Barotrauma of the paranasal sinuses is a risk factor for anyone exposed to ambient pressure changes. These pressure changes most often result from travel through mountainous regions, flying, or diving. [1, 2] Barosinusitis is characterized by inflammation of one or more of the paranasal sinuses. Inflammation is caused by a pressure gradient, almost always negative, between the sinus cavity and the surrounding ambient environment.
The paranasal sinuses have rigid walls with relatively small ostia for gas exchange and mucus transport. Physical gas laws, particularly Boyle's Law, apply to this space. Boyle's Law states that at constant temperature, the volume of a gas is inversely proportional to the pressure placed upon it.
To show how Boyle's Law affects the sinuses, consider the case of an individual with normal sinuses exposed to pressure changes while flying in an unpressurized aircraft. As the individual transitions to higher altitude, the ambient pressure surrounding the sinus cavity decreases, and the air in the sinuses expands and equalizes through the natural ostium. Upon descent, ambient air pressure increases, the air in the sinuses contracts, and air moves into the sinus cavity, preventing a pressure gradient from developing.
Now consider the same flight in someone who has an upper respiratory tract infection (URTI) with tissue edema and secretions blocking the natural sinus ostia. In this individual, tissue edema and debris will not allow free pressure equalization. Again, as the individual moves up in altitude, the ambient pressure decreases, and volume in the sinus cavity increases. A positive pressure develops in the sinus. With this positive pressure, tissue edema gradually decreases enough to allow debris and air to escape the natural ostium. Air pressure then equalizes. When the individual descends, the ambient pressure increases. Pressure cannot equalize across the nasal cavity to the sinus because of blockage at the ostium. Air volume decreases in the sinus cavity, creating a negative pressure.
At this point, a condition exists in which the volume of the sinus must be filled if the pressure gradient is to be eliminated. In mild-to-moderate cases, vascular engorgement and generalized submucosal edema occur. Over time, transudate and mucus fill the volume, reducing negative pressure and decreasing symptoms. In severe cases, especially with rapid onset, the sinus mucosa is stripped from the subjacent bone, resulting in severe pain and hematoma formation.
Prevalence is approximately 3-4 episodes per 100,000 exposures in a generally healthy population.
In contrast, middle ear barotrauma (aerotitis media) is approximately 6-10 times more prevalent than barosinusitis.
Frontal sinuses are most often affected, followed by maxillary sinuses.
Ethmoid sinuses are infrequently affected as isolated events.
Data are heavily skewed toward people who participate in activities subject to rapid pressure changes.
Race predilection is not widely reported.
Sex predilection is not widely reported.
Barosinusitis is not typically reported in children. Frontal sinuses are most frequently affected, and these do not fully develop until late adolescence. In addition, children do not routinely participate in activities that lend themselves to rapid pressure changes.
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