Proceedings of The Physiological Society

Europhysiology 2018 (London, UK) (2018) Proc Physiol Soc 41, PCA011

Poster Communications

INFLUENCE OF CHANGING GRAVITY AND EXERTED EXHALATION - LINKAGE BETWEEN OXYGEN UPTAKE AND CARDIAC OUTPUT

A. Werner1,2, J. Koschate3, U. Drescher4, U. Hoffmann3

1. Diagnostic and Research, German Air Force - Centre of Aerospace Medicine, Königsbrück, Germany. 2. Institute of Physiology - Center for Space Medicine and extreme environments, University Medicine Charité Berlin, Berlin, Berlin, Germany. 3. Institute of Physiology and Anatomy, German Sport University Cologne, Cologne, North Rhine-Westphalia, Germany. 4. Institute for Preventive Medicine - German Armed Forces, Koblenz, Germany.


Purpose: The study was designed to show that gravity changes comparing human centrifuge (HCF) runs to parabolic flight (PFC) maneuvers induce similar changes in pulmonary oxygen uptake in the resting and exercise condition, without metabolic processes. Methods: 12 subjects having flight medical certificate and signed written inform consent (age: 30 ± 4 y, weight: 79 ± 8kg, height: 179 ± 8 cm, BMI: 24 ± 2 kg×m-2) were tested on a long-arm human centrifuge applying a posGz-protocol. The cycle of a real parabola was transcribed as follows: 1.7 g for baseline (equiv. 0 g), 25 s with 2.1 g (hyper-g, pull up), 22 s of 1.2 g (transition, μg), and 25 s of 2.1 g (hyper-g, pull down); this sequence was repeated 16 times. The 1.2g intervals of the protocol were performed in relaxed rest or with exhalation on exertion (forced pressure ventilation, lower extremity muscle contraction, and a combination). Cardiac output (Q') was measured beat to beat, and oxygen uptake (V'O2pulm) as well as carbon dioxide output (V'CO2pulm) were analyzed breath by breath. The same setting was flown in two parabolic flight campaigns. Results: At rest, after gravity change ‘2.1 g - 1.2 g' an increase in Q' from 7.2 L/min (± 1.8 L/min) up to 9.1 (± 2.3 L/min) with transients for V'O2pulm from 0.50 L/min (± 0.15 L/min) to 0.72 L/min to (± 0.15 L/min) were found and for V'CO2pulm from 0.42 L/min to (± 0.33 L/ min) to 0.60 L/min to (± 0.28 L/min), respectively. Six seconds after the onset of 1.2 g both, V'O2pulm and V'CO2pulm were decreased until the change ‘1.2 g - 2.1 g'. In contrast, with exhalation on exertion only a slight, unsystematic Q' increase was observed. V'O2pulm and V'CO2pulm were not increased above resting baseline. After exhalation on exertion V'O2pulm and V'CO2pulm showed a low significant (P<.05) increase of approximately 0.4 L/min. The characteristic of the curve progression comparing HCF and PFC are comparable. Conclusion: The results demonstrate a dependency between Q' and pulmonary V'O2 as well as V'CO2. Exhaling on exertion seem to empty the lung tissue and leads to a significant increase in gas exchange which only partially is a companied by Q' changes in recovery. These data allow further refining of modeling of cardiovascular influences on pulmonary V'O2 to estimate muscular V'O2 kinetics. We assume based on these findings that it could be possible to have a model of cardiovascular and pulmonary research using a long-arm human centrifuge.

Where applicable, experiments conform with Society ethical requirements