Ayisha,
Nicely done and very thorough.
There is a difference between true immersion pulmonary edema and pulmonary edema that is aggravated by, or occurs in conjunction with, immersion. True IPE is often seen in triathletes or military special operations divers whose cardiac outputs are extremely high. In these individuals, the pulmonary arteries fail to dilate sufficiently in response to the increased blood flow brought on by the combination of immersion, exercise and cold water, though as you noted, IPE has occurred in warm water as well.
Other divers with pre-existing cardiac problems may have no symptoms while on the surface, but the fluid shift brought on by immersion can overwhelm a heart that's not working as efficiently as it should, and blood can back up in the lungs, with resultant pulmonary edema. This is cardiogenic pulmonary edema that's aggravated by immersion and should be differentiated from true IPE.
Negative pressure pulmonary edema has been documented in post-surgical patients. It typically happens in young, athletic males who are extubated (have breathing tubes removed) after surgery and experience subsequent upper airway edema. Attempting to inhale through an airway that's swollen can create a negative pressure in the lungs, which can draw fluid from the pulmonary capillaries and cause pulmonary edema. I've heard rumblings of it in divers, but to my knowledge it hasn't been reported in the literature, so if you have references would you please share? We've been involved with one possible case of it in a diver and even spoke with the equipment manufacturer, but that case was confounded by other medical factors so ultimately we couldn't pin it on NPPE.
Best regards,
DDM