People do not get sick for no reason, there is a process of development of any disease, and this process allows us to better understand respiratory diseases. Everyone has had a cold, right? If not treated properly in time, the condition may worsen and progress to acute bronchitis (cough, sputum, fever), and if not treated properly in time, the condition will further develop and may progress to pneumonia (cough, sputum with fever), and may develop into chronic bronchitis. If chronic bronchitis is not controlled in time, the disease will progress further with age, forming chronic obstructive pulmonary disease, and if chronic obstructive pulmonary disease is not well controlled, it will progress to chronic pulmonary heart disease or even pneumothorax, and the disease may progress to pulmonary encephalopathy due to respiratory failure, until the patient comes to the end of life because of this disease! This is only a longitudinal approximation of the development of lung disease, and I hope you have a preliminary understanding.