Aerosinusitis or Barosinusitis

This is painful inflammation or edema of the sinuses (especially the frontal sinuses), which may be accompanied by bleeding and preceded by an upper respiratory tract infection or acute exacerbation of allergies. It occurs when flying in an aircraft or during deep sea diving and is due to non-equilibration or pressure differences of the internal (within the sinuses) and  the external atmospheric pressure.
It can also be called Barotrauma or Sinus squeeze

Paranasal Sinusis (Picture Credit ;Central Coast ENT)

It occurs about 3-4 episodes per 100,000 exposures, has no racial or gender predilection & rarely reported in children, as the frontal sinuses are not fully developed.

Risk Factors

• Upper respiratory tract infection
• Allergy
• Ambient pressure changes or rapid altitude changes; High altitude flyers, high-performance aircraft, military pilots, Deep-sea Divers, Sport divers, Caisson or tunnel workers.
• Nasal polyps
• Anatomic abnormalities of the nose
• Smoking; in children and older adults
• Flying in an airplane after diving

Pathophysiology

Normally,for ventilation and mucocilliary clearance to occur, the sinuses drain through a small ostia into the nasal cavity. This leads to an equilibrium in pressure between the sinuses and the external atmosphere. But when this opening/ostia is blocked by mucousal thickening (as seen in allergies, upper respiratory tract infection, nasal polyps etc) there is no free flow of air (or equilibrium) between the sinuses and the nasal cavity. Following a rapid change in altitude (during flight or diving), there may be compression on the fifth cranial nerve, thus resulting in the Severe frontal headache which is experienced during Aerosinusitis.

There are 2 types of acute barotrauma: The Squeeze and The Reverse Squeeze.
Squeeze occurs during descent; when the sinuses contracts producing a negative pressure, air is trapped causing a partial vacuum within the sinus cavities. If the vacuum is great enough, it causes rupture of the blood vessels in the sinus cavities and may tear the membrane lining. The pain involved is usually sharp, piercing, and severe; upon descent the sinuses may fill with fluids/transudates, and there may be nose bleeding.

The Reverse squeeze occurs during ascent, when the sinuses expand and the pressure increases within the sinuses, but the air within the sinuses cannot escape to the nasal cavity because the ostia is blocked. The expanded sinuses compresses on the fifth cranial nerve, producing frontal headache.

This pathophysiology can be explained by Boyle's law, which states that "the volume of a gas is inversely proportional to the pressure on it, when temperature is constant (V = CT/P)".


Grades
Weissman grading of aerosinusitis;
    Grade I; mild transient sinus discomfort without visible features on X-ray.
    Grade II; pain lasting up to 24 hrs, with some mucosal thickening on X-ray, Serosanguinous Rhinorrhea.
    Grade III; Severe pain lasting more than 24 hrs with X-ray film showing severe mucosal thickening or opacification of the affected sinus; subsequent sinusitis may be observed. Epistaxis, Hematoma and mucosal avulsion.

Signs and symptoms
The predominant symptom is sudden & sharp facial pain or headache during ascent or descent
Mild
 mild pain just above the brow, rarely referred to other regions of the head
 rarely or occassionally have nose bleeding (epistaxis)
Severe
Sudden, sharp and severe pain in the face,and refered to other regions of the head (retroorbital, midface etc).
Accompanied by Nose bleeding (Epistaxis)

Diagnosis
This is Clinical; positive history of the risk factors and symptoms following exposure.
Radiological examination is not really necessary for the diagnosis as this can be done from the history and physical examination. However it may be useful for grading of the Barotrauma.

X-Ray shows mucosal thickening.
CT scanning shows the sinuses involved, extent of any hematoma, and mucosal thickening. It can also suggest the predisposing factor.

Differential Diagnosis
Nasal Polyposis
Turbinate Dysfunction
Seasonal or perineal allergic rhinitis
Nasal septal deviation
Concha bullosa

Prevention
Use a nasal decongestant before ascending or descending,
Avoid rapid descent or ascent,
Avoiding airplanes or scuba diving when you have an upper respiratory infection,
Use valsalva maneuvers to help equalize pressure in the sinuses and inner ears,
Chew gum during take off or landing,
Yawn during flight,
Use filtered earplugs,
Be properly trained before diving.
To prevent pulmonary barotrauma, do not hold your breath during ascent (divers).
Don’t smoke before diving.
Don’t stay under the water at greater depths for so long.
Avoid flying or going to a higher altitude within 24 hours after diving.

Treatment
Most often, immediate treatment is not always possible, but ideally the following should be done;
Immediately return to the altitude which the symptom started (this may be difficult if it happens in a commercial flight) apply topical nasal decongestants before ascending/descending slowly.
Treatment should be aimed at; pain control, ventilation and to prevent infection.
Pain control with analgesics. Depending on the severity, nacortics can be prescribed. Avoid NSAIDs as it may worsen the Hematoma
Ventilation can be aided with nasal decongestants; oral or nasal spray,
Prevent secondary infections using broad spectrum antibiotics (e.g cephalosporins) because the accumulated transudates, hematoma and damaged mucosa can serve as a medium for bacterial growth.
Surgery can be done for very severe cases lasting more than 24hrs and when the analgesics fail to relieve pain. The following surgeries can be performed; Septoplasty, turbinectomy,balloon sinuplasty, Endoscopic sinus surgery etc.


Complications
 Long-term or permanent hearing loss,
 Ear infection,
 Perforated eardrum.
 Orbital cellulitis,
 Meningitis,
 Brain abscess,
 Osteomyelitis (Pott's puffy tumour when the frontal bone is affected)
 Cavernous sinus thrombosis.

Paranasal Sinusis (picture Credit; Pediatrics ENT Associates)

Notes
1) American Academy of Otolaryngology—Head and Neck Surgery; Barosinusitis

2) Brubakk, A. O.; T. S. Neuman (2003). Bennett and Elliott's physiology and medicine of diving, 5th Rev ed. United States: Saunders Ltd. p. 800. ISBN 0-7020-2571-2

3) Encyclopedia Britannica; Aerosinusitis

4) Fitzpatrick DT, Franck BA, Mason KT, Shannon SG (1999). "Risk factors for symptomatic otic and sinus barotrauma in a multiplace hyperbaric chamber". Undersea Hyperb Med 26 (4): 243–7. PMID 10642071.

5) Gunn DJ, O'Hagan S. Unilateral optic neuropathy from possible sphenoidal sinus barotrauma after recreational scuba diving: a case report. Undersea Hyperb Med. Jan-Feb 2013;40(1):81-6.

6) Hanna HH, Tarington CT. Otolaryngology in aerospace medicine. In: DeHart RL, ed. Fundamentals of Aerospace Medicine. Philadelphia: Lippincott Williams & Wilkins; 1985:520-530.

7) Kristin Hayes, Preventing Sinus Squeeze, Ent About. Updated October 30, 2014.

8) Medical Dictionary; Segen's Medical Dictionary. © 2012 Farlex,

9) Medscape; Aerosinusitis

10) US Navy Diving Manual, 6th revision. United States: US Naval Sea Systems Command. 2006.

11) Wikipedia; Aerosinusitis