![]() 22 The pressure change that occurs during a rapid 5 m underwater dive is equivalent to that seen during a 5500 m descent above sea level the latter will also occur more gradually. Air, by contrast, is compressible and amorphous, which thereby requires much greater changes in altitude to cause similar changes in pressure. ![]() Water is noncompressible, and pressure increases linearly at a rate of 1 atmosphere every 10 m. The differences between the physical properties of water and air explains why barosinusitis is reported to be more common in divers than in pilots. Aviation and diving studies indicate that decompression barosinusitis events associated with descent and increased gravity are twice as common as sinus barotrauma that is related to ascent, compression, and reverse squeeze phenomena. The corresponding injuries that may result from uncompensated centripetal, “pulling” forces can range from mild mucosal edema, to complete avulsion of the mucosal surface from the bone, to hematoma formation, depending on the degree and rapidity of the pressure shifts ( Fig. According to Boyle's Law, this results in a decrease in gaseous volume within the nasal cavity and sinuses themselves, and this, therefore, creates a decompression or squeeze effect. (C) Type 3 frontal cell that compromises sinus outflow a reverse squeeze or compression injury may occur in both the frontal sinus and obstructing type 3 cell, producing severe, but focal, symptoms.īy contrast, during descent, ambient air and water pressures increase due to the effects of gravity and/or water mass. Decrease in gaseous volume within the sinuses during descent creates intrasinus decompression without inward pressure equalization this results in “pulling” forces within the sinus cavity that can cause mucosal edema, avulsion of the mucosal surface from the bone, and hematoma formation, depending on the degree and rapidity of the pressure shifts. ![]() (B) A squeeze or decompression injury in an inflamed or partially obstructed sinus. Increased air expansion and elevated intrasinus pressure during ascent, without compensated pressure release, produces an outward, “expansile” compression injury of the sinus mucosa against the bony sinus outer walls this results in mucosal edema and rupture. (A) Reverse squeeze or compression injury in an inflamed or partially obstructed sinus. Illustrations that depict scenarios of sinus barotrauma. The numerous downstream mechanistic pathways are further discussed by etiology. 18– 20 The uncompensated changes in intrasinus pressure can result in the mucosal injuries observed in barosinusitis. In patients with barosinusitis, the ostia may be anatomically smaller (due to minor fluctuations in the wall positions around the ostia) or become narrowed or obstructed due to local inflammation, edema, or trauma, which compromise the ability of the ostia to compensate and facilitate air exchange. Communication between the central nasal cavity and more laterally located sinuses allows changes in pressure to be compensated by small changes in the volume of gas within the sinuses. Under normal circumstances, barometric air pressure within the sinus cavities equilibrates with the pressure in the surrounding nasal passages through the openings into the sinuses, known as the sinus ostia. The paranasal sinuses are labyrinthine air-filled spaces bounded by thick, fixed bony outer walls, and by thin, pliable, internal walls. PATHOPHYSIOLOGY AND REPORTED CAUSES OF BAROSINUSITISīoyle's Law, which states that, at a given temperature, the volume of a gas varies inversely with pressure, is highly applicable to understanding the pathogenesis of barosinusitis.
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