The paranasal sinuses are air-filled cavities within the skull that connect to the nasal passages through small openings called ostia. These spaces are typically in pressure equilibrium with the surrounding atmosphere. When a person rapidly changes altitude, such as during air travel or mountain ascent, the atmospheric pressure outside shifts faster than the air pressure inside these cavities can adjust, creating a pressure differential. This mismatch causes the discomfort and pain many people experience when traveling to different elevations. Altitude impacts the sinuses significantly, primarily through the physics of changing barometric pressure.
The Physics of Pressure Changes in Sinuses
The relationship between altitude and barometric pressure is inverse: as altitude increases, the ambient pressure decreases because there is less air pressing down from above. This principle is governed by gas laws, which dictate that the volume of a gas is inversely proportional to the pressure exerted on it. When external pressure drops as a person ascends, the air trapped inside the fixed volume of the sinuses attempts to expand.
If the sinuses are clear, the expanding air vents out through the ostia, allowing the internal pressure to equalize with the lower external pressure. However, if the ostia are narrowed or blocked—often due to congestion from a cold, allergies, or an infection—the air becomes trapped. This inability to equalize pressure causes a buildup of positive pressure during ascent, pushing outward on the sinus walls.
The reverse occurs during descent, which typically presents a more common and severe problem. As a person descends, the external pressure rapidly increases, causing the air inside the sinuses to contract. If the sinus opening is blocked, the external pressure effectively pushes inward, creating a vacuum or negative pressure within the cavity. This negative pressure can cause the mucosal lining of the sinus to swell and become engorged with blood and fluid, generating intense pain.
Recognizing Barosinusitis and Related Symptoms
The physical injury and inflammation caused by this rapid pressure change within the sinus cavities is medically known as barosinusitis, or sinus barotrauma. Barosinusitis most often affects the frontal sinuses, located behind the forehead, and the maxillary sinuses, situated behind the cheeks.
The most common symptom is severe facial pain or pressure, which frequently starts over the frontal area and may spread to behind and between the eyes. This pain can be sudden and sharp, increasing in intensity as the pressure gradient worsens, particularly during a flight’s descent. Other symptoms include intense headaches, a feeling of fullness or congestion, and, in some cases, a toothache known as barodontalgia, which occurs when the maxillary sinus is affected.
Less frequent but more severe manifestations of barosinusitis include nosebleeds, or epistaxis, or the discharge of serous fluid from the nasal passages. The negative pressure created during descent can physically strip the mucosal lining from the underlying bone, leading to swelling and hematoma formation. Individuals with pre-existing conditions like an upper respiratory infection or allergic rhinitis are at a higher risk of experiencing barosinusitis due to already compromised ostia.
Strategies for Prevention and Relief
Preventing barosinusitis centers on ensuring the sinus openings remain clear to allow for pressure equalization during altitude changes. The most effective preventative step is to avoid air travel or mountain ascents when experiencing a cold, flu, or allergic flare-up, as these conditions cause the tissue swelling that blocks the ostia. If travel is unavoidable, medical intervention can help mitigate the risk.
Using a decongestant, such as an oral tablet containing pseudoephedrine or a topical nasal spray like oxymetazoline, is recommended 30 to 60 minutes before ascent or descent. These medications constrict blood vessels in the nasal lining, reducing swelling and helping to keep the sinus drainage pathways open. Saline nasal sprays or rinses can also help by clearing irritants and moisturizing the nasal passages, which supports proper mucosal lining function.
During pressure changes, performing the Valsalva maneuver—gently attempting to exhale with the mouth closed and nose pinched—can help force air into the sinuses to equalize pressure. Swallowing, chewing gum, or yawning are simple actions that can help open the eustachian tubes, aiding in sinus pressure regulation. Staying well-hydrated before and during travel helps keep mucus thin and flowing, further supporting natural drainage.
If barosinusitis symptoms occur, supportive care and symptom management are the primary forms of relief. Over-the-counter pain relievers can help manage facial pain and headaches, and continued use of decongestants can reduce mucosal swelling in the short term. For symptoms that persist for more than 24 hours, a medical professional may recommend a short course of oral steroids to reduce inflammation or, in rare cases, antibiotics if a bacterial infection is suspected.