Simulated Hypergravity Activates Hemostasis in Healthy Volunteers

Background Hypergravity may promote human hemostasis thereby increasing thrombotic risk. Future touristic suborbital spaceflight will expose older individuals with chronic medical conditions, who are at much higher thromboembolic risk compared with professional astronauts, to hypergravity. Therefore, we tested the impact of hypergravity on hemostasis in healthy volunteers undergoing centrifugation. Methods and Results We studied 20 healthy seated men before and after 15 minutes under 3 Gz hypergravity on a long-arm centrifuge. We obtained blood samples for hemostasis testing before, immediately after, and 30 minutes after centrifugation. Tests included viscoelastic thromboelastometry, platelet impedance aggregometry, endothelial activation markers, blood rheology testing, microparticle analyses, and clotting factor analysis. Exposure to hypergravity reduced plasma volume by 12.5% (P=0.002) and increased the red blood cell aggregation index (P