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PubMed1987

Effects of cerebral and myocardial ischemia on diving bradycardia in rats.

The simulated diving in awake rats was performed before, during and after cerebral or myocardial ischemia. Diving bradycardia was attenuated at 1 hr and 3 days, but recovered 7 days after cerebral ischemia. EEG became flat promptly after cerebral ischemia and maintained low amplitude at 1 day, but recovered at 7 days. Diving bradycardia did not change at 1 hr, but was attenuated at 3 and 7 days after myocardial ischemia. A combination of cerebral and myocardial ischemia attenuated diving bradycardia through 1 hr, 3 days and 7 days. The results indicate that either cerebral or myocardial ischemia attenuated diving bradycardia.

Animals↗
PubMed1987

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.

Adult↗
PubMedDate not supplied

The diving response depresses ventilation in man.

When the face of diving animals comes into contact with water, the diving response is elicited, resulting in bradycardia, peripheral vasoconstriction and ventilatory depression. The cardiovascular aspects of the diving response have been described in man; little is known about the ventilatory depression in man. Compresses with water of various temperatures were applied to the cheeks of 16 normal volunteers and of two hyperventilating subjects. Ventilation was measured with a spirometer or with a pneumatic thoracic transducer: an accordion shaped balloon, strapped around the thorax. When the ventilation was measured with the spirometer via mouth-piece and nose-clip, the diving response caused ventilatory depressions to 60-70% of control. Water temperatures of 10, 20 and 37 degrees C had no significantly different effects from one another on ventilation. When the face of the subjects was left free of nose-clip and mouth-piece and the ventilation was measured by a thoracic transducer, the diving response caused a ventilatory depression to approximately 60% of control. The ventilatory depression did not adapt within 5 min. The two subjects who hyperventilated reacted qualitatively and quantitatively the same as the other subjects.

Adult↗
PubMed1978

Diving experience and emotional factors related to the psychomotor effects of nitrogen narcosis.

Simple and complex psychomotor performance were tested among 21 Navy divers under normal conditions and during nitrogen narcosis in simulated dives to 170 ft of sea water. Complex psychomotor performance was impaired significantly during narcosis, while simple psychomotor performance remained essentially normal. Differences between baseline scores for complex psychomotor performance (pre- and post-dive combined) and scores obtained from the two combined testing sessions administered during narcosis were correlated with official Navy records of diving experience and self-reported moods. None of the diving experience measures was associated significantly with these difference scores. The moods of Fatigue and Happiness were, however, correlated significantly with impairment. These results indicate that, although previous experience with nitrogen narcosis and diving tasks do not mediate the performance effects of nitrogen narcosis, the complex psychomotor effects nitrogen narcosis are related to emotional traits.

Adult↗
PubMed1982

The sport diving employee.

As scuba diving becomes an increasingly popular recreational activity, the probability of the occupational health physician seeing diving-related disorders increases. Recognition of many of these disorders is unlikely if not specifically looked for and if any account of diving activities is not forth-coming. Diagnosis and management of diving diseases range from simple ear squeeze to decompression sickness. There are relative and absolute contradictions to sport diving.

Decompression Sickness↗
PubMed1982

Operator performance in the one-atmosphere diving system JIM in water at 20 degrees C and 30 degrees C.

Performance and physiology of five operators of the one-atmosphere diving system JIM were assessed when diving JIM in mild (20 degrees C) and warm (30 degrees C) water. Each operator completed a minimum of 3 dives at each water temperature; during each dive 5 walks of 18 m and 3 step maneuvers were accomplished. At the conclusion of 40-min dives in water at 30 degrees C, operator heart rate averaged 151 beats/min, system interior temperature averaged 32.6 degrees C, and the mean respiration rate of operators was 28 breaths/min. Task completion times were faster in warm water. Thermal considerations in the deployment of the JIM system are discussed in relation to these data.

Adult↗
PubMed1995

Diving at altitude: a review of decompression strategies.

Diving at altitude requires different tables from those at sea level due to the reduction in surface ambient pressure. Several algorithms extrapolating sea-level diving experimental data have been proposed to construct altitude diving tables. The rationale for these algorithms is reviewed together with the conservatism of the resulting tables and decompression computer outputs. All algorithms are based on the adaptation of critical tissue tensions to altitude. These are linear extrapolation (LEM), constant ratio translation (CRT), and constant ratio extrapolation (CRE) of maximum permissible tissue tensions (M values). Either new tables using the altitude-adapted M values were put forward or sea-level tables are to be used through an operation called correction. In this review it is shown that for a given set of M values, CRT and CRE give the same result for no-decompression-stop dives; they always yield more conservative results than LEM. When decompression stops are used, CRT is more conservative than CRE. When applied to different sets of M values, the conservatism becomes a function of bottom time, depth, and altitude. The analysis shows that the tables derived using CRT of U.S. Navy (USN) schedules and CRE Boni et al. tables give more conservative results than LEM Bühlmann tables for higher altitude, longer bottom time, and deeper dives. Aviation altitude exposure decompression sickness (DCS) data are also addressed to compare different model outputs. When applied to USN and Royal Navy tables, LEM yields an altitude DCS limit of 8,581 and 8,977 m, respectively. On the other hand, the altitude limit calculated using CRE applied to USN M values and LEM Bühlmann tables is found to be below 6,000 m.

Aerospace Medicine↗
PubMed1995

Pulmonary oedema in healthy persons during scuba-diving and swimming.

The prevalence of pulmonary oedema during scuba-diving is unknown. In our referral centre for diving accidents we have observed several episodes of pulmonary oedema in four previously healthy persons while scuba-diving or swimming. Four events were documented by physical findings, typical chest radiographic changes, and arterial hypoxaemia. Four additional episodes were identified in one of the individuals by a suggestive history. No technical problems with the diving equipment were detectable and none of the individuals reported aspiration of water. In order to gather information about the incidence of pulmonary oedema, we carried out a survey among 1,250 divers. To elucidate possible underlying mechanisms of this complication we investigated forearm vascular resistance, levels of vasoreactive hormones, and left ventricular function by Doppler echocardiography, at room temperature and during cold exposure, in four patients and in healthy control subjects. We found only one additional person with a history suggestive of pulmonary oedema among 460 responders to the survey. We found no differences in forearm vascular resistance, left ventricular systolic and diastolic function, and plasma levels of epinephrine, norepinephrine, cortisol, aldosterone, renin and atrial natriuretic peptide between the patients with a history of pulmonary oedema and the control subjects. We conclude that the occurrence of pulmonary oedema during scuba-diving or swimming is an extremely rare event in healthy individuals. The mechanisms responsible remain unclear.

Adult↗
PubMedDate not supplied

The effect of peripheral vasodilators on the human diving response.

Five healthy subjects performed seated, 30-second mid-inspiratory breath hold, facial immersions in water at 1 degree C, 10 degrees C and 25 degrees C under control conditions and under the influence of three separate vasodilators. A temperature dependent bradycardia and decrease in forearm blood flow were observed during control dives. Nitropaste produced little change in diving bradycardia. Hydralazine reduced diving bradycardia only in 1 degrees C immersion. Prazosin produced consistent reductions in temperature dependent bradycardia. There was a temperature dependent change in dive forearm blood flow which was not affected by vasodilators. This data suggest the importance of acute peripheral vasoconstriction to the bradycardia of the human diving response.

Adult↗
PubMed1998

Diving response and apneic time in humans.

The aim of this study was to compare apneic time with the human diving response, defined as heart rate (HR) reduction and reduced skin blood flow, in groups with varying degrees of breath-hold diving experience. Apneic time and HR reduction at apneas in air and apneas with face immersion in cold water were thus recorded in nine groups. Skin capillary blood flow was recorded in six of the groups. All subjects received the same information on maximizing apneic duration, and no information about their progress during the apneas. The longest apneas and the most pronounced cardiovascular adjustments were found in the young, trained divers. It was found that apneic time was significantly correlated to HR reduction among the nine groups (r = 0.94, P < 0.001), and to skin capillary blood flow reduction among the six groups where the parameter was measured (r = 0.82, P < 0.05). The correlation between HR reduction and skin capillary blood flow reduction was also significant (r = 0.85, P < 0.05). When the difference in HR reduction and apneic time between apneas in air and apneas with face immersion were compared in the nine groups, it was found that all groups reacted with a more pronounced HR reduction during apneas with face immersion. All groups without prior breath-hold diving experience were found to perform shorter apneas with face immersion than apneas in air, or apneas of the same duration in both conditions, which has been reported in other studies. However, in all groups with diving experience, the apneic time was prolonged during apneas with face immersion. The results of this study suggest an oxygen-conserving effect of the diving response in trained apneic divers.

Adult↗
PubMed1998

Deaths associated with occupational diving--Alaska, 1990-1997.

During 1989-1997, the Occupational Safety and Health Administration (OSHA) recorded 116 occupational diving fatalities in the United States (OSHA, unpublished data, 1998). During 1990-1997, nine persons in Alaska died in work-related diving incidents (four were investigated by OSHA); only one had training beyond a recreational diving certificate, and three lacked any certification. In response to concerns about adequate training of occupational divers in Alaska and recent public inquiry, CDC's National Institute for Occupational Safety and Health (NIOSH) reviewed the nine occupational diving fatalities in Alaska. This report describes three of these incidents, summarizes the results of the review, and provides recommendations to improve the safety of commercial diving.

Accidents, Occupational↗
PubMed1993

Physiological responses of firefighting students during simulated smoke-diving in the heat.

While wearing a self-contained breathing apparatus and fire-protective clothing, 35 healthy firefighting students aged 19-27 years performed smoke-diving (entry into a smoke-filled room) during a simulated shipboard fire. The mean (+/- SD) ambient temperature inside the simulator was 119 +/- 12 degrees C, and the task lasted 17 +/- 4 min. All subjects were fit according to their maximal oxygen consumption, which was 52.4 +/- 5.2 mL/min/kg (4.08 +/- 0.45 l/min). During the smoke-diving the average heart rate was 150 +/- 13 beats/min (79 +/- 6% of maximal heart rate attained in a cycle-ergometer test), and the peak heart rate was 180 +/- 13 beats/min (95 +/- 6% of maximal heart rate). The estimated oxygen consumption was 2.4 +/- 0.5 L/min (60 +/- 12% of maximal oxygen consumption). Neither ability to tolerate stress (as determined by the instructors) nor previous experience in smoke-diving tasks seemed to influence the heart rate or estimated oxygen consumption during experiment. Smoke-diving was physically very demanding even for the young and fit subjects, showing the importance of regular evaluation of the health and physical fitness of every firefighter who has to carry out smoke-diving tasks.

Adult↗
PubMed2005

Cormorants dive through the Polar night.

Most seabirds are visual hunters and are thus strongly affected by light levels. Dependence on vision should be problematic for species wintering at high latitudes, as they face very low light levels for extended periods during the Polar night. We examined the foraging rhythms of male great cormorants (Phalacrocorax carbo) wintering north of the Polar circle in West Greenland, conducting the first year-round recordings of the diving activity in a seabird wintering at high latitudes. Dive depth data revealed that birds dived every day during the Arctic winter and did not adjust their foraging rhythms to varying day length. Therefore, a significant proportion of the dive bouts were conducted in the dark (less than 1 lux) during the Polar night. Our study underlines the stunning adaptability of great cormorants and raises questions about the capacity of diving birds to use non-visual cues to target fish.

Adaptation, Physiological↗
PubMed1998

An rne-1 pnp-7 double mutation suppresses the temperature-sensitive defect of lacZ gene expression in a divE mutant.

A divE mutant, which has a temperature-sensitive mutation in the tRNA1Ser gene, exhibits differential loss of the synthesis of certain proteins, such as beta-galactosidase and succinate dehydrogenase, at nonpermissive temperatures. In Escherichia coli, the UCA codon is recognized only by tRNA1Ser. Several genes containing UCA codons are normally expressed after a temperature shift to 42 degrees C in the divE mutant. Therefore, it is unlikely that the defect in protein synthesis at 42 degrees C is simply caused by a defect in the decoding function of the mutant tRNA1Ser. In this study, we sought to determine the cause of the defect in lacZ gene expression in the divE mutant. It has also been shown that the defect in lacZ gene expression is accompanied by a decrease in the amount of lacZ mRNA. To examine whether inactivation of mRNA degradation pathways restores the defect in lacZ gene expression, we constructed divE mutants containing rne-1, rnb-500, and pnp-7 mutations in various combinations. We found that the defect was almost completely restored by introducing an rne-1 pnp-7 double mutation into the divE mutant. Northern hybridization analysis showed that the rne-1 mutation stabilized lacZ mRNA, whereas the pnp-7 mutation stabilized mutant tRNA1Ser, at 44 degrees C. We present a mechanism that may explain these results.

Alleles↗
PubMedDate not supplied

[Multinodular diving goiters: 100 cases in Morocco].

OBJECTIVE: To assess 100 cases of multinodular diving goiters, the authors review the literature to compare the epidemiology, clinical pictures, additional required work-up, treatments, complications, and sequelae. METHOD: Records of 100 cases of multinodular diving goiters were collected in the surgical department of the Military Hospital of Marrakesh in Morocco from 1991 through 2004. They accounted for 6% of all goiters. The sex ratio was clearly female, and the mean age 50 years. The clinical symptoms of diving goiters involves mainly signs of compression, with dyspnea seen in 50% of cases. Thyroid dysfunction was found in only 25% of our patients. A diagnosis of diving goiter must be suspected when there are signs of mediastinal compression and a palpable cervical goiter, as seen in all our patients. The diagnosis can often be confirmed with thoracic radiography and thyroid scintigraphy. Treatment is mainly surgical and depends on disease course. Cervicotomy was performed in 97% of our patients and was sufficient to extract even most voluminous goiters and those deepest in the mediastinum. RESULTS: Immediate operative results were satisfactory. More long-term results were also generally satisfactory, except for 4 cases of recurrent paralysis and 5 cases of hypoparathyroidism. Both have been reported by several authors. CONCLUSION: Surgical management of multinodular diving goiters is necessary. In general, cervicotomy is sufficient, and the results generally satisfactory, except some complications and neoplasms.

Adult↗
PubMed1998

Personality patterns of anxiety during occupational deep dives with long-term confinement in hyperbaric chamber.

Extreme environments are generally thought to be stressful situations. Occupational deep diving inflicts periods of long-term confinement in hyperbaric chambers and high-pressure exposure on divers. Such extreme environmental conditions have been demonstrated to produce acute responses of anxiety in individual divers. Although these studies have mentioned personality as a factor explaining why some divers reported an increase in ratings of anxiety, the role of personality traits still remains unclear. The present study examines the possible role of personality traits in the development of diving anxiety. Results confirm that diving anxiety remains at the individual level and relatively transient and suggest that personality factors, such as low self-control and emotional instability, that reflect an incapacity to control and express tension in an appropriate manner would play a crucial role in the occurrence of diving anxiety.

Adult↗
PubMed1983

Recurrent alternobaric facial paralysis resulting from scuba diving.

Only one detailed case of alternobaric (referring to alternating pressure changes) facial paralysis resulting from scuba diving has been reported in the world literature. This article describes the dive profile and clinical course of a commercial diver who developed facial paralysis after scuba diving on three different occasions. Probable pathophysiologies, identification of the diver at risk, treatment and prophylactic measures are reviewed. Additional cases from the literature due to scuba diving and flying are cited.

Acoustic Impedance Tests↗
PubMed1993

Diving metabolism and thermoregulation in common and thick-billed murres.

The diving and thermoregulatory metabolic rates of two species of diving seabird, common (Uria aalge) and thick-billed murres (U. lomvia), were studied in the laboratory. Post-absorptive resting metabolic rates were similar in both species, averaging 7.8 W.kg-1, and were not different in air or water (15-20 degrees C). These values were 1.5-2 times higher than values predicted from published allometric equations. Feeding led to increases of 36 and 49%, diving caused increases of 82 and 140%, and preening led to increases of 107 and 196% above measured resting metabolic rates in common and thick-billed murres, respectively. Metabolic rates of both species increased linearly with decreasing water temperature; lower critical temperature was 15 degrees C in common murres and 16 degrees C in thick-billed murres. Conductance (assuming a constant body temperature) did not change with decreasing temperature, and was calculated at 3.59 W.m-2 x degrees C-1 and 4.68 W.m-2 x degrees C-1 in common and thick-billed murres, respectively. Murres spend a considerable amount of time in cold water which poses a significant thermal challenge to these relatively small seabirds. If thermal conductance does not change with decreasing water temperature, murres most likely rely upon increasing metabolism to maintain body temperature. The birds probably employ activities such as preening, diving, or food-induced thermogenesis to meet this challenge.

Animals↗