Ask DAN: Immersion Pulmonary Oedema

I had difficulty breathing during a dive and was in respiratory distress when I got back on the boat. I was later diagnosed with immersion pulmonary oedema (IPE). How can I prevent IPE from happening again?

‍DAN Answer: Pulmonary oedema is believed to be a manifestation of relative pulmonary capillary hypertension, which means there is increased pressure in the capillaries relative to the pressure in the alveoli. This condition causes fluid to leak from the capillaries into the alveoli, where gas exchange occurs, and inhibits your body from necessary gas exchange, causing you to feel like you’re drowning.

Immersion in water causes a fluid shift from the extremities to the core circulation. Normal physiology can deal with reasonable volume shifts, but factors may arise that prevent the system from handling the additional fluid as needed and can cause pulmonary oedema. These factors, for example, can be issues involving the heart chambers, valves, hypertension, pulmonary conditions, overhydration, constrictive gear, negative airway pressures (e.g., from a poorly tuned regulator), or excessive effort. Several of these factors are usually present to cause IPE.

Immersion in water always comes with some risk, but we can help mitigate these risks by hydrating appropriately (but not too much), ensuring gear fits well and is serviced, getting regular checkups, and having fitness-to-dive examinations prior to diving when your health status changes.World.DAN.org