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PubMed1989

[Observations on the diving tables used by athletes].

Only ten years ago, divers from the Fédération française d'études et de sport sous-marins followed the GERS (French Navy) tables. Today this technique, designed for military purposes, mainly observation dives, has been discarded spontaneously by many sports divers. They prefer using professional divers' tables, as described in a french ordinance of 1974. These tables permit physical activities at the bottom. In cave diving, it now often happens that divers use respiratory gas mixtures based on helium. During surfacing, oxygen is added according to a modified U.S. Navy method. Consequently, the physician has sometimes difficulty in making out the true cause of a diving incident or accident. Moreover, certain divers do successive dives following two different table procedures. Others undertake rapid surfacing according to the now obsolete procedure of half-depth. Hence, time is now pressing that we think about this problem, in order to specify more clearly the safety standards.

Accident Prevention↗
PubMed1989

The effects of forced and voluntary diving on plasma catecholamines and erythrocyte pH in the aquatic anuran, Xenopus laevis.

The lactacidosis and hypoxaemia associated with enforced diving in Xenopus leads to a marked increase in circulating catecholamines, a phenomenon not observed during periods of voluntary diving. The magnitude of the catecholamine surge (predominantly noradrenaline) during an enforced dive appears to be matched to the severity of the hypoxaemia and/or acid-base disturbance. Indeed, a strong linear correlation was found between the decrease in arterial pH and the rise in plasma catecholamines that resulted from an enforced 60 min dive. During that time, the levels of plasma adrenaline and noradrenaline showed a strong inverse exponential correlation with arterial oxygen tensions (PaO2). Simultaneous measurements of red cell pH showed that Xenopus does not regulate its erythrocyte pH in the face of a plasma acidosis, unlike the adrenergically mediated pH regulation of red cells of certain teleost fish.

Anaerobiosis↗
PubMed1988

Breath-hold duration in man and the diving response induced by face immersion.

The objective of this study in 5 selected volunteer subjects was to see whether the circulatory diving response which is elicited by breath holding and by cold water on the face would affect the duration of maximal-effort breath holds. Compared to control measurements (breath holding during resting, breathing with 35 degrees C water on the face) breath holding with the face cooled by 20 degrees C water caused a 12% reduction of heart rate, 6% reduction of cardiac output, 33% reduction in [corrected] forearm blood flow, and 9% rise in mean arterial blood pressure, but there was no difference in breath-hold duration (control and experimental both 94 s). There were also no differences in time of appearance of the first involuntary respiratory efforts during breath holding, in alveolar gas exchange, or in breaking-point alveolar O2 and CO2 tensions. When the diving response was magnified by a brief bout of exercise so that there was a 19% [corrected] reduction in heart rate, 23% reduction in cardiac output, and 48% reduction in forearm blood flow, breath-hold duration was still unaffected by face cooling. Compared to intermittent immersions, continuous exposure of the face to cold water abolished the diving response, probably by a cold adaptation of facial thermal receptors. These results with cooling of the face only are consistent with our earlier finding that there was a negative correlation between the duration of a maximal-effort breath hold and the diving response during whole-body submersion in cold water.

Adult↗
PubMed1988

Scuba diving injuries.

Scuba diving has become increasingly popular, and family physicians may encounter patients who have been injured in a dive. Manifestations of diving injuries may not occur until 12 hours or more after a dive. Initial treatment, based on knowledge of the pathophysiology of decompression sickness, lung expansion injuries and ear barotrauma, may prevent severe and permanent sequelae. Decompression sickness and air embolism are medical emergencies.

Air Pressure↗
PubMed1987

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.

Adult↗
PubMed1986

On the use of a bubble formation model to calculate diving tables.

Previous decompression tables for humans were based upon unsupported assumptions because the underlying processes by which dissolved gas is liberated from blood and tissue were poorly understood. Some of those assumptions are now known to be wrong, and the recent formulation of a detailed mathematical model describing bubble nucleation has made it possible to calculate diving tables from established physical principles. To evaluate this approach, a comprehensive set of air diving tables has been developed and compared with those of the U.S. and British Navies. Conventional decompressions, altitude bends, no-stop thresholds, and saturation dives are all successfully described by one setting of four global nucleation parameters, which replace the U.S. Navy's matrices of M-values. Present air diving tables show great irregularity, even within sets created by the same authors. In contrast, this new approach is remarkably self-consistent, permitting accurate interpolation and extrapolation.

Biophysical Phenomena↗
PubMed1979

Urinary excretion of water and electrolytes during open-sea saturation diving to 850 fsw.

The dive was carried out in the open sea to a depth of 850 fsw (26.7 ATA) for 6 days (DD 1--6) in the saturated mode, with personnel transfer capsule (PTC) excursions between 0 and 150 fsw and diver excursions between 0 and 50 fsw from the saturation base. Each diver had two excursion dives on alternate days. Although each PTC excursion lasted approximately 7 h, the actual time spent in the water averaged 10.5 min per diver. For 12 divers, daily excretion of water, electrolytes, aldosterone, and antidiuretic hormone (ADH) was studied, along with plasma composition (including prolactin), before, during, and after hyperbaric exposure. A significant increase in urine flow was observed on DD2--4 (1604 ml/day predive vs. 2300 ml/day on DD 4; P less than 0.05), after which the degree of diuresis decreased to about 1800 ml/day. Urine osmolality changed inversely with urine flow, with the lowest value of 532 mOsm/kg on DD 4. During the postdive period, both urine flow and urine osmolality returned to the predive level. The endogenous creatinine clearance was maintained at about 200 liters/day throughout the dive. The fractional excretion of Na+ remained unchanged while that of K+ increased significantly during hyperbaric exposure, thus decreasing the urinary Na+/K+ ratio. The fractional excretion of total osmotic substances showed a small hyperbaric exposure. Body weight decreased progressively during the initial 4 days of pressure exposure, equalling 2.6 kg on DD 4. These findings suggest that the observed diuresis may be accompanied by a net loss of body water. Neither the plasma prolactin level nor urinary excretion of aldosterone and ADHshowed any consistent change throughout the dive. It thus appears that, although there is a small osmotic component, the observed diuresis is primarily due to the ADH-independent inhibition of fre water reabsorption from the collecting duct by means of a mechanism yet to be identified.

Adult↗
PubMed1984

Selection and training of disabled persons for scuba-diving. Medical and psychological aspects.

Sixteen persons with a wide range of disabilities were subjected to a formal scuba-diver training course, after passing a medical and psychological assessment specific for divers. Subjects with brain damage and with impaired bladder and bowel control were included. The current general guidelines for the medical assessment of non-disabled divers appear to be suitable for disabled persons, but additionally each particular disability demands careful individual assessment. Such assessment requires knowledge of diving and rehabilitative medicine and diving practice. The study supports the argument that scuba-diving may improve the physical self-concept of selected disabled persons. It is stressed that specialized diving supervision is essential for such people.

Adolescent↗
PubMed1984

Commercial diving fatalities.

The distributions of fatal diving accidents in commercial diver populations were examined in the Gulf of Mexico from 1968 to 1975 and in the British sector of the North Sea from 1971 to 1978. Influences and causes of death were analyzed by examining the interaction between host, environmental and agent factors. The interaction of host and environmental factors appeared to be the greatest contributing factor to diving fatalities among the estimated 900 commercial divers in the Gulf of Mexico and the 700 in the North Sea. The most significant host factors were level of experience and behavioral dysfunction. They are also the host characteristics most amenable to change through improved and more thorough training. The most significant environmental factors were equipment failure and supervisor/tender errors. These factors would be minimized by improved selection, maintenance and operation of equipment, together with improved operating and emergency diving procedures. In recent years there has been a significant downward trend in mortality rates in the commercial diver populations of this study due to improved diving techniques and operations. Further research is needed, however, on the cause(s) of diver unconsciousness and inexplicable actions that occur at depths below 91.44m (300 ft.).

Accidents, Occupational↗
PubMed1984

Relations of smoking and diving experience to pulmonary function among U.S. Navy divers.

The relations of 4 pulmonary function parameters (measured from the forced expiratory spirogram) with diving experience (in years) and indices of cigarette smoking were examined in a group of 93 healthy U.S. Navy divers. Years of diving was not significantly related to lung function. The value for pack-years of smoking was inversely associated with both percentage of predicted forced expiratory volume in 1 s (FEV1) and percentage of predicted maximal midexpiratory flow rate (MMFR). Divers who have relatively heavy smoking histories may be at greater risk for developing significant decline in pulmonary function, and diving exposure factors other than years of diving may contribute to this risk.

Adult↗
PubMed1981

Apnoeic diving safety - experimental approaches to oxygen augmentation.

Oxygen augmentation during ascent for distressed apnoeic divers has recently been both advocated and criticized. Experiments involving 111 apnoeic divers have been conducted, shedding light on diving safety when oxygen augmentation is used at the onset of the apnoeic black-out, and are summarized in this report. It is maintained that black-out sets in gradually during ascent, taking the form of progressive tunnel vision, leaving scope for rational action by a distressed diver before complete loss of consciousness. By triggering a device (e.g. a 50 - 100 ml syringe) loaded with oxygen by means of pressure or otherwise at the onset of symptoms of hypoxic black-out during a 10 m dive, unconsciousness is believed to be delayed. This is because it takes a diver 12 seconds to rise to the surface from 10 m, while the lung-brain circulation time, inferred from textbook lung-ear circulation times for oxyhaemoglobin, is approximately 5.2 seconds. Since the oxygen is injected into the trachea by force and because of simulated involuntary ventilatory activity which dynamically mixes mouth and alveolar gas during apnoeic diving stress, the injected oxygen is believed to be quickly delivered at the alveoli. Such gas injection was shown to raise the amount of oxygen available to the diver by 25 - 50%. Intrathoracic pressure increases could ensure delivery of enough oxygen to the capillaries to delay unconsciousness. Recommendations for using the syringe at present apply only to 10 m dives and do not exclude use of other safety devices currently in use by divers or envisaged for their safety.

Adolescent↗
PubMed1982

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.

Accidents↗
PubMed1980

Venous gas bubbles while flying with cabin altitudes of airliners or general aviation aircraft 3 hours after diving.

Decompression venous gas bubbles were detected with the precordial Doppler utrasound technique in humans at simulated altitudes of 1,000-3,000 m 3 h after no-stage decompression dives to 15 or 39 m. Bubbles were detected at 3,000 m in a total of 60% of the subjects: in 90% after the 100-min shallow dives to 15 m with some bubbles present in the first minutes (mean onset 12 min), and in only 30% after the 10-min deeper dives to 39 m with later appearances of bubbles (mean onset 28 min). At both 2,000 and 1,000 m bubbles could also be detected, sometimes in the first minutes. The risk of decompression sickness must be considered high with the amount of gas bubbles found, even though only uncertain symptoms appeared in this study. Thus, a safe interval between ordinary SCUBA-diving and flying in airliners or general aviation aircraft seems to be more than 3 h.

Adult↗
PubMed1995

Decreased protein synthesis during dry saturation diving.

Changes in metabolism during saturation dives have been reported; however, these changes have not been well defined. This study was conducted to determine the effect of saturation diving on protein metabolism. Whole body protein synthesis was measured by the ammonia and urea endpoint methods, following a single oral dose of 15N-glycine in 11 Navy divers 33.9 +/- 1.9 yr of age. The divers were fed a controlled diet throughout the three trials. Trial I was on the surface, and trials II and III were during dry saturation dives at 0.56 MPa. The protein synthesis results in gram protein per kilogram lean body mass per day, least square mean +/- SD: [formula: see text]. Under the conditions of this series of dry saturation dives, protein synthesis was depressed by up to 30-50% for the urea and ammonia endpoint methods, respectively. An estimate of liver protein synthesis was made by measuring the incorporation of the 15N label into plasma fibrinogen. The 15N enrichment of fibrinogen glycine and the hippurate precursor for fibrinogen were decreased significantly. This dramatic decrease in protein synthesis was observed despite positive nitrogen balance in these divers. Although further investigation is needed to elucidate the mechanism, the decrease in the incorporation of 15N glycine into fibrinogen suggests alteration in liver nitrogen metabolism at 0.56 MPa.

Adult↗
PubMedDate not supplied

[Changes of static and dynamic characteristics of external respiration in divers after short-term dives down to 100 m].

In a series of short (up to 45 min without considering time of decompression) dives (SD) at depths down to 100 m under conditions of the Barentsev Sea five professional deep-sea divers were examined. In dives down to 40 m compressed air was used as breathing media, in dives to 60, 80 and 100 m--nitrogen-heliox mixture. Before the SD series the volume and velocity lung variables at rest and during forced expiration in air and heliox media were measured between separate SDs and on the 3rd day after the end of decompression with dive to 100 m, using computer spiro- and pneumotachometry methods. Bronchospastic syndrome, playing the leading role in the development of transient isolated or generalized airway obstruction, was shown to be evoked in divers during conduction of SD series. Obstructive phenomena are presumed to be connected with elastic properties' disturbance of lung tissue and development of expiratory collapse; they might cause continuous lung dilatation.

Adult↗
PubMed1993

[Otorhinolaryngologic aspects of diving sports].

ENT disorders are the most common of all medical problems of diving. This review summarizes the specific conditions and ENT diseases in Scuba diving. During compression failure to equalize the pressure of air-filled cavities surrounded by bone deprives the middle ear or sinuses of aeration. Middle ear barotrauma is the most common barotrauma encountered in divers while sinus barotrauma and especially inner ear barotrauma (with rupture of the round or oval window) are less common. Decompression sickness in primarily the result of inert gas bubbles; deafness and vertigo may result if the inner ear is involved. The ENT examination necessary for assessment of diving fitness focuses on the middle and inner ear as well as the nose, sinuses and larynx. A list of ENT contra-indications is presented that mandate temporary or permanent disqualification from diving.

Barotrauma↗
PubMed1995

Ascent rate, post-dive exercise, and decompression sickness in the rat.

The effects of ascent rate and post-dive exercise on the incidence of decompression sickness (DCS) were investigated in six groups of 20 rats exposed for 2 h at a pressure equivalent to 240 feet of sea water (fsw; 735 kPa). Ascent rates were 30, 45, and 60 fsw/min (92, 138, 184 kPa/min), and the rats either rested after the exposure or exercised by walking for 30 min on a treadmill at 1.6 m/min. Post-dive signs included respiratory distress, difficulty walking, paralysis, and death. DCS was scored as non-fatal at 30-min post-dive or fatal at any time. Analysis by ordinal logistic regression indicated more DCS with post-dive exercise (P = 0.0112) and at 45 (P = 0.0011) and 60 fsw/min (P = 0.0001) compared to 30 fsw/min. Survival analysis suggested earlier death at 60 fsw/min compared to 30 fsw/min (P = 0.0006). Similar effects have been reported for the less severe DCS that occurs in humans.

Animals↗
PubMed1996

Recreational scuba diving injuries.

Because of the increasing popularity of recreational scuba diving, primary care physicians should be familiar with common diving injuries. One form of barotrauma, middle ear squeeze, is the most common diving injury. Other important diving injuries include inner ear barotrauma and pulmonary barotrauma. Arterial gas embolism, a potentially life-threatening form of pulmonary barotrauma, requires hyperbaric treatment. Decompression sickness is the result of bubble formation in body tissue. Symptoms of decompression sickness range from joint pain to neurologic or pulmonary problems. Recompression is the mainstay of treatment.

Barotrauma↗