I have a grandmother who had a lot of pneumonias. She had lung physiotherapy and one of the elements was a PEP Valve also. It is a sort of 'whistle' that you exhale into and it creates a pressure against your lungs, helping to loosen up mucus etc.
You may want to investigate or inquire about this - it is meant to be used 3-4 times a day for about 10-20 deep breaths and although I don't have the scientific data, I can see how having less mucus etc sat still in your lungs can help prevent an infection from growing.
You can google 'Positive Expiratory Pressure' and see if that looks like something you would want to consider.