Hello, Accumulation of fluid around the lung called pleural effusion which impair the expansion of lung. Numerous medical condition can cause pleural effusion like- pneumonia, tuberculosis, congestive heart failure, cirrhosis, end stage kidney disease, cancer, nephrotic syndrome. You should consult the treating doctor for exact cause of the disease. Some investigations like chest x ray PA- view, tuberculin test, CT scan chest, echocardiography, liver & kidney function test, pleural fluid analysis. The treating doctor will prescribe drug according to the cause like antibiotic for bacterial infection, diuretics and other medications for CHF, chemotherapy and radiation therapy for cancer treatment. But first of all Thoracocentesis should be done to make the breathing easier. Take care of your husband, bye.