Kari Troland

Cerebral diffusion and perfusion deficits in North Sea divers

Background: Diving is associated with a risk of cerebral decompression illness, and the prevalence of neurological symptoms is higher in divers compared with control groups. Microvascular dysfunction due to gas microembolism and exposure to hyperoxia are possible mechanisms, which may result in cerebral diffusion and perfusion deficits. Purpose: To investigate if possible functional derangements of the microvasculature and microstructure would be more prevalent among symptomatic divers. Material and Methods: Magnetic resonance imaging (MRI) was performed in 91 former divers and 45 controls. Individual parametric images of apparent diffusion coefficient (ADC), cerebral blood flow (CBF), cerebral blood volume (CBV), and mean transit time (MTT) were generated on the basis of diffusion- and perfusion-weighted imaging. To identify regions with statistically significant differences between groups (P < 0.05, corrected for false discovery rate), voxel-wise ANCOVA analysis was performed for each of the four parametric images. Results: Significant regional group differences were found in all four parametric comparisons. Gross regional ADC differences were seen throughout the brain, including large frontal and temporal white-matter regions, the hippocampus, and parts of the cerebellum. Differences in the perfusion maps were localized in fewer and smaller clusters, including parts of the cerebellum, the putamen, and the anterior watershed regions. Conclusion: Regional functional abnormalities as measured by diffusion- and perfusion-weighted imaging were identified in the divers, and there was a partial co-localization of the regions identified in the perfusion and the diffusion images. The findings may explain some of the long-term clinical symptoms reported among professional divers.

Mortality among professional divers in Norway

BACKGROUND Diving operations are technically complex, and the underwater environment poses a high risk of fatal or near miss accidents. Furthermore, long-term effects of diving on bone, the central nervous system and the lung have been observed in divers who have not experienced any diving-related accidents. AIMS To compare total and cause-specific mortality among Norwegian professional divers by class of diving certificate, relative to the general population. METHODS Data on mortality were obtained for divers in the Norwegian Inshore Diving Registry, which comprises data on all divers with a certificate valid for professional diving after 1980. By August 2010, 5526 male divers born between 1950 and 1990 were identified, 3130 of whom were fully certified professional divers. The rest of the Norwegian male population born in the same period (1 604 147) served as referents. Data on mortality were obtained by linkage to the Cause of Death Registry. RESULTS Mortality was 23 per 1000 in professional divers and 24 per 1000 in referents. The hazard ratio was 0.79 (confidence interval [CI] 0.63-0.997). Diving-related accidents and suicide were the most common causes of death among divers. Both were significantly more common among divers with the higher level diving certificates. CONCLUSIONS Overall, mortality in professional divers was lower than that of the general population. However, professional divers had a higher risk of dying from work-related accident or suicide.

A Confirmatory Factor Analytic Study of the Wechsler Memory Scale-III in an Elderly Norwegian Sample

This study compared the factor structure of the translated Wechsler Memory Scale-III (WMS-III), which is the latest available version in Norway, with the original U.S. version. A sample of 122 healthy, elderly Norwegians (mean age: 74; standard deviation = 8.8) completed the WMS-III. The factor structure of the translated WMS-III was tested, using Confirmatory Factor Analysis, with comparison of model fit based on five a priori hypothesized models. Several model fit indices pointed to a three-factor model (working memory, visual memory, and auditory memory) providing the best fit to the data. Our study supports updated findings of the original WMS-III in nonclinical samples and suggests that the translated version is structurally equal to the original. The study supports the cross-cultural validity of the WMS-III. However, based on the present data, one might expect scores on the Family Pictures subtest to fall below scores on other WMS-III subtests in elderly Norwegians.

Diving and intrapulmonary shunting of venous gas microemboli

We have read the case report by Obad et al, 1 where a diver was subjected to three dives and heavy exercise postdive for the purpose of ‘‘further investigations’’ after he had been excluded from an experiment because of signs of intrapulmonary shunting of venous gas microemboli. There was a high bubble grade after all dives, the highest ever reported in the literature. During exercise to 85% of maximal oxygen uptake after the dives, intrapulmonary shunting was demonstrated. The experimental protocol from which the diver was excluded was approved by the local ethics committee, but the ‘‘further investigations’’ were supposedly not. The three dives exposed the diver repeatedly to arterial gas embolism. The authors are aware of the risks and are discussing possible mechanisms for brain damage in divers. We totally agree that the diver’s condition required further investigation. What the investigation needed, however, was a thorough neurologic, neurophysiologic, and neuropsychologic examination and not additional diving exposure. The authors did not discuss the well-known effects of venous gas microembolism on pulmonary hemodynamics obtained in animal studies in the early 1980s when gas microembolism was used as a model for studying adult respiratory distress syndrome. Existing knowledge should preclude this type of ‘‘further investigations,’’ which, we suppose, would not have been approved by any ethics committee. The procedure to which this diver was subjected is not in accordance with the Declaration of Helsinki.