I have always wondered if PFT clinic machines spread bacteria among CF patients? I understand that there is a 'disposable point of contact mouth piece' used for each patient. I wonder about the filtration mechanism itself and how it filters bacteria past the disposable piece itself, through the tubing and in-though the PFT machine. Does anyone have any background information on these filters that could give me peace about letting my young son with CF PFT's do PFT's at clinic every 90 days? Since we all can have our own nebulizer machine, our own Vest machine.... then why not a calibrated PFT machine that allows us to report to the clinic?