The normal value of venous partial pressure of oxygen is 35-40 mmHg, which mainly reflects the body’s ability to carry oxygen and respiratory function, and normal blood oxygen is relatively high in arterial saturation. When the body has special diseases, such as arteriovenous shunts or arteriovenous fistulas, the arterial partial pressure of oxygen may fluctuate to varying degrees. In respiratory failure, the venous partial pressure and arterial partial pressure of oxygen both drop significantly, suggesting a problem with gas exchange, as well as varying degrees of impairment in oxygen-carrying capacity and respiratory function. The partial pressure of venous oxygen is used as a reference indicator of respiratory function and oxygen-carrying capacity, and the arterial partial pressure is usually not checked separately in clinical practice. When checking blood gas, pH, partial pressure of carbon dioxide, partial pressure of oxygen, BE, and transdermal oxygen saturation should be clarified to make a synergistic analysis and comprehensive judgment to evaluate the respiratory function and oxygen carrying capacity.