responsiveness in astronauts living for 2-6 months on the ISS. Overall, there was no change in
indicators of cardiovascular stability during long-duration spaceflight and only relatively small
changes postflight at rest in the seated position. In-flight measurements of heart rate (HR),
blood pressure (BP), and BP regulation versus preflight revealed no significant changes. Very
small increases in resting HR and a 25-34% reduction in the arterial blood pressure reflex
response postflight reflected relatively modest levels of decreased cardiovascular muscle tone
and fitness. It was also found that astronauts maintained their preflight heart rate during daily
activities while living on the ISS (Fraser 2012). These postflight changes suggests that while the
current countermeasures on ISS maintain cardiovascular stability in resting conditions in space;
key aspects of cardiovascular health with potential long-term consequences are not yet
protected (Hughson 2012). Studies have shown a consistent impairment of dynamic
cerebrovascular autoregulation and CO 2 reactivity in astronauts chronically exposed to elevated
atmospheric CO 2 from long-duration spaceflight; however, there were between-person
differences in the magnitude of impairment. Evidence also suggests possible cerebrovascular
damage, such as thickening of the cerebral arteries, from pro-longed elevation in cerebral blood
pressure. It is unclear, at the moment, whether these changes have harmful effects associated
with the complications in vision attributed to increased intracranial pressure. Future studies
should investigate in-depth pre to postflight changes in cerebral blood flow and CO 2 reactivity
to determine whether they are predictors of health complications resulting from long-duration
spaceflight (Zuj 2012).
PUBLICATION(S)
Hughson RL, Shoemaker JK, Arbeille P. CCISS, Vascular and BP Reg: Canadian space life science
research on ISS. Acta Astronautica. 2014;104(1); 444 -448.
Xu D, Shoemaker JK, Blaber AP, Arbeille P, Fraser KS, Hughson RL. Reduced heart rate variability
during sleep in long-duration spaceflight. American Journal of Physiology: Regulatory,
Integrative and Comparative Physiology. July 15, 2013;305(2):R164-R170. doi:
10.1152/ajpregu.00423.2012.
Fraser KS, Greaves D, Shoemaker J, Blaber A, Hughson R. Heart rate and daily physical activity
with long-duration habitation of the International Space Station. Aviation, Space, and
Environmental Medicine. 2012; 83(6):577-584.
Hughson R, Shoemaker J, Blaber A, et al. Cardiovascular regulation during long-duration
spaceflights to the International Space Station. Journal of Applied Physiology. 2012;112(5):719-
727.
Zuj KA, Arbeille P, Shoemaker JK, et al. Impaired cerebrovascular autoregulation and reduced
CO 2 reactivity after long-duration spaceflight. American Journal of Physiology: Heart and
Circulatory Physiology. 2012; 302(12):H2592-H2598. doi: 10.1152/ajpheart.00029.2012.
This investigation is ongoing and additional results are pending publication.