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At least 73 records · Page 4Linked to original sources
PubMed1996

Diagnosis and management of diving accidents.

Humans experience significant physiological stresses while diving, which can result in disease on occasion. With the increasing popularity of sports diving, it is critical that both physicians and divers be aware of the spectrum of illness associated with diving. An overview of common diving-related disorders is presented. After a brief discussion of relevant physics principles, the clinical presentation of ear and sinus squeeze is covered along with preventive strategies and treatment. This is followed by a discussion of the pathophysiology, clinical settings, and manifestations of pulmonary barotrauma along with a review of the pathophysiology and presentation of decompression illness. Initial emergency measures and referral procedures for decompression related disorders are addressed. A brief discussion of recompression therapy is included.

Accidents↗
PubMed1964

DIVING DEPTHS OF THE WEDDELL SEAL.

Dives as deep as 350 meters have been recorded for the Weddell seal in the waters of McMurdo Sound, Antarctica. It is suggested that Weddell seals possess a well-developed navigational system which enables them to swim long distances under thick ice shelves where light and breathing holes are limited.

Animals↗
PubMed2005

Breathing at depth: physiologic and clinical aspects of diving while breathing compressed gas.

When diving, human beings are exposed to hazards that are unique to the hyperbaric underwater environment and the physical behavior of gases at higher ambient pressure. Hypercapnia, hyperoxia, carbon monoxide intoxication, inert gas (predominantly nitrogen) narcosis, and decompression illness all may lead to impaired consciousness, with a high risk of drowning in this non-respirable environment. Proper physiologic function and adaptation of the respiratory system are of the utmost importance to minimize the risks associated with compressed gas diving. This article provides an introduction to the diving techniques, the physics, and the pertinent human physiology and pathophysiology associated with this extreme environment. The causes of the major medical problems encountered in diving are described, with an emphasis on the underlying respiratory physiology.

Barotrauma↗
PubMed1986

The human dive reflex: an experimental, topographical and physiological analysis.

This study examined the eliciting conditions, response topography and autonomic nervous system (ANS) control of the dive reflex as evoked in humans. Twenty-four subjects received eight trials in each of the three treatment conditions: breath holding without face immersion (BH); face immersion without breath holding (FI); and the "full dive" FIBH condition. It was the combination of both FI and BH in 23 +/- 0.5 degrees C water that was necessary to elicit the dive reflex. A precise topographical analysis differentiated the FIBH condition from the FI and BH control conditions in terms of the emergence of a secondary component initiated approximately 12 seconds after trial onset. During this secondary component, augmentation of bradycardic (mean = 16.3 bpm) and digital vasoconstrictive (mean = -24.9%) responses were maintained throughout the duration of the 40-second dive. A joint consideration of the heart rate and the T-wave amplitude measures as indices of the action of both branches of the ANS suggested that the dive reflex involves concurrent sympathetic and parasympathetic activation. A potential conditioning application of the dive reflex for countering paroxysmal supraventricular tachycardia was discussed.

Adolescent↗
PubMed1993

[Who may dive?].

There are no statutory regulations concerning sport diving or diving ability tests. Ability tests should only be performed by practitioners who are familiar with the physiology of diving. The requirements for diving are familiarity with the diving technique, basic knowledge of human body behaviour under water as well as a sound organism and a good psychic balance. There is no fixed age limit. Diving is even possible under certain circumstances in the case of some chronic illnesses (asthma, diabetes). The medical examination should focus on possible drug intake, on ear, nose and throat as well as on the cardiopulmonary and psychic state. The pathophysiological significance of selected illnesses for diving are described briefly. Relative and absolute contraindications are discussed.

Barotrauma↗
PubMed2005

Breathing hypoxic gas affects the physiology as well as the diving behaviour of tufted ducks.

We measured the effects of exposure to hypoxia (15% and 11% oxygen) and hypercapnia (up to 4.5% carbon dioxide) on rates of respiratory gas exchange both between and during dives in tufted ducks, Aythya fuligula, to investigate to what extent these may explain changes in diving behaviour. As found in previous studies, the ducks decreased dive duration (t(d)) and increased surface duration when diving from a hypoxic or hypercapnic gas mix. In the hypercapnic conditions, oxygen consumption during the dive cycle was not affected. Oxygen uptake between dives was reduced by only 17% when breathing a hypoxic gas mix of 11% oxygen. However, estimates of the rate of oxygen metabolism during the foraging periods of dives decreased nearly threefold in 11% oxygen. Given that tufted ducks normally dive well within their aerobic dive limits and that they significantly reduced their t(d) during hypoxia, it is not at all clear why they make this physiological adjustment.

Animals↗
PubMed2001

Extreme human breath-hold diving.

In this paper, the respiratory, circulatory and metabolic adjustments to human extreme breath-hold diving are reviewed. A survey of the literature reveals that in extreme divers, adaptive mechanisms take place that allow prolongation of apnoea beyond the limits attained by non-diving subjects, and preservation of oxygen stores during the dives. The occurrence of a diving response, including peripheral vasoconstriction, increased arterial blood pressure, bradycardia and lowered cardiac output, is strongly implicated. Some peripheral regions may be excluded from perfusion, with consequent reliance on anaerobic metabolism. In addition, extreme breath-hold divers show a blunted ventilatory response to carbon dioxide breathing, possibly as a consequence of frequent exposure to high carbon dioxide partial pressures during the dives. These mechanisms allow the attainment of particularly low alveolar oxygen (< 30 mmHg) and high alveolar carbon dioxide (> 50 mmHg) partial pressures at the end of maximal dry breath-holds, and reduce oxygen consumption during the dive at the expense of increased anaerobic glycolysis (rate of blood lactate accumulation > 0.04 mM.s-1). The current absolute world record for depth in breath-hold diving is 150 m. Its further improvement depends upon how far the equilibrium between starting oxygen stores, the overall rate of energy expenditure, the fraction of energy provided by anaerobic metabolism and the diving speed can be pushed, with consciousness upon emersion. The ultimate limit to breath-hold diving records may indeed be imposed by an energetic constraint.

Adaptation, Physiological↗
PubMed1993

Compressed air diving and respiratory disease. A discussion document of the Thoracic Society of Australia and New Zealand.

OBJECTIVE: To review the pathophysiology and respiratory complications of compressed air diving, and to formulate guidelines for assessing respiratory fitness to dive so that diving candidates can be advised of the risks associated with respiratory disease, in particular asthma. DATA SOURCES: Specialist medical journals in the areas of respiratory medicine, physiology and diving medicine. Morbidity and mortality statistics were obtained from international diving bodies, diving medicine scientific meetings, and papers. SYNTHESIS: The major complications of underwater diving in subjects with compromised respiratory function are drowning, pulmonary barotrauma and arterial gas embolism. Diving candidates with a history of asthma, pneumothorax, obstructive or restrictive lung disease, lung cysts or thoracic trauma should be advised not to dive in view of these risk factors. CONCLUSIONS: Several respiratory diseases carry an increased risk of morbidity and mortality from compressed air diving. An accurate history and measurement of lung function are an essential part of assessing fitness to dive, both to advise potential divers appropriately and to reduce risks associated with this increasingly popular recreational activity.

Asthma↗
PubMed2006

Laurence Irving: an appreciation.

Laurence Irving (1895-1979) contributed significantly over five decades to the development of environmentally oriented physiological studies. He is best known for his investigations of the physiology of diving mammals, the respiratory properties of fish blood, and cold adaptation and acclimatization in poikilotherms and homeotherms, including man. Beyond his own research contributions, Irving benefited American comparative physiology through his key roles in the immigration of Per F. Scholander and Knut and Bodil Schmidt-Nielsen to the United States. The Irving-Scholander research collaboration provides a substantial legacy for comparative physiology. Laurence Irving's administrative contributions include service as the first scientific director of the Arctic Research Laboratory at Barrow, Alaska, and as the founding director of the Institute of Arctic Biology at the University of Alaska, Fairbanks. These units have assured the implementation of his philosophy of combining laboratory and field studies in the investigation of environmentally oriented physiological problems. Laurence Irving was an ardent advocate for Alaskan research, and his efforts were an important help in the advancement of science in the state.

Animals↗
PubMed2000

Pinniped diving response mechanism and evolution: a window on the paradigm of comparative biochemistry and physiology.

Starting even before the end of World War II, the discipline of comparative physiology and biochemistry experienced a period of unprecedented growth and development that pioneers in this field thought would never end. However, by the mid-1970s many of the major mechanistic problems in the field were pretty well understood in principle, and by the mid-1980s workers in the field widely recognized that the discipline was at the point of diminishing returns. One response to this was disillusionment, which turned out to be premature because the field was already absorbing molecular biology tools which has now caused a kind of renaissance in mechanistic physiology studies. The second major response to the sense of disillusionment led to a search for new approaches, and out of this endeavor the newly rejuvenated field of evolutionary physiology arose, and this research area too is now in a growth phase. These general patterns of growth and development in our discipline as a whole are particularly clearly evident in the field of aquatic mammals and birds. Between the 1930s and the 1970s, studies of diving physiology and biochemistry made great progress in mechanistically explaining the basic diving response of aquatic mammals and birds. Key components of the diving response (apnea, bradycardia, peripheral vasoconstriction, redistribution of cardiac output) were found in essentially all species analyzed and were generally taken to be biological adaptations. By the mid-1970s, this approach to unraveling the diving response had run 'out of steam' and was in conceptual stasis. The breakthrough which gave renewal to the field at this time was the development of microprocessor based monitoring of diving animals in their natural environments, which led to a flurry of studies mostly confirming the essential outlines of the diving response based upon laboratory studies and firmly placing it into a proper biological context, underlining its plasticity and species specificities. Now as we begin a new millenium, despite ever more detailed field monitoring of physiology, behavior and ecology, studies aimed at improving understanding of physiological mechanisms in diving are again approaching a point of diminishing returns. To avoid another conceptual stasis, what seems required are new initiatives which may arise from two differing approaches. The first is purely experimental, relying on magnetic resonance imaging (MRI) and spectroscopy (MRS) to expand the framework of the original 'diving response' concept. The second, evolutionary study of the diving response, is synthetic, linked to both field and laboratory studies. To date the evolution of the diving response has only been analyzed in pinnipeds and from these studies two kinds of patterns have emerged. (1) Some physiological and biochemical characters, required and used in diving animals, are highly conserved not only in pinnipeds but in all vertebrates; these traits are necessarily similar in all pinnipeds and include diving apnea, bradycardia, tissue specific hypoperfusion, and hypometabolism of hypoperfused tissues. (2) Another group of functionally linked characters are more malleable and include (i) spleen mass, (ii) blood volume, and (iii) hemoglobin (Hb) pool size. Increases in any of these traits (or in a morphological character, body size) improve diving capacity. Assuming that conserved physiological function means conserved sequences in specific genes and their products (and that evolving function requires changes in such sequences), it is possible to rationalize both the above trait categories in pinniped phylogeny. However, it is more difficult for molecular evolution theory to explain how complex regulatory systems like those involved in bradycardia and peripheral vasoconstriction remain the same through phylogenetic time than it is to explain physiological change driven by directional natural selection.

Animals↗
PubMed1984

Development of an organic affective syndrome during a hyperbaric diving experiment.

The authors describe the clinical and pharmacologic management of a patient who developed an organic affective syndrome during a simulated deep-diving experiment. The physiological complexities of deep-diving research are reviewed, as well as the neuropsychiatric symptoms of the high pressure nervous syndrome.

Atmosphere Exposure Chambers↗