[Behavior of the cardiovascular system in outer space].
One of the important factors in outer space is the absence of gravity (OG). During longterm missions, this factor is responsible for the larger number of anatomical and physiological changes that astronauts experience. The cardiovascular system undergoes these changes with severe intensity, which is part of an adaptation process to the new environmental conditions. The modifications observed in both the anatomy of the cardiovascular system and its hemodynamics occur in two phases. The first phase begins when the astronauts enter into Earth orbit or in interplanetary trajectory and extends until the second or fourth day of the mission. It is characterized by an important shifting of fluids from the lower extremities to the cephalic regions which produces an increase of the venous return and the preload, the heart rate is increased, the blood volume in the thorax is also increased, the cardiac chambers become dilated, and by reflex action, the antidiuretic hormone diminishes, diuresis increases and leads to a virtual state of dehydration. Clinically, the first stage is manifested by headache, dizziness, space disorientation, nausea, anorexia, projectile vomiting, sweating and pallor. This constalation of data is known as "The Space Adaptation Syndrome". The second phase begins at the end of the first phase and finishes toward the fortieth or fiftieth day of the mission.(ABSTRACT TRUNCATED AT 250 WORDS)
D002320:Cardiovascular Physiological Phenomena; D006801:Humans; D013026:Space Flight
Comportamiento del aparato cardiovascular en el espacio exterior.