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PubMed1991

Vestibular problems in diving and in space.

On firm ground our sense of balance is supplied by super abundant input from several sensoric sources. In other environments insufficient or conflicting input may cause vestibular problems. In diving, vertigo may be caused by a variety of influences, like sensory deprivation, optokinetic illusion, asymmetric vestibular stimulation, inner ear barotrauma, decompression sickness, breathing gas toxicity, high pressure neurological syndrome, sea sickness and intense noise. During space flight some of the mentioned mechanisms may contribute to vestibular problems, although space motion sickness being the main cause of concern in this connection.

Barotrauma↗

PubMed1991

Venous gas emboli and complement activation after deep repetitive air diving.

Complement activity has been linked to decompression sickness (DCS), but the effects of intravascular bubbles on complement activation are poorly understood. We have investigated intravascular complement activation by measuring red blood cell (RBC)-bound C3d after repetitive air diving in man. Subjects were exposed to a single, 20 min, 170 fsw (feet of sea water) dive, or to 2 such dives with a 6-h surface interval. Doppler monitoring for venous gas emboli was performed postdive. Predive blood samples were studied to determine sensitivity of complement to activation by air bubbles. Other predive and postdive venous samples were evaluated for intravascular complement activation. No cases of DCS occurred in 39 dives. Baseline complement sensitivity appeared normally distributed, thus "sensitive" and "insensitive" subjects were not clearly distinguishable. RBC-bound C3d did not increase after 1 dive but did increase after the repetitive dive (P less than 0.05). Furthermore, maximum bubble grade was independent of complement activation.

Adult↗

PubMed1990

Advantages of a low-oxygen environment in space cabins.

The advantages of having a low-oxygen environment in space cabins are discussed. The major advantage is a sharply reduced fire hazard, which is a major threat in manned space flights. At 1 atm, for example, 15% O2 (9,000 ft altitude equivalent) would not support most fires and could accommodate the crew with respect to hypoxia, decompression sickness (DCS), and other requirements. Chronic exposure to such a hypoxic environment (altitude acclimatization) could improve major areas of crew health and safety including alleviating deconditioning effects, decreasing susceptibility to DCS, and improving tolerance to severe hypoxia.

Ecological Systems, Closed↗

PubMed1991

Venous air emboli with 15N2: pulmonary excretion and physiologic responses in dogs.

Venous air embolism occurs with decompression sickness as well as during a wide variety of surgical procedures in hospitalized patients. We developed a canine model to allow documentation and quantitation of pulmonary excretion of intravascular air emboli both in a control air breathing state and during treatment. We utilized 15N2 (a stable, nonradioactive isotope of room air nitrogen, 14N2) as the nitrogen component of venous air emboli (1 ml.kg-1) given to 27 anesthetized mongrel dogs ventilated with room air (tidal volume = 15 ml.kg-1). End-tidal 15N2 was measured and the embolism diagnosed by increased levels in exhaled gases. Exhaled gases were also collected in Douglas bags and the 15N2 recovered was quantitated by a helium dilution technique. Systemic and pulmonary artery pressure changes and quantitation of excreted 15N2 were documented after embolism during a control state with continued room air (21% oxygen) ventilation, and after treatments with either a) 100% oxygen ventilation; b) compression to 2128 mmHg, or 2.8 atm abs, and room air ventilation; or c) a combination of 100% oxygen ventilation and 2.8 atm abs compression. Increased end-tidal 15N2 was characteristic of all emboli, and use of 15N2 allowed accurate measurement of excreted gas during both room air and 100% oxygen ventilation. Embolic gas recoveries were not increased significantly by any of the treatments.

Animals↗

PubMedDate not supplied

The role of hyperbaric oxygen in current emergency medical care.

HBO is the definitive treatment for carbon monoxide poisoning, air or gas embolism, and decompression sickness. It is an important adjunct to other treatment modalities in the management of patients with cyanide poisoning, exceptional blood loss (anemia), crush injury, and gas gangrene. In addition, HBO has many investigational uses such as reduction of edema in acute bowel obstruction before surgical intervention. It should be remembered that the best hope for tissue recovery occurs when HBO is initiated within 4 to 6 hours of injury. After this time irreversible muscle and peripheral nerve damage usually will have occurred in ischemic tissue.

Adult↗

PubMed1989

Human tolerance to 100% oxygen at 9.5 psia during five daily simulated 8-hour EVA exposures.

Extravehicular activity (EVA) currently involves decompression to 4.3 psia. This degree of decompression carries a significant potential for decompression sickness (DCS) which could be alleviated if a pressure of 9.5 psia could be maintained in the pressure suit. Previous studies have not evaluated the potential for oxygen toxicity at 9.5 psia. Twenty-one subjects were exposed to 100% oxygen at 9.5 psia for 5 consecutive days, 8 h.d-1 while performing moderate exercise to simulate a typical work-week in the proposed pressure suit environment. No DCS or venous gas bubbles were detected. Pulmonary function tests, physical exams, blood analyses, arterial oxygen saturation monitoring, and X-rays showed no evidence of oxygen toxicity under these conditions. These results suggest that a 100% oxygen, 9.5 psia pressure suit environment could avoid both DCS and oxygen toxicity during EVAs of comparable duration and physical activity.

Adult↗

PubMed1989

Arterial gas tensions and hemoglobin concentrations of the freely diving Weddell seal.

Heart rate, body temperature, arterial blood gas tensions, pHa and hemoglobin concentrations were measured during and after free diving of the Weddell seal (Leptonychotes weddelli), beneath the fast ice of McMurdo Sound, Antarctica. To examine arterial nitrogen tensions (PaN2), 47 samples of arterial blood were obtained from 4 seals diving up to 23 min to depths of 230 m. Peak arterial nitrogen tensions between 2000 and 2500 mmHg were recorded at depths of 40-80 m during descent, indicating that the seal's lung collapses by 25-50 m. Then arterial blood nitrogen tensions slowly decreased to about 1500 mmHg near surfacing. Thus during diving alveolar collapse and redistribution of blood nitrogen allow the seal to avoid nitrogen narcosis and decompression sickness. The arterial PO2 (PaO2) at rest (78 +/- 13 mmHg, mean +/- SD) increased with diving compression to a maximum measured value of 232 mmHg and then rapidly decreased to 25-35 mmHg. The lowest diving PaO2 was 18 mmHg just before the seal surfaced from a 27-min dive. A consistent increase of arterial hemoglobin concentrations occurred during each dive. We suggest that an extension of the sympathetic outflow of the diving reflex caused profound contraction of the Weddell seal's spleen.

Animals↗

PubMed1988

[Otologic aspects of diving].

Ear diseases are the most common of all occupational diseases of diving. Otitis externa is the most frequent and troublesome infection in divers especially when the environment is humid. During compression, failure to equalize the pressure of the air-filled cavities surrounded by bone (middle ear, sinus) deprives the middle ear (or sinus) of aeration. Middle ear barotrauma is the most common barotrauma encountered in divers while external ear barotrauma (reversed ear) and inner ear barotrauma (with rupture of the round or oval window) are less common. Decompression sickness (Caisson disease) is primarily the result of inert gas bubbles; deafness and vertigo may result if the inner ear is involved. The most dramatic cause of disorientation under water is that due to vertigo. This vertigo is commonly a transient effect due to unequal caloric stimulation of the two labyrinths. The physical examination of the ear and nose necessary for assessment of diving fitness are discussed. A list of ENT contra-indications is presented which mandate temporary or permanent disqualification from diving.

Barotrauma↗

PubMed1986

Health risks of diving among U.S. Navy officers.

The objectives were to compare hospitalization, medical board, and mortality rates of diving-related disorders and stress-induced diseases between U.S. Navy male diving officers (n = 1977) and a matched sample of nondiving officers (n = 1973). Less experienced diving officers had significantly higher hospitalization rates than more experienced diving officers for total admissions, stress-related disorders (primarily alcoholism), and cardiovascular disease. Diving officers had significantly higher hospitalization rates than controls for nervous system diseases and joint disorders; none of these hospitalized diving officers had a recorded incident of decompression sickness. To ensure the safety and overall excellent health status of diving officers, it is necessary to promote and continue adherence to the procedures developed for safe diving in the U.S. Navy diving community.

Administrative Personnel↗

PubMed1985

A direct test for the survival of gaseous nuclei in vivo.

It has recently been demonstrated that bubble formation in the crab Pachygrapsus crassipes is induced by limb motions following decompression from nitrogen pressures as low as 2 atm. Preformed gaseous nuclei are not involved in this process and are absent from this animal. We further demonstrate here that nuclei do not remain in the body fluids when the motion-induced bubbles dissolve. This shows that gas phases do not become protected against dissolution in vivo as has been proposed by other workers. This may have important implications concerning the origin of bubbles causing decompression sickness in higher animals.

Aerospace Medicine↗

PubMed1978

Aseptic bone necrosis among U.S. Navy divers: survey of 934 nonrandomly selected personnel.

Nine hundred thirty-four U.S. Navy divers were selected and surveyed radiographically using standard techniques developed for detecting aseptic bone necrosis (ABN). X rays were read by qualified radiologists. A total of 16 positive cases was detected, and another 11 were interpreted as doubtful. ABN was found to be related to age and number of months in diving. After controlling for these factors, ABN could not be related to any of seven indices of diving activity. Divers with ABN did, however, have a history of more treatments for decompression sickness (DCS) than did divers without ABN. Implications of these findings are discussed, and the suggestion is made that ABN and DCS may not be related causally, but may be related to a third common factor. The need for controlled studies is discussed. The conclusion is made that the low prevalence rates of ABN among U.S. Navy divers cannot be related to any specific index of diving activity, and may not be causally related to DCS.

Adolescent↗

PubMed1983

Report of an isolated mid-frequency hearing loss following inner ear barotrauma.

A case describing an isolated mid-frequency hearing loss as a result of inner ear barotrauma is presented. The onset of symptoms was insidious but progressed to a profound total-range hearing loss in the right ear. This loss resolved rapidly with cessation of diving activity, bed rest, and head elevation, leaving only an isolated 20-dB hearing decrement at 1000 Hz. Since the diver was participating in evaluation of experimental decompression tables, differentiation had to be made between barotrauma and inner ear decompression sickness.

Adult↗

PubMed1983

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.

Adult↗

PubMed1982

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.

Adult↗

PubMed1978

Laryngeal problems in space travel.

A start has been made in enumerating possible problems of the larynx, in short or moderately long space voyages, based on our current knowledge of laryngeal diseases. The gravity-free state does not seem to be a threat to the physiology of the larynx. A relatively nonspecialized medical team must be able to recognize and manage Earth-type diseases. They must also be capable of managing both the special problems associated with various degrees of decompression sickness and the increased possibility of inhaling a foreign body, which are inherent in the gravity-free state. In crew selection, a special attempt should be made to eliminate those members with an increased risk of laryngeal disease development. Simplified methods of examining the larynx, including flexible fiberoptic laryngoscopy, should be available. Airway management, including coaxial endotracheal intubation with a bivalved laryngoscope, would be possible. An audiovisual tape library of simple and moderately complex procedures would be highly valuable.

Humans↗

PubMed1995

Diving patterns of ama divers of Hegura Island, Japan.

Daily diving patterns, especially depth-time profiles, were continuously recorded during the entire work shift in four cachido and four funado divers of Hegura Island, Japan. All Hegura divers (cachido and funado alike) were female and habitually wore wet suits. Cachidos dive free and unassisted from a boat or float, whereas funado divers are assisted by weighted descent and during the ascent by being pulled by a partner into a boat on the water surface. Both funado and cachido divers spent 250-280 min/day on the sea at their diving locations; the actual diving time was 100-120 min. The divers made 90-120 dives/day to a depth of 13-22 m, each dive lasting approximately 60 s, considerably longer and deeper than those observed and recorded previously in ama divers in the Chiba and Miura regions. These dive profiles are similar to those reported by Paulev in which he observed apparent signs of decompression sickness when the subject dived to a depth of 15-20 m 100 times in 5 h. The average bottom time for each dive of Hegura funados was 23.6 s which is approximately 10 s longer than that of Korean female ama. The rate of ascent in the funado divers was 1.5 m/s, which is nearly twice that of the cachido divers (0.8 m/s). The dive frequency of Hegura funados (109 dives/day) was greater than the Chiba male funados (23 dives/day). Accordingly, cumulative bottom time of Hegura funado was 48 min/day, whereas that of Chiba funado was 17 min/day.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1995

Perfluorocarbon emulsions: one approach to intravenous artificial respiratory gas transport.

The PFC emulsions have had a developmental history of promise as yet unfulfilled. Today, second-generation PFC emulsions are poised with the right gas-carrying capabilities to be able to make significant contributions to oxygen transport and delivery. The dream of stable, safe, easily transportable intravenous fluid, with universal rapid application is not yet at hand. However, we appear to be a great deal closer than in the mid 1980s. If these 40% volume-to-volume emulsions prove safe, then an entirely new realm of therapeutic options will become available. Not only will the uses for trauma and acute blood loss replacement become a reality, but extremes of euvolemic hemodilution may become possible. The use of these compounds for prevention of stroke, ischemic organ salvage, and prevention of air embolism or decompression sickness are particularly exciting. It is clear from the recent developments in PFC technology that some product will come to market in the not-too-distant future. How such a PFC will be utilized as compared with hemoglobin preparations is yet to be discerned, but the two concepts are quite different. Each will have its own specific indications.

Animals↗

PubMed1995

Rupture of the stomach complicating diving accidents.

All reported cases of rupture of the stomach after a diving accident were reviewed for this study. This is a rare event that complicates brief and deep dives. It is always the consequence of equipment failure or panic reactions which induce swallowing air while under water. During a rapid ascent, the gas expands causing rupture. Diagnosis is based on the presence of abdominal distention associated with pneumoperitoneum on the x-ray and with gastric tears seen on gastroscopy. Pneumoperitoneum from gastric rupture must be distinguished from that caused by pulmonary barotrauma. Peritoneal decompression by paracentesis may quickly improve the patient's condition. After air embolism or decompression sickness has been ruled out, a surgical operation is necessary. Exploratory laparotomy exposes, in two thirds of cases, a gastric full-thickness tear that requires closing by suture. The outcome is good because subjects are young and healthy. The rupture of a filled stomach may lead to postoperative complications (abscess or fistulas).

Accidents↗