Bronchoalveolar breath sounds can be heard in the area of normal alveolar breath sounds. Both inspiration and expiration are difficult with increased lower airway resistance. Because of the expansion of the alveoli in the inspiratory phase, the diameter of the airway is relatively large, so the airway resistance in the inspiratory phase is smaller than that in the expiratory phase, so the increase in airway resistance is mainly manifested in the prolongation of expiratory time. The strength of alveolar breath sounds in normal people is related to the depth of respiration, the elasticity of lung tissues, the thickness of the chest wall, as well as the age and gender of the examinee. What are the relevant examinations for prolonged expiratory sounds? 1, X-ray examination: the thorax is expanded, the rib gap is widened, the ribs are parallel, the activity is weakened, the diaphragm is lowered and flattened, and the translucency of the two lung fields is increased. 2.Electrocardiography: generally no abnormality, sometimes can be low voltage. 3.Respiratory function test: it is important for diagnosing obstructive emphysema. 4.Blood gas analysis: If there is obvious hypoxia carbon dioxide retention, the partial pressure of arterial blood oxygen (PaO2) decreases, the partial pressure of carbon dioxide (PaCO2) increases, and there may be uncompensated respiratory acidosis with decreased pH value. 5.Blood and sputum examination: generally there is no abnormality, when secondary infection, it seems to be the manifestation of acute attack of chronic bronchitis.