure environment increases due to intrasinus volume expansion. If the difference between these pressures is great enough, a sinus can rupture, leading to an orbital fracture or pneumocephalus.

Staging

Barosinusitis can be classified in several ways, as follows.

The Weissman classification includes 3 grades of sinus barotraumas, which are classified based on symptoms.

• Grade I involves mild, temporary sinus discomfort without changes visible on x-rays.
• Grade II involves severe pain for up to 24 hours, with some mucosal thickening seen on x-ray.
• Grade III involves severe pain lasting more than 24 hours, along with x-rays showing mucosal thickening or opacification of the sinus; epistaxis or subsequent sinusitis may also be present.

A newer classification system has been proposed, which is as follows: (a) acute, isolated barosinusitis; (b) recurrent acute barosinusitis; and (c) chronic barosinusitis.[10]

Prognosis

The prognosis for sinus squeeze is generally good after treatment with NSAIDs, decongestants, and prophylactic antibiotics. Surgery is only reserved for recurrent cases or after complications.

Complications

Sinus squeeze is the second most common complication occurring during underwater diving. The most common disorder seen among divers is ear barotrauma. During the descent, increases in ambient pressure can lead to mucosal engorgement and edema. This can cause a blockage of the sinus ostia, trapping fluid in the sinus cavity and ultimately increasing intrasinus pressure. The frontal sinus is most commonly affected due to the relatively long and tortuous nature of its duct. Common symptoms include a headache, epistaxis, and localized sinus pain. Suppose a blockage of a sinus ostium occurs during the descent. In that case, the subsequent ascent can lead to intrasinus volume expansion and a resulting pressure differential that may be sufficient to rupture the sinus. Pneumocephalus is a serious clinical diagnosis in such cases. The treatment is careful observation and prophylactic antibiotics for possible meningitis. Antibiotic coverage has traditionally included agents in the penicillin or cephalosporin classes.

Maxillary sinus involvement can compress the maxillary branch of the trigeminal nerve, ultimately causing hyperesthesia over the cheek.

Sphenoid sinus involvement may lead to compression of the optic nerve, leading to decreased vision or even blindness.