Pulmonary hypertension is a common clinical condition with complex etiology, which can be caused by various cardiac, pulmonary, or pulmonary vascular diseases. The current diagnostic criteria for pulmonary hypertension are an average pulmonary arterial pressure greater than 25 mmHg at sea level in a resting state, or greater than 30 mmHg during exercise, as measured via right heart catheterization. The severity of pulmonary hypertension can be categorized based on resting average pulmonary arterial pressure levels into mild (26 to 35 mmHg), moderate (36 to 45 mmHg), and severe (greater than 45 mmHg). Echocardiography is the most important non-invasive screening method for pulmonary hypertension. Assessing the severity of moderate pulmonary hypertension not only involves the measurement of average pulmonary arterial pressure but also necessitates identifying its etiology. Since pulmonary hypertension is a disease with a complex etiology, it is crucial to first clarify the cause, and then further determine the patient's cardiopulmonary function status, whether it is in a compensatory or decompensatory stage. Additionally, it is important to determine if there are any related complications, such as pulmonary hypertension stemming from lung-induced conditions. When patients exhibit complications like pulmonary encephalopathy, acid-base imbalance, electrolyte disturbances, arrhythmias, or even shock and gastrointestinal bleeding, the severity of pulmonary hypertension can be extremely severe.