The authors offer a way of estimation of safety modes of decompression, based on definition of intensity of venous gas embolism (VGE) at each decompression and account of probability of illness of divers in series of tests. Intensity of VGE was determined with the help of ultrasonic gas bubbles Doppler radar. Comparative safety of standard modes of decompression of divers of the Navy was estimated, and also the modes, designed in accordance with mathematical model of decompression, offered by I. A. Voitsekhovich (1990), were done. The results testify, that use of ultrasonic radar for estimation of intensity of VGE at decompression and account of average and maximum probability of decompression illness in series of tests of modes permit to receive the comparative characteristic of safety of modes at small number of decompressions.
Skin infections in saturation diving are caused by microbes that flourish in saturation environments. Improvements in the prevention of infections must therefore be based on environmental control and elimination. Furthermore, only a few genotypes seem to be responsible for the majority of infections in the Norwegian sector of the North Sea, and these have all been demonstrated in saturation systems for many years. Although reservoirs of infectious genotypes have been identified, their true sources have not been identified.
The purpose of this field study was to log the contamination by Pseudomonas aeruginosa of the saturation system throughout a diving operation.
Daily water samples from the vessels drinking water system and from the heated seawater systems to divers suits were taken throughout the diving period of 1 month in the summer of 2001. All P.aeruginosa isolates were genotyped by pulsed field gel electrophoresis.
A total of 17 P.aeruginosa genotypes were identified in the course of this field study. None of the most common infectious genotypes previously observed in the Norwegian sector were among these strains. Two genotypes were involved in skin infections during the period of operation: TP2 and TP12. TP2 was shown to be an inhabitant of the diving systems throughout the investigation period, while TP12 was introduced from seawater in the course of the operation and rapidly spread and established itself throughout the diving system.
The study has demonstrated seawater as a true source of an infectious P.aeruginosa genotype in occupational diving systems.
This is a report of two cases of arterial gas embolism (AGE) occurring during the course of routine pressure tolerance testing (PTT) of Canadian Forces divers in a dry hyperbaric chamber. PTT is used by many military organizations as a means to determine whether divers can sustain a hyperbaric challenge similar to that to which they will be exposed during their diving duties. Problems arising from such testing are usually limited to issues of equalization and minor otic barotraumas. Incidents of AGE resulting from hyperbaric chamber exposures in general are very unusual. The incidents reported here are the first such cases arising in military divers during PTT to be reported in the extant literature. In one case a potential precipitating pulmonary lesion was identified during post-event chest imaging. In the other case, while presenting with all the usual hallmarks of an AGE, no predisposing pulmonary lesion was identified. Ascent rates were within the limits considered acceptable by the Canadian Forces for PTT. The cases are useful in examining the pathophysiologic mechanisms underlying pulmonary barotrauma and AGE, and raise questions as to the appropriate screening procedures for military divers in this regard.
Competitive breath-hold divers try to achieve maximum times, depths, or distances underwater, thereby risking hypoxic syncope. In the present study, the cardiorespiratory responses to dynamic apnea (simultaneously initiated apneas and dynamic leg exercise) were investigated in 10 breath-hold divers. The divers performed 60 s dynamic apneas with the face in air (A) or face immersed in cold water (AFI). During apneas, the arterial oxygen saturation was reduced (A: -10%), but to a lesser extent during AFI (-6%, P
Leatherback turtles in the Northwest Atlantic Ocean have a broad geographic range that extends from nesting beaches near the equator to seasonal foraging grounds as far north as Canada. The ability of leatherbacks to maintain core body temperature (Tb) higher than that of the surrounding water is thought to be a key element of their biology that permits them to exploit productive waters at high latitudes. We provide the first recordings of Tb from freely swimming leatherbacks at a northern foraging ground, and use these data to assess the importance of behavioral adjustments and metabolic sources of heat for maintenance of the thermal gradient (Tg). The mean Tb for individual leatherbacks ranged from 25.4 ± 1.7 to 27.3 ± 0.3 °C, and Tg ranged from 10.7 ± 2.4 to 12.1 ± 1.7 °C. Variation in mean Tb was best explained by the amount of time that turtles spent in the relatively warm surface waters. A diel trend in Tb was apparent, with daytime cooling suggestive of prey ingestion and night-time warming attributable to endogenous heat production. We estimate that metabolic rates necessary to support the observed Tg are ~3 times higher than resting metabolic rate, and that specific dynamic action is an important source of heat for foraging leatherbacks.
Exercising before, during, or after diving is proscribed because of the assumption that it would increase incidence of decompression sickness. Our findings show that exercise performed in a timely fashion before diving or during decompression will reduce the number of venous gas bubbles formed. Exercise after diving did not increase the number of bubbles. Nitric oxide seems to play a protective role.
A major challenge for diving birds, reptiles, and mammals is regulating body temperature while conserving oxygen through a reduction in metabolic processes. To gain insight into how these needs are met, we measured dive depth and body temperatures at the core or periphery between the skin and abdominal muscles simultaneously in freely diving Brünnich's guillemots (Uria lomvia), an arctic seabird, using an implantable data logger (16-mm diameter, 50-mm length, 14-g mass, Little Leonardo Ltd., Tokyo). Guillemots exhibited increased body core temperatures, but decreased peripheral temperatures, during diving. Heat conservation within the body core appeared to result from the combined effect of peripheral vasoconstriction and a high wing beat frequency that generates heat. Conversely, the observed tissue hypothermia in the periphery should reduce metabolic processes as well as heat loss to the water. These physiological effects are likely one of the key physiological adaptations that makes guillemots to perform as an efficient predator in arctic waters.