Exhalation

Expiratory sound: Bronchial alveolar breathing sounds are heard in the normal alveolar breathing sound area. When the lower airway resistance increases, it is difficult to inhale and exhale. Because the inspiratory alveoli dilate and the airway diameter is relatively large, the inspiratory airway resistance is smaller than the expiratory phase. Therefore, the increase in airway resistance is mainly manifested in the extended expiration time