European isolation and confinement study. Mental performance.

Six EMSInauts were confined for 28 days in a hyperbaric chamber complex at a low overpressure. During this period they were repeatedly given four different standard mental performance tests: (1) Operational Test of sustained attention vigilance; (2) short-term memory; (3) visual reaction time; and (4) cognitive evoked brain potentials (N100 and P300). The aim of the study was to determine whether there were any general or specific effects on mental performance during the isolation period. For the simple mental performance tests (operational test and visual reaction time), a distinct learning effect over the 28 days of isolation could be detected. On the more cognitive demanding tasks such as in the short-term memory test, patterns of impairment were found. Of the cognitive evoked brain potentials recorded, the noncognitive N100 wave latency was unchanged throughout the isolation period. The P300 wave latency, related to cognitive functioning, showed lower values in the middle and higher values at the end of the isolation period, compared with the pre-isolation values. Although a few individual, transient impairments of function were noticed in the more demanding tests, it is concluded that the mental performance of the six EMSInauts appeared to remain basically unchanged throughout the isolation phase, both at the group level and the individual level.

European isolation and confinement study. Group functioning and communication.

Six EMSInauts were isolated in the hyperbaric chambers at NUTEC for a period of 28 days at 5-msw overpressure. Based on previous studies of analogous conditions, the hypothesis was advanced that group and communication problems could possibly occur during the isolation period, and that this could be partly related to personality aspects. The scientific methods for the present study consisted of the following: (1) the team members were systematically observed through wide-angle cameras, and the activities in the working chamber were taped during the entire isolation period; (2) daily questionnaires regarding group functioning and communication were administered; and (3) post-isolation assessment interviews were given. Results were obtained by analysis of: (1) video tapes from the daily meetings; (2) questionnaires on group behavior and communication; (3) post-isolation interviews; and (4) personality inventories (DMT, Helmreich Test, MMPI). The following observations were made: 1. All team members were able to complete the 4-week isolation period while remaining functioning. 2. The commander became ever more central during the isolation period. Communications went more directly through him and less between the EMSInauts. At the same time he became evaluated less positively by the other EMSInauts. 3. There was a steady increase in emotional responses among all EMSInauts during the isolation period. In particular, there was an increase in negative emotional content. 4. Week 3 was evaluated by the EMSInauts as being the most positive period. They scored themselves then as being very task oriented. 5. The EMSInauts gave a low score to problems with the mission control room personnel, indicating few problems. There were indications of temporary increases during week 2 and at the end of the isolation period. In summary, it can be stated that all team members completed the 4-week isolation in good condition. The commander developed increasing control during the isolation period, which resulted in increasingly negative responses towards him from the other team members. During the isolation period there was an increase in emotional content. In particular, during the last week there was an increase of frustrations. There were few communication problems with mission control, though the scores were elevated in week 2 and on the final two days.

European isolation and confinement study. Workload and stress: effects on psychosomatic and psychobiological reaction patterns.

Six healthy males, the EMSInauts, were isolated in hyperbaric chambers for a period of 28 days at 5-msw overpressure. During that period they had to carry out meaningful operational and research tasks in addition to monitoring their psychological and physiological reactions. The actual workload was evaluated and compared with the planned workload, and its effects on symptomatology and psychobiology. The perceived workload and its effects on psychosomatic symptomatology and on some biological indices were monitored. Thus it was possible to evaluate how the workload carried during 4 weeks of isolation affected the psychological and biological well-being of the six EMSInauts. The following three types of assessments were performed: 1. Workload assessment: The objective workload was calculated based on the schedule which was revised daily, and the actual load calculated by the commander. A workload questionnaire was administered daily after each working session. 2. Psychosomatic assessment: Morning and evening questionnaires were administered daily. The state of health and of anxiety were also evaluated. 3. Biological indices: Cortisol, testosterone, adrenalin, and noradrenaline were determined once a week. In addition, cardiac activity was monitored every day. The workload assessment showed that on the average the planned workload was accomplished in slightly less than the scheduled time. The workload was not perceived as severe in terms of cognitive, emotional, and physical load. The group rated the support received from each other and from the mission control personnel as average, with minor changes during the isolation period. They gave a high rating to the amount of control they had over their activities. Fatigue and tension were scored in the middle range. The psychosomatic assessment showed that there were few symptoms, and these were mostly of low severity. The most common symptom was general fatigue. Furthermore, minor dizziness, headache and light tremor was in some cases reported. The sleep quality was good, but complaints about poor sleep increased somewhat with the passing of time. Few and mostly minor health problems were experienced during isolation. Only one EMSInaut had to miss one day of work due to a bout of flu. The state of anxiety was below that of the general population throughout the isolation period. The biological indices used showed no evidence of stress from the workload handled during the isolation period. The level of the "stress hormone" cortisol actually decreased during isolation. The adrenalin excretion, which tends to go up during acute stress, remained unchanged during this period. Neither was there any evidence of changes in cardiac activity throughout the isolation period.(ABSTRACT TRUNCATED AT 400 WORDS)

Evoked potential and other CNS reactions during a heliox dive to 360 msw.

Six divers were compressed to 360 msw on heliox. Visual and cognitive evoked responses were performed repeatedly predive, during the dive, and postdive. The evoked response changes were compared with other neuropsychological and neurophysiological results from the dive. The individual diver analysis revealed normal visual evoked responses (P100) for 5 out of 6 divers. The diver with significant increase in P100-latency had more marked HPNS than the others. On the cognitive evoked responses, the P300-waves were not obtainable at the deepest depths (for 4 out of 6 divers) even if the shorter wave forms were normal. The P300-wave was obtainable at 354 msw and 215 msw for 4 divers, and 3 of them had increase in the P300-latency compared with their predive average. There was a significant correlation between P100 change and the sign-index on the other CNS-tests. In conclusion, valid results on the visual and cognitive evoked responses were obtained at pressure. Mild symptoms and signs of HPNS led to normal visual evoked responses, while more marked effects gave significant increases in the visual evoked latency. The more major changes in cognitive evoked responses at pressure, even on minor HPNS-affected divers, indicated that higher cortical functions are affected at high pressures (greater than 300 msw).

Neuropsychologic effects of saturation diving.

Neuropsychologic status of saturation divers was assessed before and after 300-500 msw dives (deep saturation diving--DSD group) and before and after 3.5 yr of ordinary saturation diving (saturation diving--SD group). Average baseline results showed the divers to be slightly superior to nondiving controls. Mild-to-moderate neuropsychologic changes (greater than 10% impairment) were found in measures of tremor, spatial memory, vigilance, and automatic reactivity in 20% of the divers after deep dives (DSD group). One year postdive no recovery was observed except for a vigilance test. In the SD group, 20% of the divers showed greater than 10% impairment after 3.5 yr of ordinary saturation diving. Significant reduction in autonomic reactivity was also found and there was a relationship between low autonomic reactivity before saturation diving and number of greater than 10% impairments. For the whole group (DSD + SD divers), negative correlations were found between saturation experience and results on memory and complex visuomotor tests. Years of diving from first to last examination was positively correlated with number of greater than 10% impairments and with reduction in autonomic reactivity. No similar correlations were found to dive variables after about 3 yr of air diving. The mild-to-moderate changes seen in some divers, therefore, seem to be the effects of saturation diving. Since one deep dive may cause an effect similar to the effect of 3.5 yr of ordinary saturation diving, there is reason to believe that repeated deep diving may lead to more pronounced neuropsychologic impairment.

HPNS effects among 18 divers during compression to 360 msw on heliox.

Heliox compression deeper than 16 ATA can lead to EEG changes associated with confusion and somnolence. In man the symptoms termed the high pressure neurologic syndrome (HPNS) can also include increased tremor, memory problems, dizziness, nausea, and vomiting. In a series of 3 dives at NUTEC, a compression profile developed for operational use down to 360 msw was evaluated. In each dive 6 different divers were compressed to 360 msw on heliox. Neuropsychologic and neurophysiologic testing were performed repeatedly. The HPNS testing revealed only mild effects of the compression. Only 3 divers had impairments of more than 2 SD in peripheral motor function compared to their predive average. Memory was impaired periodically in 2 divers. The same was found for perceptual speed and reasoning. Fifty percent of the divers had an increase of more than 2 SD in postural tremor, but that had minimal effect on their motor performance. Six of the 18 divers had an EEG power spectrum with both alpha band inhibition and theta increase. While the performance impairment was most marked around 240 msw, the EEG changes occurred mainly deeper than 300 msw. In only 1 of the 18 divers marked EEG changes, marked tremor increase, and marked cognitive performance impairment were observed at the same time. Although mild HPNS was observed, the divers were little impaired during the compression to 360 msw. The results confirm that using a compression profile with rates decreasing progressively with increasing depth, and with several intermediate stops, provides fit divers at depth. By using standard batteries of HPNS testing we were able to obtain evidence for the acceptability of this compression profile.

Differential neuropsychological effects of diving to 350 meters.

Six divers were compressed on heliox to 350 m. Repeated neuropsychological and neurological tests were conducted during the dive. Averaged increased tremor during the compression was found. Two divers had major EEG changes, while two divers had a completely normal EEG. Memory was most impaired among the cognitive variables. At 350 m there was some normalization in the EEG, and the tremor levels returned to normal. Memory impairment, however, was sustained. Three months later nine divers performed an open sea dive to 300 m. Whereas minor fatigue effects were found for the experimental dive, examinations after the open sea dive indicated more specific cerebral after effects. An increased tremor, reduced hand grip strength and foot tapping speed, lowered autonomic reactivity, and memory problems were found. Some divers had unequivocal asymmetrical plantar responses and unilateral weak abdominal reflexes, accompanied by EEG changes with corresponding laterality. In three of the divers these signs were not present 1 month later.

Central nervous reactions to a 6.5-hour altitude exposure at 3048 meters.

In this study of CNS reactions to mild hypoxia, 7 subjects were decompressed to the equivalence of 3048 m altitude breathing air, for 6.5 h. On reaching 3048 m, and for every second h thereafter, a battery of neuropsychological tests were administered. In addition, blood and performance measures were sampled and a symptom check list was administered. The performance tests indicated significant effects of hypoxia. In contrast to earlier studies on grade of hypoxia and performance, no relationship between impaired performance and duration of exposure to hypoxia was found. Repeated testing throughout exposure indicated stable individual reactions. Endocrine variables did not support the hypothesis that activation or 'stress' caused the impairment observed. In addition to impaired neuropsychological test performance and impaired task performance, the subjects reported headache, weakness and some dizziness. Comparisons between different tests confirmed previous results showing that mild hypoxia yields varying degrees of impairment on different cognitive functions.

Central nervous dysfunctions after near-miss accidents in diving.

The possible differences in specific central nervous system functions in 2 groups of divers were studied: Divers with a history of diving accidents (accident group, N = 9) and accident-free divers (non-accident group, N = 15). Both groups were characterized with a mean I.Q. level (WAIS) within the normal range. Of the nine accident group divers, 8 showed abnormalities on neuropsychological tests implicating lesions on higher CNS levels. In addition, five of the accident group divers had a syndrome of subcortical/limbic dysfunctions--specific memory deficits, low autonomic reactivity, sustained attention problems, and emotional lability. The data confirmed previous findings that a severe diving accident may lead to cerebral dysfunctions. However, in contrast to the previous studies, our study indicated that divers with average intellectual levels can develop specific CNS dysfunctions after a near miss diving accident. Therefore, we conclude that a combined effect of emboli with multifocal lesions and/or a more specific effect on limbic structures represent the pathophysiology of a severe near-miss diving accident.