Recommend Treatment For Breathing Problem And Chest Congestion

Hi my mother was suffering with breathing problem. after lots of consultation she underwent goiter operation as doctor said that it was pressing the wind pipe. but after surgery she is still facing the breathing problem. now i m consulting with chest specialist. he has given her a nebulizer and mucolite saying may be chest congestion i am tensed. nobody is able to find the real problem. xray of chest was also clean. now what to do. is there any reason for breathing problem majorly in the night when she try to sleep.