Getting Closer to A Complete Understanding of Decompression Sickness

Decompression sickness is a major risk for subjects exposed to a significant decrease of ambient pressure, like what occurs in underwater diving, tunneling, flying at high altitude or in space exploration. While we know that there is an association between post-decompression occurrences of gas bubbles in body tissues and DCS, we still do not know where the bubbles originate, why they do not occur in all divers on the same dive, and how they lead to DCS. An increasing number of studies are focusing on possible role of micro particles in DCS.

EUO_female-diver-over-under-Thailand-boat_iStock-473093334.jpg

Microparticles are particles with diameters of 0.1

to 1 micrometer that various cells shed when exposed to noxious factors or various stimulations, and they play role in many biological processes and diseases. Microparticles are also elevated in divers after dive, and they seem to be related to bubbles. Some interventions that decrease number of post-dive bubbles, have been shown to diminish elevation of microparticles. It has also been shown that if animals not previously exposed to decompression receive microparticles from animal that were decompressed, they will develop symptoms of DCS. In blood samples from human divers who were admitted to recompression chambers for treatment of DCS, more microparticles were found than in a blood samples of the control group of divers who did not develop DCS.

A group of scientists led by Steven R. Thom of University of Maryland, previously University of Pennsylvania, did pioneering work in this area. They are identifying specific groups of microparticles involved, and biological processes through which they can contribute to occurrence or severity of DCS.

A group from Second Military Medical University in Shanghai led by Weighang Xu, recently published a series of articles describing their studies of how MPs may be related to DCS. Specifically, they studied a subgroup of endothelial microparticles (EMPs). The endothelium is a single cell layer that lines the inner surface of our blood and lymphatic vessels. There are more than a trillion endothelial cells in the body covering 3000 square meters area — they are involved in the control of vasomotor tonus, maintenance of structure and integrity of blood vessels, growth of new blood vessels, maintenance of blood fluidity, repair of tissue damage, regulation of blood clotting and prevention of hemorrhage, initiation and control of inflammation. It was shown previously that diving affects endothelial function and that it may be related to DCS.

In a series of in-vivo and in-vitro studies, Xu and his coworkers demonstrated how contact with bubbles changes endothelial cells and their function, described some of the mechanism and demonstrated how the adverse effects of bubbles may be prevented by various pre-treatments.

The progress of science is never smooth and straightforward and we cannot predict how long will it take to learn enough about bubbles, endothelium and DCS to be able to produce efficient prevention of DCS, but we know that science is making significant inroads into this matter and that we are every day closer to the ideals of precision medicine and individualized medical solutions.

Author: Petar J. Denoble

References
Yu X, Xu J, Huang G, Zhang K, Qing L, Liu W, et al. (2017) Bubble-Induced Endothelial Microparticles Promote Endothelial Dysfunction. PLoS ONE 12(1): e0168881. doi:10.1371/journal.pone.0168881.
Zhang, K. et al. Endothelia-Targeting Protection by Escin in Decompression Sickness
Rats. Sci. Rep. 7, 41288; doi: 10.1038/srep41288 (2017).
Yu  X,  Xu J,  Liu W,  Xu W. (2018): Bubbles Induce Endothelial Microparticle Formation via a Calcium-Dependent Pathway Involving Flippase Inactivation and Rho Kinase Activation. Cell Physiol Biochem 2018;46:965-974. DOI: 10.1159/000488825
Published online: April 17, 2018

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