Effects Of Artificial Gravity On Human Haemodynamics And Cardiovascular Function

Abstract

PURPOSE: Short radius centrifuge (SRC) devices have been amongst the most important facilities for astronauts for several decades, requiring a high relative velocity in order to generate adequate g-loads for experiments and training. SRCs caught the attention of space agencies due to ongoing plans for interplanetary missions to Mars and the Moon. This study aimed to assess changes in haemodynamics induced by artificial gravity (AG) during centrifugation on a SRC. METHODS: Eleven healthy subjects (29.57 ± 6.61 years, 183.21 ± 5.11 cm, 82.14 ± 7.24 kg) participated, none of them showing any history of vasovagal syncope. Two different AG-protocols were conducted with at least a 48h time lag in between. The continuous AG-protocol included an acceleration phase of 1g, 2g and 3g for 120 s each, followed by a continuous acceleration of 2g for 30 min and a final acceleration phase of 1g, 2g and 3g for 120 s each. In contrast, the intermittent protocol included a phase of intermittent g-load of 2g for 180 s interrupted by a pause of 180 s (baseline rotation of 5RPM). This sequence of acceleration was repeated four times. Changes in oxygenated blood (O2Hb) and deoxygenated blood (HHb) in the underlying tissue were recorded using a 4-channel Near Infrared Spectroscopy (NIRS) system on the prefrontal cortex (PFC), musculus biceps brachii (MBB) and musculus gastrocnemius (MG). RESULTS: Concentration in O2Hb decreased (F(13, 130) = 26,356, p < .05) and in HHb increased (F(13, 130) = 11.119, p < .05) during acceleration phases 1 and 2 in the PFC in both AG profiles. Similarly, concentration in O2Hb decreased (F(13, 130) = 16,478, p < .05) and in HHb increased (F(13, 130) = 11,178, p < .05) during same phases in the MBB. Peripheral venous pooling was indicated by increased concentration in both, O2Hb (F(13, 117) = 11,830, p < .05) and HHb (F(13, 117) = 5,3686, p < .05) during acceleration phases in the MG. Continuous acceleration induced peripheral accumulation of both O2Hb and HHb, whereas intermittent acceleration kept concentration in both parameters stable. CONCLUSION: NIRS is an appropriate method for assessing cranial blood oxygenation and venous pooling in the peripheral extremities during application of AG. Haemodynamics and the regulation of the cardiovascular system appear to be affected by the g-load applied by an SRC.