Instead of lying flat, it is recommended that you lie in a semi-recumbent position or on your side when you have a pneumothorax. As the abdominal organs as well as the diaphragm can be lifted upwards when lying flat, this reduces the volume of the lungs. It may also cause increased chest tightness and shortness of breath due to the pneumothorax compressing the lung tissue on the affected side, inducing symptoms such as dyspnea. In addition, lying flat may also increase the volume of return blood, thus increasing the pressure of the pulmonary circulation, and symptoms such as chest tightness of varying degrees, especially for the elderly with heart disease. The affected side should be kept in the lying position. In the case of pneumothorax, since the affected lung has been compressed, the healthy lung can play a major respiratory function at this time. If you continue to lie on the healthy side, it may limit the lung activity, thus aggravating the symptoms such as shortness of breath. It is recommended to choose the correct position under the guidance of your doctor.