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PubMed2000

[Medical aspects of diving in otorhinolaryngology. I. Barotrauma and decompression sickness].

Recreational scuba diving has become immensely popular in recent years and is no longer restricted to individualists or adventurers. During a dive, the human body with its gas-filled cavities is exposed to an increased ambient pressure. In the present review article, aspects of diving and hyperbaric medicine related to the otolaryngology field are presented. The basics of physics, physiology and pathophysiology that are essential to understand the effects of an increased and varying ambient pressure are reviewed. Barotrauma of the outer, middle and inner ear, the paranasal sinuses, face, teeth and larynx are explained and classified in those during the compression and decompression phase. This is followed by a discussion of inner ear decompression sickness. The present article will provide a background and foundation for both, an adequate treatment of these diseases and a critical and responsible health education of the diver.

Athletic Injuries↗
PubMed2001

Effect of ambient temperature on the risk of decompression sickness in surface decompression divers.

BACKGROUND: Several studies have noted an apparent increase in decompression sickness (DCS) risk with surface decompression diving in warm water or with hot water suits (Van Der Aue 1951, Shields 1986, Leffler 1997), but did not perform statistical tests to control for the pressure-time profile. METHODS: The 1986 data, including 73 DCS cases out of 14,891 dives, were analyzed by Mantel-Haenszel analysis to control for depth and bottom time. Dive profiles from the 1951 U.S. Navy report, including 147 DCS cases from 1507 dives, were analyzed with logistic regression analysis to control for depth, bottom time, and aspects of the decompression profile. RESULTS: In the 1986 data, hot water suits, as compared with passive thermal protection, were associated with an odds ratio (OR) of 1.81 (95% confidence interval, CI = 0.96 to 3.42) for DCS. In the 1951 data, each 10 degree C increase in water temperature yielded an OR for DCS of 1.96 (95% CI = 1.33 to 2.90). The interaction of temperature and bottom time suggested that the effect was more pronounced in shorter dives. Among DCS cases, the OR for type 2 symptoms with hot water suits was not significant in the 1986 data (p = 0.18). In the 1951 data, the probability of type 2 symptoms among DCS cases was better explained by the dive profile than by the temperature. Thermal effects on gas physics, metabolism, hemostasis, and nociception were reviewed. CONCLUSION: Surface decompression divers who are warm at depth face an increased risk of DCS. Vasodilatation in warm divers may result in more rapid on-gassing of tissues with short time constants. A full evaluation of DCS risk should consider physiological and physical effects of ambient temperature.

Decompression Sickness↗
PubMed2005

Warm eyes provide superior vision in swordfishes.

Large and powerful ocean predators such as swordfishes, some tunas, and several shark species are unique among fishes in that they are capable of maintaining elevated body temperatures (endothermy) when hunting for prey in deep and cold water . In these animals, warming the central nervous system and the eyes is the one common feature of this energetically costly adaptation . In the swordfish (Xiphias gladius), a highly specialized heating system located in an extraocular muscle specifically warms the eyes and brain up to 10 degrees C-15 degrees C above ambient water temperatures . Although the function of neural warming in fishes has been the subject of considerable speculation , the biological significance of this unusual ability has until now remained unknown. We show here that warming the retina significantly improves temporal resolution, and hence the detection of rapid motion, in fast-swimming predatory fishes such as the swordfish. Depending on diving depth, temporal resolution can be more than ten times greater in these fishes than in fishes with eyes at the same temperature as the surrounding water. The enhanced temporal resolution allowed by heated eyes provides warm-blooded and highly visual oceanic predators, such as swordfishes, tunas, and sharks, with a crucial advantage over their agile, cold-blooded prey.

Adaptation, Physiological↗
PubMed1985

Seal lungs collapse during free diving: evidence from arterial nitrogen tensions.

Arterial blood nitrogen tensions of free-diving Weddell seals (Leptonychotes weddelli) were measured by attaching a microprocessor-controlled blood pump and drawing samples at depth to determine how these marine mammals dive to great depths and ascend rapidly without developing decompression sickness. Forty-seven samples of arterial blood were obtained from four Weddell seals during free dives lasting up to 23 minutes to depths of 230 meters beneath the sea ice of McMurdo Sound, Antarctica. Peak arterial blood nitrogen tensions of between 2000 and 2500 millimeters of mercury were recorded at depths of 40 to 80 meters during descent, indicating that the seal's lung collapses by 25 to 50 meters. Then arterial blood nitrogen tensions slowly decreased to about 1500 millimeters of mercury at the surface. In a single dive, alveolar collapse and redistribution of blood nitrogen allow the seal to avoid nitrogen narcosis and decompression sickness.

Animals↗
PubMed1983

Liquid ventilation in dogs: an apparatus for normobaric and hyperbaric studies.

A liquid-breathing apparatus is described for remote surface studies and for use in experiments of near-hydraulic compression in dogs. It consists of a flexible tank sealed against chamber gas, containing a supply of clean warmed (38 degrees C) fluorocarbon (FC-80) equilibrated with 1 bar O2 and an electronically controlled means of delivering the liquid to the dog. Each breath (tidal volume 290 ml) was "weighed" into the animal by the signal from a force platform supporting the dog and a digital control unit that automatically actuated inspired-and expired-line solenoid valves. The apparatus was successfully used to remotely maintain liquid ventilation in awake dogs for 2 h during surface studies (5 dogs) and in dives to 1,000 m seawater (5 dogs). During liquid breathing, mean arterial O2 partial pressure was always adequate (congruent to 300 Torr) and mean arterial CO2 partial pressure was normal (less than or equal to 40 Torr). An uncompensated metabolic acidosis was indicated by low pH values and a decrease in arterial base excess to--4.5 meq x 1(-1). O2 uptake and CO2 output appeared to be significantly lower (42 and 35%, respectively) during liquid ventilation.

Animals↗
PubMed2001

[Activation of the antioxidant system as a factor in increasing the body resistance during combined adaptation].

In semi-aquatic mammals (minks and muskrats) significant changes were found to occur in the leukocyte formula during adaptation to hypoxia, as compared with non-adapted rats and mice, although no increase in lipid peroxidation was found in any of their organs. This latter finding seems to be due to simultaneously enhanced activities of superoxide dismutase and catalase. In humans under professional stress, treatment with combined technology of adaptation: cold-and-hypoxic exposure, yields a positive therapeutic result accompanied by a decrease in lipid peroxidation and increase in superoxide dismutase and catalase activities in the blood. The data obtained suggest that the strategy of formation of protection against hypoxia and toxic free radical oxidation is common for the animals and humans.

Adaptation, Physiological↗
PubMed1989

[Structural-functional organization of the cerebral circulatory system in birds].

The literature reference and own data on structural-functional organization of the cerebral circulation system in birds are summed up. The regularities of cerebral hemodynamics in alteration of the blood gaseous composition, arterial pressure and in rise of the body temperature are emphasized. Possible physiological role of the regulatory specifics of the cerebral circulation system of birds in diving and flying, is discussed.

Animals↗