I used to get bronchitis regularly (long story involving 12-hour shifts and small working office). Out of desperation one year, I finally listened to my mom and tried an old trick from my great-grandma: take a hand towel and wring it out with warm water (get as much water out as possible) right before bed. Drape the towel around the neck and use pins to hold it. Then put on two t-shirts. Stay with me, I know this sounds weird AND you'll feel like a football player... But the towel acts as a natural humidifier while you sleep, your body warming it. I've rarely had bronchitis since then, but I use the towel trick right away and it never lasts more than two days.