a 53-year-old woman presents with a 1-year history of chronic cough. the cough produces large volumes of grossly purulent sputum. she has a history of recurrent respiratory infections; they resulted in five hospitalizations in the past year. she also had similar complaints during the previous year. shortness of breath limits her daily activity. upon pulmonary examination, bilateral breath sounds are audible, with inspiratory and expiratory crackles at the lung bases. chest x-ray reveals increased bronchovascular markings and cardiomegaly. what is the initial diagnosis?