After years of using 7%, my lungs refused to allow me to continue. While they didn't bleed, they went into terrible shortness of breath and bronchospasms. I was able to tolerate 3% for a year or so but then the same thing happened. I am now nebulizing with .9%, normal saline. While it doesn't kill any bacteria, it does soak the sputum that the bacteria feast on and helps me get it out of my lungs. You might want to try it.