Factors affecting the effect of hyperbaric oxygen therapy on cerebral dysfunction after cardiopulmonary resuscitation: 1. Cardiac arrest time and effective duration of cardiopulmonary resuscitation: for patients with cardiac arrest time over 10 min, none of them recovered consciousness with HBO treatment, and among patients with cardiac arrest of 4~10 min, one case achieved significant effect only after insisting on HBO treatment for 50 times. Therefore, we should not easily give up HBO treatment for critically ill patients. 2.In the case of stable vital signs and no contraindications, perform hyperbaric oxygen therapy as early as possible: Based on successful cardiopulmonary resuscitation, the earlier the start of HBO, the better the clinical treatment effect, that is, the time from the onset to the time of HBO treatment is within 12h. It has also been reported that striving to perform HBO treatment within 10 h before the onset of cerebral edema is the key to improve the success rate of resuscitation, and HBO should not be used as the last remedy for cerebral resuscitation. As long as there is no contraindication to HBO, HBO treatment should not be easily abandoned, and a long course of HBO treatment can be tried for patients with severe central nervous system damage, so that some patients with decortical state can be revived. 3, should not ignore the comprehensive treatment: such as stabilization of the internal environment to ensure effective circulation; pay attention to the control of cerebral edema; pay attention to strengthen respiratory management; active hypothermia treatment; correct acidosis and pay attention to nutritional support and other treatment. 4.Focus on objective evaluation in treatment to assess the prognosis: before and during HBO treatment, the central nervous system function score, such as MMSE, is performed regularly; EEG, cognitive function, brainstem auditory and visual evoked potentials are examined to evaluate the prognosis. 5.Hyperbaric oxygen treatment method: HBO treatment advocates the use of intermittent oxygen inhalation method; treatment pressure is generally 2~2.5 ATA. Closely observe the pupil, blood pressure, respiration and heart rate of the patient in the chamber. When decompression, attention should be paid to the phenomenon of intracranial pressure rebound, and the decompression speed should be slow. In summary, hyperbaric oxygen therapy can improve brain dysfunction after cardiopulmonary resuscitation. As a non-invasive clinical treatment, hyperbaric oxygen therapy, with the increasing use of hyperbaric ICU unit (hyperbaric oxygen, intensive care and mechanical ventilation integrated into one), has long broken the traditional practice that hyperbaric oxygen therapy cannot be performed in the early stage of disease. Therefore, our department can enable critically ill patients after cardiopulmonary resuscitation to enter the hyperbaric oxygen chamber for safe and effective treatment at an early or even ultra-early stage.