Development of a Platform for In Vitro Hemodynamic Measurements in Varying Gravity Profiles

INTRODUCTION: Understanding cerebrovascular flow under varying gravity is critical to mitigating flight risks such as acceleration-induced near-loss-of-consciousness and, at higher loads, gravity-induced loss-of-consciousness. While in vivo studies offer insight into carotid responses during gravitational transitions and microgravity, detailed vascular flow mapping remains limited by imaging constraints. This work presents a novel in vitro carotid bifurcation model enabling high-resolution analysis of flow behavior across static and transient gravity profiles and orientations, focusing on mechanisms driving cerebral hypoperfusion. METHODS: The platform uses a patient-derived polydimethylsiloxane carotid model perfused with a glycerol-water blood analog seeded with tracer particles. Flow was tracked using a high-speed camera and particle image velocimetry. Parabolic flight experiments spanned 0 Gz, +1 Gz, and "push-pull" +2 Gz transitions in supine and vertical orientations. Velocity, vorticity, wall shear stress, and recirculation dynamics were derived from the velocity fields. RESULTS: Flow behavior depended on gravity and orientation. Under 0 Gz, separation points were stable at 3.6-3.8 mm downstream of the apex. With increasing Gz, they shifted upstream to 1.22 mm in vertical +2 Gz. Recirculation height increased by 22% (+1 Gz supine), 40% (+1 Gz vertical), and 62% (+2 Gz vertical) vs. 0 Gz. Peak wall shear stress increased by 19% from 0 Gz to +1 Gz supine, 59% from supine to vertical at +1 Gz, and reached 4.02 Pa in +2 Gz vertical. Vorticity declined with +Gz, indicating reduced rotational fluid motion. DISCUSSION: This in vitro platform advances cerebrovascular hemodynamics research under varying gravity, enabling analysis of phenomena difficult to capture in vivo. It enables controlled study of flow phenomena, orientation effects, and validation of computational models. Mani C, Bates K, Mongrain R, Leask RL. Development of a platform for in vitro hemodynamic measurements in varying gravity profiles. Aerosp Med Hum Perform. 2026; 97(5):316-326.