Pulmonary embolism can be caused by the dislodgement of various emboli in the body circulation, and the most common pulmonary embolism is thrombus. The most important indicators of pulmonary embolism are d-dimer and blood gas analysis, because d-dimer is an indicator of fibrinogen degradation products, which is an important indicator for assessing the degree of thrombolysis or pulmonary embolism, and also for assessing the success of pulmonary embolism thrombolysis. Blood gas analysis may indicate whether the patient has severe hypoxemia or even shock, and is used to assess the severity of pulmonary embolism and the effectiveness of treatment.