Pneumothorax (pneumothorax) is a condition in which gas enters the pleural cavity and causes pneumatization, called pneumothorax. Mostly due to pulmonary diseases or external forces that rupture the lung tissue and dirty pleura, or rupture the fine emphysema bubble near the surface of the lung, the air in the lung and bronchus escapes into the pleural cavity. Pneumothorax caused by trauma to the chest wall or lung is called traumatic pneumothorax; pneumothorax caused by rupture of lung tissue due to disease is called “spontaneous pneumothorax”, and pneumothorax caused by artificially injecting air into the pleural cavity due to treatment or diagnosis is called “artificial pneumothorax”. Pneumothorax can be divided into closed pneumothorax, open pneumothorax and tension pneumothorax. Spontaneous pneumothorax is mostly seen in young and middle-aged men or those suffering from bronchiectasis, emphysema and tuberculosis. This disease is one of the pulmonary emergencies, serious cases can be life-threatening, timely treatment can be cured. 1.Examination 1.Imaging X-ray examination is an important method to diagnose pneumothorax. Chest X-ray as a routine means of pneumothorax diagnosis, if there is a high clinical suspicion of pneumothorax and the posterior anterior chest X-ray is normal, lateral chest X-ray or lateral recumbent chest X-ray should be performed. Most of the pneumothorax chest films have clear pneumothorax line, which is the junction line between the atrophied lung tissue and the gas in the pleural cavity, showing the convex line shadow, and the pneumothorax line is a translucent area without lung texture outside, and the compressed lung tissue inside the line. The mediastinum and heart can be displaced to the healthy side when there is a large amount of pneumothorax. In the case of combined pleural effusion, the pneumothorax surface can be seen. A restricted pneumothorax is easily missed on posteroanterior X-ray, and lateral chest radiographs can assist in the diagnosis, and can also be detected by turning the body under X-ray fluoroscopy. A mediastinal emphysema should be considered if there is a transilluminated band around the parietal border of the heart. Chest radiograph is the most commonly applied test to diagnose pneumothorax, and CT is a good diagnostic aid for small amount of pneumothorax and limited encapsulated pneumothorax. In addition, CT scan is the only effective means to differentiate pneumothorax from certain difficult cases (e.g. surgical emphysema with no obvious lung compression and asphyxia, complex cystic lung disease with suspicious pulmonary pneumothorax, etc.). 2.Signs The signs of pneumothorax depend on the amount of air accumulation. A small amount of pneumothorax may have no obvious signs; when the amount of gas is large, the affected side of the chest is full, the respiratory movement is weakened, the palpatory fibrillation is weakened or disappeared, the percussion sound is drummed, and the auscultatory breath sounds are weakened or disappeared. In patients with emphysema complicated by pneumothorax, although the respiratory sounds are weakened on both sides, the weakening on the pneumothorax side is more obvious, even if the amount of pneumothorax is not much, so attention should be paid to the left-right comparison and the up-down comparison during percussion and auscultation. The mediastinum is shifted to the healthy side when there is a large amount of pneumothorax. In right-sided massive pneumothorax, the hepatic turbid boundary is shifted downward, and in left-sided pneumothorax or mediastinal emphysema, a click sound or high-pitched metallic sound consistent with heartbeat is heard at the left sternal border (Ham-man sign). The presence of tension pneumothorax should be considered when the patient presents with cyanosis, profuse sweating, severe shortness of breath, tachycardia and hypotension. 3.Intra-thoracic pressure measurement is helpful for pneumothorax typing and treatment. 4.Blood gas analysis and pulmonary function test Most patients with pneumothorax have abnormal arterial blood gas analysis, with PaO2 below 80 mmHg in more than 75% of patients. 16% of patients with secondary pneumothorax have PaO2 < 55 mmHg and PaCO2 > 50 mmHg. pulmonary function test is not recommended because it is not very helpful to detect the occurrence of pneumothorax or the size of the volume. 5.Thoracoscopy The site of pleural rupture and the underlying lesion can be clarified, and treatment can be carried out at the same time. Diagnosis Based on clinical manifestations, signs and imaging data, the diagnosis of pneumothorax is usually not difficult. Although clinical manifestations including the degree of dyspnea are not reliable indicators of the size of pneumothorax, pneumothorax can often be detected based on symptoms and physical examination. Many patients, especially those with primary pneumothorax, do not present to the hospital for several days after onset because of mild symptoms, and 46% of patients with pneumothorax present after 2 days. This clinical feature is important because the recurrent pulmonary edema that occurs after lung re-expansion may be related to the length of time the lung has been compressed.