Brain is one of the organs with the most vigorous metabolism in the human body, which has a special dependence on oxygen, and similarly, has a special sensitivity to hypoxia. Brain tissue only accounts for 2% – 3% of the body weight, but the oxygen consumption accounts for about 20% of the whole body oxygen consumption. Brain tissue oxygen storage is small, oxygen consumption is large, hypoxia, brain oxidation metabolism will appear obstacles, brain function is impaired. The central nervous system, especially the cerebral cortex, is very sensitive to hypoxia, therefore, once hypoxia, the effect on the central nervous system is especially obvious. Hyperbaric oxygen (HBO) is considered to be one of the important means to promote the awakening of patients in long-term coma and vegetative state due to its ability to rapidly increase the concentration of oxygen in the blood, increase the oxygen content of the brain tissues, and improve the cerebral dysfunction caused by the lack of oxygen in the brain tissues, so as to promote the recovery of the cerebral function. During hyperbaric oxygen therapy, the blood flow in the vertebrobasilar artery system (posterior circulation) does not decrease, but even increases, thus the partial pressure of oxygen in the brainstem and the reticularis superior activating system, etc., relatively increases, thus contributing to the improvement of the awakening state. This is a favorable aspect of hyperbaric oxygen therapy. However, it should be noted that hyperbaric oxygen can constrict the carotid artery system (anterior circulation), thereby reducing blood flow to the cerebral hemispheres. Transcranial Doppler (TCD) examination shows that the anterior and middle cerebral arteries (anterior circulation) of patients in a vegetative state have a slow or bloodless blood flow, while the vertebral basilar artery system supplying the brain stem has a relatively good blood flow. Therefore, hyperbaric oxygen therapy is accompanied by increased hypoxia in the cerebral cortex as well as in the deep brain nuclei, such as the thalamus. This is the unfavorable side of hyperbaric oxygen therapy. Hyperbaric oxygen therapy has both favorable and unfavorable sides, how to solve this contradiction? Based on the above analysis, our experience is that anti-vascular spasm and vasodilator drugs are given to the patients before entering the cabin to minimize the adverse effects of hyperbaric oxygen and to exert the beneficial effects of hyperbaric oxygen.