Thoracentesis is increasingly used in clinical practice as an important adjunct to respiratory care. Thoracentesis generally has two main purposes: First, it is a therapeutic puncture to relieve the compression of lung tissue by pneumothorax or fluid accumulation and improve respiratory function, or to inject drugs into the chest cavity for therapeutic purposes. The second is diagnostic puncture, where samples are taken and sent for examination to guide clinical diagnosis and treatment. For the possible problems in the puncture procedure, the author briefly summarizes, hoping to help clinicians, especially beginners (note: this article to deep venous catheter placement of closed drainage of the chest as an example): a. Accurate positioning This is the key to successful operation, anatomy is the basis. Generally speaking, the lower border of the right lung is in the 6th intercostal space on the midclavicular line, the 7th intercostal space on the anterior axillary line, the 8th intercostal space on the midaxillary line, the 9th intercostal space on the posterior axillary line, and the 10th intercostal space on the subscapular angle line. The inferior border of the left lung is not easily determined at the midclavicular line because of the influence of the turbid zone of the heart and the bulging zone of the gastric alveoli, but otherwise it is the same as that of the right lung. The lower border of the lung can be shifted down by one rib space in long and lean body types, and slightly higher by one rib space in short and fat body types. In fact, due to the right side of the liver, the right diaphragm can be slightly elevated about one rib space higher than the left. The common pneumothorax and pleural effusion have their own techniques in localization. The gas is free in the upper part of the chest cavity, but it can also be seen in the peripheral type, that is, the lung tissue is concentrated and compressed toward the hilum. Combined with the results of chest examination, the puncture point is usually taken as the 2nd-3rd intercostal space in the midclavicular line or the 4th intercostal space in the anterior axillary line, and the 4th-5th intercostal space in the midaxillary line. When a small amount of pleural fluid needs to be characterized, this location can be selected for needle entry, but it must be held well, preferably under the guidance of imaging localization. When the amount of fluid accumulation is large, puncture is performed in the most obvious part of the chest percussion turbid sound, usually the 5th intercostal area in the anterior axillary line, the 6th-7th intercostal area in the mid-axillary line or the 7th-8th intercostal area in the posterior axillary line and the subscapular angle line as the puncture point. In case of limited pneumothorax, encapsulated pleural effusion, etc., imaging localization is required to guide the operation. It is important to note that in some patients with pleural effusions who initially have a large volume of fluid and whose diaphragm is elevated after drainage, the site where the cloudy boundary was evident at the initial puncture may change and the puncture point must change accordingly. This must be noted especially in patients who have had a lobectomy. The selection of position is also important. Pneumothorax is usually done in the prone or semi-prone position, and pleural effusion is usually done in the recoil or semi-prone position. If accurate positioning is the first step to success, then successful anesthesia is half of the operation is completed. Conventional anesthesia procedure, take the upper edge of the next intercostal rib as the puncture point, which is not easy to damage the vascular nerves, and play orange peel-like mound under the skin, then enter the needle while drawing back, if drawing back coagulable blood, suggesting possible misperforation of blood vessels, immediately stop pushing the anesthetic, change the depth or direction of needle entry, retreat the needle to the skin if necessary, or re-elect the puncture point, and closely observe the patient’s reaction. Once the thoracic cavity is entered and gas or fluid is withdrawn, continue needle feeding should be stopped to prevent damage to the lungs. Third, fix the puncture needle The feed length of the puncture needle can be roughly estimated according to the feed length of the anesthesia needle, enter vertically into the subcutaneous and then feed the needle while pumping back until there is a sense of falling into the pleural cavity, fix the puncture needle to prevent it from moving back and forth to damage the organs or exit the pleural cavity. Fourth, the drainage setting after the completion of the operation prevents a large amount of drainage in a short period of time, which can lead to pulmonary edema due to rapid lung reopening and even more serious respiratory distress due to rapid deterioration of oxygenation status. Generally speaking, the first drainage should not exceed 600 ml, and thereafter it should be controlled at about 1000 ml, but sometimes it can be handled flexibly according to the actual situation of the patient, and the patient’s reaction should be closely observed and the blood pressure should be monitored if necessary. V. Complications of thoracentesis In addition to pleural reaction, hemothorax, pneumothorax, bleeding from the puncture port, chest wall cellulitis, abscess chest, air embolism, diaphragm injury, etc. can also be complicated. Injury to the lung can easily lead to hemopneumothorax, and injury to the liver can cause hematoma or hemorrhage. Accidental injury to the lung is often caused by entering the needle too deeply or scratching the pleura of the dirty layer. In mild cases, there are no obvious symptoms and can heal spontaneously, while in severe cases, respiratory distress occurs and imaging can show the manifestation of hemopneumothorax. Injury to the liver is most commonly caused by inaccurate positioning or tilting the needle direction toward the abdominal cavity, resulting in a small amount of bleeding or hematoma formation in mild cases, which can be self-absorbed in a short period of time, and in severe cases, hemorrhage or even hemorrhagic shock, which is usually accompanied by discomfort in the liver area. If the puncture operation is suspected to have the possibility of organ damage, relevant tests should be performed as soon as possible for immediate treatment.