Danilo Cialoni is the doctor in charge of heading Apnea Academy research into lung barotrauma, and I have talked to him extensively about the tests and surveys that they have been doing. At this stage he is hypothesizing that the cause is predominantly 'sudden exertion at depth,' such as during the turn at the bottom or a struggle with a holed up snapper. The idea is that huge pulmonary blood pressure, combined with a sudden tachycardia due to transfer from a sedentary (freefall) to an active (swimming ascent) state, causes leaking of blood across the capillary/alveolar membrane. Packing isn't suspected, as most Italians don't pack (or aren't allowed to pack by Pelo!), yet incidence is still reasonably high.