There are many reasons for chest distension, including breast diseases, intrathoracic diseases, cardiac diseases and so on. 1. Breast diseases: female patients with breast swelling should pay attention to the occurrence of breast hyperplasia, breast fibroadenoma and other diseases. In addition, when women menstruate, due to changes in hormone levels in the body, there will also be symptoms of chest swelling. 2. Intrathoracic diseases: such as spontaneous pneumothorax, tuberculosis, pleural effusion caused by various reasons, thoracic tumors, etc., which can lead to chest swelling symptoms. 3. Heart disease: such as coronary heart disease, due to insufficient blood supply to the heart muscle, it can lead to chest distension, chest tightness and other symptoms. In addition, patients with cardiac insufficiency, due to the large amount of blood stagnation in the lungs, patients can also feel chest swelling, chest tightness and other symptoms. Patients with cardiac neurosis can also experience chest swelling and tightness. Chest distension may also be due to other reasons, it is recommended that patients go to the relevant departments of regular hospitals in a timely manner, under the guidance of specialized physicians to avoid delays in the condition.