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      Static Metabolic Bubbles as Precursors of Vascular Gas Emboli During Divers’ Decompression: A Hypothesis Explaining Bubbling Variability

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          The risk for decompression sickness (DCS) after hyperbaric exposures (such as SCUBA diving) has been linked to the presence and quantity of vascular gas emboli (VGE) after surfacing from the dive. These VGE can be semi-quantified by ultrasound Doppler and quantified via precordial echocardiography. However, for an identical dive, VGE monitoring of divers shows variations related to individual susceptibility, and, for a same diver, dive-to-dive variations which may be influenced by pre-dive pre-conditioning. These variations are not explained by currently used algorithms. In this paper, we present a new hypothesis: individual metabolic processes, through the oxygen window (OW) or Inherent Unsaturation of tissues, modulate the presence and volume of static metabolic bubbles (SMB) that in turn act as precursors of circulating VGE after a dive.


          We derive a coherent system of assumptions to describe static gas bubbles, located on the vessel endothelium at hydrophobic sites, that would be activated during decompression and become the source of VGE. We first refer to the OW and show that it creates a local tissue unsaturation that can generate and stabilize static gas phases in the diver at the surface. We then use Non-extensive thermodynamics to derive an equilibrium equation that avoids any geometrical description. The final equation links the SMB volume directly to the metabolism.

          Results and Discussion

          Our model introduces a stable population of small gas pockets of an intermediate size between the nanobubbles nucleating on the active sites and the VGE detected in the venous blood. The resulting equation, when checked against our own previously published data and the relevant scientific literature, supports both individual variation and the induced differences observed in pre-conditioning experiments. It also explains the variability in VGE counts based on age, fitness, type and frequency of physical activities. Finally, it fits into the general scheme of the arterial bubble assumption for the description of the DCS risk.


          Metabolism characterization of the pre-dive SMB population opens new possibilities for decompression algorithms by considering the diver’s individual susceptibility and recent history (life style, exercise) to predict the level of VGE during and after decompression.

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          Most cited references 88

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          Physicochemical approach to nanobubble solutions

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            Microparticles initiate decompression-induced neutrophil activation and subsequent vascular injuries.

            Progressive elevations in circulating annexin V-coated microparticles (MPs) derived from leukocytes, erythrocytes, platelets, and endothelial cells are found in mice subjected to increasing decompression stresses. Individual MPs exhibit surface markers from multiple cells. MPs expressing platelet surface markers, in particular, interact with circulating neutrophils, causing them to degranulate and leading to further MP production. MPs can be lysed by incubation with polyethylene glycol (PEG) telomere B surfactant, and the number of circulating MPs is reduced by infusion of mice with PEG or antibody to annexin V. Myeloperoxidase deposition and neutrophil sequestration in tissues occur in response to decompression, and the pattern differs among brain, omentum, psoas, and leg skeletal muscle. Both MP abatement strategies reduce decompression-induced intravascular neutrophil activation, neutrophil sequestration, and tissue injury documented as elevations of vascular permeability and activated caspase-3. We conclude that MPs generated by decompression stresses precipitate neutrophil activation and vascular damage.
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              The Prevention of Compressed-air Illness.


                Author and article information

                Front Physiol
                Front Physiol
                Front. Physiol.
                Frontiers in Physiology
                Frontiers Media S.A.
                11 July 2019
                : 10
                1Divetech , Biot, France
                2Department of Computer Engineering, Galatasaray University , Istanbul, Turkey
                3DAN Europe Research Division, Divers Alert Network (DAN) , Roseto, Italy
                4Centre for Hyperbaric Oxygen Therapy, Military Hospital Brussels , Brussels, Belgium
                5Environmental, Occupational and Ageing Physiology Laboratory, Haute Ecole Bruxelles-Brabant (HE2B) , Brussels, Belgium
                Author notes

                Edited by: Richard D. Boyle, National Aeronautics and Space Administration (NASA), United States

                Reviewed by: Danilo Cialoni, Dan Europe Foundation, Italy; Jacek Kot, Medical University of Gdańsk, Poland; Rodrigue Pignel, Université de Genève, Switzerland

                *Correspondence: Salih Murat Egi, smegi@ 123456daneurope.org

                This article was submitted to Environmental, Aviation and Space Physiology, a section of the journal Frontiers in Physiology

                Copyright © 2019 Imbert, Egi, Germonpré and Balestra.

                This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

                Page count
                Figures: 2, Tables: 1, Equations: 8, References: 95, Pages: 12, Words: 0
                Hypothesis and Theory

                Anatomy & Physiology

                pre-conditioning, oxygen window, desaturation, decompression sickness, diving


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