Chasse Royale, Belgium
Chasse Royale, Belgium

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Papadopoulou V.,Imperial College London | Papadopoulou V.,Paul-Henri Spaak College | Tang M.-X.,Imperial College London | Balestra C.,Paul-Henri Spaak College | And 3 more authors.
Advances in Colloid and Interface Science | Year: 2014

Bubbles can form in the body during or after decompression from pressure exposures such as those undergone by scuba divers, astronauts, caisson and tunnel workers. Bubble growth and detachment physics then becomes significant in predicting and controlling the probability of these bubbles causing mechanical problems by blocking vessels, displacing tissues, or inducing an inflammatory cascade if they persist for too long in the body before being dissolved. By contrast to decompression induced bubbles whose site of initial formation and exact composition are debated, there are other instances of bubbles in the bloodstream which are well-defined. Gas emboli unwillingly introduced during surgical procedures and ultrasound microbubbles injected for use as contrast or drug delivery agents are therefore also discussed. After presenting the different ways that bubbles can end up in the human bloodstream, the general mathematical formalism related to the physics of bubble growth and detachment from decompression is reviewed. Bubble behavior in the bloodstream is then discussed, including bubble dissolution in blood, bubble rheology and biological interactions for the different cases of bubble and blood composition considered. © 2014 The Authors.


Papadopoulou V.,Imperial College London | Papadopoulou V.,Paul-Henri Spaak College | Eckersley R.J.,King's College London | Balestra C.,Paul-Henri Spaak College | And 3 more authors.
Advances in Colloid and Interface Science | Year: 2013

Bubbles are known to form in the body after scuba dives, even those done well within the decompression model limits. These can sometimes trigger decompression sickness and the dive protocols should therefore aim to limit bubble formation and growth from hyperbaric decompression. Understanding these processes physiologically has been a challenge for decades and there are a number of questions still unanswered. The physics and historical background of this field of study is presented and the latest studies and current developments reviewed. Heterogeneous nucleation is shown to remain the prime candidate for bubble formation in this context. The twomain theories to account formicronuclei stability are then to consider hydrophobicity of surfaces or tissue elasticity, both ofwhich could also explain some physiological observations. Finally themodeling relevance of the bubble formation process is discussed, together with that of bubble growth as well as multiple bubble behavior. © 2013 Elsevier B.V. All rights reserved.


Calzia E.,Universitatsklinikum | Asfar P.,University of Angers | Hauser B.,Semmelweis University | Matejovic M.,Interni Klinika | And 3 more authors.
Critical Care Medicine | Year: 2010

The current practice of mechanical ventilation comprises the use of the least inspiratory O2 fraction associated with an arterial O 2 tension of 55 to 80 mm Hg or an arterial hemoglobin O2 saturation of 88% to 95%. Early goal-directed therapy for septic shock, however, attempts to balance O2 delivery and demand by optimizing cardiac function and hemoglobin concentration, without making use of hy-peroxia. Clearly, it has been well-established for more than a century that long-term exposure to pure O2 results in pulmonary and, under hyperbaric conditions, central nervous O2 toxicity. Nevertheless, several arguments support the use of ventilation with 100% O2 as a supportive measure during the first 12 to 24 hrs of septic shock. In contrast to patients without lung disease undergoing anesthesia, ventilation with 100% O2 does not worsen intrapulmonary shunt under conditions of hyperinflammation, particularly when low tidal volume-high positive end-expiratory pressure ventilation is used. In healthy volunteers and experimental animals, exposure to hyperoxia may cause pulmonary inflammation, enhanced oxidative stress, and tissue apoptosis. This, however, requires long-term exposure or injurious tidal volumes. In contrast, within the timeframe of a perioperative administration, direct O2 toxicity only plays a negligible role. Pure O2 ventilation induces peripheral vasoconstriction and thus may counteract shock-induced hypotension and reduce vasopressor requirements. Furthermore, in experimental animals, a redistribution of cardiac output toward the kidney and the hepato-splanchnic organs was observed. Hyperoxia not only reverses the anesthesia-related impairment of the host defense but also is an antibiotic. In fact, perioperative hyperoxia significantly reduced wound infections, and this effect was directly related to the tissue O2 tension. Therefore, we advocate mechanical ventilation with 100% O2 during the first 12 to 24 hrs of septic shock. However, controlled clinical trials are mandatory to test the safety and efficacy of this approach. (Crit Copyright © 2010 by the Society of Critical Care Medicine and Lippincott Williams & Wilkins.


Grant
Agency: Cordis | Branch: FP7 | Program: MC-ITN | Phase: FP7-PEOPLE-2010-ITN | Award Amount: 3.40M | Year: 2011

Decompression sickness (DCS) is caused by circulating inert gas bubble formation in blood vessels and tissues resulting from supersaturation during inadequate decompression. It is an acknowledged risk of situations involving variations in ambient pressure, such as space flight and extravehicular activity, exposure to altitude, hyperbaric tunnelling intervention, as well as recreational and commercial underwater diving. Because new industrial challenges (human space flight programs, deeper planed tunnelling interventions and offshore oil excavation) and emerging recreational demands, the range of both environmental conditions and population characteristics involved in such activities regularly widen. Thus, new interdisciplinary approaches of decompression are needed to reduce risk for DCS. To foster knowledge of decompression phenomena, the PHYPODE ITN proposes to : - Develop an educational and research framework for cross-fertilization of currently fragmented research activities on physiopathology of decompression; - Give young researchers opportunities to share research techniques and resources, benefit from the best international scientists knowledge in this field, have the advantages of strong interactions between industry, medical centres and academia; - Widen career prospectives of young researchers by embracing the whole chain of research : from fundamental research for pathophysiological understanding of decompression to applied research in the industry for management of decompression. To achieve this training programme, academic partners, non profit association with worldwide activities, hyperbaric medical centres and industrial partners, with complementary expertises will build up the common agreed program concerning education and research.


Hemelryck W.,Military Hospital Queen Astrid | Hemelryck W.,Paul-Henri Spaak College | Germonpre P.,Military Hospital Queen Astrid | Papadopoulou V.,Paul-Henri Spaak College | And 4 more authors.
Scandinavian Journal of Medicine and Science in Sports | Year: 2014

We investigated long-term effects of SCUBA diving on cognitive function using a battery of neuropsychometric tests: the Simple Reaction Time (REA), Symbol Digit Substitution (SDS), Digit Span Backwards (DSB), and Hand-Eye Coordination tests (EYE). A group (n=44) of experienced SCUBA divers with no history of decompression sickness was compared to non-diving control subjects (n=37), as well as to professional boxers (n=24), who are considered at higher risk of long term neurological damage. The REA was significantly shorter in SCUBA divers compared to the control subjects, and also more stable over the time course of the test. In contrast, the number of digits correctly memorized and reordered (DSB) was significantly lower for SCUBA divers compared to the control group. The results also showed that boxers performed significantly worse than the control group in three out of four tests (REA, DSB, EYE). While it may be concluded that accident-free SCUBA diving may have some long-term adverse effects on short-term memory, there is however, no evidence of general higher cognitive function deficiency. © 2013 John Wiley & Sons A/S.


Balestra C.,DAN Europe Research Division | Balestra C.,Military Hospital Queen Astrid | Lafere P.,DAN Europe Research Division | Lafere P.,Military Hospital Queen Astrid | And 3 more authors.
European Journal of Applied Physiology | Year: 2012

One of the possible risks incurred while diving is inert gas narcosis (IGN), yet its mechanism of action remains a matter of controversy. Although providing insights in the basic mechanisms of IGN, research has been primarily limited to animal studies. A human study, in real diving conditions, was needed. Twenty volunteers within strict biometrical criteria (male, age 30-40 years, BMI 20-23, non smoker) were selected. They performed a nodecompression dive to a depth of 33 mfw for 20 min and were assessed by the means of critical flicker fusion frequency (CFFF) measurement before the dive, during the dive upon arriving at the bottom, 5 min before the ascent, and 30 min after surfacing. After this late measurement, divers breathed oxygen for 15 min and were assessed a final time. Compared to the pre-dive value the mean value of each measurement was significantly different (p<0.001). An increase of CFFF to 104 ± 5.1 % upon arriving to the bottom is followed by a decrease to 93.5 ± 4.3 %. This impairment of CFFF persisted 30 min after surfacing, still decreased to 96.3 ± 8.2 % compared to pre-dive CFFF. Post-dive measures made after 15 min of oxygen were not different from control (without nitrogen supersaturation), 124.4 ± 10.8 versus 124.2 ± 3.9 %. This simple study suggests that IGN (at least partially) depends on gas-protein interactions and that the cerebral impairment persists for at least 30 min after surfacing. This could be an important consideration in situations where precise and accurate judgment or actions are essential. © Springer-Verlag 2012.


Piquet M.,Paul-Henri Spaak College | Balestra C.,Paul-Henri Spaak College | Sava S.L.,University of Liège | Schoenen J.E.,University of Liège
BMC Neurology | Year: 2011

Background: Transcutaneous neurostimulation (TNS) at extracephalic sites is a well known treatment of pain. Thanks to recent technical progress, the Cefaly ®device now also allows supraorbital TNS. During observational clinical studies, several patients reported decreased vigilance or even sleepiness during a session of supraorbital TNS. We decided therefore to explore in more detail the potential sedative effect of supraorbital TNS, using standardized psychophysical tests in healthy volunteers.Methods: We performed a double-blind cross-over sham-controlled study on 30 healthy subjects. They underwent a series of 4 vigilance tests (Psychomotor Vigilance Task, Critical Flicker Fusion Frequency, Fatigue Visual Numeric Scale, d2 test). Each subject was tested under 4 different experimental conditions: without the neurostimulation device, with sham supraorbital TNS, with low frequency supraorbital TNS and with high frequency supraorbital TNS.Results: As judged by the results of three tests (Psychomotor Vigilance Task, Critical Flicker Fusion Frequency, Fatigue Visual Numeric Scale) there was a statistically significant (p < 0.001) decrease in vigilance and attention during high frequency TNS, while there were no changes during the other experimental conditions. Similarly, performance on the d2 test was impaired during high frequency TNS, but this change was not statistically significant.Conclusion: Supraorbital high frequency TNS applied with the Cefaly ®device decreases vigilance in healthy volunteers. Additional studies are needed to determine the duration of this effect, the underlying mechanisms and the possible relation with the stimulation parameters. Meanwhile, this effect opens interesting perspectives for the treatment of hyperarousal states and, possibly, insomnia. © 2011 Piquet et al; licensee BioMed Central Ltd.


Cialoni D.,DAN Europe Foundation | Pieri M.,DAN Europe Foundation | Balestra C.,Paul-Henri Spaak College | Marroni A.,DAN Europe Foundation
Aviation Space and Environmental Medicine | Year: 2014

Introduction: Flying after diving may increase decompression sickness risk (DCS), but strong evidence indicating minimum preflight surface intervals (PFSI) is missing. Methods: On return flights after a diving week on a live-aboard, 32 divers were examined by in-flight echocardiography with the following protocol: 1) outgoing flight, no previous dive; 2) during the diving week; 3) before the return flight after a 24-h PFSI; and 4) during the return flight. Results: All divers completed similar multiple repetitive dives during the diving week. All dives were equivalent as to inert gas load and gradient factor upon surfacing. No bubbles in the right heart were found in any diver during the outgoing flight or at the preflight control after a 24-h PFSI following the diving week. A significant increase in the number and grade of bubbles was observed during the return flight. However, bubbles were only observed in 6 of the 32 divers. These six divers were the same ones who developed bubbles after every dive. Conclusions: Having observed a 24-h preflight interval, the majority of divers did not develop bubbles during altitude exposure; however, it is intriguing to note that the same subjects who developed significant amounts of bubbles after every dive showed equally signifi- cant bubble grades during in-flight echocardiography notwithstanding a correct PFSI. This indicates a possible higher susceptibility to bubble formation in certain individuals, who may need longer PFSI before altitude exposure after scuba diving. © by the Aerospace Medical Association, Alexandria, VA.


Salem W.,Free University of Colombia | Salem W.,Paul-Henri Spaak College | Klein P.,Free University of Colombia
Manual Therapy | Year: 2013

Segmental range of motion (ROM) during high-velocity manipulative spinal treatment is generally considered an important factor for the risk of adverse side effects, especially in the cervical spine region. Among the many techniques reported, the so-called multiple-component technique (MCT) is increasingly recommended. Such a technique is assumed to induce a relatively low three-dimensional (3D) segmental ROM compared with other techniques. The aims of our study are to quantify the 3D segmental ROM and to determine the pattern of motion between cervical vertebrae during the pre-manipulative position at the C4-C5 level. Ten healthy volunteers participated in this study. Two CT scans were conducted: one in a neutral position and the other in the pre-manipulative positioning. The manipulation using MCT was carried out by a skilled practitioner. During positioning, the head was rotated to the left and bent laterally to the right, and the upper cervical spine was rotated to the left and bent laterally to the right. In contrast, the lower cervical spine underwent right rotation and was bent laterally to the right. Segmental ROM was lower than the values obtained during active physiological rotation (P<0.05). This study provides new insight into the 3D kinematics of the cervical spine during manipulation. An unexpected mechanism of counter-rotation was identified at the lower cervical levels and could represent a valuable and convenient way for precisely focussing on the level for manipulation. © 2013 .


Peeters A.,Paul-Henri Spaak College
Safety, Reliability, Risk and Life-Cycle Performance of Structures and Infrastructures - Proceedings of the 11th International Conference on Structural Safety and Reliability, ICOSSAR 2013 | Year: 2013

In any model, a large number of uncertainties has to be taken into account and they have to be combined. The way they are combined has a large influence on the uncertainties linked to the final result but also on the possible evolutions of the studied system. The Sti imulus-Driven Theory of Probabilistic Dynamics (SDTPD) allows investigating the different possible evolutions and the probability of each evolution.Nevertheless the SDTPD leads to complex equations. Hence, a computer code - MoSt - has been developed. It combines the SDTPD approach for the occurrence (or not) of events, a computing of the process variables for the system evolution and the Monte Carlo simulation techniques for the probabilistic aspect. Through a small example, this article presents the way uncertainties can be modeled thanks to the SDTPD and the results obtained with MoSt. Indeed, with this method, it is easily possible to combine various kinds of uncertainties but also to investigate the impact of numerous uncertainties. © 2013 Taylor & Francis Group, London.

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