BACKGROUND: It has been reported that early intervention of hyperbaric oxygen (HBO) can promote the intellectual rehabilitation of infants with severe hypoxic-ischemic encephalopathy (HIE) and can prevent mental retardation recently. However, the prior observations on the therapeutic effect almost were short-term.How about the observations on prospective efficacy and the following up on systematic intelligence test? OBJECTIVE: To investigate the short-term and long-term effects of HBO therapy on the promotion of the intellectual rehabilitation in infants with severe HIE.DESIGN: A comparative observation.SETTING: Department of Pediatrics, Affiliated Hospital, Qingdao University Medical College.PARTICIPANTS: Forty-seven infants with severe HIE (35 males and 12 females) were treated with HBO in the Department of Pediatrics, the Affiliated Hospital of the Medical College of Qingdao University from October 1996 to July 1999. All of them were consistent with the diagnostic criteria and clinical grading on severe HIE which were designed by Chinese Medical Association pediatrics committee neonate group in Hangzhou, October, 1996. Informed contents were obtained from the relatives of all the infants.METHODS: ① Grouping: The infants were randomly divided into two groups according to the order of admission, those of odd numbers were HBO group (n =24) and those of even numbers were control group(n =23). All the infants were treated with routine therapy for 3 months, in addition to HBO therapy in the HBO group, once a day for 4 courses of 10 days with the interval of 10 - 15 days since 8 to 10 days after birth. HBO chamber produced by the 701 Institute of China Ship Industry Company was used, and the therapy pressure was 0.14 - 0.16 Mpa, and the time of compression and decompression were both 15 minutes while voltage-stabilizing was 30 minutes. ② In order to evaluate the short-term and long-term effects of HBO on intellectual rehabilitation in infants with HIE, neonatal behavioral neurological assessment (NBNA) was employed at 7 and 28 days after birth, and Bayley scale of infant development (BSID) was got at two years old in both groups, as well as Wechsler preschool and primary scale of intelligence (WPPSI) at five years.MAIN OUTCOME MEASURES: Comparison of short-term and long-term intelligence between the two groups.RESULTS: ① Results of NBNA: The NBNA score at 28 days was significantly higher in the HBO group than in the control group (P ＜ 0.01). ② Results of BSID: The score of mental development index (MDI) of BSID at two years old in the HBO group was significantly higher than that in the control group (P ＜ 0.05).③ Results of WPPSI: The score of full-scale intelligence quotient (FIQ) and verbal intelligence quotient (VIQ) of WPPSI in the HBO group were significantly higher than those in the control group (P ＜ 0.05). In addition, the rate of mental retardation in the HBO group was significantly lower than that in the control group [12.5% (3/24), 39.1%(9/23), P ＜ 0.05].CONCLUSION: Not only the short-term intellectual rehabilitation but also the long-term one in infants with severe HIE could be promoted by HBO therapy, which might be benefit to the prevention of mental retardation.