An inflatable ‘finger-lock’ for stabilizing nailfold capillary videos and modulating blood flow velocities

High-resolution video capillaroscopy shows promise as a non-invasive method to directly observe blood cells as they flow through and interact with the microvas-culature. When imaging microvasculature in the nailfold, the inherent shaking of the fingers requires physical stabilization for image noise reduction. However, any external force applied to the fingers will affect the rate of blood flow. We designed an inflatable ‘finger-lock’ for nailfold capillaroscopy, which stabilizes the finger against a coverslip with constant pressure. Testing 72 participants, we demonstrated that increasing ‘finger-lock’ pressure improves video stability and decreases the velocity of capillary blood cells. This shows that capillary blood cell velocity measurements should monitor and control external pressure. Our work introduces a method to perturb local capillary blood flow and measure the microvascular response, enabling further studies investigating how person-specific factors (e.g. age, disease) impact vascular health.