Yesterday, the sputum culture came back and we discovered that there was probably a gram negative bacteria in your lungs. In other words? A second lung infection. It's hard news, but it isn't a surprise. There are two doctors I go to in the NICU for honest answers, and when I did yesterday, he revealed that there are very few things that could cause the rapid, precipitous decline that you experienced over the weekend: a collapsed lung or an infection.
I suppose that the only good thing is that we have an answer. In the medical literature, lung infections are referred to as "profound setbacks," but at least its a "profound setback" that can be treated.