REVIEW ARTICLE Aerosinusitis: Pathophysiology, Prophylaxis, and Management in Passengers and Aircrew Erik K. Weitzel , K. Christopher McMains , Suresh Rajapaksa , and Peter-John Wormald W EITZEL EK, MCMAINS KC, RAJAPAKSA S, WORMALD P-J. Aerosinus- pressure decreases and gases within the sinuses expand, itis: pathophysiology, prophylaxis, and management in passengers escaping through the sinus ostium. During descent, the and aircrew. Aviat Space Environ Med 2008; 79:50 – 3. Patients presenting before fl ight with an upper respiratory infection are ostium becomes obstructed by a ball-valve effect, pro- at risk for aerosinusitis. Prophylaxis of this condition consists of an oral hibiting additional air from entering the sinus. This re- decongestant before fl ight and nasal decongestant spray during the fl ight sults in negative pressure within the sinus. The negative just prior to descent. Evaluation of the patient presenting with aerosinus- intrasinus pressure developed during a squeeze gener- itis consists of a careful physical exam with emphasis on diagnosing treat- Delivered by Ingentaally to: causesGuest painUser and mucosal edema, but in severe cases able nasal and sinus pathology. CategorizationIP: 185.101.68.55 of the patient into On: the Sun, 26 Jun 2016 05:25:51 Weissman classifi cation is important for determiningCopyright: prognostic Aerospace factors Medicalcauses mucosal Association hemorrhage. Risk factors for squeeze in- for recovery. Management of this condition is based on the Weissman clude mucosal edema of tissues surrounding the sinus stage. Stage I or II lesions are generally treated conservatively with a 1-wk ostia, pus, thick mucin, extrasinus polyps, and tumors. course of topical sprays, analgesics, a tapering course of steroids, and oral decongestants. Use of antibiotics is reserved for those cases initiated by It is currently not known if otherwise benign radiolog- bacterial sinusitis. Additionally, antihistamines are reserved for cases ical anomalies such as septal deviation and concha where allergies were the inciting cause. Stage III lesions are rarely seen in bullosa place patients at increased risk for squeeze. civilian air travelers due to the relatively low fl uctuations in ambient air However, when coupled with mucosal edema, these pressure. Aircrew that suffer Stage III aerosinusitis are at risk for recurrent sinus barotrauma that may require an expertly performed functional en- same space-occupying bony structures will tend to mag- doscopic sinus surgery to successfully manage it. nify the obstructive effects. Reverse squeeze can occur Keywords: sinus barotrauma , rhinologic barosinusitis . from the same activities that cause squeeze ( 15 ), but may also be caused by any phenomenon which forces air into the sinuses (e.g., mask ventilation). Reverse squeeze PATIENT presenting with an upper respiratory generally results from intrasinus pathology; however, Atract infection in preparation for an airline fl ight is a tumors ( 20 ), skullbase bony dehiscences ( 21 ), and dehis- frequent clinical scenario. Although there are a tremen- cent cranial nerves ( 7 , 17 , 18 ) have been implicated as dous number of considerations in fl ight medicine ( 2 ), well. During ascent, intrasinus pathology will act in a the most common fl ight-related disorders to be consid- ball-valve fashion to obstruct the maxillary ostium and ered are barotrauma to the middle ear space and the prevent air escape. Pressurized air will eventually paranasal sinuses. dissect into surrounding tissue, fi nding a path of least Sinus barotrauma, or aerosinusitis, is 4 – 6 times less resistance, leading to pathologic sequelae. The air that common than middle ear barotrauma ( 8 , 12 , 20 ). Since escapes the sinus by non-physiologic routes during a the sinuses are not equipped with an active pressure reverse squeeze can cause severe consequences, includ- equalization system like the Eustachian tube, rhinologic ing subcutaneous or orbital emphysema, blindness, pressure differences cannot be controlled and can cause pneumocephalus, meningitis, and trigeminal nerve dys- devastating sequelae. Thus, sinus barotrauma tends to function ( 1 ). be more dramatic in presentation and the more diffi cult to manage of the two. This article focuses on the physics, clinical presentation, evaluation, and treatment of sinus From the Department of Surgery, Otolaryngology Head & Neck barotrauma. Surgery, The Queen Elizabeth Hospital, Woodville, SA, Australia (E. K. Weitzel, S. Rajapaksa, P-J. Wormald) and the Department of Otolaryngology, University of Texas Health Science Center at San Background Antonio, San Antonio, TX (K. C. McMains). This manuscript was received for review in September 2007 . It was Sinus barotrauma can occur during either ascent or accepted for publication in October 2007 . descent. Although descent barotrauma or “ squeeze ” is Address reprint requests to: Maj. Erik Weitzel, M.D., MC, USAF, more common by a ratio of at least 2:1 ( 5 , 18), ascent ENT Department, Queen Elizabeth Hospital, 28 Woodville Rd., barotrauma or “ reverse squeeze ” has more severe Woodville, SA 5011, Australia; [email protected] . Reprint & Copyright © by the Aerospace Medical Association, sequelae. Squeeze occurs due to a ball-valve effect caused Alexandria, VA. by intranasal pathology. During ascent, atmospheric DOI: 10.3357/ASEM.2203.2008 50 Aviation, Space, and Environmental Medicine x Vol. 79, No. 1 x January 2008 AEROSINUSITIS — WEITZEL ET AL. Sinus barotrauma can be explained by Boyle’s law. and sphenoid sinuses have rarely been implicated in This law states that, at constant temperature, a volume this condition ( 10 , 18 ). of dry gas varies inversely with surrounding pressure Aerosinusitis diagnosis requires the coincident (V 5 CT /P). This implies that an elastic chamber fi lled occurrence of a sinus cavity pressure differential and si- with air will expand as surrounding pressure decreases, nus related discomfort ( 20 ). The pain is usually localized as seen with increased altitude. This expansion occurs over the frontal or maxillary sinuses, but may also be even more rapidly with the humidifi ed or “ wet ” air that retroorbital or in the region of maxillary dentition ( 19 ). exists within the paranasal sinus cavities ( 20). As an ex- Numerous case series in military pilots confi rm the pre- ample, at sea level, atmospheric pressure is 760 mmHg; dominant symptom of frontal pain (97%), followed by at maximum decompression, the typical commercial air- malar pain (27%) and bloody rhinorrhea (13 – 58%). Fron- liner pressurizes to 560 mmHg, the equivalent of 8000 ft tal pain is also the most common symptom in civilian of elevation ( 11 , 22 ). By the ideal gas law (PV 5 nRT), dry barotrauma; however, bloody discharge has rarely been air will expand/contract by more than one-third its reported in this demographic ( 18 , 22 ). This gives clinical original volume on a standard fl ight. Factoring in the support to the physical principles mentioned earlier, humidifi ed status of intrasinus air, this expansion be- suggesting that the typical airline passenger suffering comes even more dramatic. Clinically, this means that a from sinus barotrauma is not exposed to pressure differ- typical passenger will have to accommodate signifi cant entials large enough to cause mucosal hemorrhage. The gas exchange during both ascent and descent within Weissman classifi cation system correlates the clinical as- their sinuses during any commercial fl ight or expect to pects of sinus barotrauma to radiographic examination suffer some degree of barotrauma. ( Table I ) . The rate of descent is also an important factor in the development of barotrauma. The faster the change in Prophylaxis and Treatment Delivered by Ingenta to: Guest User ambient pressure, the less time IP:the 185.101.68.55sinus has to adjust On: Sun, 26 Work-up Jun 2016 for 05:25:51 sinus barotrauma includes a thorough his- before developing a critical pressure Copyright:differential. Aerospace Typical Medicaltory to determineAssociation the prefl ight risk factors. Radiographs descent rates experienced by passengers on a civilian 21 are then obtained to stage the patient according to aircraft are 300 – 350 ft z min , whereas military jet fi ght- Weissman classifi cation ( 19 ). The fi rst step in prophy- ers expose their crew to descent rates in excess of 10,000 laxis is identifying the at-risk individual. The major 21 ft z min ( 12 ). Negative intrasinus pressure of 100 –150 identifi able prefl ight risk factors for civilian aerosinus- mmHg creates mild barotrauma with mucosal edema or itis include active upper respiratory infection and aller- serous discharge. Severe cases of barotrauma with mu- gic rhinitis ( 5 , 14 , 20 ). In addition, the patient history cosal bleeding are noted when pressure differentials should be queried for repeated episodes of sinus baro- reach 260 – 300 mmHg ( 23 ). Two authors have suggested trauma, which is generally restricted to military aircrew, that as extravascular blood accumulates, the mucosa but conceivably exists in civilian patients with nasal tears from the periosteum and forms submucosal hema- polyps and ball-valving soft tissue structures (recurrent tomas ( 10 ,14 ). This has been confi rmed by MRI ( 16 ) and sinus barotrauma). plain radiograph ( 19). Since the maximal pressure dif- Prophylactic treatment for at-risk individuals should ferential sustained on a commercial fl ight is 200 mmHg, include an oral decongestant before fl ight and nasal severe cases of sinus barotrauma are not