Analysis of human microcirculation in weightlessness: Study protocol and pre-study experiments.

Background: In weightlessness, alterations in organ systems have been reported. The microcirculation consists of a network of blood vessels with diameters of a few μm. It is considered the largest part of the circulatory system of the human body and essential for exchange of gas, nutrients and waste products. An investigation of the microcirculation in weightlessness seems warranted but has not yet been performed.

Objective: In this paper, we outline a study in which we will investigate the possible interrelations between weightlessness and microcirculation. We will induce weightlessness in the course of parabolic flight maneuvers, which will be conducted during a parabolic flight campaign. In this study protocol also an evaluation of a possible influence of parabolic flight premedication on microcirculation will be described.

Methods: The microcirculation will be investigated by sublingual intravital measurements applying sidestream darkfield microscopy. Parameters of macrocirculation such as heart rate, blood pressure and blood oxygenation will also be investigated.

Results: In our pre-study experiments, neither dimenhydrinate nor scopolamine altered microcirculation.

Conclusions: As the application of motion sickness therapy did not alter microcirculation, it will be applied during the parabolic flight maneuvers of the campaign. Our results might deepen the understanding of microcirculation on space missions and on earth.