Pneumothorax refers to the condition where gas enters the pleural cavity. Normally, the pleural cavity is a sealed space formed by the visceral pleura covering the lung surface and the parietal pleura on the chest wall. When gas enters the pleural cavity due to some reason, causing a state of gas accumulation, it is called pneumothorax. The causes of pneumothorax can be diseases of the lungs themselves or gas produced after the lungs and chest wall are injured by external forces. Typically, the condition occurs when the pleura near the lung surface ruptures, allowing gas to enter the pleural cavity, which is referred to as pneumothorax.