When there is gas accumulation in the subcutaneous tissue of the chest, it is called subcutaneous emphysema. When the skin of subcutaneous emphysema is pressed by hand, it can cause the gas to move in the subcutaneous tissue, and the feeling of twisting hair or gripping snow can appear. When pressing the subcutaneous emphysema with a stethoscope, a sound similar to the twisting of hair can be heard. Subcutaneous emphysema in the chest is usually caused by gas escaping from the lesion and accumulating under the skin after damage to the lung, trachea or pleura. Occasionally it occurs as a result of localized gas-producing bacillus infection. In severe cases, the gas may spread from the chest wall subcutaneously to the neck, abdomen or other parts of the skin. Patients with subcutaneous emphysema usually have no conscious symptoms, and the only effect on the patient is difficulty in opening the eyes. Patients with mediastinal emphysema often complain of chest tightness or pain behind the sternum, and may also have hoarseness of voice. The subcutaneous tissue is swollen and has a spongy sensation to touch and a twisting and snowing sensation. If a rough crunching sound is heard along with the heartbeat, this is seen in mediastinal emphysema. Severe mediastinal emphysema may affect venous return, resulting in jugular venous dilatation, tachycardia, respiratory distress, and even heart failure. The skin of chest wall is swollen after chest injury, and if sponge sensation and twisting pronunciation are palpated by light finger pressure, it indicates subcutaneous emphysema, which is generally not easily missed or misdiagnosed. Careful clinical observation is helpful to clarify the source of emphysema. If the emphysema first manifests in the neck, its source should be considered as a possible mediastinal emphysema. X-ray examination can help to further identify the source of the emphysema.