Respiratory index is the ratio of alveolar arterial oxygen partial pressure difference to arterial oxygen partial pressure, which is used to reflect the ventilation and oxygen exchange function of the lungs as an indicator, if the respiratory index is abnormal, we should go to the hospital in time. If the respiratory index is normal, it should be ≤1, and if it is >1, it suggests that the patient’s lung function is abnormal. If it is >2, it indicates that the patient’s lung function is seriously impaired. Respiratory index is mainly used to evaluate adult respiratory distress syndrome, but also used in the application of ventilator withdrawal and in the clinical application of acute pancreatitis. The respiratory index can be used in clinical work to monitor the changing condition of patients with respiratory distress and to assist doctors in making medical decisions. In addition, it is necessary to combine with other indicators, such as blood gas analysis, oxygen saturation, heart rate, respiratory rate, etc. to make an assessment and develop an appropriate treatment plan. Patients with abnormal respiratory indexes are advised to go to the hospital in time, and under the guidance of the doctor to clarify the cause of the disease and then actively treat it.