Press Release NASA’s Johnson Space Center: - Space Station Investigation Goes With the Flow "...It could also impact the medical community on Earth, especially for physicians treating patients with chronic heart failure and neurological disorders. The strain-gauge plethysmography, complemented by ultrasound analysis of the jugular pulse, could potentially make measuring blood flow in these sets of patients much easier, allowing patients and doctors to better go with the flow..."
http://www.nasa.gov/mission_pages/station/research/news/drain-Braintree

On Earth, blood flows down from a person’s brain back toward the heart thanks in part to gravity, but very little is known about how this flow happens in microgravity.