Mechanism of brain and spinal cord tissue injury following decompression sickness in experimental rabbits and the effect of hyperbaric oxygen

Abstract

Objective To investigate the mechanism of brain and spinal cord injury in experimental rabbits with decompression sickness (DCS) and the effect of hyperbaric oxygen (HBO).Methods Twentyeight adult male healthy New Zealand rabbits were randomly divided into 4 groups:the normal control group,the DCS group,the safe decompression group and the HBO group,each consisting of 7 animals.The rabbits in the DCS group were compressed with air in 5 minutes to a pressure 0.8 MPa and maintained at the said pressure for 60 min,and then were decompressed to normal pressure within 5 min.The animals in the HBO group underwent the same compression and decompression procedures,as the animals in the DCS group,but were immediately put into the hyperbaric chamber to receive HBO therapy.The safe decompression group was compressed and decompressed with the profile of the Chinese Navy Diving Decompression Tables.Changes in pathological morphology and apoptosis of brain and spinal cord tissue cells in the thoracic and lumbar segments were observed with light microscopy and terminal deoxynucleotidyl transferase-mediated DUTP nick end labeling (TUNEL) method.Results For the animals in the DCS group,cavity in the white matter of the spinal cord and proliferation of gliocytes around the damaged tissue could obviously be observed.TUNEL results showed that more positive apoptotic cells were detected in the DCS group (28.29 ± 2.56)/HP,as compared with those of the normal control group (0.57 ± 0.54)/HP,the safe decompression group (2.29 ± 1.11)/HP and the HBO group (3.71 ± 1.11)/HP,with statistical significance (P ＜ 0.05).More positive apoptotic cells were also seen in the HBO group (3.71 ± 1.1 1)/HP,as compared with those of the normal control group (P ＜0.05),but were significantly less,as compared with those of the DCS group (P ＜ 0.05),also with statistical significance (P ＜ 0.05).Slightly more positive apoptotic cells were detected in the animals of the HBO group,when compared with those of the safe decompression group,but without statistical significance (P ＜ 0.05).No significant apoptosis of cells could be seen in the brain tissue.Conclusions Spinal core was the main site involved in the central nervous system injury induced by rapid decompression.The spinal cord injury induced by rapid decompression was the result of the apoptosis of gliocytes,and gliocytes might play a key role in the recovery of spinal cord injury.HBO therapy could obviously inhibit the apoptosis of gliocytes,following spinal cord injury. Key words: Decompression sickness ; Spinal cord injury ; Brain injury ; Apoptosis ; Gliocyte ; Hyperbaric oxygen; Rabbit