This disorder may follow the occlusion of sinus openings by mucosal congestion, folds or sinus polyps, preventing escape of expanding gases (Figure 8.4). The ostium or its mucosa will then blow out into the nasal cavity, with or without pain, and haemorrhage commonly follows. Bleeding from the nostril on the same side as the sinus disorder is sometimes the only manifestation. This disease is aggravated by rapid ascent, as in free ascent training, emergency ascents, submarine escape and so forth.
Uncommonly, other manifestations may develop. If the expanding air cannot escape through the sinuses, it may fracture the walls and track along the soft tissues and cause surgical emphysema. Rupture of air cells may cause severe and sudden pain, often affecting the ethmoidal or mastoid sinuses, on ascent. Occasionally, the air may rupture into the cranial cavity and cause a pneumocephalus or a small intracranial haemorrhage.