Sinus squeeze, also known as barosinusitis and aerosinusitis, is irritation of the mucosal lining in the paranasal sinuses as a result of the failure to equalize intrasinus pressures with the ambient environment pressure. Sinus squeeze is associated with rapid ascent or descent while scuba diving, rapid altitude changes during flights, and hyperbaric treatments. Symptoms include pain, epistaxis, lacrimation, and rhinorrhea. Pain is the most common symptom, and the frontal sinuses are most commonly affected. Referred tooth pain can occur when the maxillary sinuses are involved.
Most underwater injuries are due to barotrauma. Barosinusitis occurs during rapid descent or increases in pressure twice as often as during ascent. Barotrauma occurs more readily in individuals with preexisting upper respiratory pathology or infections. Individuals who have a history of middle ear or sinus barotrauma are more likely to experience recurrent episodes and symptoms. Some common risk factors for barosinusitis include allergic rhinitis, bacterial sinusitis, viral upper respiratory infections, nasal polyps, and idiopathic sinus congestion. There has not been a proven correlation between sinus squeeze and septal deviation, alcohol, or tobacco use.
The prevalence of sinus squeeze is roughly 34% in divers and 20% to 25% in pilots. Interestingly, high-performance pilots, such as fighter pilots, experience barosinusitis less than commercial pilots. Prevalence in commercial pilots increases to 55% with a concurrent upper respiratory infection. Hyperbaric oxygen treatments account for 3% of annual barosinusitis cases. Concomitant sinusitis of any etiology increases the incidence of barosinusitis.
The air within the paranasal sinuses is subject to Boyle's law 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 isn't 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.
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, an equilibrium will not occur, and sinus mucosal damage and symptoms ensue. During ascent the volume of air in the sinus wants to expand but is not allowed to, resulting in painful compression of the sinus mucosa. During the descent, the relative negative-pressure environment in the center of the sinus draws fluid from mucosal capillaries with resultant mucosal edema and pain. Sinus squeeze may result in a bloody nose due to pressure induced vascular damage.
Macroscopically, the nasal mucosa is usually edematous with inflammatory changes. Sometimes there is accompanying bloody discharge. Microscopically, mucosal layer thickening is the most common pathological change noted. Polyps and vesicles can also be seen on histology.
The most common chief complaint in patients suffering from sinus squeeze is localized frontal pain. Maxillary and ethmoid sinuses are less significant and infrequent. The pain can radiate up the crown of the head, and behind the orbits, lacrimation is frequently associated in these cases. Epistaxis is the second most common patient concern. Epistaxis is more closely associated with rapid ascent than descent.
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 coming from the middle meatus located between the middle and inferior conchae.
Imaging studies are not necessary unless a complication is suspected, for example, a ruptured sinus and pneumocephalus, or if it is a recurrent case. The preferred imaging study is a sinus CT with contrast. 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, and fractures.
Pain is usually adequately controlled with NSAIDs. Nasal lavage and topical or oral decongestants can help to equalize pressure. Prophylactic oral antibiotics may be indicated due to the damaged mucosa. First-line treatment is amoxicillin. If allergic, trimethoprim/sulfamethoxazole is recommended. Cephalosporins are also an option.
Preventative actions include avoiding diving with concurrent upper respiratory infection and/or active allergic rhinitis. Prophylactic oral decongestants such as oxymetazoline spray, pseudoephedrine, and topical intranasal glucocorticoids can also be used.
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 there is a blockage of a sinus ostium 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 orbital fracture and/or pneumocephalus.
Sinus squeeze can be considered acute, chronic, recurrent, or complicated.
The prognosis for sinus squeeze is generally good after treatment with NSAIDs, decongestants, and prophylactic antibiotics.
Sinus squeeze is the second most common complication occurring with 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. If blockage of a sinus ostium does occur during descent, 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 in such cases is careful observation and prophylactic antibiotics for meningitis. Antibiotic coverage has traditionally included agents in the penicillin or cephalosporin classes.
Otolaryngology should be consulted for chronic, recurrent, and suspected complicated cases of sinus squeeze. They will evaluate for surgically correctable anatomical abnormalities with various endoscopic techniques.
Advise patients to either avoid diving with active allergic rhinitis and upper respiratory infections or use prophylactical treatments such as decongestants like oxymetazoline spray and over-the-counter analgesics like NSAIDS.