OTO 2001/090

A double blind study of the neuropathology in goats exposed to hyperbaric conditions

A number of goats exposed to numerous simulated dives by the Defence Evaluation and Research Agency (DERA) had reached the end of their natural lives and were planned to be culled. Some of these goats had experienced, and been treated for decompression sickness while others had shown no clinical signs. The study was designed in such a way that the material was to be examined without knowledge of the decompression history of the goats. A blinded detailed examination of formalin-fixed, paraffin-embedded central nervous system (CNS) material stained by haematoxylin and eosin and glial fibrillary acid protein (GFAP) immunohistochemistry found that lesions of decompression sickness are more likely to be found in animals that have experienced clinical signs of decompression sickness than those that have not. The study also illustrated that the extent of axon degeneration increased with age, however; no evidence was found for an accumulation of damage to spinal cord axons in animals exposed to repeated hyperbaric conditions over that found in non-exposed animals. These conclusions are drawn from examination of post-mortem material derived from 30 exposed goats and 6 control animals. The low number and suitability of the control animals makes it impossible to state categorically whether this age related incidence of axon damage in the animals exposed to hyperbaric conditions was greater than would be expected as a normal ageing phenomenon.

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Updated 2021-04-14