Emotional and physiological effects of nitrous oxide and hyperbaric air narcosis.

Measurements of seven self-reported emotional states (happiness, activity, fear, anger, depression, fatigue, and anxiety) and three physiological variables (heart rate, systolic blood pressure, and diastolic blood pressure) were made among 16 subjects under four conditions: all subjects breathing normobaric air; several days later, immediately after half the subjects had breathed 30% nitrous oxide and the other half had breathed nomobaric air; the following day, subsequent to exposure of all subjects to a simulated depth of 57 m on air in a hyperbaric chamber; and several weeks after the hyperbaric chamber exposure, with all subjects breathing nomobaric air. The results showed that the physiological responses of the group that breathed nitrous oxide did not differ significantly from the control group following the hyperbaric chamber exposure, while self-reported happiness was lower among the nitrous oxide group than among the control group following hyperbaric chamber exposure. Nitrous oxide does not appear to benefit emotional or physiological adaptation to nitrogen narcosis associated with breathing hyperbaric air, and may even impair emotional adaptation, at least under these experimental conditions.

Personality and demographic variables related to individual responsiveness to diving stress.

Thirty U.S. Navy divers were tested for 4 personality and 2 demographic variables. They subsequently were exposed to the stress of being pressurized in a small diving chamber for several hours. Stress responsiveness to this condition was assessed using 3 physiologic and 4 subjective emotionality measures before and after the dive. These physiologic and emotionality measures were factor analyzed and correlated with personality and demographic variables. Difference scores among the physiologic and emotionality measures, indicating responsiveness to stress, correlated significantly with education, diving experience, internality-externality, disinhibition, and socialization. These data indicate that measures of achievement (i.e., diving experience and education), perceived control, sensation seeking, and social adjustment are useful in accounting for individual differences in acute emotional and physiologic responsiveness to stressful diving conditions.

Biochemical and mood responses predictive of stressful diving performance.

Measures of six self-reported moods (assessed using the Mood Questionnaire), serum cholesterol levels, and serum uric acid (SUA) levels were obtained from 26 divers attending the Saturation Diver Training (SDT) course, the most sophisticated and arduous diving course offered by the U.S. Navy. These measures were correlated with various types of diving activity that occurred during the seven years following graduation from the SDT course. Multiple regression analyses showed that two moods, Fear and Happiness, from the Mood Questionnaire, were independently related to years of subsequent diving experience, while mood Fear and cholesterol levels were associated with total number of dives made during this period. The number of dives made to depths of over 100 feet of sea water was related independently to cholesterol levels and mood Happiness. A high frequency of saturation diving (i.e., dives that last for periods in excess of 12 hours) was found for divers with high SUA levels and low scores on mood Fear. Variations in significant mood and biochemical measures across the different types of diving criteria are discussed in terms of the level of stress involved, prior diving experience, psychological traits including perceived control and achievement motivation, and attitudes formed toward diving during the SDT course.

Comparison of diving experience factors between divers classified as positive and negative for bone cysts.

Official U.S. Navy diving records for enlisted divers who were 35 years of age and older were examined for differences in diving experience between those who were classified as positive or negative for bone cysts. One-third of the divers (n = 31) were classified as positive, and two-thirds (n = 62) as negative, for bone cysts. Diving experience factors included total years of diving experience, frequency of dives between 15 and 31 m, frequency of dives deeper than 31 m, number of saturation dives, number of dives involving decompression, and number of cases of decompression sickness. None of these factors differed significantly between the two groups. While previous findings showed that bone cysts are twice as prevalent among divers as among a comparison group of Navy enlisted men matched to divers for age, rank, and occupational specialty, these results indicate that this high prevalence rate does not appear to be related to specific types of diving exposure. Other environmental factors such as long-bone injury, disease, or exposure to hazardous or toxic substances may account for differences in the prevalence of bone cysts between the two groups.

Altered circadian periodicities in oral temperature and mood in men on an 18-hour work/rest cycle during a nuclear submarine patrol.

A group of nuclear submariners was studied to examine whether an 18-h routine (6-h on, 12-h off watch) during a 10-week submerged patrol affected the 24-h circadian rhythm in oral temperature, Thayer's activation, Mood 'Activity' (MA) and Mood 'Happiness' (MH). They were observed during three phases of the patrol: Phase 1, the beginning 8-day period; Phase 2, the middle of the voyage; and Phase 3, the last 7-8 day period. The group-synchronized 24-h rhythm in oral temperature disappeared during Phase 3. The group-synchronized 24-h rhythms in Thayer's activation and in MA and MH disappeared during Phases 2 and 3. A group-synchronized 18-h rhythm was not produced in any of the variables in any phase, except MH during Phase 2. Periodicity analysis of the individuals' data showed that a loss of 24-h rhythmicity in oral temperature was due not only to reduced circadian amplitude but also to a dispersion of Time of Peak (TOPs). Loss of 24-h rhythm in 'Activation', 'Happiness', and 'Activity' was predominantly due to a wider dispersion of TOPs. The 18-h routine did appear to exert a small modulating effect on rhythmic activity in the variables examined in this study. Since the sleep/wakefulness cycle was well entrained by the 18-h routine, the submariners experienced a spontaneous internal desynchronization between the activity cycle and the cycles or oral temperature and psychological states. The performance and health consequences of this chronic dyschronism have yet to be explored. We suggest further research to determine the usefulness of an index of synchronization among the physiological and psychological variables, and the relationship of the desynchronizing effects to performance.

Fetal development: effects of stimulated diving and hyperbaric oxygen treatment.

Fetuses from hamsters exposed to repetitive 5.2-ATA (140 fsw) air dives during early pregnancy showed no significant differences from the control group in birth weight, frequency of malformation, or death. Also, exposure of mothers to hyperbaric oxygen as required for treatment of decompression sickness (DCS) has no adverse effect on fetal development or survival. Although the number of females who suffered and survived DCS in this study was small (n = 3), teratogenic effects were nevertheless found among the fetuses of this group. In fact, at least one fetus from each female undergoing DCS was found to have serious malformations. These results suggest that DCS during early organogenesis may have significant deleterious effects on fetal development.

Serum ferritin increases during deep saturation dives.

Serum ferritin levels were determined in six U.S. Navy divers during a 29d helium-oxygen saturation dive. Progressive increases in serum ferritin were observed during compression. These increases were maintained during decompression and for 1 week postdive. No relationship was found between serum ferritin increases and the development of decompression sickness (DCS). However, the two divers who subsequently developed DCS had significantly higher serum ferritin levels than those divers who remained free of DCS. These findings indicate that DCS does not result in differential serum ferritin variability and may, therefore, not be involved directly in aseptic bone necrosis (ABN) as postulated earlier by others. However, high baseline levels of serum ferritin may be involved in both DCS and ABN.

Medical evaluation of fire fighters: How fit are they for duty?

Aside from the obvious dangers to life and limb associated with the job, fire fighting subjects the body to environmental and physical stressors that can adversely affect various systems. In fact, the effects of these stressors on the cardiovascular system have made coronary heart disease a greater killer among fire fighters than among other occupational groups. The approach to medical evaluation of fire fighters presented here is based on an appreciation of these stressors.

Comparison of long-bone radiographs between U.S. Navy divers and matched controls.

The long-bone radiographs of a group of nondivers consisting of 177 U.S. Navy enlisted men were compared to the long-bone radiographs of 93 U.S. Navy enlisted divers who were 35 years of age and older. The nondiver control group was matched to the diver group for age, rank, and occupational specialty. Divers were found to have significantly more films classified as positive for aseptic bone necrosis (ABN) and bone cysts than nondivers, while the nondiver group had more films classified as doubtful for ABN than the diver group. The two groups were similar in the number of members classified as having bone islands and sclerotic areas. X-ray classifications by highly experienced radiologists were found to be only moderately reliable. These data indicate that diving as practiced by the U.S. Navy contributes independently to the development of ABN and bone cysts evidenced among divers in this age group. Some caution must be exercised in interpreting these findings, however, because of the larger number of doubtful films found for the nondiver group than for the diver group, the small number of positive and doubtful cases found in either group, the age of the samples used (35 years of age and older), and the substantial degree of unreliability demonstrated in classification of the films.

Effect of a 68-day submarine patrol on serum 25-hydroxyvitamin D levels in healthy men.

Serum 25-OH-D levels were determined for 30 submariners prior to, and near the end (day 63), of a patrol lasting 68 d. A significant reduction occurred in serum 25-OH-D levels during the patrol compared to levels obtained before the patrol. Nearly one-third of the sample has serum 25-OH-D levels that were below the minimum normal levels. The late-patrol depletion of serum 25-OH-D was not associated with lower levels of calcium. On the contrary, serum calcium levels were found to be significantly elevated during the late-patrol period compared to pre-patrol levels, even among those submariners who had serum 25-OH-D levels in the low normal or below normal range. This calcium effect may be mediated by the high levels of carbon dioxide maintained in the submarine breathing atmosphere.

Biochemical variability in a tem sports situation.

Using 13 members of an amateur softball team during the last seven games of the regular season, associations were determined between overall offensive and defensive performance and levels of serum uric acid (SUA) and cholesterol, and urinary adrenaline and noradrenaline. Skilled players were found to have significantly lower cholesterol and noradrenaline levels than less skilled players whether the games were won or lost. Adrenaline and SUA levels did not differ between the two groups nor between losing or winning outcomes. The elevated cholesterol and noradrenaline levels found among the less skilled players may indicate that although they were stressed by the discrepancy between their expectations and their performance, they nonetheless maintained perceived control over performance because of the social support and reinforcement received from the other players and the coach.

A noninvasive technique for monitoring blood urea in humans during hyperbaric exposure.

A significant increase was found in parotid gland urea excretion in nine U.S. Navy divers during 8 d of air saturation hyperbaric exposure. The parotid urea levels correlated positively and reflected changes in blood concentrations. Considering the simplicity and ease of parotid sampling, it is suggested that this method be used for monitoring blood urea levels in humans during hyperbaric exposure.

Validity of self-reported work experience among U.S. Navy divers.

The validity of self-reported diving experience was assessed among 49 U.S. Navy divers. They were asked to provide frequency estimates for the following four diving categories: total dives, dives to more than 31 m, night dives, and dives at surface temperatures of less than 10 degrees C. These estimates were then correlated with official Navy diving records. The resulting correlations ranged from nonsignificant to moderate across the four diving categories. The sample was then divided into three groups according to the extent to which they overestimated diving experience-Low, Medium, and High. The Low group made more total dives and more dives greater than 31 m than either the Medium or High groups. The High and Medium groups did not differ from each other. The groups were similar in overall health status (as indicated but sick call visits) but varied in previous diving accidents. The High and Medium groups incurred substantially more diving accidents per number of total dives made than the Low group. These results indicate that self-reported diving experience information should not be used for purposes in which accuracy is required. Determining discrepancies between estimated and actual experience may also be useful in diver selection and assignment.

Comparisons of performance effectiveness among divers.

Using a criterion of performance effectiveness derived from actual dives made under operational conditions, comparisons were made between U.S. Navy divers identified as high and low in performance effectiveness. Comparison measures included intelligence, anxiety, disciplinary problems, and incidence of decompression sickness (DCS). As expected, the most effective divers made more frequent and more hazardous dives than the least effective divers. In addition they had fewer diving accidents and a lower incidence of DCS. While the most effective divers had lower intelligence scores than the least effective group, both groups were substantially above the Navy average. These findings indicate that intelligence appears to be a critical variable in the career retention of divers, as well as the frequency and types of dives to which divers are exposed. The higher incidence of diving accidents and complications, especially DCS, found among the least effective divers may also have been involved in the lower frequency of diving observed among the members of this group.

Determinants of reading performance and achievement.

Verbal, nonverbal, demographic, and eye-hand laterality measures were administered to a sample of 34 Navy recruits attending a remedial reading program and 53 recruits who were members of a regular recruit company. Verbal intelligence scores (as determined by the General Classification Test) differentiated best between the remediation and non-remediation groups. Race (being non-Caucasian) was also associated positively with the need for reading remediation. Reading achievement within the remedial group was related positively to race (being non-Caucasian). These results indicate that low intelligence and cultural factors may account for deficient reading performance among Navy recruits. The results also show that, while self-reported measures of laterality may not be especially useful in screening for remedial readers, these measures may nontheless serve to identify neuropsychological factors that may underlie the condition.