scientific-2000-2002

Scientific papers 2000 - 2002

Abstract: The risk of decompression sickness is a safety problem related to offshore diving operations. Modem safety management defines a systematic approach to such a problem based on policy edition, support from an organisation, planning and implementing, monitoring, reviewing, and auditing. These activities are analysed in light of the experience of a large diving company, achievements are listed, and areas of improvement are identfied. It is shown that the next edition of decompression procedures will require hundreds of thousands of dive records to identify the critical factors, define models, and validate new procedures. This exceeds the experience of a single diving company or even a single nation, and it is believed that efforts of decompression sickness management should be coordinated at a European level.

This document is a presentation of a diving algorithm based on the Reduced Gradient Bubble Model (RGBM).

This document is written in French by doctors from the hospital group of reunion island. It discusses herniated intervertebral disks and diving activities. The authors recall basic spinal hygiene rules, expose several neuro-radiological and therapeutic indications, and make a brief review of the literature on the impacts of diving on the spine. The differential diagnosis with a decompression accident in the spinal cord is also discussed.

The oxygen window. Inherent unsaturation. Partial pressure vacancy. Most divers with an interest in decompression diving have likely encountered one of these terms at some time. All three terms are used to describe the same physical phenomenon. For this article, the term oxygen window will be used, as it appears to be the most commonly applied term. However, the terms inherent unsaturation and partial pressure vacancy more correctly describe the physical phenomenon. Current techniques of oxygen-facilitated decompression diving are based on use of the oxygen window. Despite common use by divers of the oxygen window, it appears to be one of the least appreciated concepts in decompression diving. Understanding the oxygen window requires knowledge of circulatory and gas transport physiology, and the best place to start is with normobaric physiology.

Cerebral gas embolism is a serious consequence of diving. It is associated with decompression sickness and is assumed to cause severe neurological dysfunction. A mathematical model previously developed to calculate embolism absorption time based on in vivo bubble geometry is used in which various conditions of hyperbaric therapy are considered… To continue…

Deep stops usually reduce overall decompression time (hang time). And when coupled to the use of helium in the breathing mixture (trimix) to reduce narcotic effects of nitrogen, technical divers report feeling much better physically today when they leave the water. The reduction in hang time ranges from 10% to as high as 50%, depending on the diver, mix, depth, and exposure time. Feeling better while decompressing for shorter periods of time is certainly a win-win situation that would have been thought an impossibility not too long ago.

Physical readiness and body makeup are considered fundamental attributes of U.S. Navy divers. Methods to objectively determine body makeup are fraught with shortcomings and can be technically challenging, particularly in field operations. Two potential field methods of determining body composition, densitometry and deuterium oxide dilution, were assessed and compared in the laboratory.

Authors: R.G. Dunford, R.D. Vann , W.A. Gerth, C.F. Pieper, K. Huggins, C. Wacholtz, and P.B. Bennett. Decompression sickness (DCS) is a pathological event thought caused by intravascular and extravascular gas bubbles. The bubble theory of DCS is supported by empirical evidence, and venous gas emboli (VGE) can be detected after diving using non-invasive Doppler ultrasonic methods, but the etiology of DCS is complex, and VGE are frequent after symptom-free dives. High VGE levels, however, are associated statistically with increased DCS incidence suggesting that VGE and DCS may share a common origin. Further, VGE might initiate DCS should they cross or bypass the pulmonary capillary filter and be transported by the arterial circulation to organs such as the brain or spinal cord.

Du 6 au 10 juin 1988 eut lieu à Kongsvoll, en Norvège, un symposium international consacré au thème de la sursaturation et la formation de bulles dans les fluides et les organismes. La première partie du document présentent les participants et le thème qu’ils ont développés. ). La deuxième partie du document est la traduction d’un article du Dr Hennessy qui présente une hypothèse concernant la décompression en plongée. A la suite de cet article, figure la retranscription de la discussion qui suivit entre les participants à propos de cette nouvelle hypothèse.

Cells from virtually all organisms respond to various stresses by the rapid synthesis of a highly conserved set of polypeptides termed heat shock proteins (HSPs). The precise functions of HSPs are unknown, but there is considerable evidence that these stress proteins are essential for survival at both average and elevated temperatures. HSPs also appear to play a critical role in developing thermotolerance and protection from cellular damage associated with stresses such as ischemia, cytokines, and energy depletion. These observations suggest that HSPs play an essential role in normal cellular homeostasis and the stress response. This mini-review examines recent evidence and hypotheses suggesting that the HSPs may be important modifying factors in cellular responses to various physiologically relevant conditions such as hyperthermia, exercise, oxidative stress, metabolic challenge, and aging.

It is accepted that gas bubbles grow from pre-existing gas nuclei in tissue. The possibility of eliminating gas nuclei may be of benefit in preventing decompression sickness. The present study examined the hypothesis that hyperbaric oxygen may replace the resident gas in the nuclei with oxygen and eliminate the nuclei themselves because of its metabolic role.

There is a dispute as to whether paradoxical gas embolism is an important aetiological factor in neurological decompression illness, particularly when the spinal cord is affected. The authors performed a blind case-controlled study to determine the relationship between manifestations of neurological decompression illness and causes in 100 consecutive divers with neurological decompression illness and 123 unaffected historical control divers. The clinical effects of neurological decompression illness (including the sites of lesions and onset latency) were correlated with right-to-left shunts, lung disease, and a provocative dive profile.

Authors: A. Hjelde, s. Kotengz, 0. Eftedalz, at A. 0. Brubakk There is a considerable difference in detected venous gas emboli (VGE) between individuals following decompression. This study explores the role surface tension that may play in the differences. The authors measured serum surface tension in 26 anesthetized pigs before (predive) and after a dive (postdive) to 300 kPa for 3 hours. Gas bubbles in the pulmonary artery were monitored continuously from the beginning of decompression and continued throughout 120 minutes after the dive.

Authors: P. T. Wilmshurst, M. J. Pearson, K. P. Walsh, W. L. Morrison, and P. Bryson. A large right-to-left shunt is associated with neurological decompression illness after non-provocative dives, resulting from paradoxical gas embolism. A few observations suggest that cutaneous decompression illness is also associated with a right-to-left shunt, although an embolic aetiology of a diffuse rash is more diffcult to explain. The authors performed a retrospective case- control comparison of the prevalence and sizes of right-to- left shunts determined by contrast echocardiography performed blind to history in 60 divers and one caisson worker with a history of cutaneous decompression illness and 123 historical control divers.

Authors: Carturan, D., A. Boussuges, P. Vanuxem, A. Bar- Hen, H. Burnet, and B. Gardette. This study aimed to assess the effects of ascent rate, age, maximal oxygen uptake (VO2 max), and percent body fat on the production of bubbles after diving. Fifty male recreational divers performed two dives at 35 m during 25 min and then ascended in one case at 9 m/min and in the other case at 17 m/min. They performed the same decompression stops in the two cases. Twenty-eight divers were Doppler monitored at 10- min intervals until 60 min after surfacing, and the data were analyzed by Wilcoxonsigned-rank test to compare the effect of ascent rate on the kinetics of bubbles. Twenty-two divers were monitored 60 min after surfacing.

Authors: Ulrik Wisløff , Russell S. Richardson, and Alf O. Brubakk This study determines the effect of inhibiting nitric oxide synthase (NOS) on bubble formation in acutely exercised and sedentary rats exposed to hyperbaric pressure.

Author: Shi Zhong-yuan A collaborative experiment with Chinese Underwater Technology Institute, American National Office of Research Undersea Program, and Hamilton Research Ltd. was conducted at our Institute in Shanghai. The main experiment objectives were to assess the longer, deeper repetitive excursions during nitrogen-oxygen saturation situation, oxygen exposure management, nitrox saturation decompression after excursions and performance aspects.

Authors: Anuj Chawla & Ak Lavania This short paper is not a study, but a document used to teach divers and specialists about oxyfen toxicity

Authors: Russell P. Bowler & James D. Crapo This document is purely medical. It has been integrated to provide information on the effect of oxidative stress,

Thirteen cases of decompression sickness (DCS) occurred during the construction of the 8-km long railway tunnel under the Great Belt in Denmark between January 1992 and February 1996. 320 compressed air workers were subjected to 9018 pressure exposures in four tunnel boring machines. Overall DCS incidence was 0.14%. Working pressures ranged between 0.25 bar (1.25 atm abs or 126.3 kPa) and 2.95 bar (3.91 atm abs or 396.3 kPa) and working times ranged between 2 minutes and 339 minutes.

Research on the validation of decompression tables is one of common subject area of the cooperation undertaken between the defense and civil institute of environmental medicine, Toronto, Canada, and the Naval academy of Gdynia - Poland

This document from Unimed Scientific Ltd, written in 2002 by Valerie Flook for “Well Ops UK Ltd”, is a theoretical study of heliox excursion, evaluating the extent of bubble formation and suggesting changes that would reduce decompression bubbles. To complete the analysis quickly, only the depths of 75 msw, 100 msw, and 130 msw have been considered, and the maximum downward excursions considered for each was 25, 29, and 33 msw.

Authors: R. S. Lillo, & E. C. Parker A mixed-gas model for rats was developed to further explore the role of different gases in decompression and to provide a global model for possible future evaluation of its usefulness for human prediction. A Hill equation dose response model was fitted to over 5,000 rat dives by using the technique of maximum likelihood. These dives used various mixtures of He, N 2 , Ar, and O2 and had times at depth up to 2 h and varied decompression profiles.

Publisher: Divers Alert Network (DAN), Durham This document is the proceedings of a nitrox workshop organized by the Diver Alert Network (DAN) in November 2000. DAN is a non-profit organization associated with Duke University Medical Center in Durham, North Carolina, USA. The organization operates as a lifeline for scuba/recreational divers with a 24 hours hotline. It is registered in our website (see in “Entertainment”)

Authors: Z. Nachum, A. Shupak, O. Spitzer, Z. Sharoni, Y. Ramon, A. Abramovich, I. Doweck, C.R. Gordon Inner ear decompression sickness (IEDCS) may result in permanent, severe cochleo-vestibular deficits, unless immediate diagnosis is reached and the correct treatment is commenced early. Previously reported IEDCS cases were mostly associated with deep mixed helium diving, whereas after sport air diving this entity is considered to be rare.

Authors: Frederick W. Rudge This document, explains that decompression sickness may occur during flights due to the problems posed by the pressurization of airplane cabins. It is initially written for aviation personels. However, it should be considered to understand the guidelines DMAC 7.

Authors: A Onoo, M Kiyosawa, H Takase, Y Mano Pneumatic caisson engineering has been developed for large civil engineering constructions. Because of complaints of blurred vision by personnel working in pneumatic caissons, the development of myopia was suspected. The aim of this study was to determine the cause of the blurred vision and the mechanism underlying the changes. 12 caisson workers underwent a complete ophthalmological examination after completing up to 11 weeks of work (4 days/week) in a pneumatic caisson. Six months later, nine of the workers were examined again.

Authors: O. Hyldegaard, D. Kerem, Y. Melamed This document discusses the resolution of micro air bubbles injected into adipose tissue, spinal white matter, muscle, and tendon of anesthetized rats recompressed to and held at 284 kPa while rats breathed air, oxygen, heliox 80:20, or heliox 50:50.

Authors: S.E. Mawle and C.A. Jackson A sample of 142 divers, including technical divers, recreational divers, and instructors, were examined via questionnaire to determine the prevalence of ear barotrauma, related barotrauma symptoms, and middle ear infections. Sixty-four percent of divers reported symptoms of barotrauma, which included pain (47.9%), temporary deafness with tinnitus (27.5%) and vertigo (9.9%). The prevalence of middle ear infection was found in over a third of the total sample (37.3%), and was significantly more prevalent in the left ear than in the right ear (P=.016).

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Authors: David M. Domsky, Charles B. Toner, Shalini Survanshi, Andreas Fahlman, Erich Parker, & Paul Weathersby The authors developed a model to investigate severe decompression sickness (DCS) from rapid ascents in deep water. They used neutered Yorkshire pigs, exposing them to depths of 50-150 feet and surfacing them after 22 hours of exposure. Out of 128 pigs, 78 suffered severe DCS; 42 of 51 with cardiopulmonary complications died within an hour. Most neurological symptoms in survivors resolved within a day without any intervention. This study provides insights into the impact of severe DCS and treatment options, suggesting a need to reassess current human models.

Publisher: University College London https://www.ucl.ac.uk Bioimpedance explores the electrical characteristics of biological tissues, which are assessed by passing a current through them. This impedance not only varies across different types of tissues but also changes with frequency and is highly sensitive to the specific histology involved. This document offers a concise overview of the fundamental principles associated with bioimpedance.

Authors: VM Lee, and AE Hay The conclusions of this paper should be linked to post- diving travel procedures, such as DMAC 7. Typically, UK military aircrew are not exposed to altitudes above 18,000 feet, but certain situations, such as cabin depressurization or parachute operations, may require higher exposure. Experiments assessed the risk of venous gas embolism (VGE) and decompression illness (DCI) symptoms up to 35,000 ft. The results show that VGE formation is likely in aircraft, although only 7% of the subjects exhibited symptoms.

Authors: Andreas Fahlman, Peter Tikuisis, Jeffrey F. Hlimm, Paul K. Weathersby, & Susan R. Kayar A probabilistic model has been developed to predict decompression sickness (DCS) in pigs exposed to hyperbaric hydrogen. This model helps quantify the impact of hydrogen biochemical decompression, where the metabolism of hydrogen by intestinal microbes aids in safer decompression processes. The model integrates a hypothesis that predicts the positive effects of biochemical decompression across various compression and decompression scenarios involving pigs in hyperbaric hydrogen environments. This physiological interpretation lays the groundwork for future research in this area.

Authors: John D. Kalbfleisch and Ross L. Prentice This paper is an invaluable asset for researchers, statisticians, and enthusiasts in the field of statistical analysis. It encompasses both parametric and nonparametric approaches to failure time data. Parametric models assume that the data adheres to a specific distribution, necessitating the estimation of one or more parameters from the data. In contrast, nonparametric methods operate with minimal assumptions about the underlying distribution, thus avoiding the need to specify a particular distribution.

Authors: R.S. Lillo, J.F. Himm, P.K. Weathersby, D.J. Temple, K.A. Gault, & D.M. Dromsky To improve the prediction of decompression sickness risk for rescuing personnel from disabled submarines, the US Navy utilized Hill equation dose-response models. These models were applied to 898 air-saturation, direct-ascent dives involving humans, pigs, and rats, improving prediction accuracy by integrating animal data. This approach allowed for a more precise estimation of the Hill equation exponent, enhancing the reliability of predictions for human risk.

Authors: DJ Doolette, DF Gorman This study aimed to assess occupational diving practices in relation to established decompression models and to outline a method for gathering and analyzing self- reported field decompression data. The authors collected depth and time profiles using recorders worn by occupational divers at a tuna farm. The health status of the divers was evaluated daily through a self-administered health survey, which generated an interval diver health score (DHS) ranging from 0 to 30. These depth and time profiles were examined based on existing decompression models.

Authors: Kwangwook Cho, A. Ennaceur, Jon C. Cole, & Chang Kook Suh Traveling across time zones disrupts circadian rhythms and social schedules due to time shifts. The body's internal clock adapts slowly, causing a temporary misalignment with external time cues, which can negatively impact health. A study comparing airline cabin crew with ground crew found that cabin crew had higher levels of salivary cortisol, a marker of circadian disruption, on working days. This was observed only during transmeridian flights, not domestic ones. Additionally, cabin crew showed cognitive deficits, particularly in working memory, after years of chronic circadian rhythm disruption.

Authors: Ikram M. Elayam, Milton J. Axley, Paruchuri V. Prasad, Stephen T. Ahlers, & Charles R. Auker The study examines the impact of hyperbaric oxygen (HBO) treatment on nitric oxide (NO) and oxygen free radicals in the rat brain. Male rats were exposed to 100% oxygen at 3 atm pressure for 2 hours. The study concluded that NO production by NOS increases four- to five fold under HBO conditions, suggesting that elevated NO levels may contribute to HBO's neurotoxic effects.

Authors: Daniel K. Mulkey, Richard A. Henderson III, James E. Olson, Robert W. Putnam, and Jay B. Dean The study investigates oxygen levels in rat brain stem slices exposed to normobaric hyperoxia and hyperbaric oxygen (HBO2). They found that under control conditions with 95% oxygen at 1 atmosphere, the PO2 at the center of the slices was significantly higher than in the intact central nervous system. During HBO2, PO2 levels increased further, and tissue oxygen consumption decreased at high PO2 levels, similar to metabolically poisoned slices. The study concludes that the control medium used in most brain slice studies is hyperoxic at normobaric pressure, and HBO2 reduces metabolism by increasing PO2 levels.

Authors: Igor B. Mekjavic, Frank St. C. Golden, C. M. Eglin and Michael J. Tipton This study monitored the thermal status of 30 experienced saturation divers during routine deep dives from 54 to 160 meters, with durations ranging from 31 minutes to 7.5 hours. Divers ingested a radio pill, wore a data logger to measure core temperature, and provided subjective ratings of thermal perception and comfort. Results showed a significant increase in core temperature by 0.82 °C during dives, with divers feeling thermally neutral before and slightly warm during dives. The use of hot water suits was effective in preventing core temperature cooling and hypothermia.

Authors: Arvid Hope, Leif Aanderud, & Asbjorn Aakvaag This study examines dehydration and body fluid- regulating hormones during sweating in warm (38°C) freshwater and seawater immersion. It was found that body weight reductions were greater in seawater (2.5 kg) compared to freshwater (1.9 kg) during 4-hour head-out immersion experiments. Additionally, the effects of temperature on fluid loss were analyzed, showing negligible sweat production in thermoneutral (34.5°C) seawater compared to significant sweat production in warm seawater. The study recommends mandatory breaks for fluid intake during dives lasting more than 4 hours to prevent dehydration.

Authors: Hidetoshi Nagashima, Kazuya Matsumoto, Yoojin Seo, Motohiko Mohri, Nobuo Naraki, and Shigeaki Matsuoka This study examined sleep patterns during saturation dives at a 30-meter depth and habitation in a confined environment at 1 atm absolute pressure to evaluate the effects of environmental pressure. Eight inexperienced divers and nine healthy subjects participated, with sleep data recorded over 262 nights. Both conditions showed reductions in total sleep time, increased sleep latency, and decreased sleep efficiency, suggesting that these changes were due to psychological and physiological stresses from prolonged stays in a confined environment rather than the environmental pressure itself.

Authors: Thomas Heitzer, Titus Schlinzig, Karoline Krohn, Thomas Meinertz, Thomas Münzel This study investigates the relationship between endothelial dysfunction, vascular oxidative stress, and cardiovascular event rates in coronary artery disease (CAD) patients. It highlights that impaired endothelial function and increased oxidative stress are linked to atherosclerosis and may contribute to cardiovascular events. It suggests that both endothelial dysfunction and heightened oxidative stress are predictors of cardiovascular events in CAD patients, supporting the idea that oxidative stress plays a significant role in endothelial dysfunction and coronary artery disease progression.

26 - Small amounts of venous gas embolism cause delayed impairment of endothelial function and increase polymorphonuclear neutrophil infiltration

Authors: Vibeke Nossum, Atrid Hjelde, Alf O Brubakk This study investigated the effects of gas bubbles from decompression and gas embolization on endothelial function and mechanical injury in rabbits. Twelve rabbits received an infusion of 0.01 ml air/min/kg via a jugular vein catheter for 60 minutes. The endothelial response was assessed by measuring tension in the blood vessel walls and morphological changes by light microscopy. The study concludes that even small amounts of gas bubbles, similar to "silent bubbles", can impair endothelium-dependent vasoactive responses.

Author: Wulf Droge This document describes free radicals and reactive oxygen species (ROS), which can be harmful at high concentrations, damaging cellular components. However, they play crucial roles at moderate levels in cell signaling and regulatory processes, such as maintaining redox homeostasis, regulating vascular tone, and controlling oxygen tension.

Authors: Steffen Skogland, Kare Segadal, Harald Sundland, & Arvid Hope This study investigates the effects of pressure reduction, decompression rate, and repeated exposure to venous gas bubble formation in rats exposed to a heliox atmosphere. Five groups of conscious, freely moving rats were exposed to different pressure levels and decompression steps. The results showed that a larger decompression step resulted in significantly more bubbles at the same rate. Faster decompression rates also resulted in more bubbles. There was no significant difference in bubble formation between the first and second exposures.

Authors: Keith T. Palmer, Jason Poole, Jon G. Ayres, Jonathan Mann, P. Sherwood Burge, and David Coggon The authors conducted a case-control study involving men aged 20–64 admitted to hospitals in the West Midlands, England, with community-acquired pneumonia from 1996 to 1999 to test whether inhalation of metal fumes increases susceptibility to pneumonia. The study found that recent occupational exposure to metal fumes, particularly ferrous fumes, was associated with an increased risk of pneumonia.

Authors: M El-Zein, J-L Malo, C Infante-Rivard, D Gautrin The study aimed to determine the prevalence of coexisting welding-related systemic symptoms indicative of metal fume fever (MFF) and respiratory symptoms suggestive of occupational asthma (OA) among welders. Researchers administered questionnaires on respiratory and systemic symptoms, as well as occupational history, to 351 welders. The findings revealed a strong association between MFF and respiratory symptoms indicative of OA, suggesting that MFF could be a pre-marker for welding- related OA. Further investigation is needed to confirm this hypothesis. .