Cn. Mukai et al., CARDIOVASCULAR-RESPONSES TO REPETITIVE EXPOSURE TO HYPERGRAVITY AND HYPOGRAVITY STATES PRODUCED BY PARABOLIC FLIGHT, Journal of clinical pharmacology, 34(5), 1994, pp. 472-479
Physiologic changes to repetitive hyper- and hypogravity stresses occu
rring during eight to ten parabolas on NASA's KC-135 aircraft were stu
died. Hemodynamic responses in 11 subjects in 4 different postures (su
pine, standing, sitting, and semisupine Space Shuttle launch position)
were determined using noninvasive impedance cardiography. Five second
s of heart rate, cardiac index, thoracic fluid index, stroke index, ej
ection velocity index, and ventricular ejection time data were average
d during four different gravity (g) states: 1.3g (before parabola onse
t); 1.9g (parabola entry); Og (parabola peak); and 1.7g (parabola exit
) for each subject. The standing position was associated with the larg
est changes in the cardiovascular response to hypo- and hypergravity.
The thoracic fluid index did not indicate a headward redistribution du
ring transition from a simulated launch position to weightlessness. An
alysis of the eight to ten parabolas revealed that, in general, values
obtained at 1.8g differed from 1.6g, Og differed from 1.6 and 1.3g, a
nd 1.6g differed from 1.3g. The factors of gravity, thoracic fluid ind
ex, and cardiac index exhibited significant differences that were most
likely to occur between parabola 1 versus parabolas 6, 7, and 8, and
parabola 2 versus parabolas 4 through 8. Only the parameter of thoraci
c fluid index exhibited significance for parabolas 3 versus parabolas
6 and 7.