CARDIORESPIRATORY ADAPTATION TO THE SPACE ENVIRONMENT (CARDIORESPIR)
Research Area: Cardiovascular and Respiratory Systems
Expedition(s): 5
Principal Investigator(s): ● Manuel Paiva, PhD, Universite Libre de Bruxelles,
Brussels, Belgium
● Pierre Migeotte, Universite Libre de Bruxelles, Brussels,
Belgium
● Rui Carlos Sá, Universite Libre de Bruxelles, Brussels, Belgium
● Thomas Dominique, Universite Libre de Bruxelles,
Brussels, Belgium
● G. Kim Prisk, PhD, University of California San Diego, La Jolla,
California
RESEARCH OBJECTIVES
Cardiorespiratory Adaptation to the Space Environment (CardioRespir) examines the alterations
of the preload conditions of the hearts of space explorers in microgravity. Results from previous
space missions have shown that early in weightlessness cardiac filling and stroke volume
increase, there is a decrease in resting heart rate. These changes are the onset of complex
adaptation mechanisms in the cardiovascular and cardiopulmonary systems, which play a role
on mechanisms of orthostatic intolerance, one of the most important physiological problems
endured by astronauts after spaceflight and a potential hazard for longer spaceflight, especially
for future exploration missions.
RESULTS
Measurements were performed on 3 crew members with preflight, inflight, and postflight sessions
recording ECG and respiratory measurements with imposed and controlled breathing protocols.
Analysis shows that the amplitude of the respiratory sinus arrhythmia (RSA) showed a linear
relationship with the breathing period (Tresp). In flight, the slope of this relationship was slightly
decreased, with a difference more pronounced for the (on-ground) standing than the supine
posture. For the first days after return, a significant decrease of the slope was observed
compared to both supine and standing preflight slopes. Between the 15th and 25th days after
return, there was a progressive return to normal values of the RSA relationship with breathing
period.
The results of decreased amplitude of RSA and decreased slope of the relationship between RSA
and Tresp during and after exposure to weightlessness support the hypothesis that the
parasympathetic activity of the autonomic nervous system is decreased. The science team
showed also that simultaneous knowledge of HR and Tresp is required for the analysis of RSA as a
tool for following up the progressive readaptation to normal gravity of HR autonomic control. This
result stressed the importance of the influence of respiration on the interpretation of changes in
heart rate variability, and the necessity for its control.