2021年7月14日 · Mucus in the lungs is known as phlegm or sputum. It is a common symptom in chronic lung diseases such as COPD (including chronic bronchitis and emphysema), cystic fibrosis, bronchiectasis, NTM lung disease or asthma.. In undamaged airways, oxygenated air moves easily through tubes, helped along by tiny hairs that line the airways called cilia.