water around lungs

Fluid in the plural space, especially with a high WBC count, is very concerning. There is literally no way your CPAP has anything to do with this because the lungs should have no communication with the plural space surrounding them. If you blew out one of your lungs so there was suddenly communication between the pulmonary and plural spaces, you'd know in short order due to the incredible pain, and acute respiratory distress.

It's either an infection, strange bacteria, possible parasite, but how it managed to get into the plural space and cause so much trouble is an interesting question, or a cancer of the blood, as plural effusion, with a high WBC count, is not uncommon with that type of cancer. If it wasn't for the high WBC count in the fluid I'd list a few other vascular causes, but CHF, etc... are not a good match because while you can get plural effusion from that, it would be a sterile, homogeneous fluid, and would not be filled with WBCs.

Good luck and keep us posted as results develop. I'm interested to hear how this turns out.

Distilled water probably is not an issue. If you bathe and brush your teeth and drink using tap water, avoiding it in your humidifier is probably not going to protect you from whatever might be in there.

At least tap water has to be tested (and has to pass). Distilled water might as well be called "Distilled" water, because we have no idea of the chain of custody from the point it is distilled, or how it was protected from any possible contamination on the way from wherever it was distilled all the way to your CPAP hose. That all seems to be far less regulated than tap water is.

The difference between distilled water and tap water is the minerals, which do not evaporate in the humidifier. Your humidifier atomizes the water molecules, leaving all the other nasty molecules, including the minerals, behind. So what goes up the tube is essentially clean, uncontaminated, distilled water, even if you fill the tub with tap water. The minerals will precipitate onto the sides of the tub, however.

Just make sure the hose dries out promptly every single day, and rinse it out occasionally. That is all you need to keep stuff from growing in it, regardless of what water you use. Do only that, and you've all but eliminated any issues that tap or distilled water could cause.

There is no promise that distilled water is sterile, unless it is USP distilled STERILE.