Neuropsychological effects of diving

Ragnar J. Værnes

Department of Physiological Psychology, University of Bergen, Norway

and

Department of Clinical Psychology, University of Bergen, Norway. May 1983

CONTENTS
Acknowledgements
Introduction
General summary
Conclusions
References
  1. Værnes RJ, Darragh A. Endocrine reactions and cognitive performance at 60 metres hyperbaric pressure. Correlations with perceptual defense reactions. Scandinavian Journal of Psychology 1982;23:193-199. Abstract
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  2. Værnes RJ, Bennett PB, Hammerborg D, Ellertsen B, Peterson R, and Tønjum S. Central nervous system reactions during heliox and trimix dives to 31 ATA. Undersea Biomed Res 1982;9:1-14. Abstract
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  3. Værnes, RJ, Hammerborg D, Ellertsen B, Peterson R, and Tønjum S. Central nervous system reactions during heliox and trimix dives to 51 ATA, Deep Ex 81. Undersea Biomed Res 1983;9: In press. Abstract
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  4. Værnes RJ, Hammerborg D, Ellertsen B, Peterson R, and Tønjum S. Saturation at 51 ATA on heliox and trimix with gas change from trimix to heliox: An analysis of recovery from HPNS and nitrogen narcosis at depth. EUBS Proceedings Lubeck/Travemunde 1982. In press. Abstract
    5.  
     
  5. Værnes RJ, Eidsvik S. Central nervous dysfunctions after near miss accidents in diving. Aviat Space Environ Med 1982;53:803-807. Abstract
 

General Summary
Article 1 In this publication correlations between perceptual defense reactions (Defense Mechanism Test (DMT), Kraqh, 1955) and diver performance was examined in subjects diving to 60 msw (N=29). The subjects were diver trainees making their first chamber dive to 60 msw. Significant increase of prolactine and growth hormone, and a significant decrease of epinephrine and testosterone was found. Memory functions were significantly impaired at 60 msw. Factor analysis of the endocrine post-dive measures yielded a cortisol, a catecholamine, and a testosterone factor similar to those reported in previous stress-studies at one atmosphere pressure. Furthermore, a correlation between perceptual defense reactions, as tested by the DMT, and cortisol was also replicated. DMT also correlated with performance on a reasoning test. For the post-dive samples there was a correlation between cortisol and performance on an arithmetic test, whereas prolactine correlated with memory impairment. These results indicate that the endocrine reactions and the impairment of cognitive performance were related to an interaction between emotional factors and the nitrogen narcosis.
 
Article 2 In this publication two experimental dives to 300 msw were reported. Two groups of divers, each composed of three subjects, were compressed to 300 msw with helium-oxygen ("heliox") or helium-nitrogen-oxygen ("trimix"). Neuropsychological and neurophysiological testing was performed repeatedly during the compression and on reaching 250 msw and 300 msw. On the second day the trimix group was tested before and after the gas-change to heliox. In the heliox QrouiD there was a marked increase of tremor and EEG slow-waves, and a reduction of EEG alpha band activity and hand-grip strength. In the trimix group, visuomotor coordination was impaired. In the cognitive performance tests the heliox group was most impaired at 250 msw, whereas the trimix group was most impaired at 300 msw. Before the gas-change to heliox the trimix group showed impaired performance on several tests. After the gas-change, performance returned to predive levels, except for perceptual speed. There was an increase in tremor immediately after the gas-change. The conclusion was: There was a marked HPNS effect during compression on heliox. This effect was not observed in the trimix group. This group was, however, impaired on several cognitive tests reaching saturation depth due to the nitrogen narcosis. The tests indicated slight narcotic effects a1so after 26 hrs, which disappeared after the chance to heliox.
 
Article 3 In this publication two groups of divers were compressed to 500 msw with heliox (N=3) and trimix (N=3). The subjects were monitored using repeated neuropsychological and neurophysiological tests during compression, at stable intermediate depths, and at 500 msw. For the heliox group there was a marked increase in tremor and EEG slow waves and reduction of hand grip strength. In the trimix group no tremor increase was observed, but the EEG chances were similar to those observed in the heliox group. On motor tests only the trimix group showed impaired finger dexterity and manual dexterity. The same was found with regard to fine visuomotor coordination. Both groups showed impaired motor static control. On cognitive tests similar group differences were found. The trimix group was markedly impaired on reasoning and long-term memory, whereas only a mild impairment was found in the heliox group. Dizziness and other HPNS symptoms occurred in both groups. The conclusion was: There were marked HPNS effects during compression in both groups. Tremor seemed to be inhibited by the nitrogen in the trimix group. In addition, the trimix group was impaired because of nitrogen narcosis. Data indicated that 10% nitrogen did not inhibit HPNS effects during compression to 500 msw. The considerable differences between subjects suggested that individual susceptibility to the effects of compression is an important area for future research.
 
Article 4 In this study central nervous system reactions during saturation depth and during gas change were analyzed. The same methods and subjects were used as in article 3. During trimix and heliox saturation there was only limited normalization of the EEG. The heliox group showed a sustained and pronounced tremor during the saturation. On visuomotor and cognitive tests the heliox group performed up to pre-dive level on the third day at saturation, whereas the trimix group was severely impaired throughout the trimix saturation period. Dizziness and tremor were the main symptoms in the heliox group, whereas the trimix group reported concentration difficulties, euphoria and upset stomach during the saturation stages. During the gas change there were minor changes in the EEG. There was, however, a marked increase in tremor and improved performance on cognitive tests related to the elimination of nitrogen. Six hours after the gas change was completed, severe symptoms occurred including visual hallucinations and myoclonic jerks, lasting up to 12 hours. After this period, only mild HPNS symptoms occurred. The main problem with the gas change was the severe withdrawal symptoms described.
 
Article 5 Possible irreversible CNS changes after severe accidents under hyperbaric conditions were studied. Differences in Performance on tests, which are particularly sensitive to the organic integrity of the CNS were studied in 2 groups of divers. One group consisted of divers with a history of diving accidents (accident group, N=9) and the other of accident-free divers (non-accident group, N=15). Both groups were characterized by mean IQ levels, (WAIS) within the average range. In the accident group, 8 subjects showed abnormalities on neuropsychological tests indicating cortical dysfunctions. In addition, 5 subjects showed a syndrome of subcortical/limbic dysfunctions including specific memory deficits, low autonomic reactivity, sustained attention problems, and emotional lability. The results confirmed previous findings showing that "severe" diving accidents may lead to cerebral dysfunctions. However, in contrast to the previous studies, our study indicated that divers may develop specific CNS dysfunctions after "severe" near miss diving accidents without showing general intellectual impairment. It was concluded that a combined effect of emboli with multifocal lesions and/or a more specific hypoxic effect on limbic structures may be the pathophysiological correlates of "severe" near-miss diving accidents.


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