I think many here use it or the Acapella and huff coughing as part of their airway clearance. It seems all the well known bronchiectasis clinics recommend them. At least a couple of people also use the Autogenic Drainage app to help get mucus out. I just started using it after a recent bout with Covid with persistent slightly elevated temps (from lungs?) and I like it. It helps with deep breathing/huff cough.