EFFECT OF MICROGRAVITY ON THE PERIPHERAL SUBCUTANEOUS VENO-
ARTERIOLAR REFLEX IN HUMANS (XENON1)
Research Area: Cardiovascular and Respiratory Systems
Expeditions: 3-5
Principal Investigator(s): ● Anders Gabrielsen, MD, Danish Aerospace Medical Center of
Research National University Hospital, Copenhagen, Denmark
RESEARCH OBJECTIVES
The Effect of Microgravity on the Peripheral Subcutaneous Veno-Arteriolar Reflex in Humans
(Xenon1) study investigates the mechanism of orthostatic intolerance (the inability to regulate
blood pressure while upright) to establish an important foundation for the development of
treatments for orthostatic intolerance following spaceflight. Orthostatic intolerance occurring
after spaceflight can interfere with normal brain function of crew members during re-entry and
landing.
EARTH BENEFITS
This study has great implications in the medical community on Earth. Currently, there are no
specific tests for orthostatic intolerance for it is not completely understood what causes
orthostatic intolerance. What this experiment may lead to is a better understanding and
improved treatment programs for orthostatic intolerance.
SPACE BENEFITS
While a person is standing (orthostasis), blood
has a tendency to pool in the legs and feet. This
collecting of blood in the lower body can lead to
a blood pressure drop in the upper body, and, if
less blood gets to the brain, an individual may
experience dizziness or fainting. It is a condition
called orthostatic intolerance, and it can affect
crew members for several days after returning
from space. The exact mechanism that creates
orthostatic intolerance is still not completely
understood. When blood pooling is detected in
the lower limbs, the body’s normal response is
tightening blood vessels below the skin to
maintain blood pressure and blood supply to the
brain. Treatments for this condition are currently
under investigation (one is the drug Midodrine,
which is being tested on crew members). This
study's method of visualizing blood flow of the
subcutaneous vessels and the venoarterial (V-A)
reflex allows for possible treatments in the future.
During the Xenon1 experiment, the crew member
is injected with small amounts of 133Xenon, which
will act as a tracer. Xenon1 will test the local veno-
arteriolar reflex in an effort to understand the
source of, and ways to combat, postflight
orthostatic intolerance. NASA’s Johnson Space
Center image.