There is a lack of effective treatments for chronic obstructive pulmonary disease (COPD) complicated with pulmonary hypertension. Previous studies have found that inhaled nitric oxide (iNO) can reduce pulmonary artery pressure and improve exercise capacity in COPD with pulmonary hypertension patients. However, the specific mechanism is unclear. The study aims to evaluate pulmonary ventilation/perfusion, pulmonary artery pressure, oxygenation, symptoms and quality of life in COPD with pulmonary hypertension patients after short-term treatment with iNO. Observing a series of pathophysiological changes caused by the treatment of pulmonary hypertension with iNO in COPD, the investigators hope to provide new theoretical basis and research ideas.