Prevalence and causes of loss of consciousness in former North Sea occupational divers.

BACKGROUND: Loss of consciousness (LOC) is a serious event during diving. The purpose of this study wasto estimate the prevalence and causes of LOC during diving in former North Sea divers, and the impacton health-related quality of life. MATERIALS AND METHODS: Up to 1990 a total of 373 Norwegian offshore divers worked in the North Sea. From 2000 to 2011, 221 of these were referred to the Department of Occupational Medicine at Haukeland University Hospital for examination due to health complaints. They filled in a questionnaire for registration of diving experience and health complaints, including the SF-36 version 1 for the assessment of quality oflife. The questionnaire and the hospital records were systematically reviewed by 2 independent observers. Episodes of LOC during diving and the causes were registered. All participants underwent a clinical neurological examination. Electroencephalogram (EEG) and the event-related brain potential (P300) were recorded. RESULTS: One or more episodes of LOC were reported by 58 of 219 divers. LOC due to gas cut was reportedby 27 of these. Divers having experienced LOC due to gas cut had lower SF-36 sub-scores then the rest of the diving population. EEG and P300 recordings did not differ between the groups. CONCLUSIONS: A high proportion of former Norwegian North Sea divers reported episodes of LOC, for whichgas cut was the most common cause. Both hypoxia and peritraumatic stress associated with the episodecould have a long term impact on the quality of life. Neurophysiological functions, however, did not differbetween the groups.

Risk of misclassification of decompression sickness.

Decompression sickness (DCS) is classified on the basis of which organ system is affected, and neurological DCS is considered more severe than DCS in joints and skin with respect to response to recompression treatment and risk of long-term sequelae. Gas bubble formation interstitially in the tissues or in the circulation is considered to be the mechanism for all types of DCS. Ten patients diagnosed as having DCS in joints or skin, by doctors experienced in diving medicine, underwent clinical examination by a neurologist and had an electroencephalogram. Eight of the ten subjects had findings suggesting central nervous system deficits. The findings indicate that DCS of the central nervous system often accompanies DCS of the joints and skin, and that local skin and joint symptoms may draw attention away from cerebral symptoms. We recommend that all cases with DCS should initially be treated as neurological DCS.

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.

Postinfectious and chronic fatigue syndromes: clinical experience from a tertiary-referral centre in Norway.

BACKGROUND: We aimed to compare patients reporting acute infection with those reporting no infection at onset of chronic fatigue syndrome (CFS). PATIENTS AND METHODS: This study includes 873 patients with CFS referred to a tertiary centre on average 4.8 years after symptom onset. Assessment was by both observer query and self-reports. Antibody analyses against infectious agents including Epstein-Barr virus and enterovirus were performed in a majority of patients. RESULTS: Females comprised 75.3% of the patient group, and the mean age was 33 years. Initial infection was reported by 77%. There was no difference as to antibody analyses. Logistic regression showed that initial infection was independently associated with acute onset of fatigue, improvement of fatigue at referral, and the following symptoms at referral: fever, tender lymph nodes, and myalgia. CONCLUSION: CFS patients with initial infection as a precipitating factor more often report acute onset of fatigue, more frequent accompanying symptoms, and more frequent improvement on referral than do patients without initial infection.

Reduced health-related quality of life in former North Sea divers is associated with decompression sickness.

BACKGROUND: Diving is associated with long-term effects on several organ systems. AIM: The objective was to investigate the impact of decompression sickness (DCS) and diving exposure on health-related quality of life (HRQL) in former Norwegian North Sea divers. METHODS: HRQL was recorded by a questionnaire in the cohort of 375 Norwegian North Sea divers registered before 1990. Demographic data, relevant health data and data on diving education, history of DCS and SF-36 were recorded in 230 divers. RESULTS: All SF-36 sub-scores were significantly reduced compared with Norwegian norms. Reduced scores were seen for all scales among divers who reported previous DCS compared to those without DCS. A decreasing trend in scores was seen when comparing no DCS, skin or joint DCS and neurological DCS. There was a decreasing trend in scores related to number of days in saturation and maximal depth. Stratification on DCS showed that the impact of saturation diving was present only in divers with DCS. CONCLUSIONS: HRQL was reduced in this study sample of divers. Having had DCS during the diving career contributed significantly to the reduction in all SF-36 scales, and apparently neurological DCS has the most pronounced impact. Cumulative diving exposure including days in saturation and maximal depth contributed to a reduced HRQL.

Vestibular symptoms and otoneurological findings in retired offshore divers.

INTRODUCTION: Inner ear barotraumas and decompression sickness (DCS) may cause acute vestibular symptoms in divers. The result may be irreversible damage to the vestibular end organs or their central connections. We examined a group of offshore divers in order to find out how many divers experience vestibular symptoms later in life and how this was related to occupational history and objective findings. METHODS: A questionnaire was sent to 230 offshore divers (mean age 52 yr) and 166 age-matched non-diving controls. Most of the divers had retired from diving. A subgroup (n=96) of the divers was referred for examination, including a clinical otoneurological examination, electronystagmography, bithermal caloric tests, and platform posturography. In addition, 42 of the controls were examined. RESULTS: The prevalence of dizziness (28%), spinning vertigo (14%), and unsteady gait (25%) was significantly higher in divers than controls (p < 0.0005). These symptoms were strongly associated with a previous history of DCS, particularly type I, which was reported by 61% of the divers. Symptoms were less strongly associated with the number of dives. In referred divers with dizziness, the prevalence of abnormal postural sway, nystagmus, canal paresis, or pathological smooth pursuit was 32%, 9%, 7%, and 11%, respectively. DISCUSSION: Reasons for the high prevalence of vestibular symptoms among the divers are discussed. The high exposure to DCS is probably an important factor.