Total anecdata, but when I was college age I would get bronchitis about annually that usually started from something that would have at least 1 nostril completely blocked for a week or so. I read about neti pots, bought a pharmacy "sinus rinse" and started using it daily.
I'm 58 now and I haven't had bronchitis like I used to since.
My theory is that it not only washes out stuff that might lead to infection, but also keeps your membranes from drying out and cracking, opening a vector for them.