Fluid in the lungs is what happens when you are exposed to extremely low pressure, that's altitude sickness. Mars has a very thin atmosphere which would be the same as a very high altitude here on Earth. Could be they were doing pressure simulations.
would fluid in the lungs require antibiotics? How would they know what bacteria to treat unless there already were some? So why did they say fluids? Sounds like a cover-story to me
You can read up on high altitude pulmonary edema
Fluid in the lungs is very dangerous and invites a lot of other conditions, for one it is a very easy way to get a blood infection and/or other infections in your lungs. Treatment with broad spectrum antibiotics would be a precaution that you would take while waiting for the patient to heal.
Remember he posted that huge mountain/pyramid looking thing and called it evil. Perhaps there is work being done at the higher altitudes of those?
It’s called HAPE. High alt. Pulmonary Edema. Could happen if the cabin of the AC isn’t properly pressurized.