A purring sound in the lungs when breathing is mainly considered to be caused by the accumulation of phlegm in the bronchi and lungs, which is often sticky and not easy to cough up. It is mainly caused by infections in the respiratory tract and is easily caused when there are acute bronchitis, chronic bronchitis, bronchial asthma, bronchial dilation and other diseases. You need to go to the hospital first for an examination, mainly a chest X-ray and a routine blood test. If necessary, sputum examination and bronchoscopy should also be done to determine the nature and location of the cause of the infection, and actively treat it with medication under the guidance of the doctor. In addition to anti-inflammatory and anti-bacterial, the sputum needs to be thinned and moistened in order to facilitate the discharge of sputum, and drugs such as Ambroxol granules and Chuanbei Loquat cream can generally be used.