Vascular Ultrasound in Space: Evaluation for Risk of Deep Vein Thrombosis During Spaceflight

By Dr James Pavela and Dr. Stephan Moll

May 3, 2022 – Today in Vascular Medicine, Dr James Pavela and colleagues published a report of the National Aeronautics and Space Administration (NASA) occupational surveillance program to screen astronauts for deep vein thrombosis (DVT) during spaceflight. Eleven astronauts with matching terrestrial (on earth) and in-flight ultrasound evaluations were included in the study.

Lead author, Dr James Pavela (NASA, Houston, TX), and senior author, Dr. Stephan Moll (University of North Carolina, Chapel Hill, NC) shared additional insight with Vascular Medicine below.

What were the key findings of this study?

“Our key findings were that the development of slow venous flow, and the irregular appearance of blood, were most pronounced in the left internal jugular vein during spaceflight; that blood flow anomalies such as creeping slow flow in the opposite (retrograde) direction occurs in some astronauts, possibly due to local anatomical circumstances; and that despite these apparent blood flow aberrations, no individual developed DVT during the study.”

How will NASA use these data to inform future considerations of human spaceflight?

“Occupational surveillance is used to identify those who may need medical intervention and to help characterize the risk that spaceflight poses to astronauts. Our data in particular help inform what medical supplies should be available for current and future spaceflight missions, e.g., blood thinners (anticoagulants) for missions to the Moon and Mars. Our data also help guide the use and development of countermeasures, i.e., interventions designed to prevent the ill effects of spaceflight. For DVT prevention, current countermeasures include screening before spaceflight and surveillance at set intervals throughout the mission. Future in-flight interventions could focus on improving head and neck venous blood flow in those with flow anomalies, potentially by the routine use of respiratory maneuvers, threshold impedance breathing, lower body negative pressure, or even artificial gravity.”

What are the next steps in your research?

“We hope publication of our initial data will lead to improvements in NASA’s ultrasound surveillance protocol going forward and help focus research attention on how venous blood flow (hemorheology) relates to thrombosis risk, both here on Earth and in microgravity conditions. Additionally, we would like to evaluate how head and neck anatomy influences the development of slow venous flow in microgravity, particularly focusing on jugular vein course, jugular valve function, and asymmetry of the cerebral venous sinuses.”

In an accompanying editorial, Drs Laura M Drudi (Centre Hospitalier de l’Université de Montréal) and S Marlene Grenon (University of California, San Francisco) state that the work by Pavela and colleagues “supports the evidence that diagnostic ultrasound evaluation could be performed in microgravity by nonexperts.” Further, they agree with the study authors that screening astronauts for DVT during spaceflight is an important consideration for future space travel, especially considering that spaceflight “may soon be accessible to anyone with the financial means to purchase their golden ticket.”

Download both articles for free from Vascular Medicine:

Pavela J, Sargsyan A, Bedi D, et al. Surveillance for jugular venous thrombosis in astronauts. Vascular Meicine, First Published May 3, 2022 DOI: 10.1177/1358863X221086619.

Drudi LM, Grenon SM. The Vascular Frontier: Exploring the diagnosis and management of vascular conditions in spaceflight. Vascular Medicine, First Published May 3, 2022, DOI: 10.1177/1358863X221093667.

About the Author:

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Stephan Moll, MD, received his medical degree from Freiburg University, Germany, including a one year of clinical training in London (Hammersmith Hospital and Institute of Neurology at Queens Square), and performed a pathology residency at the Institute of Pathology, University of Aachen, Germany. He completed an internship and residency in Internal Medicine and a Hematology-Oncology fellowship at Duke University Medical Center, North Carolina, and a one-year Clinical Coagulation fellowship at the University of North Carolina (UNC), Chapel Hill. Dr Moll has been a faculty member at the University of North Carolina in the Department of Medicine and the Division of Hematology-Oncology since 1999, now at the rank of full professor.

His clinical interest is coagulation and classical hematology, with a particular focus on thrombosis and anticoagulation. Dr Moll’s research interests include clinical trials on new anticoagulants and better use of established anticoagulants. He takes a special interest in clinical-medical education of healthcare professionals, patients and the public, and is a cofounder of the UNC Blood Clot Education Program Clot Connect, at www.clotconnect.org. His four main professional goals for the next 5-10 years are to (1) enhance national and local patient and health care provider education activities on venous thromboembolism, (2) continue to build an “Athletes and Blood Clot Program”, (3) support trainees in their career development in the field of coagulation/hematology, (4) assist in identifying the etiology and best treatment of Livedoid Vasculopathy.