Describe sinus barotrauma.

Sinus and Nasal Barotrauma

• Sinus barotrauma (aerosinusitis) is injury to the sinus mucosa caused by a pressure difference between the sinus and the surrounding atmosphere, when the ostium fails to equalise it.
• It occurs in flying, diving and hyperbaric therapy.
• The physics IS BOYLE’S law — at constant temperature, the volume of a gas is inversely proportional to the pressure. A sinus is a rigid box, so its gas volume cannot change; instead a pressure gradient develops across the ostium, and if that ostium is blocked the gradient is taken up by the mucosa
• The asymmetry between descent and ascent IS the key concept:
• On descent (or diving down), ambient pressure rises; the gas in the sinus is compressed, creating relative negative pressure inside. This produces mucosal oedema, vascular engorgement, transudation and haemorrhage into the sinus — a "squeeze"
• On ascent, ambient pressure falls; the gas expands, and if it cannot escape, the relative positive pressure causes a reverse block, with severe pain and even displacement of the orbital floor or dehiscence
• The same physics explains otitic barotrauma, which is commoner and affects the middle ear through the Eustachian tube
• The frontal sinus is most often affected.
• Predisposing factors — anything narrowing the ostium: an upper respiratory infection or a cold.
• Clinical features — sudden, severe frontal or facial pain during descent.
• Examination and imaging — endoscopy showing mucosal oedema and blood; and CT, where indicated, showing mucosal thickening, an air-fluid level, or complete opacification, occasionally with a submucosal haematoma
• Acute management — analgesia; topical and systemic decongestants to open the ostium; intranasal steroid; saline irrigation; and antibiotics only if secondary infection develops
• Most cases settle within days
• Surgery — for recurrent barotrauma with a correctable anatomical cause, or for persistent disease: septoplasty, polypectomy and FESS to widen the drainage pathway. This matters particularly for divers and aircrew whose livelihood depends on it
• Prevention, which is the whole of the useful advice — do not fly or dive with a cold or acute rhinitis; treat allergic rhinitis and chronic sinus disease before travel; use a topical decongestant before descent, choosing a long-acting agent so that it does not wear off mid-flight; descend slowly and ascend slowly when diving; and equalise frequently
• Aircrew and professional divers require formal ENT assessment and clearance before returning to duty