Whether pulmonary arterial hypertension requires oxygen therapy primarily depends on the patient's blood oxygen saturation level at rest. Generally, it is recommended to measure the oxygen saturation for patients with pulmonary arterial hypertension. Due to intrapulmonary shunting and shunting between the left and right heart during pulmonary arterial hypertension, arterial and venous blood mix directly, resulting in very low blood oxygen saturation in patients. Generally speaking, if the measured blood oxygen saturation at rest is below 90%, such patients often need oxygen therapy. Even if it does not drop below 90%, patients with moderate to severe pulmonary arterial hypertension also require oxygen therapy. Oxygen therapy can improve hypoxia, significantly dilating the pulmonary vessels and thus alleviating symptoms of high pulmonary artery pressure. It is very valuable for improving patient prognosis and survival time.