Vital Sign Accuracy May Depend on Body Position, Research Suggests

Clinicians must adjust for hydrostatic pressure in seated position to determine true arterial stiffness level

Rockville, Md. (Feb. 20, 2025)—Body position can affect the accuracy of vital sign measurements that indicate arterial stiffness—a risk factor for heart disease—according to new research. Sitting down during certain tests may cause a spike in arterial stiffness readings that does not reflect a true increase. The study is published in the American Journal of Physiology-Regulatory, Integrative and Comparative Physiology  and has been chosen as an APSselect article for February.

Arterial stiffness is when the walls of the blood vessels are not as elastic or stretchy as they should be. The condition is often a part of aging and can also occur in people who have diabetes, high cholesterol or high blood pressure. People with stiffer arteries have an increased risk of heart attack, stroke and other forms of heart disease.

Medical professionals most commonly measure markers of arterial stiffness with patients lying on their back (supine position). However, sitting may be a more practical option for people with chronic back pain or other health concerns. In this study, researchers explored whether measuring carotid-femoral pulse wave velocity—the time it takes for the pulse to travel from the carotid to the femoral artery—can be considered reliable when measured in a seated position. Carotid-femoral pulse wave velocity (cfPWV) is considered the “gold standard” for measuring arterial stiffness.

The research team assessed a small group of young, healthy volunteers in both supine and seated positions on the same day. The researchers measured heart rate and blood pressure as well as cfPWV and took measurements three times in each position. They also analyzed the difference in arterial stiffness markers after a change from one position to the other.

Blood pressure, arterial pressure and heart rate were generally higher when participants were sitting compared to lying down. The researchers found cfPWV to be much higher when seated as well. However, when looking at blood flow and blood pressure between the two postures and adjusting the calculations to account for changes in hydrostatic pressure (pressure created due to gravity), the readings were much more comparable.

In addition, these findings suggest the activation of the sympathetic nervous system that occurs while sitting is not strong enough to cause large increases in arterial stiffness.

This study may have important implications for diagnosis of arterial stiffness and, in turn, the risk of heart disease.

“[I]t is crucial to carefully consider the subject’s posture during [pulse wave velocity] measurements to accurately assess arterial stiffness,” the researchers wrote. “For patients who find it challenging to maintain a fully supine posture … values obtained in the seated position can be appropriately adjusted for [hydrostatic and transmural pressure].”

Read the full article, “The Validity of Carotid-femoral Pulse Wave Velocity in the Seated Posture as an Index of Central Arterial Stiffness.” It is highlighted as one of this month’s “best of the best” as part of the American Physiological Society’s APSselect program. Read this month’s selected research articles.  

NOTE TO JOURNALISTS: To schedule an interview with a member of the research team, please contact APS Media Relations or call 301.634.7314. Find more research highlights in our Newsroom.  

Physiology is a broad area of scientific inquiry that focuses on how molecules, cells, tissues and organs function in health and disease. The American Physiological Society connects a global, multidisciplinary community of more than 10,000 biomedical scientists and educators as part of its mission to advance scientific discovery, understand life and improve health. The Society drives collaboration and spotlights scientific discoveries through its 16 scholarly journals and programming that support researchers and educators in their work.