Why Is Fibrotic Bronchoscopy Advisable While Suffering From Lung Infection?

Dear Sir, Greetings! I am Regan from Bangladesh! This is to inform you that my mother has Lung infection that s why she is suffering almost for the last three & a half months. Since last month she had been hospitalized for 8 days & we are afraid about her Lung infection because the doctors cannot find out the problem properly. We did HRCT scan but the doctor cannot find out the disease. They told that its need to do the fibrotic Bronchoscopy. Is it critical disease or something else? I am eagerly waiting for your cordial reply.. Be fine...