Pressure pain in the left side of the chest during sleep is relatively common in clinical practice. The reasons for this include the following aspects. First of all, it may be due to incorrect sleeping posture, long-term left-sided lying, when sleeping, it is easy to cause the weight of the body to compress the left chest wall and soft tissues, including the rib cage. Long-term compression is likely to cause ischemic changes in the tissues, intercostals, and muscles, and the phenomenon of increased pain in the left lateral position while sleeping will occur. Second, it may also be due to diseases of the lungs and chest, including costochondritis, costal neuritis, and peripheral neuritis, all of which can easily lead to increased pain under the causative effect of compression. Finally, diseases such as pleurisy pleural adhesions to pleural effusion can cause this pain. Therefore, if you have pressure pain in the chest while sleeping on the left side, you must go to a regular hospital for a detailed examination to find the cause of the disease and to provide systematic and standardized treatment according to the cause.