scientific-2007-2008

Scientific papers 2007 - 2008

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.

21 - Mitchell & Doolette: Selective vulnerability of the inner earto decompression sickness in divers with right-to-left shunt: the role of tissue gas supersaturation.

This paper has been published by the department of anesthesiology of the university of Auckland (New Zealand), and the Naval experimental diving unit, Panama City, Florida, USA.

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).

Diving-related pulmonary effects are due mostly to increased gas density, immersion-related increase in pulmonary blood volume, and (usually) a higher inspired PO2. Higher gas density produces an increase in airways resistance and work of breathing and a reduced maximum breathing capacity. An additional mechanical load is due to immersion, which can impose a static transrespiratory pressure load as well as a decrease in pulmonary compliance.

Authors: Nico A.M. Schellart, Jan-JaapBrandt Corstius, Peter Germonpré, and Wouter Sterk. It is claimed that performing a “deep stop,” a stop at about half of the maximal diving depth (MDD), can reduce the amount of detectable precordial bubbles after the dive and may thus diminish the risk of decompression sickness. In order to ascertain whether this reduction is caused by the deep stop or by a prolonged decompression time, the team wanted to test the “deep stop” theory without increasing the total decompression time.

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.

Exercising before, during, or after diving is proscribed because of the assumption that it would increase the incidence of decompression sickness. The authors say that their 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. The authors also say that nitric oxide seems to play a protective role.

Author: Keith A. Gault (US Navy) Generation III Air Navy Dive Computers (AIR III) were used to record 315 ship husbandry dives conducted by divers breathing air at the Puget Sound Naval Shipyard from November 2007 to January 2008. For each profile, decompression status was assessed from the air tables in Rev. 6 of the U.S. Navy Diving Manual, and from the AIR Ills, thirty-five dives were repetitive dives (within 12 hours of previous exposure), so 280 are distinct profiles for analysis.

Abstract: Exposure to the underwater environment for recreationalor occupational purposes is increasing. Approximately 7 million divers are active worldwide and 500 000 more are training every year. Diving related illnesses are consequently an increasingly common clinical problem with over 1000 cases of decompression illness reported annually in the USA alone.

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).

20 - Preventive effect of pre-dive hydration on bubble formation in divers.

Authors: E Gempp, J E Blatteau, J-M Pontier, C Balestra, & P Louge. To investigate whether pre-hydration 90 minutes before a dive could decrease bubble formation and evaluate the consequent adjustments in plasma volume (PV), water balance, and plasma surface tension (ST), eight military divers participated in a crossover trial of pre-dive hydration using saline–glucose beverage, and a controlled dive with no pre-hydration. Drink volume was 1300 ml and drinking time was 50–60 min. The diving protocol consisted of an open sea field air dive at 30 msw depth for 30 min followed by a 9 min stop at three msw. Haemodynamic parameters, body weight measurements, urine volume, and blood samples were taken before/after fluid intake and after the dive. Decompression bubbles were examined by a precordial pulsed Doppler.

This review aims to outline advances addressing the role that reactive species of oxygen and nitrogen play in the therapeutic mechanisms of hyperbaric oxygen. The study will be organized around major categories of problems or processes where controlled clinical trials have demonstrated clinical efficacy for hyperbaric oxygen therapy. Reactive species are now recognized to play a major role in cell signal transduction cascades, and the discussion will focus on how hyperbaric oxygen acts through these pathways to mediate wound healing and ameliorate postischemic and inflammatory injuries.

Authors: Jean- Éric Blatteau, Emmanuel Gempp, Costantino Balestra, Tony Mets, and Peter Germonpre. This study investigated the influence of a far infrared-ray dry sauna-induced heat exposure before a simulated dive on bubble formation, and examined the concomitant adjustments in hemodynamic parameters.

Authors: T. Randsøe, T. M. Kvist, and O. Hyldegaard The authors of this report visually followed the in vivo changes of micro air bubbles injected into adipose tissue of anesthetized rats at 101.3 kPa (sea level), after which they were decompressed from 101.3 kPa to and held at 25 kPa (10,350 m), during breathing of oxygen or a heliox (34:66) mixture (34% helium and 66% oxygen). Furthermore, bubbles were studied during oxygen breathing preceded by a 3-h period of preoxygenation to eliminate tissue nitrogen before decompression.

The documents are classified chronologically from 2007 to 2008. Click on their descriptions to open and download them.

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.

This small study records the various contaminants that can be found in compressed gas and the control measures to implement to eliminate them.

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: Leigh A. Madden, Gerard Laden In this study, the authors hypothesize that gas bubbles are not the causative agent in the progression of DCI, rather an exacerbating factor. Endothelial dysfunction caused by a temporary loss of haemostasis due to increased total oxidant status is postulated to be the cause in this at-depth endothelial dysfunction hypothesis.

Authors: Melissa K. Brown & David C. Willms The medical use of helium-oxygen mixture (heliox) was first described as a therapy for asthma and airway obstructions in 1934 by Barach. Heliox applications have expanded from airway obstruction and asthma to bronchiolitis and chronic obstructive pulmonary disease (COPD). Helium is an odorless, colorless, non-combustible, biologically inert gas, and has other physical properties that make it medically useful when mixed with oxygen.

Authors: Nico A.M. Schellart , Jan-Jaap Brandt Corstiu, Peter Germonpré, & Wouter Sterk It is claimed that performing a “deep stop” a stop at about half of maximal diving depth (MDD), can reduce the amount of detectable precordial bubbles after the dive and may thus diminish the risk of decompression sickness. To ascertain whether this reduction is caused by the deep stop or by a prolonged decompression time, the authors tested the “ deep stop ” theory without increasing the total decompression time.

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: F. K. Butler, C. Hagan, H. Murphy-Lavoie This paper is a review of HBOT (Hyperbaric Oxygen Treatment) for ocular indications. Because some ocular disorders require rapid administration of HBOT to restore vision, patients with acute vision loss should be considered emergent when they present. Visual acuity should be checked immediately.

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.

Author: Valerie Flook This report derives from and clarifies those published by Unimed Scientific Ltd in 2002 and 2003 for “Well Ops UK Ltd”. The major part of the work was carried out for UK Health and Safety Executive, and the report is available from the HSE web site as research report number RR244.

Authors: Akin Savas Toklu, Seﬁka Korpinar, Mustafa Erelel, Gunalp Uzun, Senol Yildiz Air cysts or blebs in the lungs may predispose pulmonary barotrauma (PBT) by causing air trapping when there is a change in environmental pressure. The changes in the environmental pressure are also seen during hyperbaric oxygen treatments (HBOT). The aim of this study was to determine how patients were evaluated for pulmonary blebs or bullae, and PBT prevalence in different HBOT centers. HBOT centers were asked to participate in this study, and a questionnaire was sent via e-mail, to which 98 centers responded.

Authors: Tiina M. Makinen, Raija Juvonen, Jari Jokelainen, Terttu H. Harju, Ari Peitso, Aini Bloigu, Sylvi Silvennoinen-Kassinen, Maija Leinonen, Juhani Hassi This study examined whether the development of acute respiratory tract infections (RTIs) is potentiated by cold exposure and lowered humidity in a northern population. It should be linked to the humidity level in the diving breathing gasses.