The symptoms of headache, chest tightness, shortness of breath, and weakness of limbs are considered to be caused by ischemia and hypoxia in the brain, and chest tightness and shortness of breath are the primary diseases that cause ischemia and hypoxia in the brain. In addition, it can also be seen in patients with pulmonary embolism. Patients with pulmonary embolism have reduced effective ventilation and will have symptoms of chest tightness and shortness of breath, and the brain will also show symptoms of headache and weakness when there is a lack of oxygen in the brain.