ABSTRACT
More than 90 squirrel monkeys with bilateral myringotomies (a small hole in each ear drum) were rapidly decompressed in a hyperbaric chamber according to a special diving profile in which 35% of attempts produced disorders ("hits") confined to the inner ear. Monkeys receiving inner ear hits (as determined by the sudden onset of vigorous head or eye nystagmus during decompression) were tested and killed at times ranging from 1 h to more than 12 mo following the dive. Histologically, in monkeys killed 1 mo or less after the hit, hemorrhage and/or a deep purple-staining precipitated material were frequently found in the otic fluid spaces. In those monkeys killed more than 1 mo after a hit, ectopic new bone growth in the arms of the semicircular canals was a common sequela. New bone growth never appeared in the cochlea. In unaffected ears, and in both ears of control animals, the precipitated material was somewhat less than in ears damaged by decompression; and, furthermore, new bone growth did not occur. Behaviorally, the hit monkeys showed vestibular deficits that were consistent with the structural damage revealed by histology.
Subject(s)
Decompression Sickness/physiopathology , Labyrinth Diseases/physiopathology , Animals , Ear, Inner/pathology , Labyrinth Diseases/pathology , Male , Models, Biological , Saimiri , Vestibule, Labyrinth/physiopathologyABSTRACT
The symptoms of postural instability and dizziness associated with decompression sickness could be ascribed to either damage of the vestibular apparatus or to central nervous system damage. However, a histological study of monkeys exposed to decompression reveals that these symptoms primarily result from damage to the vestibular apparatus (unless there are accompanying central deficits). Furthermore, the damage is of a type that causes new bone growth to occlude the otic fluid spaces of the semicircular canals. In some instances, there is sufficient bone growth to render the cristae ampullares as non-functional end organs. Such diminished vestibular function would present a serious threat to the diver.
Subject(s)
Decompression/adverse effects , Vestibule, Labyrinth/physiopathology , Animals , Decompression Sickness/physiopathology , Diving , Electronystagmography , Perilymph/analysis , Saimiri , Semicircular Canals/pathology , Semicircular Canals/physiology , Vestibular Function Tests , Vestibule, Labyrinth/pathologyABSTRACT
It is known that pressure equalization via the trachea may diminish or prevent lung damage in explosive decompression. In this report, evidence is presented which demonstrates that closure of the trachea does not affect lethality in mice exposed to maximally rapid decompression. This observation suggests that in maximally rapid decompression the lungs and thorax may be treated as a closed system to which Boyle's Law might be applicable.
