scientific-2007

Scientific papers 2007

Authors: E. Bardy, J. Mollendorf, D. Pendergast This document describes active heating/cooling experiments to thermally sustain a human subject submerged in 10, 20, 30, and 40ºC water.

Authors: O. Hyldegaard, J. Madsen In this report, the authors visually followed the in vivo resolution of micro-air bubbles injected into adipose tissue of anesthetized rats decompressed from 101.3 kPa to and held at 71 kPa corresponding to 2.750 m above sea level, while the rats breathed air, oxygen, heliox (50:50), or heliox (80:20).

The presence of gas bubbles in the vascular system is often considered a sign of decompression stress and several studies in the existing literature have addressed the relationship between the amount of bubbles detected by ultrasound Doppler systems and the incidence of decompression sickness. The use of ultrasound imaging has some important advantages to Doppler systems, and here the authors have looked at the relationship between the amount of intravascular gas bubbles detected by ultrasound echocardiography and the incidence of signs and symptoms of decompression stress after 203 air dives. They conclude that bubble detection by ultrasonic scanning of the heart can be used as a tool to assess the safety of decompression procedures for air dives.

Authors: Ksenya Katsenelson, Yehuda Arieli, Amir Abramovich, Moshe Feinsod, Ran Arieli. The authors hypothesized that the number of bubbles evolving during decompression from a dive, and therefore the incidence of decompression sickness (DCS), might be reduced by pretreatment with hyperbaric oxygen (HBO). The inert gas in the gas micronuclei would be replaced by oxygen, which would subsequently be consumed by the mitochondria. To investigate whether their hypothesis holds for mammals, the authors pretreated rats with HBO at 304, 405, or 507 kPa for 20 min, after which they were exposed to air at 1,013 kPa for 33 min and decompressed at 202 kPa/min.

Authors: Jean-Eric Blatteau, Alain Boussuges, Emmanuel Gempp, Jean-Michel Pontier, Olivier Castagna, Claude Robinet, Francois-Michel Galland, Lionel Bourdon. Sixteen trained military divers, aged 27–39 years, were compressed in a hyperbaric chamber to 400 kPa for 30 min and decompressed at a rate of 100 kPa/min with a 9 min stop at 130 kPa (French Navy MN90 procedure). Each diver performed two dives three days apart, one without exercise and one with exercise before the dive. All participants performed a 40 min constant-load submaximal and calibrated exercise, which consisted of outdoor running two h before the dive. Circulating bubbles were detected with a precordial doppler at 30, 60, and 90 min after surfacing. Haemodynamic changes were evaluated with doppler echocardiography.

Authors: Andreas Møllerløkken, Christian Gutvik, Vegard J. Berge, Arve Jørgensen, Are Løset, and Alf O. Brubakk. There is a relationship between gas bubble formation in the vascular system and serious decompression sickness. Hence, control of the formation of vascular bubbles should allow safer decompression procedures. Twelve pigs were randomly divided into an experimental group (EXP) and a control group (CTR) of 6 animals each. The pigs were compressed to 500 kPa (5 ATA) in a dry hyperbaric chamber and held for 90 min bottom time breathing air. CTR animals were decompressed according to a modified USN dive profile requiring four stops. EXP followed the same profile except that 5-min recompression of 50 kPa (0.5 ATA) was added at the end of each of the last three decompression stop before ascending to the next stop depth.

Authors: C. A. Duplessis, D. Fothergill, D. Shwaller, J. Gertner. Nitric oxide (NO) may decrease bubble formation in diving. Statin medications are attractive potential options to increase NO. Statins exhibit a proven safety profile and possess a myriad of pleiotropic properties improving vascular endothelial function. Additionally, statin-mediated lipid reduction may reduce bubble generation via alterations in plasma surface tension. The authors investigated the efficacy of atorvastatin as a pharmacological intervention to reduce the risk of bubble formation after diving, a surrogate for decompression sickness (DCS).

Authors: O. Hyldegaard, T. Jensen To monitor the effects of heliox, oxygen, and air on helium bubbles, helium bubbles from saturated rat adipose tissue were studied at 101.3 kPa (1.013 bar) during breathing of either heliox (80:20), 100% oxygen, or air after decompression from exposure to heliox at 405 kPa (4.05 bar) for one hour.

Author: Ran Arieli It has been shown that the solubility of a gas in water equilibrated with a mixture of gases is not, as postulated by Henry’s law, a linear function of the gas pressure. This phenomenon was explained by the effect of one dissolved gas on the stabilization or destabilization of the water structure, which affects the saturation solubility of another gas. The theory suggests that reduced stability will decrease the saturation solubility.

Author: R B Wienke This small document from R B Wienke continues the paper above from Ran Arieli. It relates experiments made in the USN Los Alamo laboratory on Arieli’s query about reduced solubility and risk for mixed gas diving.

Authors: . Arieli, P. Svidovsky, and A. Abramovich Trimix (a mixture of helium, nitrogen, and oxygen) has been used in deep diving to reduce the risk of high- pressure nervous syndrome during compression and the time required for decompression at the end of the dive. There is no specific recompression treatment for decompression sickness (DCS) resulting from trimix diving. This study aimed to validate a rat model of DCS on decompression from a trimix dive and to compare recompression treatment with oxygen and heliox (helium- oxygen).

Authors: Pal Pacher, Joseph S. Beckman, Lucas Liaudet Nitric oxide (NO) is an omnipresent intercellular messenger in all vertebrates, modulating blood flow, thrombosis, and neural activity. The biological production of NO is also essential for nonspecific host defense, but NO is unlikely to kill intracellular pathogens and tumors directly. Although NO is often highly toxic and reactive, it is not. In addition, NO can be produced for 80 years by neurons in the human brain without overt toxicity. Paradoxically, the production of the same molecule can become highly damaging to the same neurons within a few minutes during pathological challenges occurring after cerebral ischemia.

Authors: John A. S. Ross, Jennifer I. Macdiarmid, Liesl M. Osman, Stephen J. Watt, David J. Godden, and Andrew Lawson A postal survey sent to 2958 male professional divers, registered with the UK Health & Safety Executive (HSE) before 1991, and 2708 men who had worked in the offshore oil industry in 1990–92 (non-divers). The questionnaire addressed lifestyle, occupation and health status.

Authors: Wayne A. Gerth & David J. Doolette The Thalmann Algorithm VVal-18 was a decompression algorithm developed at the Navy Experimental Diving Unit (NEDU) to produce 0.7 atmospheres absolute (ata) constant PO2 -in-N2 decompression schedules. It was used with a modified VVal-18 parameter set, designated VVal-18M. This report documents the modifications to the VVal-18 parameter set that resulted in VVal-18M and described the accompanying updates to the Thalmann Algorithm that were required to implement these modifications correctly.

Author: John Hedley-Whyte At sea level, oxygen is toxic to man when breathed for more than twenty-four hours at a percentage greater than forty percent. Pulmonary pathology is the first manifestation in subjects with previously normal lungs. In patients with pre-existing lung disease, the results are often additive. There is, however, significant variation in response from subject to subject and between patients. Queen’s Belfast and Harvard University Medical Schools have been the site of seminal investigations. Mentoring at both universities is due to training at the University of Copenhagen.

Author: Barbara Shykoff This paper reports tests performed for four-hour dives, including underwater exercise at PO2 = 1.3 atm with 20- hour surface intervals between dives and three-hour dives with 21-hour intervals. Doctor Shykoff concluded that pulmonary changes do not accumulate with three-hour dives with exercise at Pot = 1.3 atm when divers have 21 hours between dives and that this diving schedule can be repeated indefinitely.

Authors: Dror Tal, Peter Gilbey, Ronen Bar, and Avi Shupak Seasickness is thought to result from conflicting inputs from the vestibular, visual and somatosensory systems. The otolithic organs, which are responsible for the sensation of linear acceleration and tilt, are important in the pathogenesis of seasickness. The vestibular evoked myogenic potentials test is an objective evaluation of saccular function. The objective of this study is to examine whether saccular function is related to the pathogenesis of seasickness.

Authors: Alison C. Ma, and Neal W. Pollock Diver selection is primarily based on medical fitness and physical competency criteria. Physical competency is generally evaluated through certification records and initial tests of swimming skills and in-water diving abilities. Continuation of active status requires periodic medical evaluations, current emergency care certifications, and documentation of diving activity exceeding minimum requirements. While individual institutions and programs may require additional evaluations, formal requirements for periodic assessment of physical fitness are notably absent from most standards

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Author: Saul Goldman Compartmental models have long been used in medicine to study how different substances clear out of the body. These models have been updated to help predict safe decompression times for divers. The new models include a main compartment that directly impacts safety and one or two secondary compartments that exchange gases with the main compartment. Studies show that models with three compartments are more accurate than those with two. This finding could change diving practices if further tests confirm the models' predictions.

Author: Neal W Pollock Techniques for ultrasound assessment of decompression stress continue to evolve with technological advancements. While aural Doppler remains the standard, imaging techniques are becoming increasingly popular. Current initiatives to increase the resolution of three-dimensional and dual-frequency imaging promise to expand our monitoring capabilities further. Understanding the limitations and strengths of ultrasound assessment is essential for interpreting existing decompression studies and designing new studies.

Authors: Guy C. Brown, Vilmante Borutaite Nitric oxide (NO) inhibits the mitochondrial respiratory chain, reducing Adenosine triphosphate (ATP) production, increased oxidant production, and higher susceptibility to cell death. In the heart, NO is produced by endothelial NO synthase (eNOS) in the endothelium and caveolae of cardiomyocytes, by neuronal NO synthase (nNOS) in the sarcoplasmic reticulum and possibly mitochondria, and under pathological conditions by inducible NO synthase (iNOS) in the sarcoplasm.

Authors: Ivan T. Demchenko, Karen E. Welty-Wolf, Barry W. Allen, and Claude A. Piantadosi The study examined the pulmonary effects of oxygen toxicity in rats exposed to 98% oxygen at pressures of 1, 1.5, 2, 2.5, and 3 ATA. The goal was to determine if different lung injury patterns would indicate a role for CNS excitation by hyperbaric oxygen. The study concludes that extrapulmonary, neurogenic events predominate in the pathogenesis of acute pulmonary oxygen toxicity in hyperbaric oxygenation, as Neuronal Nitric Oxide Synthase (nNOS) activity drives lung injury by modulating the output of central autonomic pathways.

Authors: Zoran Valic, Ivan Palada, and Zeljko Dujic This paper examines the effects of a short-acting nitric oxide (NO) donor on decompression sickness in humans. It provides evidence that pharmacological interventions targeting nitric oxide signaling may be a promising approach for preventing decompression sickness in humans exposed to rapid changes in ambient pressure, such as during scuba diving or aerospace activities.

Authors: Andrew J. Young & John W. Castellani Participants in prolonged, physically demanding activities in cold weather are at risk of "hiker's hypothermia." This condition arises when physiological responses, clothing, and behavioral strategies do not adequately balance the body's heat loss in a cold environment. Scientific literature indicates that prolonged or repeated cold exposure, sustained physical exertion-induced fatigue, or a combination of both can impair the body's shivering and vasoconstrictor responses to cold

Authors: Olav Sande Eftedal This document is a thesis submitted by Olav Sande Eftedal in September 2007 in support of the degree of Doctor of Philosophy at the Norwegian University of Science and Technology, Faculty of Medicine / Department of Circulation and Medical Imaging in Trondheim, Torgarden, Norway

23 - Noble Gases Without Anesthetic Properties Protect Myocardium Against Infarction by Activating Prosurvival Signaling Kinases and Inhibiting Mitochondrial Permeability Transition In Vivo

Authors: Paul S. Pagel, John G. Krolikowski, Yon Hee Shim, Suneetha Venkatapuram, Judy R. Kersten, Dorothee Weihrauch, David C. Warltier, Phillip F. Pratt The study investigates whether noble gases without anesthetic properties, such as helium (He), neon (Ne), and argon (Ar), can provide cardioprotection similar to xenon. The researchers hypothesized that these gases confer cardioprotection by activating prosurvival signaling kinases and inhibiting the opening of the mitochondrial permeability transition pore (mPTP). The results showed that He, Ne, and Ar significantly reduced myocardial infarct size in rabbits, comparable to ischemic preconditioning.

Authors: Agot Irgens, Marit Grønning, Kari Troland, Endre Sundal, Harald Nyland, and Einar Thorsen. The study examined the effects of decompression sickness (DCS) and diving exposure on the health-related quality of life (HRQL) in former Norwegian North Sea divers. A questionnaire collected HRQL data from 375 divers registered before 1990, with detailed data from 230 divers. The findings indicated that HRQL was generally reduced among these divers experiencing DCS during their careers, significantly lowering scores.

Author: A.E. Talpalar This document examines the effects of high-pressure neurological syndrome that begin at around 1.3 MPa (120 meters) and worsen with depth. Initial symptoms include tremors, nausea, and cognitive disturbances, potentially leading to severe tremors, vomiting, hyperreflexia, sleepiness, psychomotor and mental impairments, fasciculations, myoclonia, psychosis, and seizures. Electrophysiological studies show changes in brain activity and nerve conduction during HPNS. Studies indicate that HPNS symptoms are progressive and pressure-dependent.

Authors: John R. Claybaugh, Yu-Chong Lin, Heinrich G. Schafstall, and Peter B. Bennett This study investigates the impact of hyperbaria on diuresis, particularly focusing on arginine vasopressin (AVP) and atrial natriuretic peptide (ANP). Results showed a significant increase in tilt-stimulated plasma renin activity (PRA), while the AVP response was generally absent, except during tilt-induced syncope. Contrary to some previous reports, both supine and tilt-suppressed levels of ANP were reduced by about 50% under hyperbaric conditions compared to control values.

Authors: David Soo-Quee Koh, Gerald Choon-Huat Koh This document highlights the advantages of using saliva as a diagnostic fluid compared to other methods like phlebotomy. It emphasizes the non-invasive nature, ease of collection, safety, and real-time biomarker reflection of saliva, making it a preferable option for both patients and researchers.

Authors: C. E. Fife, D. R. Smart, P. J. Sheffield, H. W. Hopf, G. Hawkins, D. Clarke This study provides information and guidelines regarding transcutaneous oximetry (PtcO2) as a diagnostic tool for assessing oxygen tension in wounds, ulcers, and skin flaps. It aims to educate healthcare professionals about the significance of PtcO2 measurements, the conditions under which they are taken, and their implications for patient outcomes, particularly regarding tissue hypoxia, vascular disease, and healing predictions post-amputation or revascularization. It also summarizes consensus statements from an expert panel to guide clinical practice.

Authors: Lorne R Gale, Yi Chen, Brian A Hills, and Ross Crawford The authors of this study present research findings on the identity and role of surface-active phospholipids (SAPLs) in synovial fluid as a lubricant in diarthrodial joints. They discuss the methods used to analyze these components, the results obtained from the analysis of prostheses, and the implications of these findings for the development of artificial joints and treatments for diseases related to joint lubrication.

Authors: P.B. Bennett, A. Marroni, F.J. Cronje, R. Cali- Corleo, P. Germonpre, M. Pieri, C. Bonuccelli, M.G. Leonardi, and C. Balestra This paper discusses research findings on the optimal stop times during decompression dives to reduce precordial Doppler detectable bubbles (PDDB). It evaluates the effectiveness of varying deep and shallow stop times and provides recommendations based on the results. The authors aim to clarify the optimal stop times for reducing PDDB, suggesting a deep stop of at least 2 ½ minutes at 15 msw (50 fsw) and a shallow stop of 3-5 minutes at 6 msw (20 fsw) for dives to 25 meters lasting 20 to 25 minutes.