Bronchoalveolar breath sounds can be heard in the region of normal alveolar breath sounds. When lower airway resistance increases, inspiration and expiration are both difficult. Since the alveoli in the inspiratory phase are dilated and the airway diameter is relatively large, the airway resistance in the inspiratory phase is smaller than that in the expiratory phase, so the increased airway resistance is mainly manifested by prolonged expiration time. The strength of alveolar breath sounds in normal individuals is related to the depth of breathing, the size of the elasticity of the lung tissue, the thickness of the chest wall, and the age and gender of the subject. What are the preventive efforts for prolonged expiratory sounds? 1, quit smoking: chronic bronchitis patients should not only quit smoking in the first place, but also avoid passive smoking, because the chemicals in the smoke, such as tar, nicotine, cyanuric acid, etc., can act on the vegetative nerves, causing spasm of the bronchi, thus increasing the respiratory resistance; in addition, it can also damage the bronchial mucous membrane epithelial cells and their cilia, so that the bronchial mucous membrane secretions increase, reducing the purification function of the lung, easy to cause pathogenic bacteria In the lung and bronchial reproduction, resulting in the occurrence of chronic bronchitis. 3, strengthen exercise: strengthen physical exercise to improve their own physical fitness, according to their own physique to choose medical health care exercises, taijiquan, five birds play and other items, and the use of asthma treatment belt and other medical devices to regulate and improve the function of the internal organs, adhere to the exercise, can improve the body’s ability to resist disease, the amount of activity to no obvious shortness of breath, accelerated heartbeat and excessive fatigue as the degree. Chronic bronchitis patients in remission should make appropriate physical exercise to improve the body’s immune system and heart and lung storage capacity. 4, prevention of colds: pay attention to personal protection to prevent the occurrence of colds, those who have the conditions can do cold exercise to prevent colds. 5, good environmental protection: avoid smoke, dust and irritant gas on the respiratory tract, so as not to induce chronic bronchitis.