Claudia,
It can be difficult to differentiate IPE from other respiratory issues in the field. Symptoms could include difficulty breathing, rapid breathing, productive cough (possibly with the classic pink frothy sputum but not necessarily), and acute decompensation up to cardiorespiratory arrest. First aid would begin with immediate rescue. Removing a diver from the water may be enough to allow for recovery if the symptoms are minor, but could be problematic in a diver with a decompression obligation. Give O2 on the surface, place the diver in position of comfort (Fowler's would probably be appropriate in a conscious diver) and provide a warm environment. Escalate interventions as needed, and evacuate to an ED. If a diver has a history of IPE he/she is at increased risk of reoccurrence, and the severity of one incident is not a good predictor of the severity of future incidents.
Best,
DDM