End-tidal carbon dioxide partial pressure (PETCO2) refers to the concentration of carbon dioxide in exhaled breath at the end of breathing. End-tidal carbon dioxide monitoring is a non-invasive monitoring method. For critically ill patients, bedside continuous non-invasive monitoring of PETCO2 can be performed to understand the patient's ventilatory function, adjust respiratory parameters, and maintain normal PaCO2, which is beneficial to the stability of the patient's condition. For children, experts believe that compared with pulse oxygen saturation, PETCO2 can more intuitively reflect the ventilation status of children under anesthesia. For critically ill patients, bedside continuous non-invasive monitoring of PETCO2 can be performed to understand the patient's ventilation function and adjust Respiratory parameters and maintaining normal PaCO2 are conducive to the stability of the patient's condition.