Effects of Gradual Onset +Gz on Hemodynamic Parameters and Brain Oxygenation in Military Pilots: Preliminary Study
Journal Title: The Polish Journal of Aviation Medicine, Bioengineering and Psychology - Year 2016, Vol 22, Issue 3
Abstract
Introduction: Sustained acceleration in +Gz axis may lead to blood mass-volume displacement. Currently, during centrifuge training, this displacement is not assessed directly, but the focus is on its functional correlates, such as the narrowing of the visual field and a decrease in blood oxygenation in the pilot’s brain. These are very crude measures that say little about the physiological processes taking place in the pilot’s body. Thus, the aim was to evaluate more detailed measures of the cardiovascular system: stroke volume (SV) and cardiac output (CO) and their changes with gradual onset +Gz, as well as changes in frontal brain oxygenation (OX) in relation to Gz, SV, and CO. Methods: Eight military pilots (six active with different amounts of flight experience) performed the gradual onset rate profile of Gz, Delta Gz = 0.1G/s, till 6G. Their SV, CO were evaluated with bioimpedance cardiography, while their OX with near infrared spectroscopy. ECG was constantly monitored. Results: Increase in Gz led to linear decreases in SV, while CO remained statistically unchanged; however, in most cases, OX decreased linearly with increasing Gz. Discussion: Linear increase in +Gz load on human centrifuge results in decreases in cardiac output. Increased heart rate compensates for changes in stroke volume. Nonetheless, brain oxygenation decreases with Gz, likely due to decreased lung gas exchange capacity in hypergravity. Thus, measuring blood oxygenation at the level of the brain may be a better method of monitoring pilots during centrifuge training than bioimpedance cardiography.
Authors and Affiliations
Krzysztof Kowalczuk, Liana Puchalska, Aleksander Sobotnicki, Marek Czerw, Michał Janewicz, Mariusz Wyleżoł, Stefan P. Gaździński
Keywords
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