I haven't read any responses yet, but here is my 2 cents.
My doctors first indicator is how I feel. There have been times that I haven't had a drop in lung function AT ALL, but I feel its time. There have been times I have a huge drop and feel great.
For a 5% decrease, my doc will make sure I'm being compliant, factor in the season(spring/allegies). If I feel ok then she will probably have me come back in a few weeks and just up my treatments. If I feel bad THEN she will start me on orals.
10% increase automatically gets me 4 weeks of orals. Whether or not I feel good, 10% is a huge drop. We will also discuss what else I can do.
11%+ automatic hospital stay. That is too much lung function to lose. And you increase the change of never getting it back.
You might want to have an allergy/asthma test. I know this is my BIGGEST issue. I don't normally go off my cough. It varies. I do however go off the color of my mucus. Any change normally indicates a problem. (I also get a taste). I also go off my appetite. O2 stats are a big indicator as well. You can also buy at home FEV1 monitors and peak flow meters. I love it.
I have never been on gentimycin. I have been on Ceftazidime... in fact Im on it right now. Along with nafcillin and amecasin. But my doctor also draw blood traughs to make sure the levels aren't too high. My doctor now likes to change meds every visit. However when I was younger it was ALWAYS tobramycin and maxipime.
Also I have pfts OFTEN in the hospital. I get them the day I come in, and once a week every week I am in. I also have a 4 weeks follow up for PFTs